Arq (ARQ) 10-Q 9 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 04, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-37822
Entity Registrant Name	Advanced Emissions Solutions, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-5472457
Entity Address, Address Line One	8051 E. Maplewood Ave
Entity Address, Address Line Two	Suite 210
Entity Address, City or Town	Greenwood Village
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80111
City Area Code	720
Local Phone Number	598-3500
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	ADES
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		18,853,288
Entity Central Index Key	0001515156
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash, cash equivalents and restricted cash	$ 47,335	$ 30,932
Receivables, net	11,560	13,125
Receivables, related parties	3,656	3,453
Inventories, net	8,161	9,882
Prepaid expenses and other assets	5,320	4,597
Total current assets	76,032	61,989
Restricted cash, long-term	10,000	5,000
Property, plant and equipment, net of accumulated depreciation of $5,344 and $3,340, respectively	31,204	29,433
Intangible assets, net	1,631	1,964
Equity method investments	3,564	7,692
Deferred tax assets, net	3,787	10,604
Other long-term assets, net	32,277	29,989
Total Assets	158,495	146,671
Current liabilities:
Accounts payable	8,162	7,849
Accrued payroll and related liabilities	2,660	3,257
Current portion of long-term debt	4,373	18,441
Other current liabilities	11,955	12,996
Total current liabilities	27,150	42,543
Long-term debt, net of current portion	3,670	5,445
Other long-term liabilities	11,392	13,473
Total Liabilities	42,212	61,461
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock: par value of $.001 per share, 50,000,000 shares authorized, none outstanding	0	0
Common stock: par value of $.001 per share, 100,000,000 shares authorized, 23,452,485 and 23,141,284 shares issued, and 18,834,339 and 18,523,138 shares outstanding at June 30, 2021 and December 31, 2020, respectively	23	23
Treasury stock, at cost: 4,618,146 and 4,618,146 shares as of June 30, 2021 and December 31, 2020, respectively	(47,692)	(47,692)
Additional paid-in capital	101,171	100,425
Retained earnings	62,781	32,454
Total stockholders’ equity	116,283	85,210
Total Liabilities and Stockholders’ Equity	$ 158,495	$ 146,671

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Accumulated depreciation and amortization	$ 5,344	$ 3,340
Preferred stock par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares outstanding (in shares)	0	0
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	23,452,485	23,141,284
Common stock, shares outstanding (in shares)	18,834,339	18,523,138
Treasury stock (in shares)	4,618,146	4,618,146

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues:
Total revenues	$ 19,633	$ 11,483	$ 40,730	$ 23,746
Operating expenses:
Payroll and benefits	2,908	3,812	5,377	6,554
Legal and professional fees	1,431	1,022	3,234	3,065
General and administrative	1,593	2,462	3,508	4,793
Depreciation, amortization, depletion and accretion	1,904	1,733	4,010	4,030
Impairment of long-lived assets	0	26,103	0	26,103
Gain on change in estimate, asset retirement obligation	(1,942)	0	(1,942)	0
Total operating expenses	19,194	42,548	39,961	63,452
Operating income (loss)	439	(31,065)	769	(39,706)
Other income (expense):
Earnings from equity method investments	21,437	8,168	39,749	16,441
Interest expense	(493)	(962)	(1,330)	(2,172)
Other	150	148	571	191
Total other income	21,094	7,354	38,990	14,460
Income (loss) before income tax expense	21,533	(23,711)	39,759	(25,246)
Income tax expense	4,943	103	9,432	461
Net income (loss)	$ 16,590	$ (23,814)	$ 30,327	$ (25,707)
Earnings (loss) per common share (Note 1):
Basic (in dollars per share)	$ 0.91	$ (1.32)	$ 1.66	$ (1.43)
Diluted (in dollars per share)	$ 0.90	$ (1.32)	$ 1.65	$ (1.43)
Weighted-average number of common shares outstanding:
Basic (in shares)	18,271	18,014	18,219	17,974
Diluted (in shares)	18,398	18,014	18,356	17,974
Consumables
Revenues:
Total revenues	$ 15,976	$ 8,170	$ 33,007	$ 17,387
Operating expenses:
Consumables cost of revenue, exclusive of depreciation and amortization	13,300	7,416	25,774	18,907
License royalties, related party
Revenues:
Total revenues	$ 3,657	$ 3,313	$ 7,723	$ 6,359

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings
Beginning Balance (in shares) at Dec. 31, 2019		22,960,157	(4,597,533)
Beginning Balance at Dec. 31, 2019	$ 108,292	$ 23	$ (47,533)	$ 98,466	$ 57,336
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		218,259
Stock-based compensation	506			506
Repurchase of common shares to satisfy minimum tax withholdings (in shares)		(64,198)
Repurchase of common shares to satisfy minimum tax withholdings	(376)			(376)
Cash dividends declared on common stock	(4,590)				(4,590)
Repurchase of common shares (in shares)			(20,613)
Repurchase of common shares	(159)		$ (159)
Net income (loss)	(1,893)				(1,893)
Ending Balance (in shares) at Mar. 31, 2020		23,114,218	(4,618,146)
Ending Balance at Mar. 31, 2020	101,780	$ 23	$ (47,692)	98,596	50,853
Beginning Balance (in shares) at Dec. 31, 2019		22,960,157	(4,597,533)
Beginning Balance at Dec. 31, 2019	108,292	$ 23	$ (47,533)	98,466	57,336
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(25,707)
Ending Balance (in shares) at Jun. 30, 2020		23,110,285	(4,618,146)
Ending Balance at Jun. 30, 2020	79,102	$ 23	$ (47,692)	99,732	27,039
Beginning Balance (in shares) at Mar. 31, 2020		23,114,218	(4,618,146)
Beginning Balance at Mar. 31, 2020	101,780	$ 23	$ (47,692)	98,596	50,853
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		(3,549)
Stock-based compensation	1,138			1,138
Repurchase of common shares to satisfy minimum tax withholdings (in shares)		(384)
Repurchase of common shares to satisfy minimum tax withholdings	(2)			(2)
Net income (loss)	(23,814)				(23,814)
Ending Balance (in shares) at Jun. 30, 2020		23,110,285	(4,618,146)
Ending Balance at Jun. 30, 2020	79,102	$ 23	$ (47,692)	99,732	27,039
Beginning Balance (in shares) at Dec. 31, 2020		23,141,284	(4,618,146)
Beginning Balance at Dec. 31, 2020	85,210	$ 23	$ (47,692)	100,425	32,454
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		381,339
Stock-based compensation	421			421
Repurchase of common shares to satisfy minimum tax withholdings (in shares)		(40,975)
Repurchase of common shares to satisfy minimum tax withholdings	(216)			(216)
Net income (loss)	13,737				13,737
Ending Balance (in shares) at Mar. 31, 2021		23,481,648	(4,618,146)
Ending Balance at Mar. 31, 2021	99,152	$ 23	$ (47,692)	100,630	46,191
Beginning Balance (in shares) at Dec. 31, 2020		23,141,284	(4,618,146)
Beginning Balance at Dec. 31, 2020	85,210	$ 23	$ (47,692)	100,425	32,454
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	30,327
Ending Balance (in shares) at Jun. 30, 2021		23,452,485	(4,618,146)
Ending Balance at Jun. 30, 2021	116,283	$ 23	$ (47,692)	101,171	62,781
Beginning Balance (in shares) at Mar. 31, 2021		23,481,648	(4,618,146)
Beginning Balance at Mar. 31, 2021	99,152	$ 23	$ (47,692)	100,630	46,191
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		(25,330)
Stock-based compensation	566			566
Repurchase of common shares to satisfy minimum tax withholdings (in shares)		(3,833)
Repurchase of common shares to satisfy minimum tax withholdings	(25)			(25)
Net income (loss)	16,590				16,590
Ending Balance (in shares) at Jun. 30, 2021		23,452,485	(4,618,146)
Ending Balance at Jun. 30, 2021	$ 116,283	$ 23	$ (47,692)	$ 101,171	$ 62,781

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net income (loss)	$ 30,327	$ (25,707)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax expense	6,817	11,647
Depreciation, amortization, depletion and accretion	4,010	4,030
Impairment of long-lived assets	0	26,103
Operating lease expense	912	1,353
Amortization of debt discount and debt issuance costs	945	709
Gain on change in estimate, asset retirement obligation	(1,942)	0
Stock-based compensation expense	987	1,644
Earnings from equity method investments	(39,749)	(16,441)
Other non-cash items, net	(319)	31
Changes in operating assets and liabilities:
Receivables and related party receivables	1,362	2,854
Prepaid expenses and other assets	(723)	(11,129)
Inventories, net	1,327	(590)
Other long-term assets, net	616	(224)
Accounts payable	150	(1,095)
Accrued payroll and related liabilities	(597)	134
Other current liabilities	(1,468)	(515)
Operating lease liabilities	(1,314)	(1,213)
Other long-term liabilities	(2,334)	(22)
Distributions from equity method investees, return on investment	19,144	32,516
Net cash provided by operating activities	18,151	24,085
Cash flows from investing activities
Distributions from equity method investees in excess of cumulative earnings	24,732	0
Acquisition of property, plant, equipment, and intangible assets, net	(4,573)	(4,189)
Mine development costs	(653)	(507)
Proceeds from sale of property and equipment	895	0
Net cash provided by (used in) investing activities	20,401	(4,696)
Cash flows from financing activities
Principal payments on term loan	(16,000)	(12,000)
Principal payments on finance lease obligations	(818)	(676)
Dividends paid	(90)	(4,828)
Repurchase of common shares	0	(159)
Repurchase of common shares to satisfy tax withholdings	(241)	(378)
Borrowings from Paycheck Protection Program Loan	0	3,305
Net cash used in financing activities	(17,149)	(14,736)
Increase in Cash and Cash Equivalents and Restricted Cash	21,403	4,653
Cash and Cash Equivalents and Restricted Cash, beginning of period	35,932	17,080
Cash and Cash Equivalents and Restricted Cash, end of period	57,335	21,733
Supplemental disclosure of non-cash investing and financing activities:
Acquisition of property, plant and equipment through accounts payable	163	223
Dividends payable	$ 0	$ 77

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Nature of Operations Advanced Emissions Solutions, Inc. ("ADES" or the "Company") is a Delaware corporation with its principal office located in Greenwood Village, Colorado and operations located in Louisiana. The Company is principally engaged in the sale of consumable air and water treatment options including activated carbon ("AC") and chemical technologies. The Company's proprietary technologies in the advanced purification technologies ("APT") market enable customers to reduce air and water contaminants, including mercury and other pollutants, to maximize utilization levels and improve operating efficiencies to meet the challenges of existing and pending emission control regulations. Through its wholly-owned subsidiary, ADA Carbon Solutions, LLC ("Carbon Solutions"), the Company manufactures and sells AC used to capture and remove contaminants for coal-fired power plants and industrial and water treatment markets. Carbon Solutions also owns an associated lignite mine that supplies the primary raw material for manufacturing AC. Through its equity ownership in Tinuum Group, LLC ("Tinuum Group") and Tinuum Services, LLC ("Tinuum Services"), both of which are unconsolidated entities, the Company generates substantial earnings. Tinuum Group provides reduction of mercury and nitrogen oxide ("NOx") emissions at select coal-fired power generators through the production and sale of refined coal ("RC") that qualifies for tax credits under the Internal Revenue Code ("IRC") Section 45 - Production Tax Credit ("Section 45 tax credits"). The Company also earns royalties for technologies that are licensed to Tinuum Group and used at certain RC facilities to enhance combustion and reduced emissions of NOx and mercury from coal burned to generate electrical power. Tinuum Services operates and maintains the RC facilities under operating and maintenance agreements with Tinuum Group and owners or lessees of the RC facilities. Both Tinuum Group and Tinuum Services expect to commence significantly winding down their operations starting in the third quarter of 2021 due to the expected expiration of the Section 45 tax credit period as of December 31, 2021. The Company’s sales occur principally in the United States. See Note 17 for additional information regarding the Company's operating segments. Basis of Presentation The accompanying Condensed Consolidated Financial Statements of ADES are unaudited and have been prepared in conformity with accounting principles generally accepted in the United States ("U.S. GAAP") and with Article 10 of Regulation S-X of the Securities and Exchange Commission. In compliance with those instructions, certain information and footnote disclosures normally included in annual consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. The unaudited Condensed Consolidated Financial Statements of ADES in this quarterly report ("Quarterly Report") are presented on a consolidated basis and include ADES and its wholly-owned subsidiaries (collectively, the "Company"). Also included within the unaudited Condensed Consolidated Financial Statements are the Company's unconsolidated equity investments: Tinuum Group, Tinuum Services and GWN Manager, LLC ("GWN Manager"), which are accounted for under the equity method of accounting, and Highview Enterprises Limited (the "Highview Investment"), which is accounted for in accordance with U.S. GAAP applicable to equity investments that do not qualify for the equity method of accounting. Results of operations and cash flows for the interim periods are not necessarily indicative of the results that may be expected for the entire year. All significant intercompany transactions and accounts were eliminated in consolidation for all periods presented in this Quarterly Report. In the opinion of management, these Condensed Consolidated Financial Statements include all normal and recurring adjustments considered necessary for a fair presentation of the results of operations, financial position, stockholders' equity and cash flows for the interim periods presented. These Condensed Consolidated Financial Statements of ADES should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 (the "2020 Form 10-K"). Significant accounting policies disclosed therein have not changed. Earnings (Loss) Per Share Basic earnings (loss) per share is computed using the two-class method, which is an earnings allocation formula that determines earnings (loss) per share for common stock and any participating securities according to dividend and participating rights in undistributed earnings (losses). Pursuant to U.S. GAAP, the Company has elected not to separately present basic or diluted earnings per share attributable to participating securities in the Condensed Consolidated Statements of Operations. Diluted earnings (loss) per share is computed in a manner consistent with that of basic earnings per share, while considering other potentially dilutive securities. For the three and six months ended June 30, 2021, potentially dilutive securities consist of unvested non-participating restricted stock awards ("RSA's"), as well as contingent performance stock units ("PSU's"). For the three and six months ended June 30, 2020, potentially dilutive securities consist of both unvested, participating and non-participating RSA's, as well as outstanding options to purchase common stock ("Stock Options") and PSU's. The dilutive effect, if any, for non-participating RSA's, Stock Options and PSU's is determined using the greater of dilution as calculated under the treasury stock method or the two-class method. Potentially dilutive securities are excluded from diluted earnings per share when their effect is anti-dilutive. When there is a net loss for a period, all potentially dilutive securities are anti-dilutive and are excluded from the calculation of diluted loss per share for that period. The following table sets forth the calculations of basic and diluted earnings (loss) per share: Three Months Ended June 30, Six Months Ended June 30, (in thousands, except per share amounts) 2021 2020 2021 2020 Net income (loss) $ 16,590 $ (23,814) $ 30,327 $ (25,707) Less: Dividends and undistributed income (loss) allocated to participating securities — (17) — (19) Income (loss) attributable to common stockholders $ 16,590 $ (23,797) $ 30,327 $ (25,688) Basic weighted-average common shares outstanding 18,271 18,014 18,219 17,974 Add: dilutive effect of equity instruments 127 — 137 — Diluted weighted-average shares outstanding 18,398 18,014 18,356 17,974 Earnings (loss) per share - basic $ 0.91 $ (1.32) $ 1.66 $ (1.43) Earnings (loss) per share - diluted $ 0.90 $ (1.32) $ 1.65 $ (1.43) For the three and six months ended June 30, 2021 and 2020, potentially dilutive securities convertible to 0.1 million and 0.7 million and zero and 0.3 million shares of common stock, respectively, were outstanding but were not included in the computation of diluted net income (loss) per share because the effect would have been anti-dilutive. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. There have been no changes in the Company’s critical accounting estimates from those that were disclosed in the 2020 Form 10-K. Actual results could differ from these estimates. Due to the coronavirus ("COVID-19") pandemic, there has been uncertainty and disruption in the global economy and financial markets. Additionally, due to COVID-19, overall power generation and coal-fired power demand may decline, which could have a material adverse effect on the Company. The Company is not aware of any specific event or circumstance due to COVID-19 that would require an update to its estimates or judgments or a revision of the carrying values of its assets or liabilities through the date of this Quarterly Report. These estimates may change as new events occur and additional information is obtained. Actual results could differ materially from these estimates under different assumptions or conditions. Risks and Uncertainties The Company’s earnings are significantly affected by equity earnings from Tinuum Group. As of June 30, 2021, Tinuum Group has 22 invested RC facilities, of which 8 are leased to a single customer. Both Tinuum Group and Tinuum Services expect to commence significantly winding down their operations starting in the third quarter of 2021 due to the expected expiration of the Section 45 tax credit period as of December 31, 2021. During the second quarter of 2021, Tinuum Group ceased operating one RC facility, with the remaining RC facilities expected to cease operations during the second half of 2021. The loss of Tinuum Group's customers, reduction in revenue streams as a result of lease renewals and the expiration of Section 45 tax credits will have a significant adverse impact on Tinuum Group's financial position, results of operations and cash flows, which in turn will have a material adverse impact on the Company’s financial position, results of operations and cash flows. The Company's revenues, sales volumes, earnings and cash flows are significantly affected by prices of competing power generation sources such as natural gas and renewable energy. During periods of low natural gas prices, natural gas provides a competitive alternative to coal-fired power generation and therefore, coal consumption may be reduced, which reduces the demand for the Company's products. However, during periods of higher prices for competing power generation sources, the demand for the Company's products increases due to the increase in coal consumption. In addition, coal consumption and demand for the Company's products are also affected by the demand for electricity, which is higher in the warmer and colder months of the year. Abnormal temperatures during the summer and winter months may significantly affect coal consumption and thus the demand for the Company's products. Reclassifications Certain balances have been reclassified from the prior year to conform to the current year presentation. Such reclassifications had no effect on the Company’s results of operations or financial position in any of the periods presented. New Accounting Standards Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes ("ASU 2019-12"). The amendments in ASU 2019-12 simplify various aspects related to accounting for income taxes by removing certain exceptions contained in Topic 740 and also clarify and amends existing guidance in Topic 740 to improve consistent application. ASU 2019-12 is effective for public business entities beginning after December 15, 2020, including interim periods within those years, and early adoption is permitted. The Company adopted ASU 2019-12 effective January 1, 2021 and it did not have a material impact on the Company's financial statements and disclosures. Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). The main objective of ASU 2016-13 is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. To achieve this objective, the amendments in ASU 2016-13 replace the incurred loss impairment methodology in current U.S. GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to form credit loss estimates. ASU 2016-13 is effective for "smaller reporting companies" (as defined by the Securities and Exchange Commission) for fiscal years beginning after December 15, 2022, including interim periods within those years, and must be adopted under a modified retrospective method approach. The Company is currently evaluating the provisions of this guidance and assessing the impact on its financial statements and disclosures and does not believe this standard will have a material impact on its financial statements and disclosures.

Customer Supply Agreement

Customer Supply Agreement	6 Months Ended
	Jun. 30, 2021
Additional Term of Contract [Abstract]
Customer Supply Agreement	Customer Supply Agreement On September 30, 2020, the Company and Cabot Norit Americas, Inc., ("Cabot") entered into a supply agreement (the "Supply Agreement") pursuant to which the Company agreed to sell and deliver to Cabot, and Cabot agreed to purchase and accept from the Company certain lignite-based AC products ("Furnace Products"). As part of the Supply Agreement, the Company and Cabot agreed to additional terms whereby Cabot reimburses the Company for certain capital expenditures incurred by the Company that are necessary to manufacture the Furnace Products, and both the Company and Cabot must mutually agree on these capital expenditures in advance of procurement and commissioning. Capital expenditures incurred that benefit both the Company and Cabot ("Shared Capital") are partially reimbursable by Cabot and recognized as revenues based on a formula contained in the Supply Agreement. Revenues from, and reimbursements of Shared Capital are recognized and billable, respectively, beginning on the first day of a half year (January 1 and July 1 of a calendar year) following the placed in service date of a Shared Capital asset(s). Capital expenditures incurred that benefit Cabot exclusively ("Specific Capital") are fully reimbursable by Cabot and recognized as revenues based on a formula contained in the Supply Agreement. Revenues earned from Specific Capital are recognized beginning on the first day of a half year following the placed in service date of a Specific Capital asset(s). Reimbursements of Specific Capital are billable in quarterly installments beginning on the first day of a half year following the placed in service date of a Specific Capital asset(s). In the event that Cabot ceases to make purchases under the Supply Agreement, Cabot is obligated to pay the balance of any outstanding amounts for Specific Capital. Revenues earned from both Shared Capital and Specific Capital are reported in the Consumables revenue line item in the Statements of Operations.

Acquisition of Marshall Mine

Acquisition of Marshall Mine	6 Months Ended
	Jun. 30, 2021
Business Combination and Asset Acquisition [Abstract]
Acquisition of Marshall Mine	Acquisition of Marshall Mine Concurrently with the execution of the Supply Agreement, on September 30, 2020, the Company entered into an agreement to purchase from Cabot 100% of the membership interests in Marshall Mine, LLC (the "Marshall Mine Purchase Agreement") for a nominal cash purchase price. Marshall Mine, LLC owns a lignite mine located outside of Marshall, Texas (the "Marshall Mine"). The Company concluded that the Marshall Mine did not have any remaining economic reserves and independently determined to immediately commence activities to shutter it. On September 30, 2020 the Company entered into a reclamation contract (the "Reclamation Contract") with a third party that provided a capped cost agreement, subject to certain contingencies, in the amount of approximately $19.7 million plus an obligation to pay certain direct costs estimated to be $3.6 million (collectively, the "Reclamation Costs") over the estimated reclamation period of 10 years (the "Reclamation Period"). Under the terms of the Supply Agreement, Cabot is obligated to reimburse the Company for $10.2 million of Reclamation Costs (the "Reclamation Reimbursements"), which are payable semi-annually over 13 years and inclusive of interest. In the event that Cabot has a change in control as described in the Supply Agreement, all outstanding balances of the Reclamation Reimbursements shall be due and payable in full. See further discussion of the Reclamation Costs and Reclamation Reimbursements in Note 4. The Marshall Mine Purchase Agreement included the acquisition of certain assets that will be consumed and the assumption of certain liabilities that are to be paid in reclamation of the Marshall Mine in addition to the incurrence of an obligation for the Reclamation Costs. The Company accounted for the Marshall Mine Purchase Agreement as an asset acquisition. As the Marshall Mine Purchase Agreement represents a transaction with a customer of net assets acquired and liabilities assumed from Cabot, the Company accounted for the excess of the fair value of liabilities assumed over assets acquired as upfront consideration transferred to a customer, Cabot (the "Upfront Customer Consideration"). The amount of the Upfront Customer Consideration was also recognized net of an additional asset recognized in the Marshall Mine Acquisition, which was comprised of a receivable from Cabot (the "Cabot Receivable") for the Reclamation Reimbursements. The Cabot Receivable is further discussed in Note 4. The total Upfront Customer Consideration is being amortized as a reduction to revenues on a straight-line basis over the expected 15-year contractual period of the Supply Agreement. As part of the Marshall Mine Purchase Agreement, the Company assumed liabilities, whose fair value exceeded the fair value of assets acquired. A summary of the net assets acquired and liabilities assumed and the additional assets recorded in the Marshall Mine Purchase Agreement as of September 30, 2020 are shown in the table below. The Company completed additional analysis of the assets acquired and liabilities assumed and recorded adjustments as of December 31, 2020 as shown in the table below. (in thousands) As Originally Reported Adjustments As Adjusted Assets acquired: Receivables $ — $ 513 $ 513 Property, plant and equipment 3,863 — 3,863 Spare parts 100 — 100 Liabilities assumed: Accounts payable and accrued expenses (673) 160 (513) Asset retirement obligation (21,328) — (21,328) Net assets acquired and liabilities assumed from Marshall Mine acquisition (18,038) 673 (17,365) Cabot Receivable 9,749 — 9,749 Upfront Customer Consideration $ 8,289 $ (673) $ 7,616 The Company also evaluated the Marshall Mine entity as a potential variable interest entity ("VIE"), and determined that Marshall Mine, LLC was a VIE and the Company was its primary beneficiary. Therefore, the Company consolidates Marshall Mine, LLC's assets and liabilities in the consolidated financial statements.

Marshall Mine Asset Retirement

Marshall Mine Asset Retirement Obligation and Cabot Receivable	6 Months Ended
	Jun. 30, 2021
Asset Retirement Obligation and related Long-Term Receivable [Abstract]
Marshall Mine Asset Retirement Obligation and Cabot Receivable	Marshall Mine Asset Retirement Obligation and Cabot Receivable Asset Retirement Obligation As of September 30, 2020, the Company recorded an asset retirement obligation (the "Marshall Mine ARO") for the total Reclamation Costs of $21.3 million as measured at the expected future cash flows of $23.7 million, inclusive of contingency costs, discounted to their present value using a discount rate based on a credit-adjusted, risk-free rate of 7.0%. As of June 30, 2021 and December 31, 2020, the carrying value of the Marshall Mine ARO was $11.7 million and $18.1 million, respectively. As of June 30, 2021, the Company revised its estimate of future obligations owed for the reclamation of Marshall Mine primarily based on scope reductions related to future reclamation requirements. As a result, the Company reduced the Marshall Mine ARO by $1.9 million as of June 30, 2021 and recorded a corresponding gain on change in estimate for the three and six months ended June 30, 2021. This is included as "Gain on change in estimate, asset retirement obligation" in the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2021. Cabot Receivable As of September 30, 2020, the Company recorded the Cabot Receivable at its estimated fair value of $9.7 million, reflecting a discount rate of approximately 1.5% or $0.5 million. There were no significant related fees or costs associated with the Cabot Receivable. The Company did not elect the fair value option in its initial or subsequent accounting for the Cabot Receivable. The Cabot Receivable requires Cabot to pay the Reclamation Reimbursements to the Company in the amount of $10.2 million inclusive of interest based on a mutually agreed-upon payment schedule through 2033. Interest is accreted on the Cabot Receivable and recognized as interest income. An allowance for the Cabot Receivable asset is assessed periodically, and no allowance was deemed necessary as of June 30, 2021 and December 31, 2020. Surety Bond As the owner of the Marshall Mine, the Company is required to post a surety bond to ensure performance of its reclamation activities. On September 30, 2020, the Company and a third party entered into a surety bond indemnification agreement (the "Surety Agreement") pursuant to which the Company secured and posted a $30.0 million surety bond (the "Bond") with the local regulatory agency. On June 7, 2021, the third party agreed to reduce the Surety Bond amount to $16.6 million. The Bond will remain in place until the Marshall Mine is fully reclaimed, and may be further reduced in amount from time to time as the Company progresses with its reclamation activities. As of June 30, 2021, the Company was required to post collateral of $10.0 million for the obligations due under the Reclamation Contract, which is recorded as long-term restricted cash on the Condensed Consolidated Balance Sheet.

COVID-19

COVID-19	6 Months Ended
	Jun. 30, 2021
CARES Act, Grant Income [Abstract]
COVID-19	COVID-19 In March 2020, the federal government passed the Coronavirus Aid, Relief, and Security Act (the "CARES Act"), which provided among other things the creation of the Paycheck Protection Plan ("PPP"), which is sponsored and administered by the U.S. Small Business Administration ("SBA"). On April 20, 2020, the Company executed a loan agreement (the "PPP Loan") under the PPP, evidenced by a promissory note, with BOK, NA dba Bank of Oklahoma ("BOK"), providing for $3.3 million in proceeds, which was funded to the Company on April 21, 2020. In June 2020, the Paycheck Protection Program Flexibility Act of 2020 (the "PPPFA") was signed into law and established the payment dates in the event that amounts borrowed under the PPP are not forgiven. The PPP Loan matures April 21, 2022, but may be forgiven subject to the terms of the PPP and approval by the SBA. The Company recorded the PPP Loan as a debt obligation and accrues interest over the term of the PPP Loan. The interest rate on the PPP Loan is 1.00%. The PPP Loan is unsecured and contains customary events of default relating to, among other things, payment defaults, making materially false and misleading representations to the SBA or BOK, or breaching the terms of the PPP Loan. The occurrence of an event of default may result in the repayment of all amounts outstanding, collection of all amounts owing from the Company, or filing suit and obtaining judgment against the Company. Under the PPPFA, monthly payments of principal and interest commence on the later of 10 months following the "covered period" (as defined in the PPPFA) or the date that BOK notifies the Company that the SBA has notified BOK that all or a portion of the PPP Loan has not been forgiven. In January 2021, the Company submitted its application to the SBA for forgiveness of the PPP Loan. As of June 30, 2021, the PPP Loan principal and accrued interest are classified as current in the Condensed Consolidated Balance Sheets. On July 27, 2021, the Company received formal notification in the form of a letter dated July 19, 2021 from BOK that the SBA approved the Company’s PPP Loan forgiveness application for the Company’s Loan in the amount of $3.3 million (including accrued interest). The Company will account for the debt forgiveness during its fiscal third quarter of 2021 and will recognize a gain on extinguishment of debt in the amount of $3.3 million in the Consolidated Statements of Operations.

Equity Method Investments

Equity Method Investments	6 Months Ended
	Jun. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments Tinuum Group, LLC As of June 30, 2021 and December 31, 2020, the Company's ownership interest in Tinuum Group was 42.5%. Tinuum Group supplies technology equipment and technical services at select coal-fired generators, but its primary purpose is to put into operation facilities that produce and sell RC that lower emissions and also qualify for Section 45 tax credits. The Company concluded that Tinuum Group was a VIE, but the Company does not have the power to direct the activities that most significantly impact Tinuum Group's economic performance, as the voting partners of Tinuum Group have identical voting rights, equity control interests and board control interests, and therefore power is shared. Accordingly, the Company has accounted for its investment in Tinuum Group under the equity method of accounting since inception. The following table summarizes the results of operations of Tinuum Group: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Gross profit $ 8,820 $ 6,868 $ 11,495 $ 11,878 Operating, selling, general and administrative expenses 12,429 11,919 26,231 24,695 Loss from operations (3,609) (5,051) (14,736) (12,817) Other income (expenses), net 3,150 2,144 4,003 5,787 Loss attributable to noncontrolling interest 29,038 18,823 64,616 38,094 Net income available to members $ 28,579 $ 15,916 $ 53,883 $ 31,064 ADES equity earnings from Tinuum Group $ 19,125 $ 6,764 $ 35,487 $ 13,202 For the three and six months ended June 30, 2021, the Company recognized earnings from Tinuum Group's net income available to members that were different from its pro-rata share of Tinuum Group's net income available to members, as cash distributions for the three and six months ended June 30, 2021 exceeded the carrying value of the Tinuum Group equity investment. For 2021, the Company expects to recognize such excess contributions as equity method earnings in the period the distributions occur, limited to the carrying value of the Tinuum Group equity investment. For the three and six months ended June 30, 2020, the Company recognized its pro-rata share of Tinuum Group's net income available to its members for the respective period. The following tables present the Company's investment balance, equity earnings and cash distributions in excess of the investment balance, if any, for the three and six months ended June 30, 2021 and 2020 ( in thousands ): Description Date(s) Investment balance ADES equity earnings Cash distributions Memorandum Account: Cash distributions and equity earnings in (excess) of investment balance Beginning balance 12/31/2020 $ 3,387 $ — $ — $ — ADES proportionate share of income from Tinuum Group First Quarter 10,755 10,755 — — Cash distributions from Tinuum Group First Quarter (19,749) — 19,749 — Adjustment for current year cash distributions in excess of investment balance First Quarter 5,607 5,607 — (5,607) Total investment balance, equity earnings and cash distributions 3/31/2021 — $ 16,362 $ 19,749 (5,607) ADES proportionate share of income from Tinuum Group Second Quarter 12,146 $ 12,146 $ — — Recovery of prior cash distributions in excess of investment balance (prior to cash distributions) Second Quarter (5,607) (5,607) — 5,607 Cash distributions from Tinuum Group Second Quarter (19,125) — 19,125 — Adjustment for current year cash distributions in excess of investment balance Second Quarter 12,586 12,586 — (12,586) Total investment balance, equity earnings and cash distributions 6/30/2021 $ — $ 19,125 $ 19,125 $ (12,586) Description Date(s) Investment balance ADES equity earnings Cash distributions Beginning balance 12/31/2019 $ 32,280 $ — $ — ADES proportionate share of income from Tinuum Group First Quarter 6,438 6,438 — Cash distributions from Tinuum Group First Quarter (13,764) — 13,764 Total investment balance, equity earnings and cash distributions 3/31/2020 24,954 $ 6,438 $ 13,764 ADES proportionate share of income from Tinuum Group Second Quarter 6,764 $ 6,764 $ — Cash distributions from Tinuum Group Second Quarter (13,600) — 13,600 Total investment balance, equity earnings and cash distributions 6/30/2020 $ 18,118 $ 6,764 $ 13,600 Tinuum Services, LLC The Company has a 50% voting and economic interest in Tinuum Services as of June 30, 2021 and December 31, 2020. The Company determined that Tinuum Services was not a VIE and further evaluated it for consolidation under the voting interest model. Because the Company does not own greater than 50% of the outstanding voting shares, either directly or indirectly, it has accounted for its investment in Tinuum Services under the equity method of accounting since inception. As of June 30, 2021 and December 31, 2020, the Company’s investment in Tinuum Services was $3.5 million and $4.2 million, respectively. The following table summarizes the results of operations of Tinuum Services: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Gross loss $ (22,641) $ (20,418) $ (41,163) $ (42,677) Operating, selling, general and administrative expenses 47,355 43,515 101,722 89,268 Loss from operations (69,996) (63,933) (142,885) (131,945) Other income (expenses), net 32 (330) (394) (615) Loss attributable to noncontrolling interest 74,587 67,071 151,802 139,043 Net income $ 4,623 $ 2,808 $ 8,523 $ 6,483 ADES equity earnings from Tinuum Services $ 2,312 $ 1,404 $ 4,262 $ 3,242 Included in the Consolidated Statements of Operations of Tinuum Services for the three and six months ended June 30, 2021 and 2020 were losses attributable to noncontrolling interests of Tinuum Services' VIE entities, which were eliminated in the calculations of Tinuum Services' net income attributable to the Company's interest. The following table details the carrying value of the Company's respective equity method investments included in the Equity method investments line item on the Condensed Consolidated Balance Sheets and indicates the Company's maximum exposure to loss: As of (in thousands) June 30, December 31, Equity method investment in Tinuum Group $ — $ 3,387 Equity method investment in Tinuum Services 3,501 4,242 Equity method investment in other 63 63 Total equity method investments $ 3,564 $ 7,692 The following table details the components of the Company's respective equity method investments included in the Earnings from equity method investments line item on the Condensed Consolidated Statements of Operations: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Earnings from Tinuum Group $ 19,125 $ 6,764 $ 35,487 $ 13,202 Earnings from Tinuum Services 2,312 1,404 4,262 3,242 Earnings (loss) from other — — — (3) Earnings from equity method investments $ 21,437 $ 8,168 $ 39,749 $ 16,441 The following table details the components of the cash distributions from the Company's respective equity method investments included as a component of cash flows from operating activities and investing activities in the Condensed Consolidated Statements of Cash Flows. Distributions from equity method investees are reported in the Condensed Consolidated Statements of Cash Flows as "Distributions from equity method investees, return on investment" within Operating cash flows until such time as the carrying value in an equity method investee company is reduced to zero. Thereafter, such distributions are reported as "distributions in excess of cumulative earnings" as a component of cash flows from investing activities. Six Months Ended June 30, (in thousands) 2021 2020 Distributions from equity method investees, return on investment Tinuum Group $ 14,142 $ 27,364 Tinuum Services 5,002 5,152 $ 19,144 $ 32,516 Distributions from equity method investees in excess of investment basis Tinuum Group $ 24,732 $ — $ 24,732 $ —

Inventories, net

Inventories, net	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Inventories, net	Inventories, net The following table summarizes the Company's inventories recorded at the lower of average cost or net realizable value as of June 30, 2021 and December 31, 2020: As of (in thousands) June 30, 2021 December 31, 2020 Product inventory, net $ 6,639 $ 8,361 Raw material inventory 1,522 1,521 $ 8,161 $ 9,882

Debt Obligations

Debt Obligations	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Debt Obligations	Debt Obligations As of (in thousands) June 30, 2021 December 31, 2020 Finance lease obligations $ 4,738 $ 5,526 PPP Loan 3,305 3,305 Senior Term Loan due December 2021, related party — 16,000 Less: net unamortized debt issuance costs — (465) Less: net unamortized debt discount — (480) Senior Term Loan due December 2021, net — 15,055 8,043 23,886 Less: Current maturities (4,373) (18,441) Total long-term debt $ 3,670 $ 5,445 Senior Term Loan On December 7, 2018, the Company, and ADA-ES, Inc. ("ADA"), a wholly-owned subsidiary, and certain other subsidiaries of the Company as guarantors, The Bank of New York Mellon as administrative agent, and Apollo Credit Strategies Master Fund Ltd and Apollo A-N Credit Fund (Delaware) L.P. (collectively "Apollo"), affiliates of a beneficial owner of greater than five percent of the Company's common stock and a related party, entered into the Term Loan and Security Agreement (the "Senior Term Loan") in the amount of $70.0 million less original issue discount of $2.1 million. Proceeds from the Senior Term Loan were used to fund the acquisition of Carbon Solutions. The Company also paid debt issuance costs of $2.0 million related to the Senior Term Loan. The Senior Term Loan bore interest at a rate equal to 3-month LIBOR (subject to a 1.5% floor) + 4.75% per annum, which was adjusted quarterly to the current 3-month LIBOR rate, and interest was payable quarterly in arrears. The Senior Term Loan was secured by substantially all the assets of the Company, including the cash flows from Tinuum Group and Tinuum Services (collectively, the "Tinuum Entities"), but excluding the Company's equity interests in the Tinuum entities. On June 1, 2021 and prior to the Senior Term Loan's maturity date, the Company paid-off in its entirety the Senior Term Loan and all remaining accrued interest through this date in the amount of $6.1 million. The Company did not incur any prepayment fees associated with the early pay-off. Line of Credit In September 2013, ADA, as borrower, and the Company, as guarantor, entered into a line credit (the "Line of Credit") with a bank (the "Lender") for an aggregate borrowing amount of $10.0 million, which was secured by certain amounts due to the Company from certain Tinuum Group RC leases. The Line of Credit has been amended 15 times from the period from December 2, 2013 through June 30, 2021 and included a reduction in the borrowing amount to $5.0 million in September 2018. On March 23, 2021, ADA, the Company and the Lender entered into an amendment to the Line of Credit (the "Fifteenth Amendment"), which extended the maturity date of the Line of Credit to December 31, 2021 and increased the minimum cash requirement from $5.0 million to $6.0 million. As of June 30, 2021 and December 31, 2020, there were no outstanding borrowings under the Line of Credit. On July 29, 2021, the Company and the Lender entered into the Sixteenth Amendment (the "Sixteenth Amendment") to the Line of Credit. The Sixteenth Amendment amends certain terms and conditions related to collateral securing the Line of Credit.

Leases

Leases	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Leases	LeasesAs of June 30, 2021 and December 31, 2020, the Company had obligations under finance leases of $4.7 million and $5.5 million, respectively, and obligations under operating leases of $5.0 million and $3.0 million, respectively. As of June 30, 2021 and December 31, 2020, the Company had right of use ("ROU") assets, net of accumulated amortization, under finance leases of $2.0 million and $2.4 million, respectively, and ROU assets, net of accumulated amortization, under operating leases of $4.4 million and $1.9 million, respectively. Finance leases ROU assets under finance leases and finance lease liabilities are included in Property, plant and equipment and Current portion and Long-term portion of borrowings, respectively, in the Condensed Consolidated Balance Sheets as of June 30, 2021 and December 31, 2020. Interest expense related to finance lease liabilities and amortization of ROU assets under finance leases are included in Interest expense and Depreciation, amortization, depletion and accretion, respectively, in the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2021 and June 30, 2020. Operating leases ROU assets under operating leases and operating lease liabilities are included in Other long-term assets and Other current liabilities and Other long-term liabilities, respectively, in the Condensed Consolidated Balance Sheets as of June 30, 2021 and December 31, 2020. Lease expense for operating leases for the three and six months ended June 30, 2021 was $0.9 million and $1.9 million, respectively, of which $0.8 million and $1.7 million, respectively, is included in Consumables - cost of revenue, exclusive of depreciation and amortization, and $0.1 million and $0.2 million, respectively, is included in General and administrative in the Condensed Consolidated Statement of Operations. Lease expense for operating leases for the three and six months ended June 30, 2020 was $1.1 million and $2.4 million, respectively, of which $1.0 million and $2.0 million, respectively, is included in Consumables - cost of revenue, exclusive of depreciation and amortization, and $0.2 million and $0.4 million, respectively, is included in General and administrative in the Condensed Consolidated Statement of Operations. Lease financial information as of and for the three and six months ended June 30, 2021 and 2020 is provided in the following table: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Finance lease cost: Amortization of right-of-use assets $ 174 $ 465 $ 348 $ 979 Interest on lease liabilities 70 93 149 187 Operating lease cost 453 676 912 1,529 Short-term lease cost 406 424 973 706 Variable lease cost (1) 12 44 21 137 Total lease cost $ 1,115 $ 1,702 $ 2,403 $ 3,538 Other Information: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 149 $ 187 Operating cash flows from operating leases $ 1,314 $ 1,213 Financing cash flows from finance leases $ 818 $ 676 Right-of-use assets obtained in exchange for new operating lease liabilities $ 3,362 $ 60 Weighted-average remaining lease term - finance leases 3.3 years 3.8 years Weighted-average remaining lease term - operating leases 2.9 years 2.1 years Weighted-average discount rate - finance leases 6.4 % 6.1 % Weighted-average discount rate - operating leases 7.8 % 8.5 % (1) Primarily includes common area maintenance, property taxes and insurance payable to lessors.
Leases	LeasesAs of June 30, 2021 and December 31, 2020, the Company had obligations under finance leases of $4.7 million and $5.5 million, respectively, and obligations under operating leases of $5.0 million and $3.0 million, respectively. As of June 30, 2021 and December 31, 2020, the Company had right of use ("ROU") assets, net of accumulated amortization, under finance leases of $2.0 million and $2.4 million, respectively, and ROU assets, net of accumulated amortization, under operating leases of $4.4 million and $1.9 million, respectively. Finance leases ROU assets under finance leases and finance lease liabilities are included in Property, plant and equipment and Current portion and Long-term portion of borrowings, respectively, in the Condensed Consolidated Balance Sheets as of June 30, 2021 and December 31, 2020. Interest expense related to finance lease liabilities and amortization of ROU assets under finance leases are included in Interest expense and Depreciation, amortization, depletion and accretion, respectively, in the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2021 and June 30, 2020. Operating leases ROU assets under operating leases and operating lease liabilities are included in Other long-term assets and Other current liabilities and Other long-term liabilities, respectively, in the Condensed Consolidated Balance Sheets as of June 30, 2021 and December 31, 2020. Lease expense for operating leases for the three and six months ended June 30, 2021 was $0.9 million and $1.9 million, respectively, of which $0.8 million and $1.7 million, respectively, is included in Consumables - cost of revenue, exclusive of depreciation and amortization, and $0.1 million and $0.2 million, respectively, is included in General and administrative in the Condensed Consolidated Statement of Operations. Lease expense for operating leases for the three and six months ended June 30, 2020 was $1.1 million and $2.4 million, respectively, of which $1.0 million and $2.0 million, respectively, is included in Consumables - cost of revenue, exclusive of depreciation and amortization, and $0.2 million and $0.4 million, respectively, is included in General and administrative in the Condensed Consolidated Statement of Operations. Lease financial information as of and for the three and six months ended June 30, 2021 and 2020 is provided in the following table: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Finance lease cost: Amortization of right-of-use assets $ 174 $ 465 $ 348 $ 979 Interest on lease liabilities 70 93 149 187 Operating lease cost 453 676 912 1,529 Short-term lease cost 406 424 973 706 Variable lease cost (1) 12 44 21 137 Total lease cost $ 1,115 $ 1,702 $ 2,403 $ 3,538 Other Information: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 149 $ 187 Operating cash flows from operating leases $ 1,314 $ 1,213 Financing cash flows from finance leases $ 818 $ 676 Right-of-use assets obtained in exchange for new operating lease liabilities $ 3,362 $ 60 Weighted-average remaining lease term - finance leases 3.3 years 3.8 years Weighted-average remaining lease term - operating leases 2.9 years 2.1 years Weighted-average discount rate - finance leases 6.4 % 6.1 % Weighted-average discount rate - operating leases 7.8 % 8.5 % (1) Primarily includes common area maintenance, property taxes and insurance payable to lessors.

Revenues

Revenues	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenues	RevenuesTrade receivables represent an unconditional right to consideration in exchange for goods or services transferred to a customer. The Company invoices its customers in accordance with the terms of the contract. Credit terms are generally net 30 from the date of invoice. The timing between the satisfaction of performance obligations and when payment is due from the customer is generally not significant. The Company records allowances for doubtful trade receivables when it is probable that the balances will not be collected. Trade receivables, net The following table shows the components of the Company's Trade receivables, net: As of (in thousands) June 30, 2021 December 31, 2020 Trade receivables $ 9,983 $ 12,241 Less: Allowance for doubtful accounts (39) (37) Trade receivables, net $ 9,944 $ 12,204 Cabot Receivable The following table shows the components of the Cabot Receivable: As of (in thousands) June 30, 2021 December 31, 2020 Receivables, net $ 1,616 $ 921 Other long-term assets, net 7,952 8,852 Total Cabot Receivable $ 9,568 $ 9,773 Disaggregation of Revenue and Earnings from Equity Method Investments For the three and six months ended June 30, 2021 and 2020, all performance obligations related to revenues recognized were satisfied at a point in time. The Company disaggregates its revenues by major components as well as between its two reportable segments, which are further discussed in Note 17 to the Condensed Consolidated Financial Statements. The following tables disaggregate revenues by major component for the three and six months ended June 30, 2021 and 2020 (in thousands): Three Months Ended June 30, 2021 Six Months Ended June 30, 2021 Segment Segment APT RC Total APT RC Total Revenue component Consumables $ 15,976 $ — $ 15,976 $ 33,007 $ — $ 33,007 License royalties, related party — 3,657 3,657 — 7,723 7,723 Revenues from customers 15,976 3,657 19,633 33,007 7,723 40,730 Earnings from equity method investments — 21,437 21,437 — 39,749 39,749 Total revenues from customers and earnings from equity method investments $ 15,976 $ 25,094 $ 41,070 $ 33,007 $ 47,472 $ 80,479 Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Segment Segment APT RC Total APT RC Total Revenue component Consumables $ 8,170 $ — $ 8,170 $ 17,387 $ — $ 17,387 License royalties, related party — 3,313 3,313 — 6,359 6,359 Revenues from customers 8,170 3,313 11,483 17,387 6,359 23,746 Earnings from equity method investments — 8,168 8,168 — 16,441 16,441 Total revenues from customers and earnings from equity method investments $ 8,170 $ 11,481 $ 19,651 $ 17,387 $ 22,800 $ 40,187

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings The Company is from time to time subject to, and is presently involved in, various pending or threatened legal actions and proceedings, including those that arise in the ordinary course of its business. Such matters are subject to many uncertainties and outcomes, the financial impacts of which are not predictable with assurance and that may not be known for extended periods of time. The Company records a liability in its consolidated financial statements for costs related to claims, settlements, and judgments where management has assessed that a loss is probable and an amount can be reasonably estimated. There were no significant legal proceedings as of June 30, 2021. Restricted Cash As of June 30, 2021 and December 31, 2020, the Company had short-term restricted cash of $6.0 million and $5.0 million, respectively, as required under a minimum cash balance requirement of a Line of Credit covenant, and long-term restricted cash of $10.0 million and $5.0 million, respectively, as required under the Surety Agreement. Other Commitments and Contingencies

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Stock Repurchase Programs In November 2018, the Company's Board of Directors (the "Board") authorized the Company to purchase up to $20.0 million of its outstanding common stock under a stock repurchase program (the "Stock Repurchase Program"), which was to remain in effect until December 31, 2019 unless otherwise modified by the Board. As of November 2019, $2.9 million remained outstanding related to the Stock Repurchase Program. In November 2019, the Board authorized an incremental $7.1 million to the Stock Repurchase Program and provided that it will remain in effect until all amounts are utilized or it is otherwise modified by the Board. Under the Stock Repurchase Program, for the three and six months ended June 30, 2021, the Company did not repurchase any shares. For the three and six months ended June 30, 2020, the Company purchased zero and 20,613 shares, respectively, of its common stock for cash of zero and $0.2 million, respectively, inclusive of commissions and fees. As of June 30, 2021, the Company had $7.0 million remaining under the Stock Repurchase Program. Quarterly Cash Dividend Dividends declared and paid quarterly on all outstanding shares of common stock during the three and six months ended June 30, 2021 and 2020 were as follows: 2021 2020 Per share Date paid Per share Date paid Dividends declared during quarter ended: March 31 $ — N/A $ 0.25 March 10, 2020 June 30 $ — N/A $ — N/A $ — $ 0.25 A portion of the dividends declared remains accrued subsequent to the payment dates and represents dividends accumulated on nonvested shares of common stock held by employees and directors of the Company that contain forfeitable dividend rights that are not payable until the underlying shares of common stock vest. These amounts are included in both Other current liabilities and Other long-term liabilities on the Condensed Consolidated Balance Sheets as of June 30, 2021 and December 31, 2020. Tax Asset Protection Plan U.S. federal income tax rules, and Section 382 of the Internal Revenue Code in particular, could substantially limit the use of net operating losses and other tax assets if the Company experiences an "ownership change" (as defined in the Internal Revenue Code). In general, an ownership change occurs if there is a cumulative change in the ownership of the Company by "5 percent stockholders" that exceeds 50 percentage points over a rolling three-year period. On May 5, 2017, the Board approved the declaration of a dividend of rights to purchase Series B Junior Participating Preferred Stock for each outstanding share of common stock as part of a tax asset protection plan (the "TAPP") designed to protect the Company’s ability to utilize its net operating losses and tax credits. The TAPP is intended to act as a deterrent to any person acquiring beneficial ownership of 4.99% or more of the Company’s outstanding common stock. On April 9, 2021, the Board approved the Fourth Amendment to the TAPP ("Fourth Amendment") that amends the TAPP, as previously amended by the First, Second and Third Amendments that were approved the Board on April 6, 2018, April 5, 2019 and April 9, 2020, respectively. The Fourth Amendment amends the definition of "Final Expiration Date" under the TAPP to extend the duration of the TAPP and makes associated changes in connection therewith. At the Company's 2021 annual meeting of stockholders, the Company's stockholders approved the Fourth Amendment, thus the Final Expiration Date will be the close of business on December 31, 2022.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company grants equity-based awards to employees, non-employee directors, and consultants that may include, but are not limited to, RSA's, restricted stock units ("RSU's"), performance stock units ("PSU's") and stock options. Stock-based compensation expense related to manufacturing employees and administrative employees is included within the Cost of revenue and Payroll and benefits line items, respectively, in the Condensed Consolidated Statements of Operations. Stock-based compensation expense related to non-employee directors and consultants is included within the General and administrative line item in the Condensed Consolidated Statements of Operations. Total stock-based compensation expense for the three and six months ended June 30, 2021 and 2020 was as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 RSA expense $ 511 $ 975 $ 918 $ 1,481 PSU expense 55 163 69 163 Total stock-based compensation expense $ 566 $ 1,138 $ 987 $ 1,644 The amount of unrecognized compensation cost as of June 30, 2021, and the expected weighted-average period over which the cost will be recognized is as follows: As of June 30, 2021 (in thousands) Unrecognized Compensation Cost Expected Weighted- RSA expense $ 2,736 2.31 PSU expense 490 2.24 Total unrecognized stock-based compensation expense $ 3,226 2.30 Restricted Stock Restricted stock is typically granted with vesting terms of three years. The fair value of RSA's and RSU's is determined based on the closing price of the Company’s common stock on the authorization date of the grant multiplied by the number of shares subject to the stock award. Compensation expense for RSA's is generally recognized on a straight-line basis over the entire vesting period. A summary of RSA activity under the Company's various stock compensation plans for the six months ended June 30, 2021 is presented below: Restricted Stock Weighted-Average Grant Date Fair Value Non-vested at January 1, 2021 373,860 $ 7.25 Granted 387,632 $ 5.28 Vested (183,700) $ 7.45 Forfeited (31,623) $ 5.75 Non-vested at June 30, 2021 546,169 $ 5.88 Performance Share Units Compensation expense is recognized for PSU awards on a straight-line basis over the applicable service period, which is generally three years, based on the estimated fair value at the date of grant using a Monte Carlo simulation model. A summary of PSU activity for the six months ended June 30, 2021 is presented below: Units Weighted-Average Aggregate Intrinsic Value (in thousands) Weighted-Average PSU's outstanding, January 1, 2021 50,127 $ 6.17 Granted 62,448 7.09 Vested / Settled — — Forfeited / Canceled — — PSU's outstanding, June 30, 2021 112,575 $ 6.68 $ 834 2.24

Supplemental Financial Informat

Supplemental Financial Information	6 Months Ended
	Jun. 30, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Supplemental Financial Information	Supplemental Financial Information Supplemental Balance Sheet Information The following table summarizes the components of Prepaid expenses and other assets and Other long-term assets, net as presented in the Condensed Consolidated Balance Sheets: As of (in thousands) June 30, December 31, Prepaid expenses and other assets: Prepaid expenses $ 2,278 $ 1,690 Prepaid income taxes and income tax refunds 1,723 1,605 Other 1,319 1,302 $ 5,320 $ 4,597 Other long-term assets, net: Cabot Receivable (1) $ 7,952 $ 8,852 Upfront Customer Consideration (1) 7,236 7,490 Mine development costs, net 4,837 4,338 Right of use assets, operating leases, net 4,380 1,930 Spare parts, net 4,173 3,727 Mine reclamation asset, net 1,666 1,712 Highview Investment 552 552 Other 1,481 1,388 $ 32,277 $ 29,989 (1) See further discussion of Upfront Customer Consideration in Note 3 and Cabot Receivable in Note 4 and Note 10. Spare parts include critical spares required to support plant operations. Parts and supply costs are determined using the lower of cost or estimated replacement cost. Parts are recorded as maintenance expenses in the period in which they are consumed. Mine development costs include acquisition costs, the cost of other development work and mitigation costs related to the Five Forks Mine and are depleted over the estimated life of the related mine reserves. The Company performs an evaluation of the recoverability of the carrying value of mine development costs to determine if facts and circumstances indicate that their carrying value may be impaired and if any adjustment is warranted. There were no indicators of impairment as of June 30, 2021. Mine reclamation asset, net represents an asset retirement obligation ("ARO") asset related to the Five Forks Mine and is depreciated over the estimated life of the Five Forks Mine. The Company holds a long-term investment (the "Highview Investment") in Highview Enterprises Limited ("Highview"), a UK-based developmental stage company specializing in power storage. The Company accounts for the Highview Investment as an investment recorded at cost, less impairment, plus or minus observable changes in price for identical or similar investments of the same issuer. The Highview Investment is evaluated for indicators of impairment such as an event or change in circumstances that may have a significant adverse effect on the fair value of the investment. There were no changes to the carrying value of the Highview Investment for the three and six months ended June 30, 2021 as there were no indicators of impairment or observable price changes for identical or similar investments. The following table details the components of Other current liabilities and Other long-term liabilities as presented in the Condensed Consolidated Balance Sheets: As of (in thousands) June 30, December 31, Other current liabilities: Current portion of operating lease obligations $ 2,342 $ 1,883 Current portion of mine reclamation liability 6,986 9,370 Income and other taxes payable 2,159 1,305 Other current liabilities 468 438 $ 11,955 $ 12,996 Other long-term liabilities: Mine reclamation liabilities $ 8,137 $ 12,077 Operating lease obligations, long-term 2,698 1,109 Other long-term liabilities (1) 557 287 $ 11,392 $ 13,473 (1) Included within Other long-term liabilities is $0.3 million related to agreements the Company entered into with all of its executive officers and certain other key employees of the organization ("Retention Agreements"). The Retention Agreements are for the benefit of retaining those officers and key employees in order to maintain the Company’s current business operations while it pursues and executes on its strategic initiatives. The Retention Agreements with the executive officers were approved by the Compensation Committee of the Board of Directors and the Board of Directors on May 5, 2021. The Company is recognizing expense over the expected service period, which is based on certain conditions outlined in the Retention Agreements. The Mine reclamation liability related to the Five Forks Mine is included in Other long-term liabilities. The Mine reclamation liability related to Marshall Mine, which was assumed in the Marshall Mine Acquisition, is included in Other current liabilities and Other long-term liabilities. The Mine reclamation liabilities represent AROs. Changes in the AROs were as follows: As of (in thousands) June 30, 2021 December 31, 2020 Asset retirement obligation, beginning of period $ 21,447 $ 2,721 Asset retirement obligation assumed — 21,328 Accretion 661 543 Liabilities settled (5,043) (3,565) Changes due to scope and timing of reclamation (1,942) 420 Asset retirement obligations, end of period 15,123 21,447 Less current portion 6,986 9,370 Asset retirement obligation, long-term $ 8,137 $ 12,077 As discussed in Note 4, as of June 30, 2021, the Company reduced the Marshall Mine by $1.9 million based on scope reductions for future reclamation requirements and recorded a corresponding gain on change in estimate for the three and six months ended June 30, 2021. Supplemental Condensed Consolidated Statements of Operations Information The following table details the components of Interest expense in the Condensed Consolidated Statements of Operations: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Interest on Senior Term Loan $ 52 $ 484 $ 207 $ 1,114 Debt discount and debt issuance costs 355 355 946 709 453A interest 7 28 7 160 Other 79 95 170 189 $ 493 $ 962 $ 1,330 $ 2,172

Impairment

Impairment	6 Months Ended
	Jun. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Impairment	Impairment As of June 30, 2020 and as part of its periodic review of the carrying value of long-lived assets, the Company assessed its long-lived assets for potential impairment. In assessing impairment of its APT segment's and certain other long-lived asset groups, the Company considered factors such as the significant decline in both the APT segment's trailing twelve months revenues and current and future years’ forecasted revenues. These factors were largely due to the significant drop in coal-fired power dispatch that began in 2019 amid historically low prices of alternative power generation sources such as natural gas, leading to an increase in natural gas usage as well as other competing energy sources. As of June 30, 2020, the Company completed an undiscounted cash flow analysis of its APT segment's long-lived assets (the "Asset Group"), which are comprised of its manufacturing plant and related assets and its lignite mine assets, and estimated the undiscounted cash flows from the Asset Group at $54.7 million, which was less than the carrying value of the Asset Group of $58.3 million. Accordingly, the Company completed an assessment of the Asset Group’s fair value and estimated the fair value of the Asset Group at $32.2 million. This resulted in an impairment and write-down of the Asset Group (the "Impairment Charge") of $26.1 million as of June 30, 2020, which is reflected as "Impairment of long-lived assets" in the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2020. The following table summarizes the allocation to the Asset Group of the Impairment Charge of $26.1 million recorded as of June 30, 2020: (in thousands) Property, plant and equipment, net $ 18,986 Intangible assets, net 1,445 Other long-term assets, net 5,672 Total impairment $ 26,103 The Company engaged an independent third party to perform the valuation of the Asset Group in order to determine the estimated fair value of the Asset Group. This valuation was based on the use of several established valuation models including an expected future discounted cash flow model based on cash flows expected to be generated by market participants discounted at the risk-free rate of interest. Because of the continued future uncertainty surrounding the level of coal-fired dispatch, the impact of historically low natural gas prices and other estimates impacting the expected future cash flow, it is reasonably possible that the expected future cash flows may change in the near term and may result in the Company recording additional impairment of the Asset Group.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the three and six months ended June 30, 2021 and 2020, the Company's income tax expense and effective tax rates based on forecasted pretax income were: Three Months Ended June 30, Six Months Ended June 30, (in thousands, except for rate) 2021 2020 2021 2020 Income tax expense $ 4,943 $ 103 $ 9,432 $ 461 Effective tax rate 23 % — % 24 % (2) % The effective rate for the three and six months ended June 30, 2021 was higher than the federal statutory rate primarily from the impact of estimated state income taxes. The Company assesses the valuation allowance recorded against deferred tax assets at each reporting date. The determination of whether a valuation allowance for deferred tax assets is appropriate requires the evaluation of positive and negative evidence that can be objectively verified. Consideration must be given to all sources of taxable income available to realize deferred tax assets, including, as applicable, the future reversal of existing temporary differences, future taxable income forecasts exclusive of the reversal of temporary differences and carryforwards, taxable income in carryback years and tax planning strategies. In estimating income taxes, the Company assesses the relative merits and risks of the appropriate income tax treatment of transactions taking into account statutory, judicial, and regulatory guidance.

Business Segment Information

Business Segment Information	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Business Segment Information	Business Segment Information Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by a company's chief operating decision maker ("CODM"), or a decision-making group, to allocate resources and assess financial performance. As of June 30, 2021, the Company's CODM was the Company's CEO. The Company's operating and reportable segments are identified by products and services provided. As of June 30, 2021, the Company has two reportable segments: (1) Refined Coal ("RC"); and (2) Advanced Purification Technologies ("APT"). Effective December 31, 2020, and as reported in the 2020 Form 10-K, the Company revised its segments to RC and APT, and amounts for the three and six months ended June 30, 2020 have been recast to conform with the current year presentation. The business segment measurements provided to and evaluated by the CODM are computed in accordance with the principles listed below: • The accounting policies of the operating segments are the same as those described in the summary of significant accounting policies in the 2020 Form 10-K. • Segment revenues include equity method earnings and losses from the Company's equity method investments. • Segment operating income (loss) includes segment revenues and allocation of certain "Corporate general and administrative expenses," which include Payroll and benefits, General and administrative and Depreciation, amortization, depletion and accretion. • RC segment operating income includes interest expense directly attributable to the RC segment. As of June 30, 2021 and December 31, 2020, substantially all of the Company's material assets are located in the U.S. and substantially all significant customers are U.S. companies. The following table presents the Company's operating segment results for the three and six months ended June 30, 2021 and 2020: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Revenues: Refined Coal: Earnings in equity method investments $ 21,437 $ 8,168 $ 39,749 $ 16,441 License royalties, related party 3,657 3,313 7,723 6,359 25,094 11,481 47,472 22,800 Advanced Purification Technologies: Consumables 15,976 8,170 33,007 17,387 15,976 8,170 33,007 17,387 Total segment reporting revenues 41,070 19,651 80,479 40,187 Adjustments to reconcile to reported revenues: Earnings in equity method investments (21,437) (8,168) (39,749) (16,441) Total reported revenues $ 19,633 $ 11,483 $ 40,730 $ 23,746 Segment operating income (loss): Refined Coal $ 24,905 $ 10,777 $ 47,176 $ 21,637 Advanced Purification Technologies (1) (2) 258 (29,999) 273 (37,369) Total segment operating income (loss) $ 25,163 $ (19,222) $ 47,449 $ (15,732) (1) Included in APT segment operating income (loss) for the three and six months ended June 30, 2021 and 2020 is $1.8 million and $3.7 million, $1.5 million and $3.8 million, respectively, of depreciation, amortization, depletion and accretion expense on mine and plant long-lived assets and liabilities and $0.1 million, $0.3 million, zero and zero, respectively, of amortization of Upfront Customer Consideration. (2) Included in APT segment operating income for the three and six months ended June 30, 2021 is $1.9 million gain related to the change in the Marshall Mine ARO as of June 30, 2021. A reconciliation of reportable segment operating income to consolidated income (loss) before income tax expense is as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Total reported segment operating income (loss) $ 25,163 $ (19,222) $ 47,449 $ (15,732) Adjustments to reconcile to income (loss) before income (loss) tax expense attributable to the Company: Corporate payroll and benefits (826) (1,148) (1,465) (1,857) Corporate legal and professional fees (1,376) (925) (3,130) (2,674) Corporate general and administrative (1,049) (1,558) (2,225) (3,157) Corporate depreciation and amortization (122) (163) (276) (189) Corporate interest expense, net (348) (824) (998) (1,766) Other income, net 91 129 404 129 Income (loss) before income tax expense $ 21,533 $ (23,711) $ 39,759 $ (25,246) Corporate general and administrative expenses include certain costs that benefit the business as a whole but are not directly related to one of the Company's segments. Such costs include, but are not limited to, accounting and human resources staff, information systems costs, legal fees, facility costs, audit fees and corporate governance expenses. A reconciliation of reportable segment assets to consolidated assets is as follows: As of (in thousands) June 30, December 31, Assets: Refined Coal (1) $ 7,427 $ 11,516 Advanced Purification Technologies (2) 81,775 80,877 Total segment assets 89,202 92,393 All Other and Corporate (3) 69,293 54,278 Consolidated $ 158,495 $ 146,671 (1) Includes $3.6 million and $7.7 million of investments in equity method investees as of June 30, 2021 and December 31, 2020, respectively. (2) Includes $37.0 million and $34.6 million of long-lived assets, net. (3) Includes the Company's deferred tax assets of $3.8 million and $10.6 million as of June 30, 2021 and December 31, 2020, respectively.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value of financial instruments The carrying amounts of financial instruments, including cash, cash equivalents and restricted cash, accounts receivable, accounts payable and accrued expenses, approximate fair value due to the short maturity of these instruments. The carrying amounts of the Cabot Receivable and debt obligations approximate fair value based on credit terms and market interest rates currently available for similar instruments. Accordingly, these instruments are not presented in the table below. The following table provides the estimated fair values of the remaining financial instruments: As of June 30, 2021 As of December 31, 2020 (in thousands) Carrying Value Fair Value Carrying Value Fair Value Financial Instruments: Highview Investment $ 552 $ 552 $ 552 $ 552 Highview Obligation $ 233 $ 233 $ 228 $ 228 Concentration of credit risk The Company's financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents. The Company holds cash and cash equivalents at four financial institutions as of June 30, 2021. If an institution was unable to perform its obligations, the Company would be at risk regarding the amount of cash and investments in excess of the Federal Deposit Insurance Corporation limits (currently $250 thousand) that would be returned to the Company. Assets and Liabilities Measured at Fair Value on a Recurring Basis As of June 30, 2021 and December 31, 2020, the Company had no financial instruments carried and measured at fair value on a recurring basis. Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis As disclosed in Note 14, the Company accounts for the Highview Investment as an investment recorded at cost, less impairment, plus or minus observable changes in price for identical or similar investments of the same issuer. Fair value measurements, if any, represent either Level 2 or Level 3 measurements.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsAll significant matters that occurred subsequent to June 30, 2021 are disclosed elsewhere within the notes to the Condensed Consolidated Financial Statements.

Basis of Presentation (Policies

Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	The accompanying Condensed Consolidated Financial Statements of ADES are unaudited and have been prepared in conformity with accounting principles generally accepted in the United States ("U.S. GAAP") and with Article 10 of Regulation S-X of the Securities and Exchange Commission. In compliance with those instructions, certain information and footnote disclosures normally included in annual consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. The unaudited Condensed Consolidated Financial Statements of ADES in this quarterly report ("Quarterly Report") are presented on a consolidated basis and include ADES and its wholly-owned subsidiaries (collectively, the "Company"). Also included within the unaudited Condensed Consolidated Financial Statements are the Company's unconsolidated equity investments: Tinuum Group, Tinuum Services and GWN Manager, LLC ("GWN Manager"), which are accounted for under the equity method of accounting, and Highview Enterprises Limited (the "Highview Investment"), which is accounted for in accordance with U.S. GAAP applicable to equity investments that do not qualify for the equity method of accounting. Results of operations and cash flows for the interim periods are not necessarily indicative of the results that may be expected for the entire year. All significant intercompany transactions and accounts were eliminated in consolidation for all periods presented in this Quarterly Report.
Earnings (Loss) Per Share	Basic earnings (loss) per share is computed using the two-class method, which is an earnings allocation formula that determines earnings (loss) per share for common stock and any participating securities according to dividend and participating rights in undistributed earnings (losses). Pursuant to U.S. GAAP, the Company has elected not to separately present basic or diluted earnings per share attributable to participating securities in the Condensed Consolidated Statements of Operations. Diluted earnings (loss) per share is computed in a manner consistent with that of basic earnings per share, while considering other potentially dilutive securities. For the three and six months ended June 30, 2021, potentially dilutive securities consist of unvested non-participating restricted stock awards ("RSA's"), as well as contingent performance stock units ("PSU's"). For the three and six months ended June 30, 2020, potentially dilutive securities consist of both unvested, participating and non-participating RSA's, as well as outstanding options to purchase common stock ("Stock Options") and PSU's. The dilutive effect, if any, for non-participating RSA's, Stock Options and PSU's is determined using the greater of dilution as calculated under the treasury stock method or the two-class method. Potentially dilutive securities are excluded from diluted earnings per share when their effect is anti-dilutive. When there is a net loss for a period, all potentially dilutive securities are anti-dilutive and are excluded from the calculation of diluted loss per share for that period.
Use of Estimates	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. There have been no changes in the Company’s critical accounting estimates from those that were disclosed in the 2020 Form 10-K. Actual results could differ from these estimates.
Risks and Uncertainties	The Company’s earnings are significantly affected by equity earnings from Tinuum Group. As of June 30, 2021, Tinuum Group has 22 invested RC facilities, of which 8 are leased to a single customer. Both Tinuum Group and Tinuum Services expect to commence significantly winding down their operations starting in the third quarter of 2021 due to the expected expiration of the Section 45 tax credit period as of December 31, 2021. During the second quarter of 2021, Tinuum Group ceased operating one RC facility, with the remaining RC facilities expected to cease operations during the second half of 2021. The loss of Tinuum Group's customers, reduction in revenue streams as a result of lease renewals and the expiration of Section 45 tax credits will have a significant adverse impact on Tinuum Group's financial position, results of operations and cash flows, which in turn will have a material adverse impact on the Company’s financial position, results of operations and cash flows.The Company's revenues, sales volumes, earnings and cash flows are significantly affected by prices of competing power generation sources such as natural gas and renewable energy. During periods of low natural gas prices, natural gas provides a competitive alternative to coal-fired power generation and therefore, coal consumption may be reduced, which reduces the demand for the Company's products. However, during periods of higher prices for competing power generation sources, the demand for the Company's products increases due to the increase in coal consumption. In addition, coal consumption and demand for the Company's products are also affected by the demand for electricity, which is higher in the warmer and colder months of the year. Abnormal temperatures during the summer and winter months may significantly affect coal consumption and thus the demand for the Company's products.The Company's financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents. The Company holds cash and cash equivalents at four financial institutions as of June 30, 2021. If an institution was unable to perform its obligations, the Company would be at risk regarding the amount of cash and investments in excess of the Federal Deposit Insurance Corporation limits (currently $250 thousand) that would be returned to the Company.
Reclassifications	Certain balances have been reclassified from the prior year to conform to the current year presentation. Such reclassifications had no effect on the Company’s results of operations or financial position in any of the periods presented.
New Accounting Standards	Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes ("ASU 2019-12"). The amendments in ASU 2019-12 simplify various aspects related to accounting for income taxes by removing certain exceptions contained in Topic 740 and also clarify and amends existing guidance in Topic 740 to improve consistent application. ASU 2019-12 is effective for public business entities beginning after December 15, 2020, including interim periods within those years, and early adoption is permitted. The Company adopted ASU 2019-12 effective January 1, 2021 and it did not have a material impact on the Company's financial statements and disclosures. Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). The main objective of ASU 2016-13 is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. To achieve this objective, the amendments in ASU 2016-13 replace the incurred loss impairment methodology in current U.S. GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to form credit loss estimates. ASU 2016-13 is effective for "smaller reporting companies" (as defined by the Securities and Exchange Commission) for fiscal years beginning after December 15, 2022, including interim periods within those years, and must be adopted under a modified retrospective method approach. The Company is currently evaluating the provisions of this guidance and assessing the impact on its financial statements and disclosures and does not believe this standard will have a material impact on its financial statements and disclosures.
Business Segment Information	Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by a company's chief operating decision maker ("CODM"), or a decision-making group, to allocate resources and assess financial performance. As of June 30, 2021, the Company's CODM was the Company's CEO. The Company's operating and reportable segments are identified by products and services provided. As of June 30, 2021, the Company has two reportable segments: (1) Refined Coal ("RC"); and (2) Advanced Purification Technologies ("APT"). Effective December 31, 2020, and as reported in the 2020 Form 10-K, the Company revised its segments to RC and APT, and amounts for the three and six months ended June 30, 2020 have been recast to conform with the current year presentation. The business segment measurements provided to and evaluated by the CODM are computed in accordance with the principles listed below: • The accounting policies of the operating segments are the same as those described in the summary of significant accounting policies in the 2020 Form 10-K. • Segment revenues include equity method earnings and losses from the Company's equity method investments. • Segment operating income (loss) includes segment revenues and allocation of certain "Corporate general and administrative expenses," which include Payroll and benefits, General and administrative and Depreciation, amortization, depletion and accretion. • RC segment operating income includes interest expense directly attributable to the RC segment.
Fair Value of Financial Instruments	The carrying amounts of financial instruments, including cash, cash equivalents and restricted cash, accounts receivable, accounts payable and accrued expenses, approximate fair value due to the short maturity of these instruments.

Basis of Presentation (Tables)

Basis of Presentation (Tables)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the calculations of basic and diluted earnings (loss) per share: Three Months Ended June 30, Six Months Ended June 30, (in thousands, except per share amounts) 2021 2020 2021 2020 Net income (loss) $ 16,590 $ (23,814) $ 30,327 $ (25,707) Less: Dividends and undistributed income (loss) allocated to participating securities — (17) — (19) Income (loss) attributable to common stockholders $ 16,590 $ (23,797) $ 30,327 $ (25,688) Basic weighted-average common shares outstanding 18,271 18,014 18,219 17,974 Add: dilutive effect of equity instruments 127 — 137 — Diluted weighted-average shares outstanding 18,398 18,014 18,356 17,974 Earnings (loss) per share - basic $ 0.91 $ (1.32) $ 1.66 $ (1.43) Earnings (loss) per share - diluted $ 0.90 $ (1.32) $ 1.65 $ (1.43)

Acquisition of Marshall Mine (T

Acquisition of Marshall Mine (Tables)	6 Months Ended
	Jun. 30, 2021
Business Combination and Asset Acquisition [Abstract]
Summary of Purchase Consideration and Allocation	A summary of the net assets acquired and liabilities assumed and the additional assets recorded in the Marshall Mine Purchase Agreement as of September 30, 2020 are shown in the table below. The Company completed additional analysis of the assets acquired and liabilities assumed and recorded adjustments as of December 31, 2020 as shown in the table below. (in thousands) As Originally Reported Adjustments As Adjusted Assets acquired: Receivables $ — $ 513 $ 513 Property, plant and equipment 3,863 — 3,863 Spare parts 100 — 100 Liabilities assumed: Accounts payable and accrued expenses (673) 160 (513) Asset retirement obligation (21,328) — (21,328) Net assets acquired and liabilities assumed from Marshall Mine acquisition (18,038) 673 (17,365) Cabot Receivable 9,749 — 9,749 Upfront Customer Consideration $ 8,289 $ (673) $ 7,616

Equity Method Investments (Tabl

Equity Method Investments (Tables)	6 Months Ended
	Jun. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Method Investments	The following table summarizes the results of operations of Tinuum Group: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Gross profit $ 8,820 $ 6,868 $ 11,495 $ 11,878 Operating, selling, general and administrative expenses 12,429 11,919 26,231 24,695 Loss from operations (3,609) (5,051) (14,736) (12,817) Other income (expenses), net 3,150 2,144 4,003 5,787 Loss attributable to noncontrolling interest 29,038 18,823 64,616 38,094 Net income available to members $ 28,579 $ 15,916 $ 53,883 $ 31,064 ADES equity earnings from Tinuum Group $ 19,125 $ 6,764 $ 35,487 $ 13,202 The following tables present the Company's investment balance, equity earnings and cash distributions in excess of the investment balance, if any, for the three and six months ended June 30, 2021 and 2020 ( in thousands ): Description Date(s) Investment balance ADES equity earnings Cash distributions Memorandum Account: Cash distributions and equity earnings in (excess) of investment balance Beginning balance 12/31/2020 $ 3,387 $ — $ — $ — ADES proportionate share of income from Tinuum Group First Quarter 10,755 10,755 — — Cash distributions from Tinuum Group First Quarter (19,749) — 19,749 — Adjustment for current year cash distributions in excess of investment balance First Quarter 5,607 5,607 — (5,607) Total investment balance, equity earnings and cash distributions 3/31/2021 — $ 16,362 $ 19,749 (5,607) ADES proportionate share of income from Tinuum Group Second Quarter 12,146 $ 12,146 $ — — Recovery of prior cash distributions in excess of investment balance (prior to cash distributions) Second Quarter (5,607) (5,607) — 5,607 Cash distributions from Tinuum Group Second Quarter (19,125) — 19,125 — Adjustment for current year cash distributions in excess of investment balance Second Quarter 12,586 12,586 — (12,586) Total investment balance, equity earnings and cash distributions 6/30/2021 $ — $ 19,125 $ 19,125 $ (12,586) Description Date(s) Investment balance ADES equity earnings Cash distributions Beginning balance 12/31/2019 $ 32,280 $ — $ — ADES proportionate share of income from Tinuum Group First Quarter 6,438 6,438 — Cash distributions from Tinuum Group First Quarter (13,764) — 13,764 Total investment balance, equity earnings and cash distributions 3/31/2020 24,954 $ 6,438 $ 13,764 ADES proportionate share of income from Tinuum Group Second Quarter 6,764 $ 6,764 $ — Cash distributions from Tinuum Group Second Quarter (13,600) — 13,600 Total investment balance, equity earnings and cash distributions 6/30/2020 $ 18,118 $ 6,764 $ 13,600 The following table summarizes the results of operations of Tinuum Services: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Gross loss $ (22,641) $ (20,418) $ (41,163) $ (42,677) Operating, selling, general and administrative expenses 47,355 43,515 101,722 89,268 Loss from operations (69,996) (63,933) (142,885) (131,945) Other income (expenses), net 32 (330) (394) (615) Loss attributable to noncontrolling interest 74,587 67,071 151,802 139,043 Net income $ 4,623 $ 2,808 $ 8,523 $ 6,483 ADES equity earnings from Tinuum Services $ 2,312 $ 1,404 $ 4,262 $ 3,242 The following table details the carrying value of the Company's respective equity method investments included in the Equity method investments line item on the Condensed Consolidated Balance Sheets and indicates the Company's maximum exposure to loss: As of (in thousands) June 30, December 31, Equity method investment in Tinuum Group $ — $ 3,387 Equity method investment in Tinuum Services 3,501 4,242 Equity method investment in other 63 63 Total equity method investments $ 3,564 $ 7,692 The following table details the components of the Company's respective equity method investments included in the Earnings from equity method investments line item on the Condensed Consolidated Statements of Operations: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Earnings from Tinuum Group $ 19,125 $ 6,764 $ 35,487 $ 13,202 Earnings from Tinuum Services 2,312 1,404 4,262 3,242 Earnings (loss) from other — — — (3) Earnings from equity method investments $ 21,437 $ 8,168 $ 39,749 $ 16,441 The following table details the components of the cash distributions from the Company's respective equity method investments included as a component of cash flows from operating activities and investing activities in the Condensed Consolidated Statements of Cash Flows. Distributions from equity method investees are reported in the Condensed Consolidated Statements of Cash Flows as "Distributions from equity method investees, return on investment" within Operating cash flows until such time as the carrying value in an equity method investee company is reduced to zero. Thereafter, such distributions are reported as "distributions in excess of cumulative earnings" as a component of cash flows from investing activities. Six Months Ended June 30, (in thousands) 2021 2020 Distributions from equity method investees, return on investment Tinuum Group $ 14,142 $ 27,364 Tinuum Services 5,002 5,152 $ 19,144 $ 32,516 Distributions from equity method investees in excess of investment basis Tinuum Group $ 24,732 $ — $ 24,732 $ —

Inventories, net (Tables)

Inventories, net (Tables)	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Schedule of Inventory	The following table summarizes the Company's inventories recorded at the lower of average cost or net realizable value as of June 30, 2021 and December 31, 2020: As of (in thousands) June 30, 2021 December 31, 2020 Product inventory, net $ 6,639 $ 8,361 Raw material inventory 1,522 1,521 $ 8,161 $ 9,882

Debt Obligations (Tables)

Debt Obligations (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Schedule of Borrowings	As of (in thousands) June 30, 2021 December 31, 2020 Finance lease obligations $ 4,738 $ 5,526 PPP Loan 3,305 3,305 Senior Term Loan due December 2021, related party — 16,000 Less: net unamortized debt issuance costs — (465) Less: net unamortized debt discount — (480) Senior Term Loan due December 2021, net — 15,055 8,043 23,886 Less: Current maturities (4,373) (18,441) Total long-term debt $ 3,670 $ 5,445

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Lease, Cost	Lease financial information as of and for the three and six months ended June 30, 2021 and 2020 is provided in the following table: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Finance lease cost: Amortization of right-of-use assets $ 174 $ 465 $ 348 $ 979 Interest on lease liabilities 70 93 149 187 Operating lease cost 453 676 912 1,529 Short-term lease cost 406 424 973 706 Variable lease cost (1) 12 44 21 137 Total lease cost $ 1,115 $ 1,702 $ 2,403 $ 3,538 Other Information: Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 149 $ 187 Operating cash flows from operating leases $ 1,314 $ 1,213 Financing cash flows from finance leases $ 818 $ 676 Right-of-use assets obtained in exchange for new operating lease liabilities $ 3,362 $ 60 Weighted-average remaining lease term - finance leases 3.3 years 3.8 years Weighted-average remaining lease term - operating leases 2.9 years 2.1 years Weighted-average discount rate - finance leases 6.4 % 6.1 % Weighted-average discount rate - operating leases 7.8 % 8.5 % (1) Primarily includes common area maintenance, property taxes and insurance payable to lessors.

Revenues (Tables)

Revenues (Tables)	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Schedule of Accounts Receivable	The following table shows the components of the Company's Trade receivables, net: As of (in thousands) June 30, 2021 December 31, 2020 Trade receivables $ 9,983 $ 12,241 Less: Allowance for doubtful accounts (39) (37) Trade receivables, net $ 9,944 $ 12,204 The following table shows the components of the Cabot Receivable: As of (in thousands) June 30, 2021 December 31, 2020 Receivables, net $ 1,616 $ 921 Other long-term assets, net 7,952 8,852 Total Cabot Receivable $ 9,568 $ 9,773
Schedule of Disaggregation of Revenue	The following tables disaggregate revenues by major component for the three and six months ended June 30, 2021 and 2020 (in thousands): Three Months Ended June 30, 2021 Six Months Ended June 30, 2021 Segment Segment APT RC Total APT RC Total Revenue component Consumables $ 15,976 $ — $ 15,976 $ 33,007 $ — $ 33,007 License royalties, related party — 3,657 3,657 — 7,723 7,723 Revenues from customers 15,976 3,657 19,633 33,007 7,723 40,730 Earnings from equity method investments — 21,437 21,437 — 39,749 39,749 Total revenues from customers and earnings from equity method investments $ 15,976 $ 25,094 $ 41,070 $ 33,007 $ 47,472 $ 80,479 Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Segment Segment APT RC Total APT RC Total Revenue component Consumables $ 8,170 $ — $ 8,170 $ 17,387 $ — $ 17,387 License royalties, related party — 3,313 3,313 — 6,359 6,359 Revenues from customers 8,170 3,313 11,483 17,387 6,359 23,746 Earnings from equity method investments — 8,168 8,168 — 16,441 16,441 Total revenues from customers and earnings from equity method investments $ 8,170 $ 11,481 $ 19,651 $ 17,387 $ 22,800 $ 40,187

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Schedule of Dividends Declared	Dividends declared and paid quarterly on all outstanding shares of common stock during the three and six months ended June 30, 2021 and 2020 were as follows: 2021 2020 Per share Date paid Per share Date paid Dividends declared during quarter ended: March 31 $ — N/A $ 0.25 March 10, 2020 June 30 $ — N/A $ — N/A $ — $ 0.25

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Allocation of Compensation Expense	Total stock-based compensation expense for the three and six months ended June 30, 2021 and 2020 was as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 RSA expense $ 511 $ 975 $ 918 $ 1,481 PSU expense 55 163 69 163 Total stock-based compensation expense $ 566 $ 1,138 $ 987 $ 1,644
Schedule of Unrecognized Compensation Cost	The amount of unrecognized compensation cost as of June 30, 2021, and the expected weighted-average period over which the cost will be recognized is as follows: As of June 30, 2021 (in thousands) Unrecognized Compensation Cost Expected Weighted- RSA expense $ 2,736 2.31 PSU expense 490 2.24 Total unrecognized stock-based compensation expense $ 3,226 2.30
Summary of Restricted Stock Activity	A summary of RSA activity under the Company's various stock compensation plans for the six months ended June 30, 2021 is presented below: Restricted Stock Weighted-Average Grant Date Fair Value Non-vested at January 1, 2021 373,860 $ 7.25 Granted 387,632 $ 5.28 Vested (183,700) $ 7.45 Forfeited (31,623) $ 5.75 Non-vested at June 30, 2021 546,169 $ 5.88
Summary of Performance Shares Units	A summary of PSU activity for the six months ended June 30, 2021 is presented below: Units Weighted-Average Aggregate Intrinsic Value (in thousands) Weighted-Average PSU's outstanding, January 1, 2021 50,127 $ 6.17 Granted 62,448 7.09 Vested / Settled — — Forfeited / Canceled — — PSU's outstanding, June 30, 2021 112,575 $ 6.68 $ 834 2.24

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	6 Months Ended
	Jun. 30, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Prepaid Expenses and Other Assets and Other assets	The following table summarizes the components of Prepaid expenses and other assets and Other long-term assets, net as presented in the Condensed Consolidated Balance Sheets: As of (in thousands) June 30, December 31, Prepaid expenses and other assets: Prepaid expenses $ 2,278 $ 1,690 Prepaid income taxes and income tax refunds 1,723 1,605 Other 1,319 1,302 $ 5,320 $ 4,597 Other long-term assets, net: Cabot Receivable (1) $ 7,952 $ 8,852 Upfront Customer Consideration (1) 7,236 7,490 Mine development costs, net 4,837 4,338 Right of use assets, operating leases, net 4,380 1,930 Spare parts, net 4,173 3,727 Mine reclamation asset, net 1,666 1,712 Highview Investment 552 552 Other 1,481 1,388 $ 32,277 $ 29,989 (1) See further discussion of Upfront Customer Consideration in Note 3 and Cabot Receivable in Note 4 and Note 10.
Schedule of Other Liabilities	The following table details the components of Other current liabilities and Other long-term liabilities as presented in the Condensed Consolidated Balance Sheets: As of (in thousands) June 30, December 31, Other current liabilities: Current portion of operating lease obligations $ 2,342 $ 1,883 Current portion of mine reclamation liability 6,986 9,370 Income and other taxes payable 2,159 1,305 Other current liabilities 468 438 $ 11,955 $ 12,996 Other long-term liabilities: Mine reclamation liabilities $ 8,137 $ 12,077 Operating lease obligations, long-term 2,698 1,109 Other long-term liabilities (1) 557 287 $ 11,392 $ 13,473
Schedule of Change in Asset Retirement Obligation	The Mine reclamation liability related to the Five Forks Mine is included in Other long-term liabilities. The Mine reclamation liability related to Marshall Mine, which was assumed in the Marshall Mine Acquisition, is included in Other current liabilities and Other long-term liabilities. The Mine reclamation liabilities represent AROs. Changes in the AROs were as follows: As of (in thousands) June 30, 2021 December 31, 2020 Asset retirement obligation, beginning of period $ 21,447 $ 2,721 Asset retirement obligation assumed — 21,328 Accretion 661 543 Liabilities settled (5,043) (3,565) Changes due to scope and timing of reclamation (1,942) 420 Asset retirement obligations, end of period 15,123 21,447 Less current portion 6,986 9,370 Asset retirement obligation, long-term $ 8,137 $ 12,077
Schedule of Statement of Operations, Supplemental Disclosures	The following table details the components of Interest expense in the Condensed Consolidated Statements of Operations: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Interest on Senior Term Loan $ 52 $ 484 $ 207 $ 1,114 Debt discount and debt issuance costs 355 355 946 709 453A interest 7 28 7 160 Other 79 95 170 189 $ 493 $ 962 $ 1,330 $ 2,172

Impairment (Tables)

Impairment (Tables)	6 Months Ended
	Jun. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Impaired Intangible Assets	The following table summarizes the allocation to the Asset Group of the Impairment Charge of $26.1 million recorded as of June 30, 2020: (in thousands) Property, plant and equipment, net $ 18,986 Intangible assets, net 1,445 Other long-term assets, net 5,672 Total impairment $ 26,103

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Schedule of Income Tax Expense and Effective Tax Rates	For the three and six months ended June 30, 2021 and 2020, the Company's income tax expense and effective tax rates based on forecasted pretax income were: Three Months Ended June 30, Six Months Ended June 30, (in thousands, except for rate) 2021 2020 2021 2020 Income tax expense $ 4,943 $ 103 $ 9,432 $ 461 Effective tax rate 23 % — % 24 % (2) %

Business Segment Information (T

Business Segment Information (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Segment Operating Results	The following table presents the Company's operating segment results for the three and six months ended June 30, 2021 and 2020: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Revenues: Refined Coal: Earnings in equity method investments $ 21,437 $ 8,168 $ 39,749 $ 16,441 License royalties, related party 3,657 3,313 7,723 6,359 25,094 11,481 47,472 22,800 Advanced Purification Technologies: Consumables 15,976 8,170 33,007 17,387 15,976 8,170 33,007 17,387 Total segment reporting revenues 41,070 19,651 80,479 40,187 Adjustments to reconcile to reported revenues: Earnings in equity method investments (21,437) (8,168) (39,749) (16,441) Total reported revenues $ 19,633 $ 11,483 $ 40,730 $ 23,746 Segment operating income (loss): Refined Coal $ 24,905 $ 10,777 $ 47,176 $ 21,637 Advanced Purification Technologies (1) (2) 258 (29,999) 273 (37,369) Total segment operating income (loss) $ 25,163 $ (19,222) $ 47,449 $ (15,732) (1) Included in APT segment operating income (loss) for the three and six months ended June 30, 2021 and 2020 is $1.8 million and $3.7 million, $1.5 million and $3.8 million, respectively, of depreciation, amortization, depletion and accretion expense on mine and plant long-lived assets and liabilities and $0.1 million, $0.3 million, zero and zero, respectively, of amortization of Upfront Customer Consideration. (2) Included in APT segment operating income for the three and six months ended June 30, 2021 is $1.9 million gain related to the change in the Marshall Mine ARO as of June 30, 2021.
Reconciliation of Reportable Segment Amounts to Consolidated Balances	A reconciliation of reportable segment operating income to consolidated income (loss) before income tax expense is as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Total reported segment operating income (loss) $ 25,163 $ (19,222) $ 47,449 $ (15,732) Adjustments to reconcile to income (loss) before income (loss) tax expense attributable to the Company: Corporate payroll and benefits (826) (1,148) (1,465) (1,857) Corporate legal and professional fees (1,376) (925) (3,130) (2,674) Corporate general and administrative (1,049) (1,558) (2,225) (3,157) Corporate depreciation and amortization (122) (163) (276) (189) Corporate interest expense, net (348) (824) (998) (1,766) Other income, net 91 129 404 129 Income (loss) before income tax expense $ 21,533 $ (23,711) $ 39,759 $ (25,246)
Reconciliation of Assets from Segment to Consolidated	A reconciliation of reportable segment assets to consolidated assets is as follows: As of (in thousands) June 30, December 31, Assets: Refined Coal (1) $ 7,427 $ 11,516 Advanced Purification Technologies (2) 81,775 80,877 Total segment assets 89,202 92,393 All Other and Corporate (3) 69,293 54,278 Consolidated $ 158,495 $ 146,671 (1) Includes $3.6 million and $7.7 million of investments in equity method investees as of June 30, 2021 and December 31, 2020, respectively. (2) Includes $37.0 million and $34.6 million of long-lived assets, net. (3) Includes the Company's deferred tax assets of $3.8 million and $10.6 million as of June 30, 2021 and December 31, 2020, respectively.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Estimated Fair Values of Remaining Financial Instruments	The following table provides the estimated fair values of the remaining financial instruments: As of June 30, 2021 As of December 31, 2020 (in thousands) Carrying Value Fair Value Carrying Value Fair Value Financial Instruments: Highview Investment $ 552 $ 552 $ 552 $ 552 Highview Obligation $ 233 $ 233 $ 228 $ 228

Basis of Presentation - Calcula

Basis of Presentation - Calculations of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounting Policies [Abstract]
Net income (loss)	$ 16,590	$ 13,737	$ (23,814)	$ (1,893)	$ 30,327	$ (25,707)
Less: Dividends and undistributed income (loss) allocated to participating securities	0		(17)		0	(19)
Income (loss) attributable to common stockholders	16,590		(23,797)		30,327	(25,688)
Income (loss) attributable to common stockholders	$ 16,590		$ (23,797)		$ 30,327	$ (25,688)
Basic weighted-average common shares outstanding (in shares)	18,271		18,014		18,219	17,974
Add: dilutive effect of equity instruments (in shares)	127		0		137	0
Diluted weighted-average shares outstanding (in shares)	18,398		18,014		18,356	17,974
Earnings (loss) per share - basic (in dollars per share)	$ 0.91		$ (1.32)		$ 1.66	$ (1.43)
Earnings (loss) per share - diluted (in dollars per share)	$ 0.90		$ (1.32)		$ 1.65	$ (1.43)
Total shares excluded from diluted shares outstanding (in shares)	100		0		700	300

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Details) - Tinuum Group, LLC	3 Months Ended
	Jun. 30, 2021Facility
Concentration Risk [Line Items]
Number of instruments held	22
Number of facilities ceased	1
Customer Concentration Risk
Concentration Risk [Line Items]
Number of instruments held	8

Acquisition of Marshall Mine -

Acquisition of Marshall Mine - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2021
Business Acquisition [Line Items]
Reclamation reimbursements	$ 10.2
Marshall Mine
Business Acquisition [Line Items]
Membership interest		100.00%
Capped cost	19.7
Direct cost	$ 3.6
Estimated reclamation period	10 years
Term of contract	15 years
Marshall Mine | Cabot
Business Acquisition [Line Items]
Reclamation reimbursements	$ 10.2
Term of contract	13 years

Acquisition of Marshall Mine _2

Acquisition of Marshall Mine - Allocation (Details) - Marshall Mine - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2020
Assets acquired:
Receivables	$ 0	$ 513
Property, plant and equipment	3,863	3,863
Spare parts	100	100
Liabilities assumed:
Accounts payable and accrued expenses	(673)	(513)
Asset retirement obligation	(21,328)	(21,328)
Net assets acquired and liabilities assumed from Marshall Mine acquisition	(18,038)	(17,365)
Cabot Receivable	9,749	9,749
Upfront Customer Consideration	$ 8,289	7,616
Adjustments
Receivables		513
Property, plant and equipment		0
Spare parts		0
Accounts payable and accrued expenses		160
Asset retirement obligation		0
Net assets acquired and liabilities assumed from Marshall Mine acquisition		673
Cabot Receivable		0
Upfront Customer Consideration		$ (673)

Marshall Mine Asset Retiremen_2

Marshall Mine Asset Retirement Obligation and Cabot Receivable - ARO and Cabot Receivable (Details) - USD ($)	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Asset Retirement Obligation and related Long-Term Receivable [Abstract]
Reclamation costs	$ 21,300,000
Expected future cash flows	23,700,000
Risk-free rate		7.00%		7.00%
Gain on change in estimate, asset retirement obligation		$ (1,942,000)	$ 0	$ (1,942,000)	$ 0
Long-term receivable	$ 9,700,000
Discount rate	1.50%
Effect of discounting	$ 500,000
Reclamation reimbursements	$ 10,200,000
Allowance for credit losses		0		0		$ 0
Property, Plant and Equipment [Line Items]
Asset retirement obligation		15,123,000		15,123,000		21,447,000	$ 2,721,000
Marshall Mine
Property, Plant and Equipment [Line Items]
Asset retirement obligation		$ 11,700,000		$ 11,700,000		$ 18,100,000

Marshall Mine Asset Retiremen_3

Marshall Mine Asset Retirement Obligation and Cabot Receivable - Bonds (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Jun. 07, 2021	Dec. 31, 2020	Sep. 30, 2020
Asset Retirement Obligation and related Long-Term Receivable [Abstract]
Surety bond amount		$ 16,600		$ 30,000
Restricted cash, long-term	$ 10,000		$ 5,000

COVID-19 (Details)

COVID-19 (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Jun. 30, 2021	Jul. 19, 2021	Apr. 20, 2020
CARES Act, Grant Income [Abstract]
Payroll tax payments deferred under the CARES Act		$ 0.4	$ 0.4
Debt Instrument [Line Items]
Payroll tax payments deferred under the CARES Act		$ 0.4	$ 0.4
Promissory Note | PPP Loan
Debt Instrument [Line Items]
Face amount					$ 3.3
Interest rate, stated percentage					1.00%
Promissory Note | PPP Loan | Forecast
Debt Instrument [Line Items]
Gain on extinguishment of debt	$ 3.3
Promissory Note | PPP Loan | Subsequent Event
Debt Instrument [Line Items]
PPP Loan forgiveness application, approved amount				$ 3.3

Equity Method Investments - Nar

Equity Method Investments - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments	$ 21,437,000	$ 8,168,000	$ 39,749,000	$ 16,441,000
Equity method investments	$ 3,564,000		$ 3,564,000			$ 7,692,000
Tinuum Group, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent	42.50%		42.50%			42.50%
Earnings from equity method investments	$ 19,125,000	6,764,000	$ 35,487,000	13,202,000
Equity method investments	$ 0	18,118,000	$ 0	18,118,000	$ 0	$ 3,387,000	$ 24,954,000	$ 32,280,000
Tinuum Services, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent	50.00%		50.00%			50.00%
Earnings from equity method investments	$ 2,312,000	1,404,000	$ 4,262,000	3,242,000
Equity method investments	3,501,000		3,501,000			$ 4,242,000
Equity Method Investment | Tinuum Group, LLC
Schedule of Equity Method Investments [Line Items]
Loss attributable to noncontrolling interest	(29,038,000)	(18,823,000)	(64,616,000)	(38,094,000)
Equity Method Investment | Tinuum Services, LLC
Schedule of Equity Method Investments [Line Items]
Loss attributable to noncontrolling interest	$ (74,587,000)	$ (67,071,000)	$ (151,802,000)	$ (139,043,000)

Equity Method Investments - Res

Equity Method Investments - Results of Operations and Summary of Distributions (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Operating, selling, general and administrative expenses	$ 19,194,000		$ 42,548,000		$ 39,961,000	$ 63,452,000
Net income (loss)	16,590,000	$ 13,737,000	(23,814,000)	$ (1,893,000)	30,327,000	(25,707,000)
ADES equity earnings	21,437,000		8,168,000		39,749,000	16,441,000
Equity method investments	3,564,000				3,564,000		$ 7,692,000
Distributions from equity method investees, return on investment					19,144,000	32,516,000
Distributions from equity method investees in excess of investment basis					24,732,000	0
Tinuum Group, LLC
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
ADES equity earnings	19,125,000		6,764,000		35,487,000	13,202,000
Equity method investments	0	$ 0	18,118,000	$ 24,954,000	0	18,118,000	3,387,000	$ 32,280,000
Distributions from equity method investees, return on investment					14,142,000	27,364,000
Distributions from equity method investees in excess of investment basis					24,732,000	0
Tinuum Services, LLC
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
ADES equity earnings	2,312,000		1,404,000		4,262,000	3,242,000
Equity method investments	3,501,000				3,501,000		4,242,000
Distributions from equity method investees, return on investment					5,002,000	5,152,000
Earnings (loss) from other
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
ADES equity earnings	0		0		0	(3,000)
Equity method investments	63,000				63,000		$ 63,000
Equity Method Investment | Tinuum Group, LLC
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Gross profit (loss)	8,820,000		6,868,000		11,495,000	11,878,000
Operating, selling, general and administrative expenses	12,429,000		11,919,000		26,231,000	24,695,000
Loss from operations	(3,609,000)		(5,051,000)		(14,736,000)	(12,817,000)
Other income (expenses), net	3,150,000		2,144,000		4,003,000	5,787,000
Loss attributable to noncontrolling interest	29,038,000		18,823,000		64,616,000	38,094,000
Net income (loss)	28,579,000		15,916,000		53,883,000	31,064,000
Equity Method Investment | Tinuum Services, LLC
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Gross profit (loss)	(22,641,000)		(20,418,000)		(41,163,000)	(42,677,000)
Operating, selling, general and administrative expenses	47,355,000		43,515,000		101,722,000	89,268,000
Loss from operations	(69,996,000)		(63,933,000)		(142,885,000)	(131,945,000)
Other income (expenses), net	32,000		(330,000)		(394,000)	(615,000)
Loss attributable to noncontrolling interest	74,587,000		67,071,000		151,802,000	139,043,000
Net income (loss)	$ 4,623,000		$ 2,808,000		$ 8,523,000	$ 6,483,000

Equity Method Investments - Rol

Equity Method Investments - Rollforward of CCS Investment (Details) - USD ($)	3 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Equity Method Investments [Roll Forward]
Beginning balance		$ 7,692,000
Total investment balance, equity earnings (loss) and cash distributions	$ 3,564,000
Tinuum Group, LLC
Equity Method Investments [Roll Forward]
Beginning balance	0	3,387,000	$ 24,954,000	$ 32,280,000
ADES proportionate share of income from Tinuum Group	12,146,000	10,755,000	6,764,000	6,438,000
Recovery of prior cash distributions in excess of investment balance (prior to cash distributions)	(5,607,000)
Cash distributions from Tinuum Group	19,125,000	19,749,000	13,600,000	13,764,000
Adjustment for current year cash distributions in excess of investment balance	12,586,000	5,607,000
Total investment balance, equity earnings (loss) and cash distributions	0	0	18,118,000	24,954,000
Tinuum Group, LLC | ADES equity earnings
Equity Method Investments [Roll Forward]
Beginning balance	16,362,000	0	6,438,000	0
ADES proportionate share of income from Tinuum Group	12,146,000	10,755,000	6,764,000	6,438,000
Recovery of prior cash distributions in excess of investment balance (prior to cash distributions)	(5,607,000)
Cash distributions from Tinuum Group	0	0	0	0
Adjustment for current year cash distributions in excess of investment balance	12,586,000	5,607,000
Total investment balance, equity earnings (loss) and cash distributions	19,125,000	16,362,000	6,764,000	6,438,000
Tinuum Group, LLC | Cash distributions
Equity Method Investments [Roll Forward]
Beginning balance	19,749,000	0	13,764,000	0
ADES proportionate share of income from Tinuum Group	0	0	0	0
Recovery of prior cash distributions in excess of investment balance (prior to cash distributions)	0
Cash distributions from Tinuum Group	19,125,000	19,749,000	13,600,000	13,764,000
Adjustment for current year cash distributions in excess of investment balance	0	0
Total investment balance, equity earnings (loss) and cash distributions	19,125,000	19,749,000	$ 13,600,000	$ 13,764,000
Tinuum Group, LLC | Memorandum Account: Cash distributions and equity loss in (excess) of investment balance
Equity Method Investments [Roll Forward]
Beginning balance	(5,607,000)	0
ADES proportionate share of income from Tinuum Group	0	0
Recovery of prior cash distributions in excess of investment balance (prior to cash distributions)	(5,607,000)
Cash distributions from Tinuum Group	0	0
Adjustment for current year cash distributions in excess of investment balance	(12,586,000)	(5,607,000)
Total investment balance, equity earnings (loss) and cash distributions	$ (12,586,000)	$ (5,607,000)

Inventories, net (Details)

Inventories, net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Product inventory, net	$ 6,639	$ 8,361
Raw material inventory	1,522	1,521
Inventories	$ 8,161	$ 9,882

Debt Obligations - Schedule of

Debt Obligations - Schedule of Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 07, 2018
Debt Instrument [Line Items]
Finance lease obligations	$ 4,738	$ 5,526
PPP Loan	3,305	3,305
Long-term Debt	8,043	23,886
Less: Current maturities	(4,373)	(18,441)
Total long-term debt	3,670	5,445
Senior Term Loan due December 2021, net
Debt Instrument [Line Items]
Less: net unamortized debt issuance costs			$ (2,000)
Less: net unamortized debt discount			$ (2,100)
Senior Term Loan due December 2021, net | Senior Term Loan due December 2021, related party
Debt Instrument [Line Items]
Senior Term Loan due December 2021, related party	0	16,000
Less: net unamortized debt issuance costs	0	(465)
Less: net unamortized debt discount	0	(480)
Senior Term Loan due December 2021, net	$ 0	$ 15,055

Debt Obligations - Senior Term

Debt Obligations - Senior Term Loan (Details) - USD ($)	Jun. 01, 2021	Dec. 07, 2018	Jun. 30, 2021	Dec. 31, 2020
Senior Term Loan
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 70,000,000
Less: net unamortized debt discount		2,100,000
Debt issuance costs		$ 2,000,000
Interest rate, stated percentage		4.75%
Repayments of debt	$ 6,100,000
Prepayment fees associated with the early pay-off			$ 0
Senior Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.50%
Senior Term Loan due December 2021, related party | Senior Term Loan
Debt Instrument [Line Items]
Less: net unamortized debt discount			0	$ 480,000
Debt issuance costs			$ 0	$ 465,000
Senior Term Loan due December 2021, related party | Minimum
Debt Instrument [Line Items]
Percent of common stock owned		5.00%

Debt Obligations - Line of Cred

Debt Obligations - Line of Credit (Details) - USD ($)	Jun. 30, 2021	Mar. 23, 2021	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2014
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 5,000,000		$ 10,000,000
Line of credit	$ 0
Senior Term Loan
Debt Instrument [Line Items]
Minimum cash balance required		$ 6,000,000		$ 5,000,000

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Long-term lease liabilities	$ 4,738		$ 4,738		$ 5,526
Operating lease, liability	5,000		5,000		3,000
Finance lease, right of use asset	2,000		2,000		2,400
Operating lease, right of use asset	4,380		4,380		$ 1,930
Operating lease, expense	900	$ 1,100	1,900	$ 2,400
General and Administrative Expense
Lessee, Lease, Description [Line Items]
Operating lease, expense	100	200	200	400
Consumables
Lessee, Lease, Description [Line Items]
Operating lease, expense	$ 800	$ 1,000	$ 1,700	$ 2,000

Leases - Lease Liabilities (Det

Leases - Lease Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lease, cost
Amortization of right-of-use assets	$ 174	$ 465	$ 348	$ 979
Interest on lease liabilities	70	93	149	187
Operating lease cost	453	676	912	1,529
Short-term lease cost	406	424	973	706
Variable lease cost	12	44	21	137
Total lease cost	$ 1,115	$ 1,702	2,403	3,538
Operating cash flows from finance leases			149	187
Operating cash flows from operating leases			1,314	1,213
Financing cash flows from finance leases			818	676
Right-of-use assets obtained in exchange for new operating lease liabilities			$ 3,362	$ 60
Weighted-average remaining lease term - finance leases	3 years 3 months 18 days	3 years 9 months 18 days	3 years 3 months 18 days	3 years 9 months 18 days
Weighted-average remaining lease term - operating leases	2 years 10 months 24 days	2 years 1 month 6 days	2 years 10 months 24 days	2 years 1 month 6 days
Weighted-average discount rate - finance leases	6.40%	6.10%	6.40%	6.10%
Weighted-average discount rate - operating leases	7.80%	8.50%	7.80%	8.50%

Revenues - Narrative (Details)

Revenues - Narrative (Details)	6 Months Ended
	Jun. 30, 2021segment
Revenue from Contract with Customer [Abstract]
Collection terms	Credit terms are generally net 30 from the date of invoice.
Number of operating segments	2

Revenues - Trade Receivables (D

Revenues - Trade Receivables (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 11,560	$ 13,125
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	9,983	12,241
Less: Allowance for doubtful accounts	(39)	(37)
Total	$ 9,944	$ 12,204

Revenues - Cabot Receivables (D

Revenues - Cabot Receivables (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Cabot Receivable	$ 9,568	$ 9,773
Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Cabot Receivable	1,616	921
Other Noncurrent Assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Cabot Receivable	$ 7,952	$ 8,852

Revenues - Disaggregation of Re

Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue component	$ 19,633	$ 11,483	$ 40,730	$ 23,746
Earnings from equity method investments	21,437	8,168	39,749	16,441
Total revenues from customers and earnings from equity method investments	19,633	11,483	40,730	23,746
Total revenues from customers and earnings from equity method investments	41,070	19,651	80,479	40,187
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues from customers and earnings from equity method investments	41,070	19,651	80,479	40,187
Consumables
Disaggregation of Revenue [Line Items]
Revenue component	15,976	8,170	33,007	17,387
License royalties, related party
Disaggregation of Revenue [Line Items]
Revenue component	3,657	3,313	7,723	6,359
APT
Disaggregation of Revenue [Line Items]
Revenue component	15,976	8,170	33,007	17,387
Earnings from equity method investments	0	0	0	0
APT | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues from customers and earnings from equity method investments	15,976	8,170	33,007	17,387
APT | Consumables
Disaggregation of Revenue [Line Items]
Revenue component	15,976	8,170	33,007	17,387
APT | Consumables | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue component	15,976	8,170	33,007	17,387
APT | License royalties, related party
Disaggregation of Revenue [Line Items]
Revenue component	0	0	0	0
RC
Disaggregation of Revenue [Line Items]
Revenue component	3,657	3,313	7,723	6,359
Earnings from equity method investments	21,437	8,168	39,749	16,441
RC | Operating Segments
Disaggregation of Revenue [Line Items]
Earnings from equity method investments	21,437	8,168	39,749	16,441
Total revenues from customers and earnings from equity method investments	25,094	11,481	47,472	22,800
RC | Consumables
Disaggregation of Revenue [Line Items]
Revenue component	0	0	0	0
RC | License royalties, related party
Disaggregation of Revenue [Line Items]
Revenue component	$ 3,657	$ 3,313	$ 7,723	$ 6,359

Commitments and Contingencies (

Commitments and Contingencies (Details)	Jun. 30, 2021USD ($)entity	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Restricted cash, short term	$ 6,000,000	$ 5,000,000
Restricted cash, long-term	$ 10,000,000	5,000,000
Tinuum Group, LLC
Related Party Transaction [Line Items]
Number of entities affiliated with related parties | entity	2
Limited guarantees, percent	50.00%
Liabilities or expense	$ 0
Surety Agreement
Debt Instrument [Line Items]
Restricted cash, long-term	$ 10,000,000	$ 5,000,000

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Nov. 30, 2019	Nov. 30, 2018	May 05, 2017
Maximum
Class of Stock [Line Items]
Requirement to own shares outstanding as percent							4.99%
Common Stock
Class of Stock [Line Items]
Remaining authorized amount	$ 7,000,000		$ 7,000,000		$ 2,900,000
Authorized incremental amount					$ 7,100,000
Stock repurchased (in shares)	0	0	0	20,613
Stock repurchased		$ 0		$ 200,000
Common Stock | Maximum
Class of Stock [Line Items]
Authorized amount						$ 20,000,000

Stockholders' Equity - Dividend

Stockholders' Equity - Dividends (Details) - $ / shares	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Equity [Abstract]
Dividends declared (in dollars per share)	$ 0	$ 0	$ 0	$ 0.25	$ 0	$ 0.25

Stock-Based Compensation - Allo

Stock-Based Compensation - Allocation of Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 566	$ 1,138	$ 987	$ 1,644
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	511	975	918	1,481
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 55	$ 163	$ 69	$ 163

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Unrecognized Compensation Cost (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Cost	$ 3,226
Expected Weighted-Average Period of Recognition (in years)	2 years 3 months 18 days
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Cost	$ 2,736
Expected Weighted-Average Period of Recognition (in years)	2 years 3 months 21 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Cost	$ 490
Expected Weighted-Average Period of Recognition (in years)	2 years 2 months 26 days

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details)	6 Months Ended
	Jun. 30, 2021
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Non-vested Restricted Stock Activity (Details) - Restricted stock awards	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Number of SAR's Outstanding and Exercisable
Non-vested shares, Beginning balance (in shares) | shares	373,860
Granted (in shares) | shares	387,632
Vested (in shares) | shares	(183,700)
Forfeited (in shares) | shares	(31,623)
Non-vested shares, Ending balance (in shares) | shares	546,169
Units
Non-vested shares, Weighted-Average Grant Date Fair Value, Beginning Balance (in dollars per share) | $ / shares	$ 7.25
Granted, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	5.28
Vested in period, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	7.45
Forfeited, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	5.75
Non-vested shares, Weighted-Average Grant Date Fair Value, Ending Balance (in dollars per share) | $ / shares	$ 5.88

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Non-vested PSUs (Details) - Performance share units $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)$ / sharesshares
Number of SAR's Outstanding and Exercisable
Non-vested shares, Beginning balance (in shares) | shares	50,127
Granted (in shares) | shares	62,448
Vested / Settled (in shares) | shares	0
Forfeited / Canceled (in shares) | shares	0
Non-vested shares, Ending balance (in shares) | shares	112,575
Units
Non-vested shares, Weighted-Average Grant Date Fair Value, Beginning Balance (in dollars per share) | $ / shares	$ 6.17
Granted, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	7.09
Vested / Settled in period, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	0
Forfeited, Weighted-Average Grant Date Fair Value (in dollars per share) | $ / shares	0
Non-vested shares, Weighted-Average Grant Date Fair Value, Ending Balance (in dollars per share) | $ / shares	$ 6.68
Outstanding, Aggregate Intrinsic Value | $	$ 834
Outstanding, Weighted Average Remaining Contractual Term (in years)	2 years 2 months 26 days

Supplemental Financial Inform_3

Supplemental Financial Information - Prepaid expenses and other assets and Other assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Prepaid expenses and other assets:
Prepaid expenses	$ 2,278	$ 1,690
Prepaid income taxes and income tax refunds	1,723	1,605
Other	1,319	1,302
Other current assets	5,320	4,597
Other long-term assets, net:
Cabot receivable	7,952	8,852
Upfront Customer Consideration	7,236	7,490
Mine development costs, net	4,837	4,338
Right of use assets, operating leases, net	4,380	1,930
Spare parts, net	4,173	3,727
Mine reclamation asset, net	1,666	1,712
Highview Investment	552	552
Other	1,481	1,388
Total	$ 32,277	$ 29,989

Supplemental Financial Inform_4

Supplemental Financial Information - Other Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Other current liabilities:
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]		Other current liabilities	Other current liabilities
Current portion of operating lease obligations	$ 2,342	$ 1,883
Current portion of mine reclamation liability	6,986	9,370
Income and other taxes payable	2,159	1,305
Other current liabilities	468	438
Other current liabilities	$ 11,955	$ 12,996
Other long-term liabilities:
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities
Mine reclamation liabilities	$ 8,137	$ 12,077
Operating lease obligations, long-term	2,698	1,109
Other long-term liabilities	557	287
Other long-term liabilities	11,392	$ 13,473
Employee-related liabilities	$ 300

Supplemental Financial Inform_5

Supplemental Financial Information - Asset Retirement Obligation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation, beginning of period			$ 21,447	$ 2,721
Asset retirement obligations assumed			0	21,328
Accretion			661	543
Liabilities settled			(5,043)	(3,565)
Changes due to amount and timing of reclamation			(1,942)	420
Asset retirement obligations, end of period	$ 15,123		15,123
Less current portion	6,986		6,986		$ 9,370
Asset retirement obligations, long-term	8,137		8,137		$ 12,077
Gain on change in estimate, asset retirement obligation	$ 1,942	$ 0	$ 1,942	$ 0

Supplemental Financial Inform_6

Supplemental Financial Information - Supplemental Income Statement, Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Interest on Senior Term Loan	$ 52	$ 484	$ 207	$ 1,114
Debt discount and debt issuance costs	355	355	946	709
453A interest	7	28	7	160
Other	79	95	170	189
Interest expense	$ 493	$ 962	$ 1,330	$ 2,172

Impairment - Additional Informa

Impairment - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Impaired Long-Lived Assets Held and Used [Line Items]
Assets at carrying value	$ 158,495,000		$ 158,495,000		$ 146,671,000
Impairment of long-lived assets	0	$ 26,103,000	0	$ 26,103,000
Advanced Purification Technologies
Impaired Long-Lived Assets Held and Used [Line Items]
Assets, total		54,700,000		54,700,000
Assets at carrying value		58,300,000		58,300,000
Impairment of long-lived assets				26,103,000
Operating Segments
Impaired Long-Lived Assets Held and Used [Line Items]
Assets at carrying value	89,202,000		89,202,000		92,393,000
Operating Segments | Advanced Purification Technologies
Impaired Long-Lived Assets Held and Used [Line Items]
Assets at carrying value	$ 81,775,000		81,775,000		$ 80,877,000
Assets at fair value		$ 32,200,000		32,200,000
Impairment of long-lived assets				$ 26,100,000
Expected impairment charge			$ 0

Impairment - Components (Detail

Impairment - Components (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Impaired Long-Lived Assets Held and Used [Line Items]
Total impairment	$ 0	$ 26,103	$ 0	$ 26,103
Advanced Purification Technologies
Impaired Long-Lived Assets Held and Used [Line Items]
Property, plant and equipment, net				18,986
Intangible assets, net				1,445
Other long-term assets, net				5,672
Total impairment				$ 26,103

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 4,943	$ 103	$ 9,432	$ 461
Effective tax rate	23.00%	0.00%	24.00%	(2.00%)

Business Segment Information -

Business Segment Information - Segment Operating Results (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)segment	Jun. 30, 2020USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Revenues:
Earnings in equity method investments	$ 21,437,000	$ 8,168,000	$ 39,749,000	$ 16,441,000
Total revenues	19,633,000	11,483,000	40,730,000	23,746,000
Total reported revenues	19,633,000	11,483,000	40,730,000	23,746,000
Segment operating income (loss):
Total segment operating income (loss)	439,000	(31,065,000)	769,000	(39,706,000)
Upfront customer consideration	100,000	0	300,000	0
Gain on change in estimate, asset retirement obligation	(1,942,000)	0	(1,942,000)	0
Refined Coal
Revenues:
Earnings in equity method investments	21,437,000	8,168,000	39,749,000	16,441,000
Total revenues	3,657,000	3,313,000	7,723,000	6,359,000
Advanced Purification Technologies
Revenues:
Earnings in equity method investments	0	0	0	0
Total revenues	15,976,000	8,170,000	33,007,000	17,387,000
Segment operating income (loss):
Impairment expense on mine and plant long-lived assets				18,986,000
Consumables
Revenues:
Total revenues	15,976,000	8,170,000	33,007,000	17,387,000
Consumables | Refined Coal
Revenues:
Total revenues	0	0	0	0
Consumables | Advanced Purification Technologies
Revenues:
Total revenues	15,976,000	8,170,000	33,007,000	17,387,000
Operating Segments
Revenues:
Total reported revenues	41,070,000	19,651,000	80,479,000	40,187,000
Segment operating income (loss):
Total segment operating income (loss)	25,163,000	(19,222,000)	47,449,000	(15,732,000)
Operating Segments | Refined Coal
Revenues:
Earnings in equity method investments	21,437,000	8,168,000	39,749,000	16,441,000
License royalties, related party	3,657,000	3,313,000	7,723,000	6,359,000
Total reported revenues	25,094,000	11,481,000	47,472,000	22,800,000
Segment operating income (loss):
Total segment operating income (loss)	24,905,000	10,777,000	47,176,000	21,637,000
Operating Segments | Advanced Purification Technologies
Revenues:
Total reported revenues	15,976,000	8,170,000	33,007,000	17,387,000
Segment operating income (loss):
Total segment operating income (loss)	258,000	(29,999,000)	273,000	(37,369,000)
Impairment expense on mine and plant long-lived assets	1,800,000	1,500,000	3,700,000	3,800,000
Operating Segments | Consumables | Advanced Purification Technologies
Revenues:
Total revenues	15,976,000	8,170,000	33,007,000	17,387,000
Intersegment Eliminations | Refined Coal
Revenues:
Earnings in equity method investments	$ (21,437,000)	$ (8,168,000)	$ (39,749,000)	$ (16,441,000)

Business Segment Information _2

Business Segment Information - Reconciliation of Reportable Segment Amounts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Consolidated operating income	$ 439	$ (31,065)	$ 769	$ (39,706)
Adjustments to reconcile to income (loss) before income (loss) tax expense attributable to the Company:
Corporate payroll and benefits	(2,908)	(3,812)	(5,377)	(6,554)
Corporate legal and professional fees	(1,431)	(1,022)	(3,234)	(3,065)
Corporate general and administrative	(1,593)	(2,462)	(3,508)	(4,793)
Corporate depreciation and amortization	(1,904)	(1,733)	(4,010)	(4,030)
Other income, net	150	148	571	191
Income (loss) before income tax expense	21,533	(23,711)	39,759	(25,246)
Operating Segments
Segment Reporting Information [Line Items]
Consolidated operating income	25,163	(19,222)	47,449	(15,732)
Segment Reconciling Items
Adjustments to reconcile to income (loss) before income (loss) tax expense attributable to the Company:
Corporate payroll and benefits	(826)	(1,148)	(1,465)	(1,857)
Corporate legal and professional fees	(1,376)	(925)	(3,130)	(2,674)
Corporate general and administrative	(1,049)	(1,558)	(2,225)	(3,157)
Corporate depreciation and amortization	(122)	(163)	(276)	(189)
Corporate interest expense, net	(348)	(824)	(998)	(1,766)
Other income, net	91	129	404	129
Income (loss) before income tax expense	$ 21,533	$ (23,711)	$ 39,759	$ (25,246)

Business Segment Information _3

Business Segment Information - Segment Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Segment Reporting Information [Line Items]
Assets	$ 158,495	$ 146,671
Equity method investments	3,564	7,692
Deferred tax assets, net	3,787	10,604	$ 3,800
Advanced Purification Technologies
Segment Reporting Information [Line Items]
Assets			$ 58,300
Operating Segments
Segment Reporting Information [Line Items]
Assets	89,202	92,393
Operating Segments | Refined Coal
Segment Reporting Information [Line Items]
Assets	7,427	11,516
Operating Segments | Advanced Purification Technologies
Segment Reporting Information [Line Items]
Assets	81,775	80,877
Long-lived assets	37,000	34,600
All Other and Corporate
Segment Reporting Information [Line Items]
Assets	$ 69,293	$ 54,278

Fair Value Measurements (Detail

Fair Value Measurements (Details) $ in Thousands	Jun. 30, 2021USD ($)numberOfFinancialInstitutions	Dec. 31, 2020USD ($)numberOfFinancialInstitutions
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Highview Investment	$ 552	$ 552
Recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of instruments held | numberOfFinancialInstitutions	0	0
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Highview Investment	$ 552	$ 552
Highview Obligation	233	228
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Highview Investment	552	552
Highview Obligation	$ 233	$ 228