Montauk Renewables (MNTK) 10-Q 15 Nov 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2021	Nov. 11, 2021
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Registrant Name	MONTAUK RENEWABLES, INC.
Entity File Number	001-39919
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Tax Identification Number	85-3189583
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Address, Address Line One	680 Andersen Drive
Entity Address, Address Line Two	5th Floor Pittsburgh
Entity Address, State or Province	PA
Entity Address, City or Town	Pittsburgh
Entity Address, Postal Zip Code	15220
City Area Code	412
Local Phone Number	747-8700
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	MNTK
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		143,584,827
Entity Central Index Key	0001826600
Entity Ex Transition Period	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 20,892	$ 20,992
Restricted cash - current	118
Accounts and other receivables, net	15,308	5,449
Prepaid expenses and other current assets	3,045	6,044
Total current assets	39,363	32,485
Restricted cash - non-current	573	567
Property, plant and equipment, net	179,307	186,401
Related party receivable	7,140
Goodwill and intangible assets, net	15,033	14,678
Deferred tax assets	13,697	14,822
Operating lease right-of-use assets	378	586
Other assets	4,254	3,817
Total assets	259,745	253,356
Current liabilities:
Accounts payable	5,800	5,964
Accrued liabilities	12,441	11,539
Current portion of lease liability	294	282
Current portion of derivative instruments	841	1,185
Current portion of long-term debt	9,633	9,492
Total current liabilities	29,009	28,462
Long-term debt, less current portion	49,023	56,268
Non-current portion of lease liability	102	320
Non-current portion of derivative instruments	408	1,075
Asset retirement obligation	5,883	5,689
Other liabilities	1,226	1,920
Total liabilities	85,651	93,734
STOCKHOLDERS' AND MEMBERS' EQUITY
Members' equity		159,622
Common stock, $0.01 par value, authorized 690,000,000 shares; 143,584,827 shares issued at September 30, 2021; 141,015,213 shares outstanding at September 30, 2021	1,410
Treasury stock, at cost, 950,214 shares at September 30, 2021	(10,813)
Additional paid-in capital	193,518
Retained deficit	(10,021)
Total stockholders' and members' equity	174,094	159,622
Total liabilities and stockholders' and members' equity	$ 259,745	$ 253,356

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical)	Sep. 30, 2021$ / sharesshares
Statement of Financial Position [Abstract]
Common stock par or stated value per share | $ / shares	$ 0.01
Common stock shares authorized	690,000,000
Common stock shares issued	143,584,827
Common stock shares outstanding	141,015,213
Treasury stock shares	950,214

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Total operating revenues	$ 39,749	$ 28,250	$ 102,872	$ 74,563
Operating expenses:
Operating and maintenance expenses	13,123	11,320	36,954	31,281
General and administrative expenses	7,520	4,131	35,280	11,336
Royalties, transportation, gathering and production fuel	6,636	5,189	18,840	13,376
Depreciation, depletion and amortization	5,666	5,470	17,062	16,120
Gain on insurance proceeds	(157)	(2,694)	(238)	(3,444)
Impairment loss	0	0	626	278
Transaction costs	232		357
Total operating expenses	33,020	23,416	108,881	68,947
Operating income (loss)	6,729	4,834	(6,009)	5,616
Other expenses :
Interest expense	697	436	2,064	3,510
Other expense	617	216	662	250
Total other expenses	1,314	652	2,726	3,760
Income (loss) before income taxes	5,415	4,182	(8,735)	1,856
Income tax (benefit) expense	(3,481)	6,266	1,286	(291)
Net income (loss)	$ 8,896	$ (2,084)	$ (10,021)	$ 2,147
Loss per share:
Basic	$ 0.06		$ (0.07)
Diluted	$ 0.06		$ (0.07)
Weighted-average common shares outstanding:
Basic	141,015,213		141,015,213
Diluted	141,048,006		141,015,213

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' and Members' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Members Equity [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]
Beginning balance at Dec. 31, 2019	$ 154,257			$ 154,257
Net income (loss)	2,147			2,147
Stock-based compensation	465			465
Ending balance at Sep. 30, 2020	156,869			156,869
Beginning balance at Jun. 30, 2020	158,729			158,729
Net income (loss)	(2,084)			(2,084)
Stock-based compensation	224			224
Ending balance at Sep. 30, 2020	156,869			156,869
Beginning balance at Dec. 31, 2020	159,622			159,622
Net income (loss)	(10,021)					$ (10,021)
Stock-based compensation	19,713				$ 19,713
Effect of reorganization transactions		$ 1,383		$ (159,622)	158,239
Effect of reorganization transactions, shares		138,312,713
IPO common stock	15,593	$ 27			15,566
IPO common stock, shares		2,702,500
Treasury stock	(10,813)		$ (10,813)
Treasury stock, shares			950,214
Ending balance at Sep. 30, 2021	174,094	$ 1,410	$ (10,813)		193,518	(10,021)
Ending balance, shares at Sep. 30, 2021		141,015,213	950,214
Beginning balance at Jun. 30, 2021	162,624	$ 1,410	$ (10,813)		190,944	(18,917)
Beginning balance, shares at Jun. 30, 2021		141,015,213	950,214
Net income (loss)	8,896					8,896
Stock-based compensation	2,574				2,574
Ending balance at Sep. 30, 2021	$ 174,094	$ 1,410	$ (10,813)		$ 193,518	$ (10,021)
Ending balance, shares at Sep. 30, 2021		141,015,213	950,214

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net (loss) income	$ 8,896	$ (2,084)	$ (10,021)	$ 2,147
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation, depletion and amortization			17,062	16,120
Provision (benefit) for deferred income taxes			1,124	(372)
Stock-based compensation			19,713	465
Related party receivables				164
Derivative mark-to-market adjustments and settlements			(1,011)	1,381
Gain on property insurance proceeds			(238)	(1,169)
Gain on Pico earn-out liability reduction			(694)
Net loss on sale of assets			822
Accretion of asset retirement obligations			304	108
Amortization of debt issuance costs	123	169	395	532
Impairment loss			626	278
Changes in operating assets and liabilities:
Accounts and other receivables and other current assets			(7,272)	695
Accounts payable and other accrued expenses			488	2,287
Net cash provided by operating activities			21,298	22,636
Cash flows from investing activities
Capital expenditures			(7,702)	(14,911)
Asset acquisition			(4,142)
Cash collateral deposits, net			118	0
Proceeds from sale of assets			74
Proceeds from insurance recovery			238	1,169
Net cash used in investing activities			(11,414)	(13,742)
Cash flows from financing activities:
Borrowings of long-term debt				8,500
Repayments of long-term debt			(7,500)	(7,500)
Proceeds from initial public offering			15,593
Treasury stock purchase			(10,813)
Loan to Montauk Holdings Limited			(7,140)
Net cash (used in) provided by financing activities			(9,860)	1,000
Net increase in cash and cash equivalents and restricted cash			24	9,894
Cash and cash equivalents and restricted cash at beginning of period			21,559	10,361
Cash and cash equivalents and restricted cash at end of period	21,583	20,255	21,583	20,255
Reconciliation of cash, cash equivalents, and restricted cash at end of period:
Cash and cash equivalents	20,892	19,537	20,892	19,537
Restricted cash and cash equivalents - current	118	151	118	151
Restricted cash and cash equivalents - non-current	573	567	573	567
Cash and cash equivalents and restricted cash at end of period	$ 21,583	$ 20,255	$ 21,583	$ 20,255

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Description of Business	NOTE 1 – DESCRIPTION OF BUSINESS Operations and organization Montauk Renewables’ Business Montauk Renewables, Inc. (the “Company” or “Montauk Renewables”) is a renewable energy company specializing in the management, recovery and conversion of biogas into Renewable Natural Gas (“RNG”). The Company captures methane, preventing it from being released into the atmosphere, and converts it into either RNG or electrical power for the electrical grid (“Renewable Electricity”). The Company, headquartered in Pittsburgh, Pennsylvania, has more than 30 years of experience in the development, operation and management of landfill methane-fueled renewable energy projects. The Company has current operations at 15 operating projects located in California, Idaho, Ohio, Oklahoma, Pennsylvania, North Carolina and Texas. The Company sells RNG and Renewable Electricity, taking advantage of Environmental Attribute premiums available under federal and state policies that incentivize their use. One of the Company’s key revenue drivers is the selling of captured gas and the selling of Renewable Identification Numbers (“RINs”) to fuel blenders. The Renewable Fuel Standard (“RFS”) is an Environmental Protection Agency (“EPA”) administered federal law that requires transportation fuel to contain a minimum volume of renewable fuel. RNG derived from landfill methane, agricultural digesters and wastewater treatment facilities used as a vehicle fuel qualifies as a D3 (cellulosic biofuel with a 60% greenhouse gas reduction requirement) RIN. The RINs are compliance units for fuel blenders that were created by the RFS program in order to reduce greenhouse gases and imported petroleum into the United States. An additional program utilized by the Company is the Low Carbon Fuel Standard (“LCFS”). This is state specific and is designed to stimulate the use of low-carbon The second primary revenue driver is the selling of captured electricity and the associated environmental premiums related to renewable sales. The Company’s electric facilities are designed to conform to and monetize various state renewable portfolio standards requiring a percentage of the electricity produced in that state to come from a renewable resource. Such premiums are in the form of Renewable Energy Credits (“RECs”). All three of the Company’s electric facilities receive revenue for the monetization of RECs either as a part of a power sales agreement or separately. Collectively, the Company benefits from federal, state and local government incentives in the United States, provided in the form of RINs, RECs, LCFS credits, rebates, tax credits and other incentives to end users, distributors, system integrators and manufacturers of renewable energy projects, that promote the use of renewable energy, as Environmental Attributes. Background and Reorganization Transactions On January 4, 2021, the Company, Montauk Holdings Limited (“MNK”) and Montauk Holdings USA, LLC (a direct wholly-owned subsidiary of MNK at the time, “Montauk USA”) entered into a series of transactions, including an equity exchange and a distribution collectively referred to as the “Reorganization Transactions,” that resulted in the Company owning all of the assets and entities (other than Montauk USA) previously owned by Montauk USA, and Montauk Renewables became a direct wholly-owned subsidiary of MNK. Prior to the Reorganization Transactions, MNK’s business and operations were conducted entirely through Montauk USA and its U.S. subsidiaries, and MNK held no substantial assets other than equity of Montauk USA. The Company had no significant operations or assets prior to January 4, 2021 when it engaged in the equity exchange with Montauk USA and MNK. After completion of the Reorganization Transactions, (i) Montauk USA ceased to own any substantial assets and (ii) all entities through which MNK’s business and operations were conducted became owned, directly or indirectly, by the Company. MNK adopted a plan contemporaneously with the completion of the Reorganization Transactions that authorized the liquidation and dissolution of MNK. On January 15, 2021, MNK sold the membership interest of Montauk USA to a third party. On January 26, 2021, MNK distributed all of the outstanding shares of the Company’s common stock as a pro rata dividend to the holders of MNK’s ordinary shares (the “Distribution”), subject to any tax withholding obligations under applicable South African law. Each ordinary share of MNK outstanding on January 21, 2021, the record date for the Distribution (the “Record Date”), entitled the holder thereof to receive one share of the Company’s common stock. On January 26, 2021, the Company closed the initial public offering of its common stock on the Nasdaq Capital Market (the “IPO”) with the shares traded under the symbol “MNTK.” Montauk Renewables issued 2,702,500 shares at $8.50 per share and received gross proceeds of $22,971. The Company’s common stock was also secondarily listed on the Johannesburg Stock Exchange under the trading symbol “MKR.” On January 26, 2021, the Company entered into a Loan Agreement and Secured Promissory Note (the “Initial Promissory Note”) with MNK. MNK is currently an affiliate of the Company and certain of the Company’s directors and executive officers are also directors and executive officers of MNK. Pursuant to the Initial Promissory Note, the Company advanced a cash loan of $5,000 to MNK for MNK to pay its dividends tax liability arising from the Reorganization Transactions under the South African Income Tax Act, 1962 (Act No. 58 of 1962), as amended (the “South African Income Tax Act”). On February 22, 2021, the Company and MNK entered into an Amended and Restated Promissory Note (the “Amended Promissory Note”) to increase the principal amount of the loan to a total of $7,140, in the aggregate, in accordance with the Company’s obligations set forth in the Transaction Implementation Agreement entered into by and among the Company, MNK and the other party thereto, dated November 6, 2020, and amended on January 14, 2021. MNK was delisted from the JSE on January 26, 2021. MNK will be liquidated within 24 months of the Distribution. COVID-19 In March 2020, the World Health Organization classified the outbreak of COVID-19 COVID-19 While the Company has not experienced any material disruptions in its ability to continue business operations or experienced a material negative impact to its financial results due to COVID-19 COVID-19. The potential future impact of COVID-19

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 2 – SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with the instructions of the SEC on Form 10-Q 10-01 S-X. 10-K The historical consolidated financial information included reflects the historical results of operations and financial position of Montauk USA. The consolidated financial statements of Montauk USA became the Company’s historical financial statements following the IPO. Certain historical financial information included relates to periods prior to the Reorganization Transactions. Retrospective Presentation of Ownership Related to the Reorganization Transactions As discussed in Note 1, as a result of the Reorganization Transactions, the Company acquired the assets and entities (excluding Montauk USA) which were previously owned by MNK. As part of the Reorganization Transactions, a 1:1 pro rata distribution of shares of the Company’s common stock was made to holders of MNK’s ordinary shares. The Reorganization Transactions resulted in a pro rata distribution whereby the ownership of the Company after the Reorganization Transactions was identical to the ownership of MNK prior to the Reorganization Transaction and was therefore akin to a common control transaction. All members’ equity in the financial statements and notes have been retrospectively adjusted to give effect to the Distribution, as if such pro rata distribution on a 1:1 basis occurred as of all pre-IPO Reclassifications Certain reclassifications have been made to prior period amounts to conform to the current period financial statement presentation. The effect of the reclassifications in the December 31, 2020 condensed consolidated balance sheet is a decrease of property, plant & equipment, net and a increase to goodwill and intangibles, net, as of December 31, 2020. The effect of the reclassifications for the nine months ended September 30, 2020 condensed consolidated statement of operations is a $996 decrease of operating revenues, a $397 increase in operating and maintenance expenses and a decrease in royalties, transportation, gathering and production fuel. Use of Estimates The preparation of financial statements, in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Equity-Based Compensation The Company accounts for equity-based compensation under the provisions of ASC 718, Compensation – Stock Compensation ASC 718 Recently Issued Accounting Standards In September 2016, the FASB issued ASU No. 2016-13, Credit Losses In August 2020, the FASB issued ASU 2020-06, Debt: Debt with Conversion and Other Options (Subtopic 470-20) – Contracts in Entity’s Own Equity (Subtopic 815-40) In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848)

Asset Impairment

Asset Impairment	9 Months Ended
	Sep. 30, 2021
Asset Impairment Charges [Abstract]
Asset Impairment	NOTE 3 – ASSET IMPAIRMENT The Company recorded no impairment losses for the three months ended September 30, 2021 and 2020. Impairment losses of $626 and $278 were recorded for the nine months ended September 30, 2021 and 2020, respectively. The 2021 impairment loss was due to a notice received from a landfill host in February 2021 amending the underlying gas rights agreement to remove and begin decommissioning activities related to one of the Company’s renewable electric generation sites. The 2020 impairment loss was due to a termination of a development agreement. The Company evaluated and concluded that no other events or conditions existed during the period that suggested long-lived assets may not be recoverable.

Revenues from Contracts with Cu

Revenues from Contracts with Customers	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenues from Contracts with Customers	NOTE 4 – REVENUES FROM CONTRACTS WITH CUSTOMERS The following tables display the Company’s revenue by major source, excluding realized and unrealized gains or losses under the Company’s gas hedge program, based on product type and timing of transfer of goods and services for the three and nine months ended September 30, 2021 and 2020: Three Months Ended September 30, Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 2,983 $ 8,570 $ 11,553 Natural Gas Environmental Attributes 24,223 — 24,223 Electric Commodity — 2,305 2,305 Electric Environmental Attributes 1,668 — 1,668 $ 28,874 $ 10,875 $ 39,749 Operating Segment: RNG $ 27,206 $ 8,570 $ 35,776 REG 1,668 2,305 3,973 $ 28,874 $ 10,875 $ 39,749 Three Months Ended September 30, Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 1,594 $ 5,951 $ 7,545 Natural Gas Environmental Attributes 16,470 — 16,470 Electric Commodity — 2,492 2,492 Electric Environmental Attributes 1,743 — 1,743 $ 19,807 $ 8,443 $ 28,250 Operating Segment: RNG $ 18,064 $ 5,951 $ 24,015 REG 1,743 2,492 4,235 $ 19,807 $ 8,443 $ 28,250 Nine Months Ended September 30, 2021 Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 13,293 $ 21,620 $ 34,913 Natural Gas Environmental Attributes 56,297 — 56,297 Electric Commodity — 7,150 7,150 Electric Environmental Attributes 4,512 — 4,512 $ 74,102 $ 28,770 $ 102,872 Operating Segment: RNG $ 69,590 $ 21,620 $ 91,210 REG 4,512 7,150 11,662 $ 74,102 $ 28,770 $ 102,872 Nine Months Ended September 30, 2020 Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 4,683 $ 16,958 $ 21,641 Natural Gas Environmental Attributes 39,498 — 39,498 Electric Commodity — 8,035 8,035 Electric Environmental Attributes 5,226 — 5,226 $ 49,407 $ 24,993 $ 74,400 Operating Segment: RNG $ 44,181 $ 16,958 $ 61,139 REG 5,226 8,035 13,261 $ 49,407 $ 24,993 $ 74,400

Accounts and Other Receivables

Accounts and Other Receivables	9 Months Ended
	Sep. 30, 2021
Receivables, Net, Current [Abstract]
Accounts and Other Receivables	NOTE 5 – ACCOUNTS AND OTHER RECEIVABLES The Company extends credit based upon an evaluation of the customer’s financial condition and, while collateral is not required, the Company periodically receives surety bonds that guarantee payment. Credit terms are consistent with industry standards and practices. Reserves for uncollectible accounts, if any, are recorded as part of general and administrative expenses in the Consolidated Statements of Operations (Unaudited). For the three and nine months ended September 30, 2021 and 2020, there were no reserves for uncollectible accounts. Accounts and other receivables consist of the following as of September 30, 2021 and December 31, 2020: September 30, December 31 , Accounts receivables $ 15,188 $ 5,264 Other receivables 94 164 Reimbursable expenses 26 21 Accounts and other receivables, net $ 15,308 $ 5,449

Property, Plant and Equipment,

Property, Plant and Equipment, Net	9 Months Ended
	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Net	NOTE 6 – PROPERTY, PLANT AND EQUIPMENT, NET Property, plant and equipment consists of the following as of September 30, 2021 and December 31, 2020: September 30, December 31 , Buildings and improvements $ 28,251 $ 28,065 Machinery and equipment 249,337 246,874 Gas mineral rights 34,551 34,551 Construction work in progress 8,612 3,840 Total 320,751 313,330 Less: Accumulated depreciation and amortization (141,444 ) (126,929 ) Property, plant & equipment, net $ 179,307 $ 186,401 Depreciation expense for property plant and equipment was $4,839 and $4,623 for the three months ended September 30, 2021 and 2020, respectively, and $14,637 and $13,582 for the nine months ended September 30, 2021 and 2020, respectively. Amortization expense for gas mineral rights was $446 and $491 for the three months ended September 30, 2021 and 2020, respectively, and $1,382 and $1,473 for the nine months ended September 30, 2021 and 2020, respectively. In May 2021, the Company completed a series of transactions (the “Asset Acquisition”) with a privately-held entity. The Company paid $4,142, including $341 in acquisition costs, for land, building, mobile equipment and other property, plant and equipment. The Asset Acquisition was accounted for as an asset purchase in accordance with ASC 805, Business Combinations e 835 of the asset purchase price, with the remaining balance classified as construction work in progress as of September 30, 2021.

Goodwill And Intangible Assets,

Goodwill And Intangible Assets, Net	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill And Intangible Assets, Net	NOTE 7 – GOODWILL AND INTANGIBLE ASSETS, NET Intangible assets consist of the following as of September 30, 2021 and December 31, 2020: September 30, December 31, Goodwill $ 60 $ 60 Intangible assets with indefinite lives: Emissions allowances $ 777 $ 777 Land use rights 329 329 Total intangible assets with indefinite lives: $ 1,106 $ 1,106 Intangible assets with finite lives: Interconnection, net of accumulated amortization of $2,835 and $2,329 $ 12,488 $ 12,596 Customer contracts, net of accumulated amortization of $16,904 and $16,367 1,379 916 Total intangible assets with finite lives: $ 13,867 $ 13,512 Total Goodwill and Intangible Assets $ 15,033 $ 14,678 The weighted average remaining useful life of the customer contracts and interconnection is approximately 8 years and 16 years, respectively. Amortization expense was $381 and $356 for the three months ended September 30, 2021 and 2020, respectively, and $1,043 and $1,065 for the nine months ended September 30, 2021 and 2020, respectively.

Assets Retirement Obligations

Assets Retirement Obligations	9 Months Ended
	Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	NOTE 8 – ASSET RETIREMENT OBLIGATIONS The following table summarizes the activity associated with asset retirement obligations of the Company as of September 30, 2021 and December 31, 2020: Nine Months Ended Year Ended Asset retirement obligations - beginning of period $ 5,689 $ 5,928 Accretion expense 304 320 New asset retirement obligations — 350 Decommissioning (110 ) (909 ) Asset retirement obligations - end of period $ 5,883 $ 5,689

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2021
Derivative Instrument Detail [Abstract]
Derivative Instruments	NOTE 9 – DERIVATIVE INSTRUMENTS To mitigate market risk associated with fluctuations in energy commodity prices (natural gas) and interest rates, the Company utilizes various hedges to secure energy commodity pricing and interest rates under a board-approved program. As a result of the hedging strategy employed, the Company had the following realized and unrealized gains and losses in the Condensed Consolidated Statements of Operations (Unaudited) for the three and nine months ended September 30, 2021 and 2020: Three Months Ended Derivative Instrument Location September 30, September 30, Interest rate swaps Interest expense 287 393 Net gain (loss) $ 287 $ 393 Nine Months Ended Derivative Instrument Location September 30, September 30, Commodity contracts: Realized natural gas Gas commodity sales $ — $ 551 Unrealized natural gas Other income — (388 ) Interest rate swaps Interest expense 1,011 (993 ) Net gain (loss) $ 1,011 $ (830 )

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	NOTE 10 – FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s assets and liabilities that are measured at fair value on a recurring basis include the following as of September 30, 2021 and December 31, 2020, set forth by level, within the fair value hierarchy: September 30, 2021 Level 1 Level 2 Level 3 Total Interest rate swap derivative liabilities $ — $ (1,249 ) $ — $ (1,249 ) Asset retirement obligations — — (5,883 ) (5,883 ) Pico earn-out — — (1,226 ) (1,226 ) $ — $ (1,249 ) $ (7,109 ) $ (8,358 ) December 31, 2020 Level 1 Level 2 Level 3 Total Interest rate swap derivative liabilities $ — $ (2,260 ) $ — $ (2,260 ) Asset retirement obligations — — (5,689 ) (5,689 ) Pico earn-out — — (1,920 ) (1,920 ) $ — $ (2,260 ) $ (7,609 ) $ (9,869 ) A summary of changes in the fair values of the Company’s Level 3 instruments, attributable to asset retirement obligations is included in Note 8 non-recurring The purchase agreement for the 2018 acquisition of Pico Energy, LLC (“Pico”) included an earn-out earn-out

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2021
Payables and Accruals [Abstract]
Accrued Liabilities	NOTE 11 – ACCRUED LIABILITIES The Company’s accrued liabilities consist of the following as of September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Accrued expenses $ 4,710 $ 4,975 Payroll and related benefits 2,204 2,341 Royalty 4,044 2,620 Utility 1,059 1,147 Other 424 456 Accrued Liabilities $ 12,441 $ 11,539

Debt

Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt	NOTE 12 – DEBT The Company’s debt consists of the following as of September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Term loan $ 22,500 $ 30,000 Revolving credit facility 36,697 36,697 Less: current principal maturities (10,000 ) (10,000 ) Less: debt issuance costs (on long-term debt) (174 ) (429 ) Long-term debt 49,023 56,268 Current portion of long-term debt 9,633 9,492 $ 58,656 $ 65,760 Amended Credit Agreement On December 12, 2018, Montauk Energy Holdings LLC (“MEH”) entered into the Second Amended and Restated Revolving Credit and Term Loan Agreement (as amended, “Credit Agreement”), by and among MEH, the financial institutions from time to time party thereto as lenders and Comerica Bank, as the administrative agent, sole lead arranger and sole bookrunner (“Comerica”). The Credit Agreement (i) amended and restated in its entirety MEH’s prior revolving credit and term loan facility, dated as of August 4, 2017, as amended, with Comerica and certain other financial institutions and (ii) replaced in its entirety the prior credit agreement, dated as of August 4, 2017, as amended, between Comerica and Bowerman Power LFG, LLC, a wholly-owned subsidiary of MEH. On March 21, 2019, MEH entered into the first amendment to the Credit Agreement (the “First Amendment”), which clarified a variety of terms, definitions and calculations in the Credit Agreement. The Credit Agreement requires the Company to maintain customary affirmative and negative covenants, including certain financial covenants, which are measured at the end of each fiscal quarter. On September 12, 2019, MEH entered into the second amendment to the Credit Agreement (the “Second Amendment”). Among other matters, the Second Amendment redefined the Fixed Charge Coverage Ratio (as defined in the Credit Agreement), reduced the commitments under the revolving credit facility to $80,000, redefined the Total Leverage Ratio (as defined in the Credit Agreement) and eliminated the RIN Floor (as defined in the Second Amendment) as an Event of Default. In connection with the Second Amendment, MEH paid down the outstanding term loan by $38,250 and the resulting quarterly principal installments were reduced to $2,500. The maturity date of the Credit Agreement was not changed by the Second Amendment and remains December 12, 2023. In connection with the completion of the Reorganization Transactions and the IPO, the Company entered into the third amendment to the Credit Agreement (the “Third Amendment”). This amendment permitted the Change of Control provisions, as defined in the underlying agreement, to permit the Reorganization Transactions and IPO to be completed. The amendment also added LIBOR cessation fallback language for a transition to specified alternative SOFR-based rates, or, if those alternatives cannot be determined, to another rate selected by the administrative agent and the borrower under the Amended Credit Agreement as well as provisions that allow one or more parties to transition in advance of the dates set forth above where specified conditions are met. The Credit Agreement is secured by a lien on substantially all assets of the Company and certain of its subsidiaries and provides for a $95,000 term loan and a $80,000 revolving credit facility. The term loan amortizes in quarterly installments of $2,500 and has a final maturity of December 12, 2023 with interest rates of 2.855% and 2.961% at September 30, 2021 and December 31, 2020, respectively. As of September 30, 2021, $22,500 was outstanding under the term loan and $36,697 was outstanding under the revolving credit facility. In addition, the Company had $3,905 of outstanding letters of credit as of September 30, 2021. Amounts available under the revolving credit facility are reduced by any amounts outstanding under letters of credit. As of September 30, 2021, the Company’s capacity available for borrowing under the revolving credit facility was $39,397. Borrowings of the term loan and revolving credit facility bear interest at the LIBOR rate plus an applicable margin or the Prime Reference Rate plus an applicable margin, as elected by the Company. The Company accounted for the Credit Agreement as a debt modification in accordance with ASC 470, Debt As of September 30, 2021, the Company was in compliance with all applicable financial covenants under the Credit Agreement as amended. Capitalized Interest Capitalized interest was $0 and $322 for the three months ended September 30, 2021 and 2020, respectively, and $0 and $1,056 for the nine months ended September 30, 2021 and 2020, respectively. Interest is capitalized using the borrowing rate for the assets being constructed. Interest capitalized during 2020 was for the construction of two LFG-to-energy

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 13 – INCOME TAXES The Company’s provision for income taxes in interim periods is typically computed by applying the estimated annual effective tax rates to income or loss before income taxes for the period. In addition, non-recurring nine for the three and nine months ended Three Months Ended September 30, 2021 September 30, 2020 Provision (benefit) for income taxes $ (3,481 ) $ 6,266 Effective tax rate (64% ) 150 % Nine Months Ended September 30, 2021 September 30, 2020 Provision (benefit) for income taxes $ 1,286 $ (291 ) Effective tax rate (15 %) (16 %) Income tax expense for the three and nine months ended September 30, 2021 was calculated using the actual year to date effective tax rate. The effective tax rate differs from the U.S. federal statutory rate of 21% primarily due to the current year permanent disallowance of officers’ compensation under Section 162(m) of the Internal Revenue Code of 1986, as amended (the “Code”), of $4,381, partially offset by the favorable impact of the production tax credit of $(1,623). When the net tax expense (benefit) for the three and nine months ended September 30, 2021 is compared to the pre-tax The effective tax rate of (64%) for the three months ended September 30, 2021 was lower than the rate for the three months ended September 30, 2020 of 150% primarily due to the current year disallowance of officers’ compensation under Section 162(m) of the Code. The Company utilized a year to date effective tax rate for tax expense calculated for the three months ended September 30, 2021, which when applied to year to date pre-tax pre-tax The effective tax rate of (15%) for the nine months ended September 30, 2021 was higher than the rate for the nine months ended September 30, 2020 of (16%). The September 30, 2021 rate of (15%) is calculated based on tax expense that is driven by the 162(m) unfavorable permanent adjustment (which was not applicable in the quarter ended September 30, 2020) compared to a pre-tax n connection with the January 1, 2020 dissolution of the Montauk Energy Capital (“MEC”) partnership, which allows all entities under MEC to file as part of the Company’s consolidated federal tax group compared to a pre-tax book income position.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	NOTE 14 – SHARE-BASED COMPENSATION In January 2021, Montauk Renewables undertook the Reorganization Transactions which resulted in the Company owning all of the assets and entities (excluding Montauk USA) through which MNK’s business and operations were conducted. As a result of the Distribution, the options outstanding under MNK’s Employee Share Appreciation Rights Scheme (the “SAR Plan”) were cancelled. The Company recorded $2,050 of accelerated compensation expense in its condensed consolidated statements of operations (unaudited) within general and administrative expenses in connection with the cancellation of the options under the SAR Plan for the nine months ended September 30, 2021. The board of directors of Montauk Renewables adopted the Montauk Renewables, Inc. Equity and Incentive Compensation Plan (“MRI EICP”) in January 2021. Following the closing of the IPO, the board of directors of Montauk Renewables approved the grant of non-qualified will be In connection with the May 2021 Asset Acquisition, 1,250,000 restricted stock awards (“RS Awards”) were granted to two employees of the Company in connection with their respective employment. The RS Awards vest over a five-year period and are subject to the achievement of time and performance based vesting criteria over such period. The performance targets in the RS Awards relate to the attainment of three EBITDA goals as defined in the underlying agreements beginning on or after the third anniversary of the grant date. The Company completed its assessment and no compensation expense for the RS Awards has been recorded for the three and nine months ended September 30, 2021. The grant date fair value of the RS Awards is $11,300. The restricted stock, restricted stock unit and option awards are subject to vesting schedules that commence or conclude, in the case of the option and restricted stock unit awards, on the one-year Options granted under the MRI EICP allow the recipient to receive the Company’s common stock equal to the appreciation in the fair market value of the Company’s common stock between the grant date and the exercise and settlement of options into shares as of the exercise date(s). The fair value of the MRI EICP options was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions (no dividends were expected): Grant Date Risk-free interest rate 0.5 % Expected volatility 32.0 % Expected option life (in years) 5.5 Grant-date fair value $ 3.44 The risk-free interest rate was based on United States Treasury yields in effect at the time of the grant for notes with terms comparable to the awards. The expected option life represents an estimate of the period of time options are expected to remain outstanding based on the mid-point Company recently completed its IPO in January 2021, there is no sufficient stock volatility historical data. The expected volatility was based on the average historical stock price volatility of comparable publicly-traded companies in its industry peer group. The following table summarizes the options, restricted stock and restricted stock units outstanding under the MRI EICP as of September 30, 2021: Restricted Shares Restricted Stock Units Options Number of Weighted Average Number Weighted Average Number Weighted Average End of period - December 31, 2020 — $ — — $ — — $ — Beginning of period - January 1, 2021 — $ — — $ — — $ — Granted 3,519,827 10.43 29,304 11.38 950,214 11.38 Vested (950,214 ) 11.38 — — — — Forfeited — — (1,056 ) 11.38 — — Exercised — — — — — — End of period – September 30, 2021 2,569,613 $ 10.08 28,248 $ 11.38 950,214 $ 11.38 The following table summarizes the options and restricted stock under the SAR Plan as of September 30, 2020: Options Restricted Stock Number of Weighted Average Number of Weighted Average End of period - December 31, 2019 1,872,534 $ 1.18 1,939,200 $ 0.95 Beginning of period - January 1, 2020 1,872,534 $ 1.18 1,939,200 $ 0.95 Granted 924,779 0.90 — — Forfeited (166,666 ) 0.62 — — Exercised (50,000 ) 0.44 — — End of period – September 30, 2020 2,580,647 $ 1.13 1,939,200 $ 0.95

Defined Contribution Plan

Defined Contribution Plan	9 Months Ended
	Sep. 30, 2021
Retirement Benefits [Abstract]
Defined Contribution Plan	NOTE 15 – DEFINED CONTRIBUTION PLAN The Company maintains a 401(k) defined contribution plan for eligible employees. The Company matches 50% of an employee’s deferrals up to 4%. The Company also contributes 3% of eligible employee’s compensation expense as a safe harbor contribution. The matching contributions vest ratably over four years of service, while the safe harbor contributions vest immediately. Incurred expense related to the 401(k) plan was $145 and $119 for the three months ended September 30, 2021 and 2020, respectively, and $414 and $340 for the nine months ended September 30, 2021 and 2020, respectively.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Segment Information	NOTE 16 – SEGMENT INFORMATION The Company’s reportable segments for the three and nine months ended September 30, 2021 and 2020 are Renewable Natural Gas and Renewable Electricity Generation. Renewable Natural Gas includes the production of RNG. Renewable Electricity Generation includes generation of electricity at biogas-to-electricity Three Months Ended September 30, 2021 RNG REG Corporate Total Total Revenue $ 35,002 $ 3,872 $ 875 $ 39,749 Net income (loss) 15,071 (1,379 ) (4,796 ) 8,896 EBITDA ( 1 19,358 (44 ) (7,536 ) 11,778 Adjusted EBITDA (1) 20,180 (24 ) (7,324 ) 12,832 Total Assets 153,108 53,711 52,926 259,745 Capital expenditure 1,864 1,321 49 3,234 (1) Third quarter of 2021 EBITDA Reconciliation T Three Months Ended September 30, 2021 RNG REG Corporate Total Net income (loss) $ 15,071 $ (1,379 ) $ (4,796 ) $ 8,896 Depreciation and amortization 4,287 1,335 44 5,666 Interest expense — — 697 697 Income tax expense (benefit) — — (3,481 ) (3,481 ) EBITDA $ 19,358 $ (44 ) $ (7,536 ) $ 11,778 Net loss (gain) of sale of assets 822 — — 822 Impairment loss — — — — Transaction costs — 20 212 232 Adjusted EBITDA $ 20,180 $ (24 ) $ (7,324 ) $ 12,832 Three Months Ended September 30, 2020 RNG REG Corporate Total Total Revenue $ 23,994 $ 4,256 $ — $ 28,250 Net Income (Loss) 9,458 (661 ) (10,881 ) (2,084 ) EBITDA ( 1 12,939 1,282 (4,133 ) 10,088 Adjusted EBITDA (1) 12,939 1,282 (4,133 ) 10,088 Total Assets 135,359 80,485 35,683 251,527 Capital expenditure 3,147 1,311 - 4,458 (1) Third quarter of 2020 EBITDA Reconciliation The following table is a reconciliation of the Company’s reportable segments’ net income (loss) from continuing operations to Adjusted EBITDA for the three months ended September 30, 2020: Three Months Ended September 30, 2020 RNG REG Corporate Total Net Income (loss) $ 9,458 $ (661 ) $ (10,881 ) $ (2,084 ) Depreciation and amortization 3,481 1,943 46 5,470 Interest expense — — 436 436 Income tax expense (benefit) — — 6,266 6,266 EBITDA $ 12,939 $ 1,282 $ (4,133 ) $ 10,088 Impairment loss — — — — Non-cash — — — — Adjusted EBITDA $ 12,939 $ 1,282 $ (4,133 ) $ 10,088 For the three months ended September 30, 2021 and 2020, three and four customers, respectively, made up greater than 10% of total revenues. Three Months Ended September 30, 2021 RNG REG Corporate Total Customer A 19.6 % — — 19.6 % Customer B 15.4 % — — 15.4 % Customer C 11.4 % — — 11.4 % Three Months Ended September 30, 202 0 RNG REG Corporate Total Customer A 27.5 % — — 27.5 % Customer B 16.5 % — — 16.5 % Customer C - 13.4 % — 13.4 % Customer D 13.3 % 13.3 % The Company’s reportable segments for the nine months ended September 30, 2021 and 2020 are Renewable Natural Gas and Renewable Electricity Generation. Nine Months Ended September 30, 2021 RNG REG Corporate Total Total Revenue $ 90,707 $ 11,290 $ 875 $ 102,872 Net Income (Loss) 33,205 (3,647 ) (39,579 ) (10,021 ) EBITDA ( 2 45,991 498 (36,098 ) 10,391 Adjusted EBITDA (2) 46,813 1,144 (35,761 ) 12,196 Total Assets 153,108 53,711 52,926 259,745 Capital Expenditure 5,883 1,770 49 7,702 (2) First nine months of 2021 EBITDA Reconciliation The following table is a reconciliation of the Company’s reportable segments’ net income (loss) from continuing operations to Adjusted EBITDA for the nine months ended September 30, 2021: Nine Months Ended September 30, 2021 RNG REG Corporate Total Net Income (loss) $ 33,205 $ (3,647 ) $ (39,579 ) $ (10,021 ) Depreciation and amortization 12,786 4,143 133 17,062 Interest expense — — 2,064 2,064 Income tax expense (benefit) — 2 1,284 1,286 EBITDA $ 45,991 $ 498 $ (36,098 ) $ 10,391 Net loss (gain) of sale of assets 822 822 Impairment loss — 626 — 626 Transaction costs — 20 337 357 Adjusted EBITDA $ 46,813 $ 1,144 $ (35,761 ) $ 12,196 Nine Months Ended September 30, 2020 RNG REG Corporate Total Total Revenue $ 60,799 $ 13,282 $ 482 $ 74,563 Net Income (Loss) 18,700 (1,955 ) (14,598 ) 2,147 EBITDA ( 2 29,100 3,634 (11,248 ) 21,486 Adjusted EBITDA (2) 29,100 3,912 (10,860 ) 22,152 Total Assets 135,359 80,485 35,683 251,527 Capital Expenditure 11,493 3,360 58 14,911 (2) First nine months of 2020 EBITDA Reconciliation The following table is a reconciliation of the Company’s reportable segments’ net income (loss) from continuing operations to Adjusted EBITDA for the nine months ended September 30, 2020: Nine Months Ended September 30, 2020 RNG REG Corporate Total Net Income (loss) $ 18,700 $ (1,955 ) $ (14,598 ) $ 2,147 Depreciation and amortization 10,400 5,587 133 16,120 Interest expense — — 3,510 3,510 Income tax expense (benefit) — 2 (293 ) (291 ) EBITDA $ 29,100 $ 3,634 $ (11,248 ) $ 21,486 Impairment loss — 278 — 278 Non-cash — — 388 388 Adjusted EBITDA $ 29,100 $ 3,912 $ (10,860 ) $ 22,152 For the nine months ended September 30, 2021 and 2020, five and four customers, respectively, made up greater than 10% of total revenues. Nine Months Ended September 30, 2021 RNG REG Corporate Total Customer A 12.8 % — — 12.8 % Customer B 12.4 % — — 12.4 % Customer C 11.3 % — — 11.3 % Customer D 10.5 % — — 10.5 % Customer E 10.2 % — 10.2 % Nine Months Ended September 30, 2020 RNG REG Corporate Total Customer A — 15.2 % — 15.2 % Customer B 14.7 % — — 14.7 % Customer C 12.4 % — — 12.4 % Customer D 12.0 % — — 12.0 %

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	NOTE 17 – LEASES The Company leases office space and other office equipment under operating lease arrangements (with initial terms greater than twelve months), expiring in various years through 2024. These leases have been entered into to better enable the Company to conduct business operations. Office space is leased to provide adequate workspace for all employees in Pittsburgh, Pennsylvania and Houston, Texas. The Company determines if an arrangement is, or contains, a lease at inception based on whether that contract conveys the right to control the use of an identified asset in exchange for consideration for a period of time. For all operating lease arrangements, the Company presents at the commencement date: a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use The Company has elected, as a practical expedient, not to separate non-lease The Company uses its incremental borrowing rate as the basis to calculate the present value of future lease payments at lease commencement. The incremental borrowing rate approximates the rate to borrow funds on a collateralized basis over a similar term and in a similar economic environment. As of September 30, 2021, there were no leases entered into which have not yet commenced and that would entitle the Company to significant rights or create additional obligations. Supplemental information related to operating lease arrangements was as follows: Three Months Ended 2021 2020 Cash paid for amounts included in the measurement of operating lease liabilities $ 76 $ 75 Weighted average remaining lease term (in years) 1.83 2.35 Weighted average discount rate 5.00 % 5.00 % Nine Months Ended 2021 2020 Cash paid for amounts included in the measurement of operating lease liabilities $ 227 $ 225 Weighted average remaining lease term (in years) 1.83 2.35 Weighted average discount rate 5.00 % 5.00 % Future minimum lease payments as of September 30, 2021, are as follows: Amount Year Ending Remainder of 2021 $ 78 2022 319 2023 8 2024 1 Interest (10 ) Total $ 396

Earnings (loss) per share

Earnings (loss) per share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Earnings (loss) per share	NOTE 18 – EARNINGS (LOSS) PER SHARE Earnings (Loss) per share was computed using the following common share data for the three and nine months ended September 30, 2021: Three Months Ended Net income $ 8,896 Basic weighted-average shares outstanding 141,015,213 Dilutive effect of share-based awards 32,793 Diluted weighted-average shares outstanding 141,048,006 Basic earnings per share $ 0.06 Diluted earnings per share $ 0.06 Nine Months Ended Net loss $ (10,021 ) Basic weighted-average shares outstanding 141,015,213 Dilutive effect of share-based awards — Diluted weighted-average shares outstanding 141,015,213 Basic loss per share $ (0.07 ) Diluted loss per share $ (0.07 ) As a result of incurring a net loss for the nine months ended September 30, 2021 , 493,166

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	NOTE 19 – RELATED PARTY TRANSACTIONS In connection with the Distribution, the Company loaned MNK $7,140, in the aggregate, which is recorded in the condensed consolidated balance sheet within related party receivable, for its dividends tax liability arising under the South African Income Tax Act, 1962, as amended. As security for this loan, MNK has pledged certain of its shares in the Company to Montauk Renewables and agreed to use the proceeds from the sale of such shares to repay this loan.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	NOTE 20 – SUBSEQUENT EVENTS The Company evaluated its September 30, 2021 unaudited condensed consolidated financial statements through November 15, 2021, the date the financial statements were issued. The Company is not aware of any subsequent events which would require disclosure in the unaudited condensed consolidated financial statements, except for the matters discussed below. In October 2021, the Company closed on a $5,447 transaction to acquire approximately 146 acres and an existing approximately 500,000 square foot structure intended to expand the production processes acquired in the Montauk Ag Asset Acquisition.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with the instructions of the SEC on Form 10-Q 10-01 S-X. 10-K The historical consolidated financial information included reflects the historical results of operations and financial position of Montauk USA. The consolidated financial statements of Montauk USA became the Company’s historical financial statements following the IPO. Certain historical financial information included relates to periods prior to the Reorganization Transactions.
Retrospective Presentation of Ownership Related to the Reorganization Transactions	Retrospective Presentation of Ownership Related to the Reorganization Transactions As discussed in Note 1, as a result of the Reorganization Transactions, the Company acquired the assets and entities (excluding Montauk USA) which were previously owned by MNK. As part of the Reorganization Transactions, a 1:1 pro rata distribution of shares of the Company’s common stock was made to holders of MNK’s ordinary shares. The Reorganization Transactions resulted in a pro rata distribution whereby the ownership of the Company after the Reorganization Transactions was identical to the ownership of MNK prior to the Reorganization Transaction and was therefore akin to a common control transaction. All members’ equity in the financial statements and notes have been retrospectively adjusted to give effect to the Distribution, as if such pro rata distribution on a 1:1 basis occurred as of all pre-IPO
Reclassifications	Reclassifications Certain reclassifications have been made to prior period amounts to conform to the current period financial statement presentation. The effect of the reclassifications in the December 31, 2020 condensed consolidated balance sheet is a decrease of property, plant & equipment, net and a increase to goodwill and intangibles, net, as of December 31, 2020. The effect of the reclassifications for the nine months ended September 30, 2020 condensed consolidated statement of operations is a $996 decrease of operating revenues, a $397 increase in operating and maintenance expenses and a decrease in royalties, transportation, gathering and production fuel.
Use of Estimates	Use of Estimates The preparation of financial statements, in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Equity-Based Compensation	Equity-Based Compensation The Company accounts for equity-based compensation under the provisions of ASC 718, Compensation – Stock Compensation ASC 718
Recently Issued Accounting Standards	Recently Issued Accounting Standards In September 2016, the FASB issued ASU No. 2016-13, Credit Losses In August 2020, the FASB issued ASU 2020-06, Debt: Debt with Conversion and Other Options (Subtopic 470-20) – Contracts in Entity’s Own Equity (Subtopic 815-40) In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848)

Revenues from Contracts with _2

Revenues from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Summary of Company's Revenue by Major Source	The following tables display the Company’s revenue by major source, excluding realized and unrealized gains or losses under the Company’s gas hedge program, based on product type and timing of transfer of goods and services for the three and nine months ended September 30, 2021 and 2020: Three Months Ended September 30, Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 2,983 $ 8,570 $ 11,553 Natural Gas Environmental Attributes 24,223 — 24,223 Electric Commodity — 2,305 2,305 Electric Environmental Attributes 1,668 — 1,668 $ 28,874 $ 10,875 $ 39,749 Operating Segment: RNG $ 27,206 $ 8,570 $ 35,776 REG 1,668 2,305 3,973 $ 28,874 $ 10,875 $ 39,749 Three Months Ended September 30, Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 1,594 $ 5,951 $ 7,545 Natural Gas Environmental Attributes 16,470 — 16,470 Electric Commodity — 2,492 2,492 Electric Environmental Attributes 1,743 — 1,743 $ 19,807 $ 8,443 $ 28,250 Operating Segment: RNG $ 18,064 $ 5,951 $ 24,015 REG 1,743 2,492 4,235 $ 19,807 $ 8,443 $ 28,250 Nine Months Ended September 30, 2021 Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 13,293 $ 21,620 $ 34,913 Natural Gas Environmental Attributes 56,297 — 56,297 Electric Commodity — 7,150 7,150 Electric Environmental Attributes 4,512 — 4,512 $ 74,102 $ 28,770 $ 102,872 Operating Segment: RNG $ 69,590 $ 21,620 $ 91,210 REG 4,512 7,150 11,662 $ 74,102 $ 28,770 $ 102,872 Nine Months Ended September 30, 2020 Goods Goods Total Major Goods/Service Line: Natural Gas Commodity $ 4,683 $ 16,958 $ 21,641 Natural Gas Environmental Attributes 39,498 — 39,498 Electric Commodity — 8,035 8,035 Electric Environmental Attributes 5,226 — 5,226 $ 49,407 $ 24,993 $ 74,400 Operating Segment: RNG $ 44,181 $ 16,958 $ 61,139 REG 5,226 8,035 13,261 $ 49,407 $ 24,993 $ 74,400

Accounts and Other Receivables

Accounts and Other Receivables (Tables)	9 Months Ended
	Sep. 30, 2021
Receivables, Net, Current [Abstract]
Schedule of Accounts and Other Receivables	Accounts and other receivables consist of the following as of September 30, 2021 and December 31, 2020: September 30, December 31 , Accounts receivables $ 15,188 $ 5,264 Other receivables 94 164 Reimbursable expenses 26 21 Accounts and other receivables, net $ 15,308 $ 5,449

Property, Plant and Equipment_2

Property, Plant and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Summary of Property Plant and Equipment	Property, plant and equipment consists of the following as of September 30, 2021 and December 31, 2020: September 30, December 31 , Buildings and improvements $ 28,251 $ 28,065 Machinery and equipment 249,337 246,874 Gas mineral rights 34,551 34,551 Construction work in progress 8,612 3,840 Total 320,751 313,330 Less: Accumulated depreciation and amortization (141,444 ) (126,929 ) Property, plant & equipment, net $ 179,307 $ 186,401

Goodwill And Intangible Asset_2

Goodwill And Intangible Assets, Net (Tables)	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
schedule of Intangible Assets	Intangible assets consist of the following as of September 30, 2021 and December 31, 2020: September 30, December 31, Goodwill $ 60 $ 60 Intangible assets with indefinite lives: Emissions allowances $ 777 $ 777 Land use rights 329 329 Total intangible assets with indefinite lives: $ 1,106 $ 1,106 Intangible assets with finite lives: Interconnection, net of accumulated amortization of $2,835 and $2,329 $ 12,488 $ 12,596 Customer contracts, net of accumulated amortization of $16,904 and $16,367 1,379 916 Total intangible assets with finite lives: $ 13,867 $ 13,512 Total Goodwill and Intangible Assets $ 15,033 $ 14,678

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Summary of Activity Associated with Asset Retirement Obligations	The following table summarizes the activity associated with asset retirement obligations of the Company as of September 30, 2021 and December 31, 2020: Nine Months Ended Year Ended Asset retirement obligations - beginning of period $ 5,689 $ 5,928 Accretion expense 304 320 New asset retirement obligations — 350 Decommissioning (110 ) (909 ) Asset retirement obligations - end of period $ 5,883 $ 5,689

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Derivative Instrument Detail [Abstract]
Summary of Realized and Unrealized Gains and Losses of Derivative Instrument	As a result of the hedging strategy employed, the Company had the following realized and unrealized gains and losses in the Condensed Consolidated Statements of Operations (Unaudited) for the three and nine months ended September 30, 2021 and 2020: Three Months Ended Derivative Instrument Location September 30, September 30, Interest rate swaps Interest expense 287 393 Net gain (loss) $ 287 $ 393 Nine Months Ended Derivative Instrument Location September 30, September 30, Commodity contracts: Realized natural gas Gas commodity sales $ — $ 551 Unrealized natural gas Other income — (388 ) Interest rate swaps Interest expense 1,011 (993 ) Net gain (loss) $ 1,011 $ (830 )

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Assets and Liabilities that are Measured at Fair Value on a Recurring Basis	The Company’s assets and liabilities that are measured at fair value on a recurring basis include the following as of September 30, 2021 and December 31, 2020, set forth by level, within the fair value hierarchy: September 30, 2021 Level 1 Level 2 Level 3 Total Interest rate swap derivative liabilities $ — $ (1,249 ) $ — $ (1,249 ) Asset retirement obligations — — (5,883 ) (5,883 ) Pico earn-out — — (1,226 ) (1,226 ) $ — $ (1,249 ) $ (7,109 ) $ (8,358 ) December 31, 2020 Level 1 Level 2 Level 3 Total Interest rate swap derivative liabilities $ — $ (2,260 ) $ — $ (2,260 ) Asset retirement obligations — — (5,689 ) (5,689 ) Pico earn-out — — (1,920 ) (1,920 ) $ — $ (2,260 ) $ (7,609 ) $ (9,869 )

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Payables and Accruals [Abstract]
Summary of Accrued Liabilities	The Company’s accrued liabilities consist of the following as of September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Accrued expenses $ 4,710 $ 4,975 Payroll and related benefits 2,204 2,341 Royalty 4,044 2,620 Utility 1,059 1,147 Other 424 456 Accrued Liabilities $ 12,441 $ 11,539

Debt (Table)

Debt (Table)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Summary of Company Debt	The Company’s debt consists of the following as of September 30, 2021 and December 31, 2020: September 30, 2021 December 31, 2020 Term loan $ 22,500 $ 30,000 Revolving credit facility 36,697 36,697 Less: current principal maturities (10,000 ) (10,000 ) Less: debt issuance costs (on long-term debt) (174 ) (429 ) Long-term debt 49,023 56,268 Current portion of long-term debt 9,633 9,492 $ 58,656 $ 65,760

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The Company’s provision for income taxes in interim periods is typically computed by applying the estimated annual effective tax rates to income or loss before income taxes for the period. In addition, non-recurring nine for the three and nine months ended Three Months Ended September 30, 2021 September 30, 2020 Provision (benefit) for income taxes $ (3,481 ) $ 6,266 Effective tax rate (64% ) 150 % Nine Months Ended September 30, 2021 September 30, 2020 Provision (benefit) for income taxes $ 1,286 $ (291 ) Effective tax rate (15 %) (16 %)

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Summary of Fair Value of MRI EICP Options and Valuation Assumptions	The fair value of the MRI EICP options was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions (no dividends were expected): Grant Date Risk-free interest rate 0.5 % Expected volatility 32.0 % Expected option life (in years) 5.5 Grant-date fair value $ 3.44
Summary of Outstanding Activity of Options,Restricted Stock and Restricted Stock Units under MRI EICP	The following table summarizes the options, restricted stock and restricted stock units outstanding under the MRI EICP as of September 30, 2021: Restricted Shares Restricted Stock Units Options Number of Weighted Average Number Weighted Average Number Weighted Average End of period - December 31, 2020 — $ — — $ — — $ — Beginning of period - January 1, 2021 — $ — — $ — — $ — Granted 3,519,827 10.43 29,304 11.38 950,214 11.38 Vested (950,214 ) 11.38 — — — — Forfeited — — (1,056 ) 11.38 — — Exercised — — — — — — End of period – September 30, 2021 2,569,613 $ 10.08 28,248 $ 11.38 950,214 $ 11.38
Summary of Outstanding Activity of Options and Restricted Stock under SAR Plan	The following table summarizes the options and restricted stock under the SAR Plan as of September 30, 2020: Options Restricted Stock Number of Weighted Average Number of Weighted Average End of period - December 31, 2019 1,872,534 $ 1.18 1,939,200 $ 0.95 Beginning of period - January 1, 2020 1,872,534 $ 1.18 1,939,200 $ 0.95 Granted 924,779 0.90 — — Forfeited (166,666 ) 0.62 — — Exercised (50,000 ) 0.44 — — End of period – September 30, 2020 2,580,647 $ 1.13 1,939,200 $ 0.95

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Summary of Reconciliation of the Company's Reportable Segments' Net Income from Continuing Operations	The following tables are consistent with the manner in which the chief operating decision maker evaluates the performance of each segment and allocates the Company’s resources. In the following tables “RNG” refers to Renewable Natural Gas and “REG” refer to Renewable Electricity Generation. Three Months Ended September 30, 2021 RNG REG Corporate Total Total Revenue $ 35,002 $ 3,872 $ 875 $ 39,749 Net income (loss) 15,071 (1,379 ) (4,796 ) 8,896 EBITDA ( 1 19,358 (44 ) (7,536 ) 11,778 Adjusted EBITDA (1) 20,180 (24 ) (7,324 ) 12,832 Total Assets 153,108 53,711 52,926 259,745 Capital expenditure 1,864 1,321 49 3,234 (1) Third quarter of 2021 EBITDA Reconciliation T Three Months Ended September 30, 2021 RNG REG Corporate Total Net income (loss) $ 15,071 $ (1,379 ) $ (4,796 ) $ 8,896 Depreciation and amortization 4,287 1,335 44 5,666 Interest expense — — 697 697 Income tax expense (benefit) — — (3,481 ) (3,481 ) EBITDA $ 19,358 $ (44 ) $ (7,536 ) $ 11,778 Net loss (gain) of sale of assets 822 — — 822 Impairment loss — — — — Transaction costs — 20 212 232 Adjusted EBITDA $ 20,180 $ (24 ) $ (7,324 ) $ 12,832 Three Months Ended September 30, 2020 RNG REG Corporate Total Total Revenue $ 23,994 $ 4,256 $ — $ 28,250 Net Income (Loss) 9,458 (661 ) (10,881 ) (2,084 ) EBITDA ( 1 12,939 1,282 (4,133 ) 10,088 Adjusted EBITDA (1) 12,939 1,282 (4,133 ) 10,088 Total Assets 135,359 80,485 35,683 251,527 Capital expenditure 3,147 1,311 - 4,458 (1) Third quarter of 2020 EBITDA Reconciliation The following table is a reconciliation of the Company’s reportable segments’ net income (loss) from continuing operations to Adjusted EBITDA for the three months ended September 30, 2020: Three Months Ended September 30, 2020 RNG REG Corporate Total Net Income (loss) $ 9,458 $ (661 ) $ (10,881 ) $ (2,084 ) Depreciation and amortization 3,481 1,943 46 5,470 Interest expense — — 436 436 Income tax expense (benefit) — — 6,266 6,266 EBITDA $ 12,939 $ 1,282 $ (4,133 ) $ 10,088 Impairment loss — — — — Non-cash — — — — Adjusted EBITDA $ 12,939 $ 1,282 $ (4,133 ) $ 10,088 The Company’s reportable segments for the nine months ended September 30, 2021 and 2020 are Renewable Natural Gas and Renewable Electricity Generation. Nine Months Ended September 30, 2021 RNG REG Corporate Total Total Revenue $ 90,707 $ 11,290 $ 875 $ 102,872 Net Income (Loss) 33,205 (3,647 ) (39,579 ) (10,021 ) EBITDA ( 2 45,991 498 (36,098 ) 10,391 Adjusted EBITDA (2) 46,813 1,144 (35,761 ) 12,196 Total Assets 153,108 53,711 52,926 259,745 Capital Expenditure 5,883 1,770 49 7,702 (2) First nine months of 2021 EBITDA Reconciliation The following table is a reconciliation of the Company’s reportable segments’ net income (loss) from continuing operations to Adjusted EBITDA for the nine months ended September 30, 2021: Nine Months Ended September 30, 2021 RNG REG Corporate Total Net Income (loss) $ 33,205 $ (3,647 ) $ (39,579 ) $ (10,021 ) Depreciation and amortization 12,786 4,143 133 17,062 Interest expense — — 2,064 2,064 Income tax expense (benefit) — 2 1,284 1,286 EBITDA $ 45,991 $ 498 $ (36,098 ) $ 10,391 Net loss (gain) of sale of assets 822 822 Impairment loss — 626 — 626 Transaction costs — 20 337 357 Adjusted EBITDA $ 46,813 $ 1,144 $ (35,761 ) $ 12,196 Nine Months Ended September 30, 2020 RNG REG Corporate Total Total Revenue $ 60,799 $ 13,282 $ 482 $ 74,563 Net Income (Loss) 18,700 (1,955 ) (14,598 ) 2,147 EBITDA ( 2 29,100 3,634 (11,248 ) 21,486 Adjusted EBITDA (2) 29,100 3,912 (10,860 ) 22,152 Total Assets 135,359 80,485 35,683 251,527 Capital Expenditure 11,493 3,360 58 14,911 (2) First nine months of 2020 EBITDA Reconciliation The following table is a reconciliation of the Company’s reportable segments’ net income (loss) from continuing operations to Adjusted EBITDA for the nine months ended September 30, 2020: Nine Months Ended September 30, 2020 RNG REG Corporate Total Net Income (loss) $ 18,700 $ (1,955 ) $ (14,598 ) $ 2,147 Depreciation and amortization 10,400 5,587 133 16,120 Interest expense — — 3,510 3,510 Income tax expense (benefit) — 2 (293 ) (291 ) EBITDA $ 29,100 $ 3,634 $ (11,248 ) $ 21,486 Impairment loss — 278 — 278 Non-cash — — 388 388 Adjusted EBITDA $ 29,100 $ 3,912 $ (10,860 ) $ 22,152
Summary of Revenue by Major Customers	For the three months ended September 30, 2021 and 2020, three and four customers, respectively, made up greater than 10% of total revenues. Three Months Ended September 30, 2021 RNG REG Corporate Total Customer A 19.6 % — — 19.6 % Customer B 15.4 % — — 15.4 % Customer C 11.4 % — — 11.4 % Three Months Ended September 30, 202 0 RNG REG Corporate Total Customer A 27.5 % — — 27.5 % Customer B 16.5 % — — 16.5 % Customer C - 13.4 % — 13.4 % Customer D 13.3 % 13.3 % For the nine months ended September 30, 2021 and 2020, five and four customers, respectively, made up greater than 10% of total revenues. Nine Months Ended September 30, 2021 RNG REG Corporate Total Customer A 12.8 % — — 12.8 % Customer B 12.4 % — — 12.4 % Customer C 11.3 % — — 11.3 % Customer D 10.5 % — — 10.5 % Customer E 10.2 % — 10.2 % Nine Months Ended September 30, 2020 RNG REG Corporate Total Customer A — 15.2 % — 15.2 % Customer B 14.7 % — — 14.7 % Customer C 12.4 % — — 12.4 % Customer D 12.0 % — — 12.0 %

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Summary of Supplemental Information Related To Operating Leases	Supplemental information related to operating lease arrangements was as follows: Three Months Ended 2021 2020 Cash paid for amounts included in the measurement of operating lease liabilities $ 76 $ 75 Weighted average remaining lease term (in years) 1.83 2.35 Weighted average discount rate 5.00 % 5.00 % Nine Months Ended 2021 2020 Cash paid for amounts included in the measurement of operating lease liabilities $ 227 $ 225 Weighted average remaining lease term (in years) 1.83 2.35 Weighted average discount rate 5.00 % 5.00 %
Summary of Future Minimum Lease Payments	Future minimum lease payments as of September 30, 2021, are as follows: Amount Year Ending Remainder of 2021 $ 78 2022 319 2023 8 2024 1 Interest (10 ) Total $ 396

Earnings (loss) per share (Tabl

Earnings (loss) per share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Basic loss per share	Earnings (Loss) per share was computed using the following common share data for the three and nine months ended September 30, 2021: Three Months Ended Net income $ 8,896 Basic weighted-average shares outstanding 141,015,213 Dilutive effect of share-based awards 32,793 Diluted weighted-average shares outstanding 141,048,006 Basic earnings per share $ 0.06 Diluted earnings per share $ 0.06 Nine Months Ended Net loss $ (10,021 ) Basic weighted-average shares outstanding 141,015,213 Dilutive effect of share-based awards — Diluted weighted-average shares outstanding 141,015,213 Basic loss per share $ (0.07 ) Diluted loss per share $ (0.07 )

Description of Business - Addit

Description of Business - Additional Information (Detail) $ / shares in Units, $ in Thousands	Jan. 26, 2021USD ($)$ / sharesshares	Sep. 30, 2021	Sep. 30, 2020USD ($)	Feb. 22, 2021USD ($)
Number of years of experience		30 years
Number of current operations		15
Percent of greenhouse gas reduction requirement		60.00%
Sale of stock, Number of shares issued in transaction | shares	2,702,500
Sale of stock, price per share | $ / shares	$ 8.50
Sale of stock, Consideration received on transaction	$ 22,971
Cash loan	$ 5,000		$ 8,500
Principal amount of loan				$ 7,140

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounting Policies [Line Items]
Exchange of shares of the company's common stock	1
Pro rata exchange occurred as of all pre-IPO periods presented	1
Property, plant and equipment, net	$ 179,307	$ 186,401
Intangible Assets, Net (Including Goodwill)	15,033	14,678
Decrease to total operating revenues	996
Increase in operating and maintenance expenses	397
Revision of Prior Period, Reclassification, Adjustment [Member] | Minimum [Member]
Accounting Policies [Line Items]
Property, plant and equipment, net		645
Intangible Assets, Net (Including Goodwill)		$ 645
Decrease to royalties, transportation, gathering and production fuel	$ 1,393

Asset Impairment - Additional I

Asset Impairment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Asset Impairment Charges [Abstract]
Impairment loss	$ 0	$ 0	$ 626	$ 278

Revenues from Contracts with _3

Revenues from Contracts with Customers - Summary of Company's Revenue by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 39,749	$ 28,250	$ 102,872	$ 74,400
RNG [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	35,776	24,015	91,210	61,139
REG [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	3,973	4,235	11,662	13,261
Natural Gas Commodity [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	11,553	7,545	34,913	21,641
Natural Gas Environmental Attributes [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	24,223	16,470	56,297	39,498
Electric Commodity [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,305	2,492	7,150	8,035
Electric Environmental Attributes [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,668	1,743	4,512	5,226
Goods transferred at a point in time [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	28,874	19,807	74,102	49,407
Goods transferred at a point in time [Member] | RNG [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	27,206	18,064	69,590	44,181
Goods transferred at a point in time [Member] | REG [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,668	1,743	4,512	5,226
Goods transferred at a point in time [Member] | Natural Gas Commodity [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,983	1,594	13,293	4,683
Goods transferred at a point in time [Member] | Natural Gas Environmental Attributes [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	24,223	16,470	56,297	39,498
Goods transferred at a point in time [Member] | Electric Environmental Attributes [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,668	1,743	4,512	5,226
Goods transferred over time [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	10,875	8,443	28,770	24,993
Goods transferred over time [Member] | RNG [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	8,570	5,951	21,620	16,958
Goods transferred over time [Member] | REG [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,305	2,492	7,150	8,035
Goods transferred over time [Member] | Natural Gas Commodity [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	8,570	5,951	21,620	16,958
Goods transferred over time [Member] | Electric Commodity [Member]
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 2,305	$ 2,492	$ 7,150	$ 8,035

Accounts and Other Receivable_2

Accounts and Other Receivables - Schedule of Accounts and Other Receivables (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Receivables, Net, Current [Abstract]
Accounts receivables	$ 15,188	$ 5,264
Other receivables	94	164
Reimbursable expenses	26	21
Accounts and other receivables, net	$ 15,308	$ 5,449

Property, Plant and Equipment_3

Property, Plant and Equipment, Net - Summary of Property Plant and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 320,751	$ 313,330
Less: Accumulated depreciation and amortization	(141,444)	(126,929)
Property, plant & equipment, net	179,307	186,401
Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	28,251	28,065
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	249,337	246,874
Gas mineral rights [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	34,551	34,551
Construction work in progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 8,612	$ 3,840

Property, Plant and Equipment_4

Property, Plant and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	May 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Depreciation expense		$ 4,839	$ 4,623	$ 14,637	$ 13,582
Payments to Acquire Property, Plant, and Equipment	$ 4,142
Capitalized acquisition costs	$ 341
Gas mineral rights [Member]
Property, Plant and Equipment [Line Items]
Adjustment for amortization		446	$ 491	1,382	$ 1,473
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Capitalized acquisition costs		$ 835		$ 835

Goodwill And Intangible Asset_3

Goodwill And Intangible Assets, Net - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Intangible Assets And Goodwill [Line Items]
Goodwill	$ 60	$ 60
Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract]
Intangible assets with indefinite lives	1,106	1,106
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with finite lives	13,867	13,512
Total Goodwill and Intangible Assets	15,033	14,678
Interconnection [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with finite lives	12,488	12,596
Customer Contracts [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets with finite lives	1,379	916
Emissions Allowances [Member]
Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract]
Intangible assets with indefinite lives	777	777
Land Use Rights [Member]
Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract]
Intangible assets with indefinite lives	$ 329	$ 329

Goodwill And Intangible Asset_4

Goodwill And Intangible Assets, Net - Schedule of Intangible Assets (Detail) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Interconnection [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Finite lived intangible assets accumulated amortization	$ 2,835	$ 2,329
Customer Contracts [Member]
Schedule Of Intangible Assets And Goodwill [Line Items]
Finite lived intangible assets accumulated amortization	$ 16,904	$ 16,367

Goodwill And Intangible Asset_5

Goodwill And Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 381	$ 356	$ 1,043	$ 1,065
Customer Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible asset useful life	8 years
Interconnection [Member]
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible asset useful life	16 years

Assets Retirement Obligations -

Assets Retirement Obligations - Summary of Activity Associated with Asset Retirement Obligations (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligations - beginning of period	$ 5,689	$ 5,928
Accretion expense	304	320
New asset retirement obligations	0	350
Decommissioning	(110)	(909)
Asset retirement obligations - end of period	$ 5,883	$ 5,689

Derivative Instruments - Summar

Derivative Instruments - Summary of Realized and Unrealized Gains and Losses of Derivative Instrument (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative [Line Items]
Net gain (loss)	$ 287	$ 393	$ 1,011	$ (830)
Commodity Contract [Member] | Natural Gas and Natural Gas Liquids [Member] | Sales [Member]
Derivative [Line Items]
Net gain (loss)			0	551
Commodity Contract [Member] | Natural Gas and Natural Gas Liquids [Member] | Other Income [Member]
Derivative [Line Items]
Net gain (loss)			0	(388)
Interest Rate Swap [Member] | Interest Expense [Member]
Derivative [Line Items]
Net gain (loss)	$ 287	$ 393	$ 1,011	$ (993)

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset retirement obligations	$ (5,883)	$ (5,689)	$ (5,928)
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap derivative liabilities	(1,249)	(2,260)
Asset retirement obligations	(5,883)	(5,689)
Pico earn-out liability	(1,226)	(1,920)
Fair Value, Net Asset (Liability)	(8,358)	(9,869)
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap derivative liabilities	0	0
Asset retirement obligations	0	0
Pico earn-out liability	0	0
Fair Value, Net Asset (Liability)	0	0
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap derivative liabilities	(1,249)	(2,260)
Asset retirement obligations	0	0
Pico earn-out liability	0	0
Fair Value, Net Asset (Liability)	(1,249)	(2,260)
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap derivative liabilities	0	0
Asset retirement obligations	(5,883)	(5,689)
Pico earn-out liability	(1,226)	(1,920)
Fair Value, Net Asset (Liability)	$ (7,109)	$ (7,609)

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Additional Information (Details) - Pico Energy, LLC [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Increase Decrease in Earn Out Liability	$ 694	$ 694
Earnout Liability Adjustment	$ 0	$ 0

Accrued Liabilities - Summary o

Accrued Liabilities - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued expenses	$ 4,710	$ 4,975
Payroll and related benefits	2,204	2,341
Royalty	4,044	2,620
Utility	1,059	1,147
Other	424	456
Accrued Liabilities	$ 12,441	$ 11,539

Debt - Summary of Company Debt

Debt - Summary of Company Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Less: current principal maturities	$ (10,000)	$ (10,000)
Less: debt issuance costs (on long-term debt)	(174)	(429)
Long-term debt	49,023	56,268
Current portion of long-term debt	9,633	9,492
Debt, Long-term and Short-term, Combined Amount	58,656	65,760
Term Loans [Member]
Debt Instrument [Line Items]
Term loan	22,500	30,000
Long-term debt	22,500
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Term loan	$ 36,697	$ 36,697

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 21, 2019	Sep. 12, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Extinguishment of Debt [Line Items]
Line of Credit Facility, Interest Rate During Period					2.855%		2.961%
Payments of Debt Issuance Costs					$ 1,821
Debt Issuance Costs, costs paid to the lenders					836
Debt Issuance Costs, costs paid as arranger fees			$ 985		985
Debt Issuance Costs, Net			364		364
Debt Issuance Costs, capitalized			1,457		1,457
Legal Fees					59
Amortized debt issuance expense			123	$ 169	395	$ 532
Capitalized interest			0	322	0	1,056
Long-term debt			49,023		49,023		$ 56,268
Term Loans [Member]
Extinguishment of Debt [Line Items]
Debt Instrument Collateral Amount				$ 95,000		$ 95,000
Long-term debt			22,500		22,500
Revolving Credit Facility [Member]
Extinguishment of Debt [Line Items]
Line of Credit			36,697		36,697
Line of Credit Facility, Current Borrowing Capacity			39,397		39,397
Debt Instrument Collateral Amount			80,000		80,000
Letter of Credit [Member]
Extinguishment of Debt [Line Items]
Line of Credit Facility, Maximum Amount Outstanding During Period			$ 3,905		3,905
MEH [Member] | Second Amendment [Member]
Extinguishment of Debt [Line Items]
Line of Credit		$ 80,000
Repayments of Lines of Credit	$ 38,250
MEH [Member] | Term Loans [Member]
Extinguishment of Debt [Line Items]
Debt Instrument, Periodic Payment, Principal		$ 2,500			$ 2,500
Debt Instrument, Maturity Date		Dec. 12, 2023			Dec. 12, 2023

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ (3,481)	$ 6,266	$ 1,286	$ (291)
Effective tax rate	(64.00%)	150.00%	(15.00%)	(16.00%)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Effective tax rate, U.S. federal statutory rate	21.00%		21.00%
Effective tax rate	(64.00%)	150.00%	(15.00%)	(16.00%)
Income tax examination, increase (decrease) in liability from prior year	$ 4,381		$ 4,381
Income tax examination, liability (refund) adjustment from settlement with taxing authority	$ (1,623)		$ (1,623)

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Fair Value of MRI EICP Options and Valuation Assumptions (Detail) - MRI EICP [Member]	9 Months Ended
	Sep. 30, 2021$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.50%
Expected volatility	32.00%
Expected option life	5 years 6 months
Grant-date fair value	$ 3.44

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Outstanding Activity of Options,Restricted Stock and Restricted Stock Units under MRI EICP (Detail) - MRI EICP [Member]	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning of period | shares	0
Number of Shares, Granted | shares	3,519,827
Number of Shares, Vested | shares	(950,214)
Number of Shares, End of period | shares	2,569,613
Weighted Average Grant Date Fair Value, Beginning of period | $ / shares	$ 0
Weighted Average Grant Date Fair Value, Granted | $ / shares	10.43
Weighted Average Grant Date Fair Value, Vested | $ / shares	11.38
Weighted Average Grant Date Fair Value, End of period | $ / shares	$ 10.08
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning of period | shares	0
Number of Shares, Granted | shares	29,304
Number of Shares, Forfeited | shares	(1,056)
Number of Shares, End of period | shares	28,248
Weighted Average Grant Date Fair Value, Beginning of period | $ / shares	$ 0
Weighted Average Grant Date Fair Value, Granted | $ / shares	11.38
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	11.38
Weighted Average Grant Date Fair Value, End of period | $ / shares	$ 11.38
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning of period | shares	0
Number of Shares, Granted | shares	950,214
Number of Shares, Vested | shares	0
Number of Shares, Forfeited | shares	0
Number of Shares, End of period | shares	950,214
Weighted Average Grant Date Fair Value, Beginning of period | $ / shares	$ 0
Weighted Average Grant Date Fair Value, Granted | $ / shares	11.38
Weighted Average Grant Date Fair Value, Vested | $ / shares	0
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	0
Weighted Average Grant Date Fair Value, End of period | $ / shares	$ 11.38

Share-Based Compensation - Su_3

Share-Based Compensation - Summary of Outstanding Activity of Options and Restricted Stock under SAR Plan (Detail) - SAR Plan [Member]	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning of period | shares	1,872,534
Number of Shares, Granted | shares	924,779
Number of Shares, Forfeited | shares	(166,666)
Number of Shares, Exercised | shares	(50,000)
Number of Shares, End of period | shares	2,580,647
Weighted Average Exercise Price, Beginning of period | $ / shares	$ 1.18
Weighted Average Exercise Price, Granted | $ / shares	0.90
Weighted Average Exercise Price, Forfeited | $ / shares	0.62
Weighted Average Exercise Price, Exercised | $ / shares	0.44
Weighted Average Exercise Price, End of period | $ / shares	$ 1.13
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning of period | shares	1,939,200
Number of Shares, Exercised | shares	0
Number of Shares, End of period | shares	1,939,200
Weighted Average Exercise Price, Beginning of period | $ / shares	$ 0.95
Weighted Average Exercise Price, Exercised | $ / shares	0
Weighted Average Exercise Price, End of period | $ / shares	$ 0.95

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Detail)	Jan. 31, 2021$ / sharesshares	Sep. 30, 2021USD ($)shares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)Employeesshares	Sep. 30, 2020USD ($)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation				$ 19,713,000	$ 465,000
SAR Plan [Member] | General and Administrative Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation expense		$ 2,050,000
MRI EICP [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock shares withheld | shares	950,214
Exercise price of common stock | $ / shares	$ 11.38
Unrecognised compensation expense		11,432,000		$ 11,432,000
Unrecognised compensation expense recognised, Period				5 years
Stock-based compensation		$ 2,574,000	$ 224,000	$ 6,768,000	$ 465,000
MRI EICP [Member] | Section 83 (B) [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock shares withheld | shares		950,214		950,214
MRI EICP [Member] | General and Administrative Expense [Member] | Section 83 (B) [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation expense				$ 10,813,000
Restricted Stock [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation expense		$ 0		$ 0
Share-Based Compensation Arrangement by Share-Based Payment Award, Maximum Number of Shares Per Employee | shares				1,250,000
Number of employees | Employees				2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value				$ 11,300,000

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			50.00%
Defined contribution plan, employer matching contribution, percent of employees' gross pay			4.00%
Defined contribution plan, cost	$ 145	$ 119	$ 414	$ 340
Safe Harbor Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, maximum annual contributions per employee, percent			3.00%
Defined contribution plan, employer matching contribution, vesting period			4 years

Segment Information - Summary o

Segment Information - Summary of Reconciliation of the Company's Reportable Segments' Net Income from Continuing Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Revenue	$ 39,749	$ 28,250	$ 102,872	$ 74,563
Net income (loss)	8,896	(2,084)	(10,021)	2,147
EBITDA	11,778	10,088	10,391	21,486
Net loss (gain) of sale of assets	822		822
Adjusted EBITDA	12,832	10,088	12,196	22,152
Total Assets	259,745	251,527	259,745	251,527	$ 253,356
Capital expenditure	3,234	4,458	7,702	14,911
Depreciation and amortization	5,666	5,470	17,062	16,120
Interest expense	697	436	2,064	3,510
Income tax expense (benefit)	(3,481)	6,266	1,286	(291)
Impairment loss	0	0	626	278
Transaction costs	232		357
Non-cash hedging charges				388
RNG [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Revenue	35,002	23,994	90,707	60,799
Net income (loss)	15,071	9,458	33,205	18,700
EBITDA	19,358	12,939	45,991	29,100
Net loss (gain) of sale of assets	822		822
Adjusted EBITDA	20,180	12,939	46,813	29,100
Total Assets	153,108	135,359	153,108	135,359
Capital expenditure	1,864	3,147	5,883	11,493
Depreciation and amortization	4,287	3,481	12,786	10,400
REG [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Revenue	3,872	4,256	11,290	13,282
Net income (loss)	(1,379)	(661)	(3,647)	(1,955)
EBITDA	(44)	1,282	498	3,634
Adjusted EBITDA	(24)	1,282	1,144	3,912
Total Assets	53,711	80,485	53,711	80,485
Capital expenditure	1,321	1,311	1,770	3,360
Depreciation and amortization	1,335	1,943	4,143	5,587
Income tax expense (benefit)			2	2
Impairment loss			626	278
Transaction costs	20		20
Corporate [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Revenue	875		875	482
Net income (loss)	(4,796)	(10,881)	(39,579)	(14,598)
EBITDA	(7,536)	(4,133)	(36,098)	(11,248)
Adjusted EBITDA	(7,324)	(4,133)	(35,761)	(10,860)
Total Assets	52,926	35,683	52,926	35,683
Capital expenditure	49		49	58
Depreciation and amortization	44	46	133	133
Interest expense	697	436	2,064	3,510
Income tax expense (benefit)	(3,481)	$ 6,266	1,284	(293)
Transaction costs	$ 212		$ 337
Non-cash hedging charges				$ 388

Segment Information - Summary_2

Segment Information - Summary of Revenue by Major Customers (Detail) - Customer Concentration Risk [Member] - Revenue Benchmark [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	19.60%	27.50%	12.80%	15.20%
Customer B [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	15.40%	16.50%	12.40%	14.70%
Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	11.40%	13.40%	11.30%	12.40%
Customer D [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage		13.30%	10.50%	12.00%
Customer E [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage			10.20%
RNG [Member] | Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	19.60%	27.50%	12.80%
RNG [Member] | Customer B [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	15.40%	16.50%	12.40%	14.70%
RNG [Member] | Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage	11.40%		11.30%	12.40%
RNG [Member] | Customer D [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage		13.30%	10.50%	12.00%
REG [Member] | Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage				15.20%
REG [Member] | Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage		13.40%
REG [Member] | Customer E [Member]
Revenue, Major Customer [Line Items]
Concentration risk, percentage			10.20%

Leases - Summary of Supplementa

Leases - Summary of Supplemental Information Related To Operating Leases (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 76	$ 75	$ 227	$ 225
Weighted average remaining lease term (in years)	1 year 9 months 29 days	2 years 4 months 6 days	1 year 9 months 29 days	2 years 4 months 6 days
Weighted average discount rate	5.00%	5.00%	5.00%	5.00%

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments (Detail) $ in Thousands	Sep. 30, 2021USD ($)
Leases [Abstract]
Remainder of 2021	$ 78
2022	319
2023	8
2024	1
Interest	(10)
Total	$ 396

Earnings (loss) per share - Sch

Earnings (loss) per share - Schedule of Loss Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income (loss)	$ 8,896	$ (2,084)	$ (10,021)	$ 2,147
Basic weighted-average shares outstanding	141,015,213		141,015,213
Dilutive effect of share-based awards	32,793		0
Diluted weighted-average shares outstanding	141,048,006		141,015,213
Basic earnings loss per share	$ 0.06		$ (0.07)
Diluted earnings loss per share	$ 0.06		$ (0.07)

Earnings (loss) per share - Add

Earnings (loss) per share - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021shares
Earnings Per Share [Abstract]
Antidilutive excluded from diluted net loss per share	493,166

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) $ in Thousands	Sep. 30, 2021USD ($)
Related Party Transactions [Abstract]
Related party receivable	$ 7,140

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] $ in Thousands	Oct. 31, 2021USD ($)a
Subsequent Event [Line Items]
Payments to Acquire Land | $	$ 5,447
Area of Land | a	146