EX 10.17

  GUARANTY

       THIS GUARANTY ("Guaranty") is entered into as of December 31, 1999,
  by RENTECH, INC., a Colorado corporation ("Rentech"), and REPUBLIC
  FINANCIAL CORPORATION, a Colorado corporation ("Republic", and
  collectively with Rentech, "Guarantors"), in favor of SAND CREEK CHEMICAL
  LIMITED PARTNERSHIP, a Colorado limited partnership ("Sand Creek"), and
  STATE STREET BANK AND TRUST COMPANY, a Massachusetts trust company (both
  in its individual capacity and as Owner Trustee for General Electric
  Capital Corporation under a Trust Agreement dated as of November 1, 1993,
  "State Street Bank", and collectively with Sand Creek, "Sellers")


  RECITALS

       WHEREAS, Sand Creek Energy, LLC, a Colorado limited liability
  company ("Buyer") and Sellers are entering into an Asset Purchase
  Agreement, dated as of December 31, 1999 (such agreement, as amended or
  modified, the "Asset Purchase Agreement"); and

       WHEREAS, Sellers are willing to enter into the Asset Purchase
  Agreement only on the condition that Guarantors enter into this Guaranty;
  and

       WHEREAS, each of the Guarantors has a substantial equity interest in
  Buyer and will receive substantial benefits from Sellers entering into
  and performing their obligations under the Asset Purchase Agreement.

       NOW, THEREFORE, to induce Sellers to enter into the Asset Purchase
  Agreement, and for other valuable consideration, the receipt and
  sufficiency of which are hereby acknowledged, Guarantors agree as
  follows:

       1.  Guaranty.

            1.1  Guaranty.

                 (a)  Guarantors jointly and severally hereby irrevocably,
  absolutely and unconditionally guarantee the full and punctual
  performance and payment when due of all the Obligations (as defined
  below);

                     (i)  provided, however, that (A) no claim may be
  brought under this Guaranty unless notice of such claims or a claim
  against Buyer with respect to the Obligations is given by either Seller
  prior to the fifth anniversary of the date hereof and (B) the aggregate
  liability of Guarantors under the Guaranty shall not exceed four million
  dollars ($4,000,000);

                     (ii)  provided further, that in the event that Public
  Service Company of Colorado ("PSCo.") agrees in writing, in form and
  substance reasonably satisfactory to Sand Creek, to unconditionally and
  irrevocably release Sand Creek and Intermountain Chemical, Inc. ("ICI")
  from any and all obligations and liabilities under or relating to that
  certain letter agreement, dated September 12, 1995, among PSCo., ICI and
  Conoco, Inc. ("Conoco") (the "Letter Agreement") and the construction and
  operation of the pipeline referenced therein, then the deadline for
  bringing any claim as described in clause 1.1(a)(i)(A) above shall be
  accelerated to the second anniversary of the date hereof and the maximum
  aggregate liability of the Guarantors under the Guaranty shall be limited
  to two million dollars ($2,000,000); and

                     (iii)  provided further, that in the event that Conoco
  also agrees in writing, in form and substance reasonably satisfactory to
  Sand Creek, to unconditionally and irrevocably release Sand Creek and ICI
  from any and all obligations and liabilities under or relating to the
  Letter Agreement and the construction and operation of the pipeline
  referenced herein, then the maximum liability of each of the Guarantors
  under this Guaranty shall be limited to one million dollars ($1,000,000)
  and the guaranty of the Guarantors hereunder will become several, but not
  joint.

            (b)  This Guaranty constitutes a guaranty of performance and
  payment when due and not merely of collection.  Guarantors specifically
  agree that it shall not be necessary or required that Sellers exercise
  any right, assert any claim or demand or enforce any remedy whatsoever
  against Buyer or any other Person before or as a condition to the
  obligations of Guarantors hereunder.  For purposes of this Guaranty,
  "Person" means any individual, sole proprietorship, partnership, joint
  venture trust, unincorporated organization, association, corporation,
  limited liability company, institution, public benefit corporation,
  entity or government (including without limitation, any instrumentality,
  division, agency, body or department thereof);

            (c)  This Guaranty shall be construed as a continuing, absolute
  and unconditional guarantee of payment and performance without regard to
  (i) the validity, regularity or enforceability of any of the obligations,
  (ii) any defense, setoff or counterclaim (other than a defense of payment
  or performance) which may at any time be available to or be asserted by
  Buyer against Sellers, (iii) until Sellers shall have been paid in full,
  any right by Guarantors to subrogation or indemnification, or (iv) any
  other circumstance whatsoever (with or without notice to or knowledge of
  Buyer or Guarantors) which constitutes, or might be construed to
  constitute, an equitable or legal discharge of Buyer for the Obligations
  (other than payment in full of all Obligations), or of Guarantors under
  this Guaranty, in bankruptcy or in any other
  instance.

            1.2  Obligations Independent.  The obligations hereunder are
  independent of the Obligations of Buyer, and a separate action or actions
  may be brought and prosecuted against Guarantors whether action is
  brought against Buyer or whether Buyer is joined in any such action or
  actions.

            1.3  Authorization of Renewals, Etc.  Guarantors authorizes
  Sellers, without notice or demand and without affecting their liability
  hereunder, from time to time:

            (a)  to renew, compromise, extend, accelerate or otherwise
  change the time for payment, or otherwise change the terms of the
  Obligations;

            (b)  to receive and hold security for the payment of this
  Guaranty or any of the Obligations and exchange, enforce, waive, release,
  fail to perfect, sell, or otherwise dispose of any such security;

            (c)  to apply such security and direct the order or manner of
  sale thereof as Sellers in their discretion may determine; and

            (d)  to release or substitute any one of more of any endorsers
  or guarantors of the Obligations.

            1.4  Waiver of Certain Rights.  Guarantors waive any right to
  require Sellers:

                      (a)  to proceed against Buyer or any other Person;

                     (b)  to proceed against or exhaust any security for
  the Obligations or any other indebtedness of Buyer to Sellers; or

                      (c)  to pursue any other remedy in Sellers' power
  whatsoever.

            1.5  Waiver of Certain Defenses.  Guarantors waive any defense
  arising by reason of any disability or other defense of Buyer, or the
  cessation from any cause whatsoever of the liability of Buyer other than
  final payment in full of all Obligations, whether consensual or arising
  by operation of law or any bankruptcy, conservatorship, receivership,
  insolvency or debtor relief proceeding, or from any other cause, or any
  claim that Guarantors' obligations exceed or are more burdensome than
  those of Buyer either individually or in the aggregate.

            1.6  Waiver of Presentments, Etc.  Guarantors waive all
  presentments, demands for performance, notices of nonperformance,
  protests, notices of protest, notices of dishonor and notices of
  acceptance of this Guaranty and of the existence, creation, or incurring
  or new or additional Obligations or any other indebtedness of Buyer to
  Sellers.

            1.7  Information Relating to Buyer.  Guarantors acknowledges
  that it has the ability, and hereby assumes the obligation and
  responsibility, to keep informed of the financial condition and business
  operations of Buyer and its affiliates and of other matters of
  circumstances affecting the ability of any of them to pay or perform
  their respective obligations to Sellers or the risk of nonpayment and
  nonperformance.  Guarantors hereby waive any obligation on the part of
  Sellers to inform Guarantors of the financial condition, or any changes
  in financial condition, of Buyer or any affiliates thereof or of any
  other matter or circumstance which might affect the ability of
  Buyer to pay and perform under the Asset Purchase Agreement, or the risk
  of nonpayment or nonperformance.

            1.8  Reinstatement of Guaranty.  If any payment or transfer of
  any interest in property by Buyer to Sellers in fulfillment of any
  Obligations is rescinded or must at any time (including after the return
  of cancellation of this Guaranty) be returned, in whole or in part, by
  Sellers to Buyer or any other Person, upon the insolvency, bankruptcy or
  reorganization of Buyer or otherwise, this Guaranty shall be reinstated
  with respect to any such payment or transfer, regardless of any such
  prior return or cancellation.

            1.9  Powers.  It is not necessary for Sellers to inquire into
  the powers of Buyer or of the officers, directors, partners or agents
  acting or purporting to act on their behalf, and any Obligations made or
  created in reliance upon the professed exercise of such powers shall be
  guaranteed hereunder.

       2.  Representations, Warranties and Agreements of Guarantors.  Each
  of the Guarantors represents and warrants to, and agrees with, Sellers
  that:

            2.1  Corporate Existence and Power.  It (a) is a corporation
  duly organized, validly existing and in good standing under the laws of
  the jurisdiction of its incorporation; (b) has the power and authority
  and all governmental licenses, authorizations, consents and approvals to
  own its assets, carry on its business and to execute, deliver, and
  perform its obligations under this Guaranty; and (c) is in compliance in
  all material respects with all requirements of law the failure to comply
  with which would have a material adverse effect on its ability to fulfill
  its obligations under this Guaranty.

            2.2  Corporate Authorization: No Contravention.  The execution,
  delivery and performance by its of this Guaranty has been duly authorized
  by all necessary corporate action, and do not and will not (a) contravene
  the terms of its organizational documents; (b) conflict with or result in
  any breach or contravention of, or the creation of any lien under, any
  document evidencing any contractual obligation to which it is a party or
  any order, injunction, writ or decree of any governmental authority to
  which it is or its property is subject; or (c) violate any requirements
  of any governmental authority.

            2.3  Governmental Authorization.  No approval, consent,
  exemption, authorization, or other action by, or notice to, or filing
  with, any governmental authority is necessary or required in connection
  with the execution, delivery or performance by, or enforcement against,
  it of this Guaranty.

            2.4  Binding Effect.  This Guaranty constitutes the legal,
  valid and binding obligations of such Guarantor, enforceable against it
  in accordance with its terms, except as enforceability may be limited by
  applicable bankruptcy, insolvency, or similar laws affecting the
  enforcement of creditors' rights generally or by equitable principles
  relating to enforceability.

       3.  Miscellaneous.

            3.1  Assignment.  This Guaranty shall be binding upon
  Guarantors and their respective successors and assigns, and shall insure
  to the benefit of Sellers and their respective successors and assigns,
  except that neither of the Guarantors may assign or transfer any of its
  obligations under this Guaranty without the prior written consent of both
  Sellers.

            3.2  Notices.  Each notice, report, demand, waiver, consent and
  other communication required or permitted to be given hereunder shall be
  in writing and shall be sent (and deemed given upon receipt) (a) by
  registered or certified first-class mail, postage prepaid and return
  receipt requested, (b) by Federal Express or comparable overnight
  courier, or (c) by fax, addressed as follows:

     If to Sand Creek:    Sand Creek Chemical Limited Partnership
                             c/o Baxter Associates, Inc.
                             1250 West Northwest Highway, Suite 503
                             Palatine, Illinois 60067
                             Attn:  Reginald R. Baxter

    with a copy to:       GE Capital Services
                             Structured Finance Group
                             120 Long Ridge Road
                             Stamford, CT 06927
                             Attn:  Manager of Compliance

     and a copy to:       Pillsbury Madison & Sutro LLP
                             50 Fremont Street
                             San Francisco, CA 94105
                             Attn:  D. Stanley Rowland, Esq.

     If to State          State Street Bank and Trust Company
     Street Bank:           Goodwin Square
                            225 Asylum Street, Floor 2320
                            Hartford, CT 06103
                            Attn:  Corporate Trust Administration

     If to Rentech:       Rentech, Inc.
                            1331 17th Street, Suite 720
                            Denver, Colorado 80202
                            Attn:  Ronald C. Butz, Esq.

     If to Republic:      Republic Financial Corporation
                            3300 S. Parker Road, Suite 500
                            Aurora, CO 80014
                            Attn:  Julie Babcock, Vice President, Legal

     with a copy to:      Otten, Johnson, Robinson, Neff & Ragonetti, P.C.
                            950 Seventeenth Street, Suite 1600
                            Denver, CO 80202
                            Attn:  John R. Marcil, Esq.

            3.3  Partial Exercise; Amendment.  No delay on the part of
  Sellers in exercising any right, power or privilege hereunder shall
  operate as a waiver thereof, nor shall any single or partial exercise of
  any such right, power or privilege preclude other or further exercise
  thereof or the exercise of any other right, power or privilege or be
  construed to be a waiver of any breach under the Asset Purchase
  Agreement.  No waiver by Sellers of any such breach shall be effective
  unless in writing and signed by an authorized officer of Sellers, and no
  such waiver shall be deemed to be a waiver of a subsequent breach under
  the Asset Purchase Agreement or be deemed to be a continuing waiver.  No
  course of dealing between Buyer or Guarantors, respectively, and Sellers
  or their agents or employees shall be effective to change, modify or
  discharge any provision of this Guaranty or to constitute a waiver of any
  breach hereunder.

            3.4  Remedies Cumulative.  All rights and remedies provided in
  this Guaranty and any instrument or agreement referred to herein are
  cumulative and are not exclusive of any rights or remedies otherwise
  provided by law.  Any single or partial exercise of any right or remedy
  shall not preclude the further exercise thereof or the exercise of any
  other right or remedy.

            3.5  Costs and Expenses.  Guarantors agree to pay on demand all
  costs and expenses of Sellers, including attorney costs, in connection
  with the enforcement of, and preservation of any rights, remedies or
  interests under, this Guaranty.

            3.6  Severability.  Whenever possible, each provision of this
  Guaranty shall be interpreted in such manner as to be effective and valid
  under all applicable laws and regulations.  If, however, any provision of
  this Guaranty shall be prohibited by or invalid under any such law or
  regulation in any jurisdiction, it shall, as to such jurisdiction, be
  deemed modified to conform to the minimum requirements of such law or
  regulation, or, if for any reason it is not deemed so modified, it shall
  be ineffective and invalid only to the extent of such prohibition or
  invalidity without affecting the remaining provisions of this Guaranty,
  or the validity or effectiveness of such provision in any other
  jurisdiction.

            3.7  Governing Law.  This Guaranty shall be governed by the
  laws of the State of New York without giving effect to choice of law
  provisions included herein.

            3.8  Integration.  This Guaranty (a) integrates all the terms
  and conditions mentioned herein or incidental hereto, (b) supersedes all
  oral negotiations and prior writings with respect to the subject matter
  hereof, and (c) is intended by the parities as the final expression of
  the agreement with respect to the terms and conditions set forth in this
  Guaranty and as the complete and exclusive statement of the terms agreed
  to by the parties.

            3.9  Counterparts.  This Guaranty may be executed in a number
  of counterparts and by different parties hereto in separate counterparts,
  each of which when so executed shall be deemed to be an original and all
  of which taken together shall constitute but one and the same agreement.

       IN WITNESS WHEREOF, each of Guarantors has caused this Guaranty to
  be signed in its name by its duly authorized representative as of the
  date first above mentioned.

  RENTECH, INC.                      REPUBLIC FINANCIAL CORPORATION


  By:  Dennis L. Yakobson            By:  James H. Possehl
          President                          President

  ACCEPTED BY:
  SAND CREEK CHEMICAL LIMITED
  PARTNERSHIP

  By:  HUBBARD HOLDING COMPANY,
          as General Partner

       By:  Reginald R. Baxter
               President

  STATE STREET BANK AND TRUST
  COMPANY

  By:  K. Farimor
         AVP