Exhibit 2.1

                            STOCK PURCHASE AGREEMENT


         THIS STOCK PURCHASE  AGREEMENT  (Agreement) is made and entered into as
of August 1, 2001, by and among REN CORPORATION,  an Oklahoma corporation (Ren),
and RENTECH, INC., a Colorado corporation (Rentech). The following circumstances
precede the execution of this Agreement:

         A.       REN is a privately  owned  corporation  that is engaged in the
manufacture  of complex,  computer  controlled  test systems sold to  industrial
customers  to test  the  specifications  and  quality  of  hydraulics  and  many
additional variables of automated equipment produced by them.

         B.       Rentech  is a  publicly  owned  energy  corporation  that owns
technology  useful for converting  gases derived from  carbon-bearing  materials
into synthetic liquid  hydrocarbons  such as clean burning diesel fuel.  Rentech
also owns a subsidiary  that produces  environmentally  clean and  biodegradable
stains and sealers,  and it owns another  subsidiary  that provides well logging
services to the oil and gas industry.

         C.       REN and Rentech have agreed that Rentech will  purchase 56% of
the issued and outstanding shares of common stock of Ren.

         D.       REN is  authorized to issue 50,000 shares of its common stock,
of which 5,600 are now issued and outstanding. The issued and outstanding shares
are owned in the following amounts by the following persons (Shareholders):

         E.       As of the  date of  this  Agreement,  Rentech  has  loaned  to
REN$623,899.39  as  cash  advances  against  the  Purchase  Price   subsequently
described in this  Agreement.  Total  accrued  interest on the cash  advances is
$116,704.91.

         F.       As of the date of this  Agreement,  Rentech has issued 400,000
shares  of its  common  stock to REN equal to  $644,000.00  as  advances  of the
Purchase Price. The total of advances against the Purchase Price, including cash
and common stock, is $1,384,604.30.

         G.       On or about June 13, 2000,  REN purchased the real property it
had leased at 5900 South Perkins Road, Stillwater, Oklahoma for its office, with
a portion of the loan proceeds.

         NOW THEREFORE, in consideration of the background circumstances and the
mutual covenants and agreements herein set forth, the receipt and sufficiency of
which are hereby acknowledged, the parties hereto agree as follows:


                                   ARTICLE I.
                               SALE AND PURCHASE

         1.1      Purchase.  Subject  to the terms and  conditions  set forth in
this Agreement,  at the Closing,  (as defined in Section 3.1), REN will sell and
transfer  7,127  shares of its common  stock (the REN  Shares) to  Rentech,  and
Rentech will purchase the Ren Shares from Ren.


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         1.2      Purchase Price.  The entire purchase price (Purchase Price) to
be paid by Rentech  for the REN Shares is  $1,384,604.30,  of which  $623,899.39
will be credited  against the  indebtedness  owed by REN to Rentech for the cash
advances,  $116,704.91 will be credited against the indebtedness  owed by REN to
Rentech for interest on the cash advances,  and $644,000 will be credited to the
purchase  price for the shares of common stock of Rentech  previously  issued to
REN(the Rentech Shares).

                  (a)      Description of Ren's  Indebtedness to Rentech.  Ren's
indebtedness  to Rentech is subject to a Loan  Agreement  between them dated May
11, 1999, as amended.  The  indebtedness is evidenced by a promissory note dated
May 12, 1999 in the original  principal amount of $200,000,  made by REN payable
to Rentech,  which has been amended as of July 21,  1999,  February 29, 2000 and
May 12, 2000 (Promissory Note I). The principal  balance of Promissory Note I is
$573,899.39  as of the  date of this  Agreement.  A second  promissory  note was
executed by REN in favor of Rentech dated July 13, 2000 in the principal  amount
of $200,000 (Promissory Note II). A third promissory note was executed by REN in
favor of Rentech  dated  October  17, 2000 in the  principal  amount of $200,000
(Promissory Note III). A fourth  promissory note was executed by REN in favor of
Rentech dated February 16, 2001 in the principal amount of $122,000  (Promissory
Note IV). In addition,  Rentech  advanced Stock to REN in the amount of $122,000
on or about February 16, 2001(Stock  Advance I), and advanced cash in the amount
of $50,000 on or about July 20, 2001 (Cash Advance I).

                  (b)      Application  of Purchase Price to  Indebtedness.  The
Purchase  Price shall be credited to pay in full the  principal and interest due
as of the Closing on Promissory Note I, Promissory Note II, Promissory Note III,
Promissory  Note IV, Stock  Advance I, and Cash Advance I, all of which shall be
cancelled at Closing.

                                   ARTICLE II
                                   THE CLOSING

         2.1      Place and Time. The closing of the transaction to be completed
under this Agreement shall take place as soon as reasonably  practical after the
execution of this  Agreement by both  parties by  completion  of the actions and
delivery of the documents  described in Sections 2.2, 2.3 and 2.4 at the offices
of Rentech's  attorneys,  Brega & Winters P.C.,  located at 1700 Lincoln Street,
Suite 2222, Denver, CO 80203 (the Closing). Regardless of the actual time of the
Closing, the Closing shall be effective as of 12:01 a.m. local time on August 1,
2001 (the Effective Time).

         2.2      Payment and Delivery by Rentech. At or before the Closing, and
subject to the terms and conditions set forth herein, Rentech shall:

                  (a)      execute  and  deliver a  cancellation  of  Promissory
                  Notes I, II, III and IV; and

                  (b)      execute  and  deliver  the  certificate  required  by
                  Section 8.1 hereof.

         2.3      Delivery by Ren. At or before the Closing,  and subject to the
terms and conditions set forth herein, REN shall:

                  (a)      present  at  the  Closing  full  releases  and  other
                  evidence  of  full   payment  of  each   indebtedness
                  described in Section 2.4;

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                  (b)      execute and deliver a  certificate  representing  the
                  REN  Shares,   duly   issued  and   executed  by  the
                  authorized officers of the Ren;

                  (c)      deliver a recorded copy of the general  warranty deed
                  to REN conveying  the Real  Property  located at 5900
                  South Perkins Road, Stillwater, Oklahoma to Ren;

                  (d)      deliver a copy of the title insurance policy insuring
                  Ren's  title to the  real  property  located  at 5900
                  South Perkins Road,  Stillwater,  Oklahoma,  insuring
                  title in REN  without  exceptions  other  than  those
                  previously  approved  by  Rentech  at the time of the
                  closing of the real property;

                  (e)      deliver, if not previously  delivered,  all documents
                  and certificates  required from REN by the provisions
                  of Article VII of this Agreement;

                  (f)      deliver an executed copy of the Employment  Agreement
                  of Gary Roberts attached hereto as Exhibit A;

                  (g)      execute   and   deliver   the    Agreement    Between
                  Shareholders  attached  hereto as Exhibit B, which is
                  also executed by each of the Shareholders;

                  (h)      execute and deliver the  Confidentiality  Agreements,
                  attached hereto as Exhibit C, executed by each of the
                  employees of REN listed in Schedule 3.2;

                  (i)      execute  and deliver a  certified  resolution  of the
                  shareholders  and  board of  directors  of Ren,  duly
                  signed by its  president and  secretary,  authorizing
                  the  execution of this  Agreement,  the execution and
                  delivery  of the REN  Shares,  and the  actions to be
                  taken  by  REN   according   to  the  terms  of  this
                  Agreement, as set forth in Section 7.6.

REN will from time to time after the Closing Date, at Rentech's request, execute
such further  instruments as Rentech reasonably deems necessary to carry out the
sale of the REN Shares pursuant to this Agreement.

         2.4      Indebtedness of Ren.  Because the debts of REN described below
have  not been  paid in full as  originally  contemplated  by the  parties,  the
Shareholders shall agree in the Shareholder Agreement to assign to Rentech their
rights to  distributions  of  profits  from REN until an amount of  profits  are
distributed to Rentech equal to $252,699.76, plus 8% interest on the outstanding
balance accruing on August 1, 2001.

                  Remaining
                  Approximate           Amount
                  Amount as of          as of
Item                                    April 16, 1999    August 1, 2001
- ----                                    --------------    --------------
Accrued commission payable to
    Ren's sales representative          $235,000          $   176,036.05
KAMO Economic Development Corporation    160,000                     -0-
CDBG/Payne Co. Trust Promissory Note       4,200                     -0-
COEDD Promissory Note (generator)         33,000               19,403.23
Womack Supply Company Promissory Note     41,000                     -0-
Accounts Payable                         300,000               64,176.20
Loans from officers of REN to REN        30,000                30,600.00
Panamet (trade payable)                    -0-                 69,375.00
Less:
Cash of Ren                               (-0-)               (21,099.36)
Accounts Receivable of Ren                (-0-)               (78,929.96)
                                        --------------    --------------

         Total:                         $1,003,200        $   252,699.76
                                        ==============    ==============


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                                  ARTICLE III.
                             REPRESENTATIONS OF REN

         REN represents, promises and warrants to the Rentech as follows:

         3.1      Organization.  REN is a corporation  duly  organized,  validly
existing,  and in good standing  under the laws of the state of Oklahoma and has
all power and  authority  to own its  property  and carry on its business as now
conducted and has all necessary licenses, permits and government approvals.

         3.2      Authorization. The execution, delivery and performance of this
Agreement and any other documents or instruments  contemplated  hereby have been
duly  authorized  by all  necessary  action of Ren, and this  Agreement has been
executed  and  delivered  by REN and  constitutes  a legal,  valid  and  binding
obligation of REN enforceable in accordance with its terms.

         3.3      Financial  Reports.  True and correct  copies of the financial
statement (including a balance sheet and statement of income) of REN for each of
the last five (5) years,  and for a current  month  (collectively,  the Reports)
will be provided to Rentech by separate  delivery.  At Closing REN shall deliver
to Rentech a true and  correct  copy of the  financial  statements  including  a
balance  sheet  and  statement  of  income of REN as of the last day of the most
current month for which available,  prepared from the books of REN without audit
since  January 2001 (the Interim  Reports).  (Collectively,  the Reports and the
Interim  Reports  shall  be  referred  to as the  Financial  Reports).  All such
Financial Reports are in accordance with the books and records of Ren, have been
prepared  consistently  throughout the periods  indicated,  reflect all material
assets and, to Ren's knowledge,  material liabilities of Ren, and present fairly
and completely, in all material respects, the financial condition of REN and its
Business at such dates and results of its operations for the periods then ended,
subject  only,  in  the  case  of  the  Interim  Reports,  to  normal  year  end
adjustments.

         3.4      Absence of Adverse  Changes.  Except as reflected in Financial
Reports,  and as  disclosed on Schedule  3.4,  since  January 1, 2001,  Ren, its
business  and its assets  have not  suffered  or  undergone  any change  that is
reasonably  likely  to  have  an  adverse  effect  on  the  business,  condition
(financial or otherwise),  or prospects (whether as a result of any change as to
inventory  or other  assets,  any loss of a  competitive  position,  any natural
disaster,  accident,  strike,  or any  other  event or  condition  affecting  or
relating to its  business,  REN or its assets,  whether or not related to any of
the  foregoing),  experienced  any labor  difficulty  or  suffered  any  damage,
destruction  or loss (whether or not insured).  Except as reflected in Financial
Reports  and as  disclosed  on Schedule  3.4, as of the date of this  Agreement,
since April 16, 1999, REN and its business have not:

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         (a)      incurred any  obligations  or liabilities  (whether  absolute,
         accrued,  contingent,  or otherwise  and whether due or to become due),
         except  current  liabilities  in the  ordinary  course of business  and
         consistent with past practice;

         (b)      written  down or  written  up the  value of any  inventory  or
         equipment;

         (c)      canceled or waived any claim of right of substantial  value or
         sold,  assigned,  transferred  or encumbered  any of its  properties or
         assets, real, personal,  or mixed,  tangible or intangible,  except for
         fair   consideration  and  in  the  ordinary  course  of  business  and
         consistent with past practice;

         (d)      granted any increase in compensation,  rate of compensation or
         commission  payable or to become payable,  or made any loan, advance or
         other  extension  of credit to any of its  employees  or agents  except
         merit increases made in the usual and ordinary course of business.

         (e)      changed the methods of accounting or accounting  principles or
         practices of REN set forth in or reflected in the Financial Reports;

         (f)      lost any key employees;

         (g)      terminated  or  been  advised  of  the   termination   of  its
         relationship with any material customer or supplier;

         (h)      changed in any  material  respect  the  business  policies  or
         practices of REN or failed to operate the business of REN in good faith
         and in the ordinary course; and

         (i)      agreed, whether in writing or not, to do any of the foregoing.

         3.5  Title to  Assets.  REN has good  and  marketable  title to all its
assets, including,  without limitation, those reflected in the Financial Reports
or acquired since the date thereof  (except for property  disposed of since such
date in the ordinary course of business consistent with past practice),  in each
case free and clear of liens,  easements or title imperfections  except that, as
of the date of this  Agreement,  its assets may be subject to liens for  current
taxes not yet due and  payable.  As of the Closing  Date,  Ren's assets shall be
subject to no liens and REN shall have good and  marketable  title to all assets
free and clear of liens.

         3.6      Compliance  With  Other  Instruments.  REN  has  complete  and
unrestricted power to undertake and perform all of the obligations  contained in
this Agreement.  Neither the execution and delivery, nor the consummation of the
transactions  provided  for in this  Agreement,  will  violate  the  Articles of
Incorporation of REN or any material agreement,  mortgage,  indenture,  license,
franchise,  permit,  judgment,  decree, order, law or regulation by which REN is
bound.


         3.7      Litigation.  Except as set forth in Schedule 3.7, there are no
actions, claims, suits,  investigations,  litigation or proceedings pending, or,
to the knowledge of Ren,  threatened against or relating to REN or its business,
including  any that would  question the validity of this  Agreement or any other
agreements contemplated hereunder or any action taken or to be taken pursuant to
or in connection  with the provisions of this  Agreement or any other  agreement
contemplated  hereunder,  nor is there any reasonable basis for any such action,
claim,  suit,  proceeding  or  investigation.  There are no  judgments,  orders,
decrees,  citations,  fines or penalties heretofore assessed (and not discharged
or otherwise  satisfied)  against REN under any United  States  federal,  state,
local or foreign law, and there are no unsatisfied judgments against Ren.


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         3.8      Environmental  Matters.  REN is and has at all  times  been in
compliance with all applicable United States, federal, state, local, and foreign
laws and  regulations  relating to  environmental,  land use,  welfare,  natural
resources,  health  and  safety  matters.  There is no suit,  claim,  action  or
proceeding  pending or threatened  against REN or any reasonable basis therefor,
in respect of (a)  noncompliance  by REN with any such laws or regulations,  (b)
personal  injury,  wrongful  death or other tortious  conduct  arising out of or
resulting from materials, commodities or products held, used, sold, transferred,
manufactured  or disposed of by or on behalf of REN or one of its  shareholders,
containing or  incorporating  any hazardous or toxic  materials  commodities  or
substances,  or (c) the  presence  or release  or  threatened  release  into the
environment  of any  pollutant,  contaminant  or  toxic or  hazardous  material,
substance or waste,  whether solid, liquid or gas (each a Hazardous  Substance),
whether  generated by REN or located at or about a site currently owned,  leased
or otherwise used by REN or heretofore owned, leased or otherwise used by REN or
any predecessor  entity and for which REN would have liability.  There have been
no Hazardous  Substances  generated by REN that have been disposed of or come to
rest at any site that has been included in any published  United States federal,
state or local  "superfund"  site list or any other list of  hazardous  or toxic
waste sites published by any governmental authority in the United States. Except
as set forth on Schedule  3.8,  there are and have been no  underground  storage
tanks  located  on,  no  polychlorinated   biphenyls  (PCBs)  or  PCB-containing
equipment used or stored on, and no hazardous  waste, as defined by the Resource
Conservation and Recovery Act, as amended, 42 U.S.C. ss. 6901 et seq, stored on,
any site owned,  leased or otherwise used by Ren. No such Hazardous Substance is
stored by or on behalf of REN at any site at which REN provides services.  There
has been no release or  threatened  release by REN of Hazardous  Substances  on,
upon,  into or from (x) any site  currently  owned,  leased or otherwise used by
Ren,  (y) any site  heretofore  owned,  leased or  otherwise  used by REN or any
predecessor entity or (z) any other site at which REN provides services.

         3.9      Tax  Returns.  REN has duly filed all tax  reports and returns
required to be filed by it and has duly paid all taxes and other  charges due as
shown  thereon or claimed to be due from it by written  notice from any federal,
state, or local taxing authorities,  including, without limitation, those due in
respect of its properties,  income,  franchise,  licenses,  sales, and payrolls;
there are no tax liens upon any of its  assets  (other  than  liens for  current
taxes  not yet due);  there are no  agreements,  waivers  or other  arrangements
providing for an extension of time with respect to the  assessment of any tax or
deficiency  against  its  assets  or REN  nor  are  there  any  actions,  suits,
proceedings, investigations or claims now pending against REN or relating to its
business;  and, there are no pending  discussions  or questions  relating to, or
claims asserted for taxes or assessments against Ren.

         3.10     Leases.  REN is not bound to any leases  pursuant to which REN
leases real or personal property except as identified on Schedule 3.10.

         3.11     Intellectual  Property.  REN has no pending  applications  for
registration of any rights in Intellectual Property. No licenses, sublicenses or
covenants  have  been  granted  or  entered  into  by  REN  in  respect  of  any
Intellectual  Property.  "Intellectual  Property" means,  collectively:  (a) all
registered,  unregistered and pending (i) trade names, trade dress,  trademarks,
service marks,  assumed names,  business names and logos, and all  registrations
and applications therefor,  (ii) all computer software,  data files, manuals and
other  specifications and documentation and all know-how related thereto,  (iii)
technical  information,  data,  process  technology,  technical  papers,  plans,
drawings and blue prints, (iv) all patents, patent applications,  and inventions


                                       6


and  discoveries  that  may be  patentable,  registered  designs  and  invention
disclosures,   (v)  all  know-how,   trade  secrets,   proprietary   inventions,
proprietary processes,  proprietary formulas,  proprietary know-how, proprietary
concepts,   proprietary  ideas,   proprietary  research  and  development,   and
proprietary  designs,  and (vi) all  other  intellectual  property,  and (b) all
licenses,  sublicenses,  assignments in respect  thereto and rights  thereunder,
remedies  against  infringements  thereof and rights to  protection  of interest
therein relating to the items set forth in clause (a) above.

         3.12     Employee Matters.  Schedule 3.12 lists all employees  employed
by REN(collectively,  the Employees),  including for each such Employee: (i) his
or her  position  and  title;  (ii) his or her date of  hire;  (iii)  his or her
salary; (iv) his or her unpaid wages, accrued vacation time and accrued personal
time;  and (v) any  bonuses  paid to him or her with  respect to the fiscal year
ended  December  31,  2000 or earned by him or her with  respect to the  current
fiscal  year.  REN  shall as soon as  reasonably  practicable,  but in any event
within five days after the Closing, provide to Rentech the foregoing information
with respect to any other  Employees  hired prior to the  Closing.  There are no
continuing  contracts of employment  with any employees of Ren. REN has complied
with all applicable laws relative to employee benefits,  including COBRA and the
Employee  Retirement Income Security Act of 1974, as amended (ERISA),  and there
are no unfunded  liabilities relating to any pension or welfare benefit plan for
which  REN  could be  liable.  REN is not a party to any  collective  bargaining
agreement and there is no existing dispute or controversy between REN and any of
the  Employees.  None of the Employees are  represented by a labor union and, to
Ren's knowledge,  there is no labor union  organizing  activity by or among such
Employees. REN does not maintain or contribute to, nor has it ever maintained or
contributed  to, any  employee  benefit  plan (as  defined in ERISA)  that is an
employee  pension  benefit plan (as defined in ERISA).  REN does not maintain or
contribute to, nor has it ever maintained or contributed to, an employee benefit
plan that is an employee welfare benefit plan (as defined in ERISA).

         3.13     Contracts  and  Commitments.  The  only  continuing  contract,
agreement,  plan,  arrangement,  or commitment for the benefit of or relating to
Ren's  business  that it holds and that will continue past the Closing are those
described on Schedule 3.13.

         3.14     Compliance  with Law.  REN has not  received any notice of any
violation of and, to the best of Ren's  knowledge,  has complied in all material
respects  with all laws,  regulations,  and orders  applicable  to its  business
including  all rules and  regulations  of the  Occupational  Health  and  Safety
Administration,  and all federal,  state and local environmental laws, rules and
regulations.

         3.15     Licenses  and  Permits.  REN holds all  licenses  and  permits
which, to the best of Ren's  knowledge,  are required for Ren's operation of its
business,  all of which are in full force and effect.  REN has all  governmental
and regulatory licenses and permits necessary for the conduct of the business as
presently  conducted  for the  ownership  of its assets.  All such  licenses and
permits are set forth on Schedule 3.15, are in full force and effect, and except
as set forth on Schedule  3.15,  no written  notice of any  violations  has been
received by REN relating to such licenses or permits. REN is not in violation of
any such license or permit, and no proceeding or investigation is pending or, to
Ren's knowledge,  threatened that would have the effect, directly or indirectly,
of revoking or limiting in any way such  license or permits.  To the extent that
any such license or permit cannot be obtained  independently  by Rentech without
condition  other than  application  and the  payment of  applicable  fees,  such
licenses and permits are fully assignable to Rentech.


                                       7


         3.16     Disclosure.  No  material  representation  or  warranty by REN
contained in this Agreement and no statement contained in any exhibit,  schedule
certificate,  list,  or other  writing  furnished  to  Rentech  pursuant  to the
provision hereof, to the best knowledge of Ren, contains any untrue statement of
a material fact or omits to state a material fact necessary in order to make the
statements therein not materially misleading.

         3.17     Certain Agreements. Neither the execution and delivery of this
Agreement nor the consummation of the transactions  contemplated hereby will (i)
result in any payment (including,  without limitation,  severance,  unemployment
compensation,  parachute  payment,  bonus  or  otherwise)  becoming  due  to any
employee  of REN or any other  person  from REN under  any  plan,  agreement  or
otherwise,  (ii) increase any benefits  otherwise  payable to any Employee under
any  plan or  agreement,  or (iii)  result  in the  acceleration  of the time of
payment or vesting of any such benefits.

         3.18 Books and Records. REN has made available to Rentech true and
correct  copies of the books and of all  corporate  (including  minute books and
stock record books) and financial records of Ren.

         3.19     Standstill. Neither REN nor any shareholder of REN has entered
into any  arrangement  or  understanding  with any  person  other  than  Rentech
regarding this sale, exchange or other disposition of any of its common stock.

         3.20     Capitalization.   As  of  the  date  of  this  Agreement,  the
authorized  common  stock of REN  consists of 50,000  shares of common  stock of
which 5,600 shares were issued and outstanding.  All of such outstanding  shares
have been  validly  issued  and are fully paid and  nonassessable.  No shares of
common stock of REN are subject to preemptive rights or any other similar rights
or any liens or  encumbrances.  Except as disclosed in Schedule  3.20: (i) there
are no outstanding options,  warrants,  script, rights to subscribe to, calls or
commitments  of any  character  whatsoever  relating to, or securities or rights
convertible  into, any shares of capital stock of Ren, or  arrangements by which
REN is or may become bound to issue  additional  shares of capital stock of Ren,
and (ii) there are no outstanding debt securities.  If requested by Rentech, REN
has  furnished  to  Rentech,  and  Rentech  acknowledges  receipt of same by its
signature hereafter, true and correct copies of Ren's Articles of Incorporation,
as amended,  as in effect on the date hereof  (Articles of  Incorporation),  and
Ren's Bylaws, as in effect on the date hereof (the Bylaws).

         3.21     Issuance of Securities. At or prior to Closing, the REN Shares
shall be duly  authorized and reserved for issuance and shall be validly issued,
fully paid and  non-assessable,  free from all  taxes,  liens and  charges  with
respect to the issue  thereof,  and will not be subject to preemptive  rights or
other similar rights of stockholders of Ren.

         3.22     No Brokers; No General  Solicitation.  REN has taken no action
that  would  give rise to any claim by any  person  for  brokerage  commissions,
finder's  fees  or  similar   payments   relating  to  this  Agreement  and  the
transactions  contemplated  hereby.  REN and Rentech  both  acknowledge  that no
broker was involved with respect to the transactions contemplated hereby.


                                       8


                                   ARTICLE IV.
                      CONDUCT OF BUSINESS PRIOR TO CLOSING

         REN covenants  and agrees that prior to the Closing,  except as Rentech
shall have consented in writing:

         4.1      Operation in Ordinary Course. Ren's business will be conducted
only in the ordinary course of business consistent with past practice.

         4.2      Operation of the  Business.  REN shall use its best efforts to
keep its business  intact and to preserve the goodwill of  suppliers,  customers
and others having business relations with Ren.

         4.3      Employees.  REN shall pay all salaries,  wages, payroll taxes,
benefits,  vacation pay, all other fringe benefit costs,  and all other costs of
every nature whatsoever as they become due.

         4.4      Payment of  Liabilities.  REN shall pay as the same become due
all of its liabilities.

         4.5      Payment of Taxes.  REN shall promptly file all tax returns and
pay all federal,  state and local tax assessments and governmental charges which
are or may be lawfully levied or assessed  against Ren, its business its assets,
including,  but not limited to, ad valorem, sales, use, excise,  franchise,  and
personal property taxes.

         4.6      Maintenance of Properties. REN will maintain all its assets in
customary  repair,  order and condition,  reasonable  wear and use and damage by
fire or other casualty excepted.

         4.7      Maintenance  of Books.  REN will maintain its books,  accounts
and records in the usual manner on a basis  consistent  with prior periods.  REN
will duly comply in all material  respects with all laws and decrees  applicable
to it.

         4.8      Update  Schedules.  REN shall advise Rentech of any changes in
the information provided in the schedules attached to this Agreement.

         4.9      Exclusivity;  Acquisition  Proposals.  Unless  and until  this
Agreement  shall have been  terminated  by either party  pursuant to Article IX,
except as required by law,  REN shall not (and shall  instruct  their  officers,
directors, agents,  representatives or affiliates not to take or cause, directly
or indirectly,  any of the following  actions with any person other than Rentech
and its designees or agents: (i) solicit, encourage,  initiate or participate in
any negotiations, inquiries or discussions with respect to any offer or proposal
to  acquire  all or any  substantial  part of  Ren's  assets  or  capital  stock
(Acquisition  Transaction);   (ii)  disclose  any  information  not  customarily
disclosed  to any person  concerning  its  business or its assets  except in the
ordinary  course of  business  consistent  with past  practice  and as  required
pursuant to a governmental request for information;  (iii) enter into or execute
any agreement relating to an Acquisition Transaction, or other agreement calling
for the sale,  directly or indirectly,  of all or any significant  part of Ren's
business  or its  assets;  or  (iv)  make or  authorize  any  public  statement,
recommendation  or solicitation  with respect to any Acquisition  Transaction or
any offer or proposal  relating to an  Acquisition  Transaction  other than with
respect to the transactions contemplated hereby.


                                       9


                                   ARTICLE V.
                    PRE-CLOSING COVENANTS OF REN AND RENTECH

         5.1      Environmental   Survey.   If  Rentech   elects  to  obtain  an
environmental survey of Ren's real property,  REN and Rentech shall cooperate in
obtaining,  at Rentech's  expense,  a Phase I  environmental  survey of the Real
Property  on which  Ren's  business  is  operated.  The Phase I survey  shall be
ordered from an environmental  consultant by Rentech,  at its expense,  no later
than ten (10) days after the date hereof and shall be  completed  as promptly as
possible.  If a Phase II environmental  survey is required by the  environmental
consultant  preparing the Phase I survey,  REN shall be responsible for the cost
of the Phase II survey.

         5.2      Cooperation.  Each  of REN and  Rentech  shall  use  its  best
efforts to cause the sale contemplated by this Agreement to be consummated, and,
without  limiting the generality of the foregoing,  to make all filings with and
give notices to third parties  which may be necessary or reasonably  required in
order to effect the transactions contemplated hereby.

         5.3      Access to  Premises.  Between  the date hereof and the Closing
Date, REN will afford to the officers and authorized  representatives of Rentech
access during normal  business  hours to the  premises,  properties,  and to the
books and records of REN in order that  Rentech  shall have the  opportunity  to
make such investigations as it shall desire and to permit Rentech to review such
financial and operating data and other  information  regarding Ren's business as
Rentech  shall from time to time  reasonably  request.  Neither party shall make
public  disclosure of this Agreement  prior to the Closing except as required in
connection with transfer of permits, licenses and other such transactions.

         5.4      Confidentiality.

                  (a)      Until the Closing has been completed,  Rentech agrees
         to keep  confidential  the non-public  information that REN provides to
         Rentech  and not to use such  information  for any  purpose  whatsoever
         other than evaluating the transactions  contemplated in this Agreement.
         Rentech  further agrees that during such time it will not make any oral
         or written disclosures concerning the information provided to it to any
         person without the prior approval of Ren;  provided,  however,  Rentech
         may  disclose  such  confidential  information  to  persons  subject to
         Rentech's control who have a need to know such confidential information
         in  connection  with the  negotiations  between  Rentech  and  Ren,  to
         Rentech's  affiliates,   to  existing  or  prospective  lenders  of  or
         investors  in  Rentech,  all of whom will be directed  and  required to
         maintain such information in the strictest confidence at all times.

                  (b)      Except to the extent  that  Rentech  has made  public
         announcements  about this Agreement and its loans to and acquisition of
         stock of Ren, which Rentech is expressly permitted to do, REN agrees to
         keep in  strictest  confidence  and to refrain from  disclosing  to any
         person,  except to its legal  counsel,  any aspect of the  transactions
         contemplated  in this  Agreement,  including  (without  limitation) the
         identify of Rentech,  the  existence of this  Agreement,  the terms and
         conditions set forth in this Agreement, the contents of any discussions
         and negotiations  that already have taken place and that may take place
         in the  future,  and the fact that REN or  Rentech is  contemplating  a
         transaction  of the type set  forth in this  Agreement,  as well as any
         other matter relating to this Agreement or relating to the transactions
         contemplated thereby.


                                   ARTICLE VI.
                           REPRESENTATIONS BY RENTECH

          Rentech represents, promises and warrants to REN as follows:


                                       10


         6.1      Organization. Rentech is a corporation duly organized, validly
existing,  and in good standing under the laws of the State of Colorado, and has
all corporate  power and authority to own its property and carry on its business
as now conducted.

         6.2 Authorization. The execution, delivery and performance of this
Agreement and any other  documents or instruments  contemplated  hereby has been
duly  authorized  by all  necessary  corporate  actions  of  Rentech,  and  this
Agreement has been executed and will be delivered by Rentech and will constitute
a legal, valid and binding obligation of Rentech  enforceable in accordance with
their terms.

         6.3      Compliance  With Other  Instruments.  Rentech has complete and
unrestricted power to undertake and perform all of the obligations  contained in
this Agreement.  Neither the execution and delivery, nor the consummation of the
transactions  provided  for in this  Agreement,  will  violate  the  Articles of
Incorporation  or the  bylaws of Rentech or any  material  agreement,  mortgage,
indenture,  license,  franchise,  permit,  lease or other instrument,  judgment,
decree, order, law or regulation by which Rentech is bound.

         6.4      Litigation. There is no action, suit, litigation or proceeding
pending, or, to the best knowledge of Rentech, threatened against or relating to
Rentech  which  could  adversely  affect the  ability of Rentech to perform  the
transactions contemplated by this Agreement.


                                  ARTICLE VII.
                  CONDITIONS PRECEDENT TO RENTECH'S OBLIGATIONS

         The obligation of Rentech to consummate the  transactions  contemplated
in this  Agreement  is subject to the  fulfillment  to its  satisfaction  or the
following  conditions  prior to or at the Closing  (unless  expressly  waived in
writing by Rentech).

         7.1      Representations, Warranties and Covenants. The representations
and warranties made by REN shall be true and correct in all material respects at
and as of the Closing  Date;  and REN shall have  performed  and complied in all
material  respects with all covenants,  agreements  and conditions  contained in
this  Agreement  required to be  performed  or complied  with by it prior to the
Closing,  and REN shall provide to Rentech at the Closing a certificate  to such
effect executed by Ren.

         7.2      Closing  Documents.  REN shall have taken all the  actions and
delivered  all the  documents  required of it  according  to the  provisions  of
Article II.

         7.3      Litigation. There shall be no litigation pending or threatened
against REN with respect to the  consummation  of this  Agreement or which could
adversely affect the ability of REN to transfer the REN Shares to Rentech.

         7.4      No Adverse Effect,  etc. No material adverse effect shall have
occurred  between the date of this Agreement and completion of the Closing,  nor
shall any other fact or  circumstance  have  occurred  that could be expected to
have a material adverse effect,  and REN shall certify to that effect. REN shall


                                       11


not have become aware of any fact or circumstance materially adversely affecting
or that could be expected to materially  adversely affect Ren's right to conduct
its  business  substantially  as it was being  conducted  as of the date of this
Agreement.

         7.5      Rentech's Due Diligence.  Rentech shall have completed its due
diligence  with  respect to Ren,  its business and its assets and the results of
such due diligence shall be satisfactory to Rentech.

         7.6      Charter Documents, etc. REN shall have delivered (i) a copy of
its Articles of  Incorporation  certified by the Secretary of State of the State
of Oklahoma and a good standing  certificate  for REN issued by the Secretary of
State of the State of Oklahoma and (ii) a  certificate  of the  Secretary of REN
certifying  that attached  thereto is a copy of Ren's bylaws as in effect on the
date thereof, copies of directors' and shareholders' resolutions authorizing the
transactions contemplated by this Agreement and certifying the incumbency of the
officers  authorized to execute this Agreement and the documents and instruments
delivered by REN in connection therewith.

         7.7      Agreements Between  Shareholders.  The Shareholders shall have
executed the Agreement  Between  Shareholders  attached  hereto as Exhibit B and
incorporated herein by this reference.

         7.8      Confidentiality  Agreements.  The  employees  of REN listed on
Schedule 3.2 shall have executed Confidentiality Agreements in the form attached
hereto as Exhibit C, which is incorporated herein by this reference.

         7.9      Resignation  of Officers  and  Directors.  Rentech  shall have
received the  resignation,  effective as of the Closing,  of Nancy L. Roberts as
Secretary and Treasurer of Ren, a form of which is attached  hereto as Exhibit F
and incorporated herein by this reference.

         7.10     Election of New Directors and Appointment of New Officers. The
Shareholders  shall have  executed a written  consent  increasing  the number of
directors of REN to seven,  and shall have  appointed  Ronald C. Butz,  James P.
Samuels,  William Earl Somerville and Dennis L. Yakobson,  to fill the vacancies
in the Board of  Directors.  The  directors of REN shall have executed a written
consent to appoint the following  persons to the offices set forth next to their
names:

                  Gary A. Roberts   -       President
                  James P. Samuels  -       Vice President and Treasurer
                  Martin D. List    -       Vice President - Manufacturing
                  Ronald C. Butz    -       Secretary

Forms of the Written  Consent of  Shareholders  and Written Consent of Directors
are attached hereto as Exhibits D and E, respectively.

         7.11     General.  All instruments and legal and corporate  proceedings
in connection  with the  transactions  contemplated  by this Agreement  shall be
reasonably satisfactory in form and substance to Rentech, and Rentech shall have
received counterpart  originals,  or certified or other copies, of all documents
that it may reasonably request in connection therewith.


                                       12



                                  ARTICLE VIII.
                    CONDITIONS PRECEDENT TO REN'S OBLIGATIONS

         The obligation of REN to consummate the  transactions  contemplated  by
this  Agreement  is  subject  to  the  fulfillment  to its  satisfaction  of the
following conditions prior to at the Closing (unless expressly waived in writing
by Ren):

         8.1      Representations  Warranties and Covenants. The representations
and  warranties  made by  Rentech  shall be true  and  correct  in all  material
respects at and as of the  Closing  Date and Rentech  shall have  performed  and
complied in all material respects with all covenants,  agreements and conditions
contained in this  Agreement  required to be  performed  or complied  with by it
prior  to the  Closing,  and  Rentech  shall  provide  to REN at the  Closing  a
certificate to such effect executed by an officer of Rentech.

         8.2      Closing  Documents.  Rentech  shall have taken all the actions
and delivered all the  documents  required of it according to the  provisions of
Article II.

         8.3      Employment  Contracts.  REN shall  employ  Gary A.  Roberts as
president of REN for a period of three years from the Closing  Date  pursuant to
the terms and conditions of the employment  contract  attached hereto as Exhibit
A.

         8.4      Litigation. There shall be no litigation pending or threatened
against Rentech with respect to the consummation of this Agreement.

         8.5      Consideration.  Rentech  shall  have paid to REN the  Purchase
Price.

         8.6      General.  All instruments and legal and corporate  proceedings
in connection  with the  transactions  contemplated  by this Agreement  shall be
reasonably  satisfactory  in form  and  substance  to Ren,  and REN  shall  have
received counterpart  originals,  or certified or other copies, of all documents
that it may reasonably request in connection therewith.


                                   ARTICLE IX.
                         FAILURE OF CONDITIONS: REMEDIES

         9.1      Failure of Conditions  Precedent - No Breach. In the event any
condition  precedent to the  obligations of either party are not satisfied as of
the Closing and the failure to satisfy the  condition  precedent is not due to a
breach  of this  Agreement  by the  other  party,  the  party  whose  conditions
precedent  have not been  satisfied  shall have the option of  terminating  this
Agreement or waiving the unsatisfied  condition  precedent and closing hereunder
(and,  in either  event,  waiving  any claim for damages or  indemnity  relating
thereto).

         9.2      Failure of Conditions  Precedent of REN- Breach.  In the event
any  condition  precedent  to the  obligations  of REN is not  satisfied  on the
Closing  Date and the failure to satisfy  the  condition  precedent  is due to a
breach of this Agreement by Rentech, or in the event of any other breach of this
Agreement by Rentech, REN shall have the right to terminate this Agreement,  and
Rentech shall pay to REN$10,000  as liquidated  damages.  The parties agree that
the  foregoing   liquidated   damages  are   reasonable   considering   all  the
circumstances  existing as of the date of this Agreement and constitute the good


                                       13


faith  estimate  of the  parties of the actual  damages  reasonably  expected to
result from the termination of this Agreement by REN due to Rentech's  breach of
this Agreement.  REN agrees that, to the fullest extent  permitted by law, Ren's
right to  payment of such  liquidated  damages  shall be its sole and  exclusive
remedy,  if the Closing does not occur,  with respect to any damages  whatsoever
that REN may  suffer  or  allege  to suffer as a result of any claim or cause of
action asserted by REN relating to or arising from breaches of this Agreement by
Rentech.  Upon any  termination  of this  Agreement  for any reason,  the entire
unpaid  balance of  principal  and interest  due on the  Promissory  Notes shall
become due at once.


                                   ARTICLE X.
                                 INDEMNIFICATION

         10.1     Survival of Representations  Warranties and Covenants.  All of
Ren's  representations,  covenants and  warranties  contained  herein and in any
documents  delivered pursuant to this Agreement (except those waived pursuant to
Section 9.1) shall survive the Closing hereunder.

         10.2     Indemnity by Ren. REN shall indemnify, save, and hold harmless
Rentech from any damages as hereinafter defined.  Damages, as used herein, shall
mean and include any loss, cost, expense, or other liability,  including counsel
fees,  which Rentech may incur or suffer,  by reason of the inaccuracy of any of
Ren's representations contained in this Agreement.

         10.3     Indemnity by Rentech. Rentech shall indemnify,  save, and hold
harmless REN from any damages as hereinafter  defined.  Damages, as used herein,
shall mean and include any loss, cost,  expense,  or other liability,  including
counsel fees,  which REN may incur or suffer by reason of the  inaccuracy of any
representation of Rentech contained in this Agreement.

         10.4     Procedures   for   Indemnification.   The  party  entitled  to
indemnification  (Indemnitee)  shall,  as promptly as is reasonably  practicable
after it becomes  aware  thereof,  notify the other  party  (Indemnitor)  of the
existence  of  any  claim,   demand  or  other  matter  to  which   Indemnitor's
indemnification  obligations  apply  and  shall  give  Indemnitor  a  reasonable
opportunity  to defend the same at its own expense  and with  counsel of its own
selection reasonably acceptable to Indemnitee;  provided,  that Indemnitee shall
at all times, also have the right to fully participate in the defense at its own
expense.  Indemnitor may, at its own discretion,  settle any dispute,  demand or
claim defended by it hereunder;  provided,  any such settlement  shall be solely
for  Indemnitor's  account  and  Indemnitee  shall not be liable for any amounts
whatsoever payable in connection with any such settlement.  If Indemnitor shall,
within a reasonable time after notice to it, fail to so defend, Indemnitee shall
have the right,  but not the  obligation,  to  undertake  the defense of, and to
compromise or settle (exercising  reasonable  business  judgment),  the claim or
other matter on behalf, and at the risk of, Indemnitor.


                                   ARTICLE XI.
                                     GENERAL


                                       14


         11.1     Notice.   All   notices,    requests,    demands   and   other
communications  hereunder  shall be  furnished to the other party at its address
listed below (or such other address as provided in accordance  with this Section
11.1), shall be in writing, and shall be sent either by telecopy, hand delivery,
or reputable overnight courier, addressed as follows or to such other address or
addresses  of which the  respective  party shall have  notified the other party.
Each  such  notice or other  communication  shall be  effective  (a) if given by
telecopy,  when such telecopy is  transmitted  and the  transmission  thereof is
confirmed  by the  sender's  telecopier,  (b) if  given by  reputable  overnight
courier,  one business day after being delivered to such courier or (c) if given
by any other means, when actually received.

         (a)      If to Rentech, to:
                  -----------------
                  Rentech, Inc.
                  Attention: Ronald C. Butz, Vice President
                  1331 17th St., Suite 720
                  Denver, CO 80202

         (b)      If to Rentech, to:
                  -----------------
                  REN Corporation
                  Attention:  Gary A. Roberts, President
                  5900 S. Perkins Road
                  Stillwater, OK 74074

         11.2     Amendment. This Agreement may be amended or modified only by a
written  instrument  executed  by the  party  hereto  against  which it is to be
enforced.

         11.3     Expense of Parties.  Except as otherwise specifically provided
herein,  each party to this  Agreement  shall pay its own  expenses  (including,
without   limitation,   the  fees  and  expenses  of  their  respective  agents,
representatives,  counsel and  accountants)  incidental to the  preparation  and
carrying  out of this  Agreement.  In the event a party  commences  legal action
against another party to enforce its rights under this Agreement, the prevailing
party in such action  shall be entitled to recover all of its costs and expenses
in connection therewith, including reasonable attorneys' fees and costs.

         11.4     Brokers.  REN agrees to indemnify Rentech,  and Rentech agrees
to  indemnify  Ren,  against any claim by any third  person for any  commission,
brokerage,  finder's fee or other  payment  based upon any alleged  agreement or
understanding  between such party and such third  person,  whether  expressed or
implied from the actions of such party.

         11.5     Governing Law. This Agreement is being  delivered in and shall
be  construed  in  accordance  with and  governed  by the  laws of the  State of
Colorado.

         11.6     Headings.  The headings  contained in this  Agreement  are for
reference  purposes  only  and  shall  not in any  way  affect  the  meaning  or
interpretation of this Agreement.  Terms used with initial capital letters shall
not in any way affect the meaning or  interpretation  of this  Agreement.  Terms
used with initial capital letters will have the meanings  specified,  applicable
to both  singular  and plural  forms,  for all purposes of this  Agreement.  All
pronouns (and any variation) will be deemed to refer to the masculine,  feminine
or neuter,  as the  identify of the person may  require.  The singular or plural
includes the other,  as the context  requires or permits.  The word include (and
any variation) is used in an  illustrative  sense rather than a limiting  sense.
The word  "day"  means a calendar  day.  All  references  to  "Sections"  are to
sections of this Agreement unless indicated otherwise.


                                       15


         11.7     Prior  Agreements;  Counterparts.  This  Agreement,  with  its
Exhibits  and  Schedules,   merges  and  integrates  all  prior  agreements  and
representations  respecting  this  transaction,  whether  written  or oral,  and
constitutes  the sole  agreement of the parties in  connection  therewith.  This
Agreement may be executed simultaneously in any number of counterparts,  each of
which shall be deemed an original,  but all of which together  shall  constitute
one and the same instrument.

         11.8     Assignment.  This Agreement  shall not be assignable by REN or
Rentech, except that Rentech may assign this Agreement to a corporation of which
Rentech is the sole  shareholder  provided  Rentech  remains fully liable to REN
hereunder.  Subject to the foregoing,  this Agreement shall be binding upon, and
inure to the benefit of, and be enforceable  by, the  respective  successors and
permitted  assigns of REN and  Rentech.  Nothing in this  Agreement,  express or
implied,  is  intended  to confer  upon any other  person any rights or remedies
under or by reason of this Agreement.

         11.9     Waiver.  The failure of any party to enforce any right arising
under this Agreement on one or more  occasions  shall not operate as a waiver of
that or any other right on that or any other occasion.

         11.10    Exclusivity  of  Representations.  REN  shall not be deemed to
have made to Rentech any representation or warranty other than as expressly made
by REN in  Section  3.  Rentech  shall  not be  deemed  to have  made to REN any
representation or warranty other than as expressly made by Rentech in Section 6.

         11.11    Severability.  Any term or provision of this Agreement that is
invalid or unenforceable  in any situation in any jurisdiction  shall not affect
the validity or  enforceability  of the remaining terms and provisions hereof or
the validity or  enforceability  of the offending term or provision in any other
situation or in any other jurisdiction.

         11.12    Construction.  The parties  have  participated  jointly in the
negotiation  and  drafting  of this  Agreement.  In the  event an  ambiguity  or
question of intent or interpretation arises, this Agreement will be construed as
if drafted  jointly by the parties,  and no  presumption or burden of proof will
arise  favoring or  disfavoring  any party by virtue of the authorship of any of
the provisions of this Agreement.  The parties intend that each  representation,
warranty and covenant  contained herein will have independent  significance.  If
any party breaches any representation,  warranty or covenant contained herein in
any respect,  the fact that there  exists  another  representation,  warranty or
covenant relating to the same subject matter  (regardless of the relative levels
of  specificity)  which the  party has not  breached  will not  detract  from or
mitigate  the fact that the  party is in  breach  of the  first  representation,
warranty or covenant.

         IN WITNESS WHEREOF, the parties have duly executed this Agreement as of
the date given in the opening paragraph.

SELLER:                                              BUYER:

REN CORPORATION                             RENTECH, INC.


By:                                         By:
   --------------------------                  ---------------------------------
   Gary A. Roberts, President                  James P. Samuels,
                                               Vice President - Finance

                                       16