Exhibit 10.6

                              EMPLOYMENT AGREEMENT


         THIS AGREEMENT (the Agreement) is made effective as of August 31, 2001,
between REN CORPORATION, an Oklahoma corporation (sometimes called the Company),
and GARY A. ROBERTS (Employee).

                            Background Circumstances:

         A.       The  Company  has  agreed  with  Rentech,   Inc.,  a  Colorado
corporation  (Rentech),  that  Rentech  will  purchase  56%  of the  issued  and
outstanding  shares of common stock of the Company  pursuant to a Stock Purchase
Agreement  dated August 1, 2001 between the Company and Rentech.  The  scheduled
closing date of the purchase is August 31, 2001.  The Company and Rentech intend
that the business of the Company be continued as it was  conducted  prior to the
purchase.

         B.       The Board of  Directors  of the  Company  recognizes  that the
Employee is a founder of the business of the Company and has made a  substantial
contribution  to the growth and success of the Company.  The Board believes that
it is in the best interests of the Company and its  shareholders for the Company
to continue its employment of the Employee.  The Board has  determined  that the
Company  should enter into this Agreement to encourage and secure the Employee's
continued  dedication to the Company as a member of its management and to retain
the experience, abilities and services of the Employee.

         C.       The  Company  desires  to employ  and  retain  for  itself the
experience,  abilities  and  services of the Employee on the terms and under the
conditions set forth in this Agreement.

         NOW THEREFORE, in consideration of the background circumstances and the
following covenants and agreements, the parties hereto agree as follows:

         1.       Employment.  The Company  shall employ the Employee to provide
services as an employee of the Company,  and the Employee shall perform services
for and be employed by the Company,  all in  accordance  with the  provisions of
this Agreement, and subject to the terms and conditions hereof.

         2.       Duties and Scope of Responsibilities. The Employee shall serve
as President of the  Company,  and shall report to the Vice  President - Finance
and Chief Financial Officer of Rentech (James P. Samuels or his successor).  The
Employee shall be in charge of the day-to-day operations of the business,  which
shall be  conducted in the same  general  manner as the  business was  conducted
before the  purchase of the common  stock of the  Company,  except to the extent
that the Board of Directors of the Company,  in consultation  with the Employee,
elects to change  the  manner  and scope of the  business.  The  Employee  shall
supervise  other employees of the Company and shall have the authority to employ
and discharge  employees.  The Employee shall perform such other duties as shall
from time to time be reasonably  assigned to him by the Vice  President  Finance
and Chief  Financial  Officer of Rentech  (James P.  Samuels or his  successor).
Except  for  purchase   orders  and   contracts   that  have  terms  and  prices
substantially similar to those by which the Company has previously conducted its
business  before  this  date,  Employee  shall have no  authority  to commit the
Company  to, and may not  execute,  any  agreement  or  contract  that binds the
Company for an amount of money in excess of $50,000, to installments  payable in


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excess of that amount or for a period of time  longer  than six months,  or that
deviates from the previous business practices of the Company,  as of the date of
this  Agreement,  unless such agreement or contract has previously been approved
in writing by the Board of Directors of the Company.  The Employee  shall devote
his full working time to his responsibilities  hereunder and to the business and
affairs of the Company, and shall not be employed by any other person or entity.

         3.       Term of Employment. The term of employment shall commence upon
the date of this  Agreement and continue for a period of three years;  provided,
however, the term of employment shall be automatically renewed at the end of the
term for successive one-year periods unless either party gives the other written
notice of termination at least 90 days in advance of the applicable term.

         4.       Compensation.  The  Employee  shall  be  paid  a  salary  of X
Thousand  Dollars  ($X2,000.00)  per annum,  in semi-monthly  installments.  The
Company's  obligation to compensate the Employee shall  terminate and cease upon
the termination of the Employee's employment hereunder for any reason, except in
the event of the death of  Employee,  the Company  shall  continue to pay to the
Employee's  estate his salary for the  remainder  of the then  existing  term of
employment.

         5.       Expenses and Fringe Benefits. The Employee shall be reimbursed
for reasonable  out-of-pocket expenses incurred by him in the performance of his
duties  hereunder  in  accordance  with  the  general  policies  of the  Company
established by its Board of Directors.  During the term of this  Agreement,  the
Employee shall be entitled to participate in all those regular fringe  benefits,
including vacations, which are currently provided to employees of the Company or
are provided to them from time to time hereafter.

         6.       Non-Competition.

                  6.1      Covenant Not To Compete. The Company and the Employee
         recognize  that the  services  to be  rendered  to the  Company  by the
         Employee under this Agreement are special,  unique and of extraordinary
         character in that the Employee has been involved in the  manufacture of
         complex,  computer  controlled test systems to test the  specifications
         and quality of hydraulics  and many  additional  variables of automated
         equipment  produced  by  them.  Therefore,  during  the  term  of  this
         employment  hereunder and for three years following the termination for
         such employment for any reason whatsoever (the Non-Competition Period),
         if the Employee receives all compensation to which he is entitled under
         this Agreement,  the Employee  covenants and agrees not to, without the
         express  written  consent of the Company,  directly or indirectly  own,
         manage,   operate,   control,   advise,  lend  money  to,  endorse  the
         obligations  of,  or  participate  in or be  connected  as an  officer,
         director,  five percent or more stockholder of a publicly-held company,
         or as a stockholder,  employee, partner, agent, consultant or otherwise
         of a closely held company or of any enterprise or  individual,  that is
         engaged in the  business  of  developing,  manufacturing  or  marketing
         processes,  technology,  products  or  services  that  are  similar  to
         processes,  technology,  products or services  which have been,  or are
         being   developed  or  are  planned  (as   documented   by   memoranda,
         instruments,  writings  or other  compilations  of  information  of the
         Company) to be developed  by the Company,  and will not, in any manner,
         either  directly  or  indirectly,  compete  with  the  Company  in  its
         business.  The Company may  withhold  its consent to any such  proposed
         competition in its sole and absolute discretion.

                  6.2      Non-Solicitation.  For a period of one year following
         Employee's  termination of employment  under this  Agreement,  Employee
         will not,  without the express prior  written  approval of the Board of
         Directors  (i)  directly  or   indirectly,   in  one  or  a  series  of
         transactions,  recruit,  solicit or otherwise  induce or influence  any
         proprietor, partner, stockholder,  lender, director, officer, employee,


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         sales agent,  joint venturer,  investor,  lessor,  supplier,  licensee,
         customer,  agent,  representative  or  any  other  person  which  has a
         business  relationship with the Company or had a business  relationship
         with the Company within the twenty-four month period preceding the date
         of the Employee's termination of employment, to discontinue, reduce, or
         modify  such  employment,  agency  or  business  relationship  with the
         Company,  or (ii)  employ  or seek to  employ  or  cause  any  business
         organization  in direct or  indirect  competition  with the  Company to
         employ or seek to employ any person or agent who is then (or was at any
         time  within  six  months  prior  to  the  date  the  Employee  or  the
         competitive  business  employs or seeks to employ such person) employed
         or retained by the  Company.  Notwithstanding  the  foregoing,  nothing
         herein  shall  prevent  the  Employee   from   providing  a  letter  of
         recommendation  to an  employee  with  respect  to a future  employment
         opportunity.

                  6.3      Outside Business Activity.  The Employee,  during the
         term of his employment by the Company hereunder, shall not undertake or
         engage in any other  employment,  occupation or business  enterprise in
         which Employee actively participates.  Employee shall at all times keep
         the Company informed of any outside business activity by him, and shall
         not engage in any activity that may be in conflict with this  Agreement
         or the Company's business or its best interests.

         7.       Confidentiality.  The Employee  acknowledges that, as a result
of his employment by the Company, he has learned  Confidential  Information,  as
defined in Section 7.1, that is owned by the Company,  and which is of a special
and unique  value and nature  relating to the  business of the  Company.  In the
course of his  further  employment  by the  Company,  Employee  will  learn more
Confidential  Information  and may  add to the  Confidential  Information.  As a
material  inducement to the Company to enter into this  Agreement and to pay the
Employee the compensation described in this Agreement,  the Employee agrees that
he will not,  except in the normal and  proper  course of his duties  hereunder,
disclose or use or enable  anyone else to  disclose  or use,  either  during the
Non-Competition  Period (as defined in Section  6.1) or at any time  thereafter,
any such  Confidential  Information  without  the prior  written  consent of the
Company.  The  Company  may  withhold  its  consent  in its  sole  and  absolute
discretion.

         7.1      Confidential   Information.   "Confidential   Information"  is
         non-public  information  regarding  the  Company  and  its  proprietary
         processes for the  manufacture  of complex,  computer  controlled  test
         systems sold to test the  specifications  and quality of hydraulics and
         the many additional  variables of automated equipment produced by them;
         contractual  licensing terms and arrangements;  customers and potential
         customers;  costs  and  performance  data  relating  to  the  Company's
         products and processes; patent applications;  and trade secrets used in
         the Company's  business that provide an advantage over  competitors who
         do not know or use  them,  including  computer  software  programs  and
         source codes,  engineering  designs and specifications for the computer
         controlled test systems.

         7.2      Exception to Confidentiality. It is agreed, as an exception to
         the foregoing obligations of confidentiality, that information received
         by the Employee as a result of his  employment  shall not be considered
         confidential,  and he shall not be limited in  disclosing  the same, if
         and to the extent that the information, as shown by competent evidence:
         (i) is or becomes,  through no fault of the party obligated to maintain
         confidentiality, in the public domain; (ii) is lawfully obtained by him
         from a source  other than the Company or its agents;  (iii) was already
         known to him at the time of its receipt,  as shown by reasonable  proof
         filed with the Company within a reasonable  time after its receipt;  or
         (iv)  required  to be  disclosed  by  law or  order  of  any  court  or
         governmental authority having jurisdiction.

         7.3      Published  Disclosure.  It is agreed  that the  disclosure  of
         certain information by the Company in a publication, such as in letters
         patent or by otherwise  placing it in the public domain,  will not free
         the  Employee  from  his  obligation  to  maintain  in  confidence  any
         information not specifically  disclosed in or fairly ascertainable from


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         the  publication or other  disclosure,  such as, for example,  the fact
         that  information in the  publication or any portion of it is or is not
         used by either  party.  The  Employee  shall  have the right to publish
         information or articles pertaining to the Company's computer controlled
         test equipment only if such information is not confidential,  and, with
         respect to Confidential  Information,  only upon prior written approval
         by the Company, which it may withhold in its absolute discretion.

         7.4      Non-Use  After  Termination.  The  Employee  shall not use the
         Confidential  Information  after  termination  or  expiration  of  this
         Agreement  unless and until such time as the  information  ceases being
         Confidential Information pursuant to the provisions of Section 7.2.

         7.5      Books and Records.  The Employee agrees that all documents and
         other tangible  property of any nature  pertaining to activities of the
         Company or to any Confidential Information, in his possession now or at
         any  time  during  the  period  of his  employment  with  the  Company,
         including  without  limitation,  financial data,  formulae,  processes,
         operating results of processes, notes, memoranda,  notebooks,  manuals,
         reports, studies, data sheets, records, blueprints, designs, electronic
         or mechanical data storage devices and records,  and computer  software
         programs and their source  codes,  are and shall be the property of the
         Company.  The  Employee  will return to the Company all  originals  and
         copies in his  possession  or control that  contain  such  information,
         whenever  requested  by the  Company  from  time  to  time  during  the
         Non-Competition Period and after termination of his employment.

         8.       Inventions and Discoveries. The Employee and the Company agree
that:

         8.1      Disclosure By Employee. The Employee will promptly disclose to
         the Company in writing, complete and accurate information pertaining to
         each invention,  discovery,  improvement,  device,  design,  apparatus,
         process,  technological advance,  innovation,  idea, concept, method or
         product (the Inventions)  whether  patentable or not, and all writings,
         drawings,  software,  semiconductor  mask,  works  and  other  works of
         authorship  pertaining  to  these  Inventions  (Works  of  Authorship),
         whether  copyrightable or not, made, developed,  perfected,  devised or
         conceived  during  his  employment  with the  Company,  or  during  the
         12-month  period  following his  employment  by the Company,  which are
         within or in any way related to the existing or contemplated scope (now
         or at any later  time  during  such  period),  of the  business  of the
         Company,  whether or not  developed  on the  Employee's  own time.  The
         determination  of whether or not an Invention or Work of  Authorship is
         within the  contemplated  scope of the  business of the Company will be
         based  on the  documentary  evidence  of  the  Company,  including  all
         documents,  memoranda, writings or other compilations of information of
         the Company  relating to the scope of the business of the  Company.  An
         Invention  or Work of  Authorship  shall be  deemed  to have  been made
         within  such  period  of time if it is made or  conceived  within  such
         period and results from or was suggested by the  Employee's  employment
         by the Company.

         8.2      Assignment By Employee. The Employee will, upon request of the
         Company,  assign to the Company or to any other party designated by the
         Company,  all of his right,  title and interest in and to any or all of
         said  Inventions  or  Works  of  Authorship,  any  copyrights  obtained
         thereon,  and any patent applications filed thereon,  together with all
         extensions,  re-issues,  and  renewals  thereof in this and all foreign
         countries  and patents  granted.  He will  promptly  execute all proper
         papers for these  purposes as the Company may  request,  and for use in
         applying for, obtaining, and maintaining all such patents or copyrights
         at the expense of the Company.  The  Employee's  obligations to execute
         the papers and  assignments  specified in this Section  shall  continue
         beyond the period of his employment and shall bind his heirs,  assigns,
         executors and other legal representatives.


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         9.       Right To Injunctive Relief.  The Employee  acknowledges that a
breach  by the  Employee  of any of the  terms  of  Sections  6, 7 or 8 of  this
Agreement will cause irreparable harm to the Company, and that the Company shall
therefore  be  entitled  to any and all  equitable  relief,  including,  but not
limited to,  injunctive  relief,  and to any other  remedy that may be available
under any applicable law or agreement  between the parties,  and to recover from
the Employee all costs of litigation  including,  but not limited to, reasonable
attorneys'  fees and court costs.  The parties  hereto  further  agree that this
Agreement  shall be  enforced  wherever  the  Company is doing  business  at the
termination of the Employee's  employment  hereunder and wherever the Company at
such time  reasonably  foresees,  plans and  expects to do  business  during the
Non-Competition Period.

         10.      Entire  Agreement.  The Company and the  Employee  acknowledge
that this Agreement  contains the full and complete  agreement between and among
the parties, that there are no oral or implied agreements or other modifications
not  specifically  set forth herein,  and that this Agreement  supersedes  prior
agreements or understandings pertaining to this subject, between the Company and
the  Employee,  whether  written  or oral.  The  parties  further  agree that no
modifications  of this  Agreement  may be made  except  by  means  of a  written
agreement or memorandum signed by the parties.

         11.      Governing  Law.  The parties  acknowledge  that the  Company's
principal  place of business is located in the state of Oklahoma,  and that this
Agreement  has been  entered  into in the state of  Oklahoma  and that they wish
legal  certainty  and  predictability  as to the  terms  of  their  undertaking.
Accordingly,  the parties hereby agree that this agreement  shall be constructed
in  accordance  with  the  laws  of  the  state  of  Oklahoma,   without  giving
consideration to its choice of law provisions.

         12.      Captions.  The  captions  or  section  headings  used  in this
Agreement  are for ease of reference  only and shall have no bearing  whatsoever
upon the construction, interpretation and effect of this Agreement.

         13.      Severability.  The Employee believes and acknowledges that the
provisions  contained in this  Agreement,  including the covenants  contained in
Sections 6, 7, and 8 of this Agreement, are fair and reasonable. Nonetheless, in
the event that any  provision  or any part of any  provision  of this  Agreement
found by a court to be void or  unenforceable  for any reason  whatsoever,  then
such provision shall be stricken,  severed from this Agreement,  and of no force
and  effect.  Unless  such  stricken  provision  goes  to  the  essence  of  the
consideration  bargained  for by a  party,  the  remaining  provisions  of  this
Agreement shall continue in full force and effect,  and to the extent  required,
shall be modified to preserve their validity.

         14.      Successors and Assigns.  This Agreement  shall be binding upon
and shall inure to the benefit of the Company and its  successors  and  assigns.
This  Agreement  shall be  binding  upon and shall  inure to the  benefit of the
Employee and his personal  representatives,  but shall not be  assignable by the
Employee.

         15.      Notice.  All  notices,   requests  and  other   communications
hereunder  shall be in writing and shall be  delivered by courier or other means
of personal  service  (including  by means of a  nationally  recognized  courier
service or professional messenger service); or sent by facsimile (if a facsimile
number is provided by a party to be notified)  or mailed  first  class,  postage
prepaid, by certified mail, return receipt requested; in all cases, addressed to
each  party  at  the  following  address.  All  notices,   requests,  and  other
communications  shall be deemed given on the date of actual  receipt or delivery
as  evidenced by written  receipt,  acknowledgment  or other  evidence of actual
receipt or delivery to the address  specified  above.  Notice sent by  facsimile
shall be deemed  given on the date  printed by the  sender's  facsimile  machine
confirming receipt of the facsimile by the other party's facsimile machine.  Any
party  hereto may from time to time,  by notice in  writing  served as set forth
previously, designate a different address or a different or additional person to
which all such notices or communications thereafter are to be given.


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If to Company:                                       With Copy to:
-------------                                        ------------

Rentech, Inc.                                        Mr. James P. Samuels
1331 17th Street, Suite 720                          Rentech, Inc.
Denver, CO 80202                                     1331 17th Street, Suite 720
Attention:  Chief Operating Officer                  Denver, CO 80202

If to Employee:
--------------


         16.      Continuing  Effect.  The  covenants  and  undertakings  of the
Employee   specified  in  this  Agreement  shall  survive  expiration  or  other
termination of this Agreement to the extent expressed herein.

         IN WITNESS  WHEREOF,  the Company has hereunder signed its name and the
Employee  hereunder has signed his name,  all as of the day and year first above
written.

REN CORPORATION                             EMPLOYEE:


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