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                                                                  EXECUTION COPY

                            STOCK PURCHASE AGREEMENT


         THIS STOCK PURCHASE AGREEMENT (this "Agreement"), is made as of
March 18, 2000, by and between RENTECH, INC., a corporation organized under
the laws of the State of Colorado, with headquarters located at 1331 17th
Street, Suite 720, Denver, Colorado 80202 (the "Company") and FOREST OIL
CORPORATION, a corporation organized under the laws of the State of New York,
with headquarters located at 1600 Broadway, Suite 2200, Denver, Colorado
80202 (the "Buyer").

                            BACKGROUND CIRCUMSTANCES.

         A. The Company and the Buyer are executing and delivering this
Agreement in reliance upon the exemption from securities registration
afforded by the provisions of Regulation D ("Regulation D") as promulgated by
the United States Securities and Exchange Commission (the "SEC") under the
Securities Act of 1933, as amended (the "1933 Act");

         B. The Buyer desires to purchase from the Company, and the Company
desires to sell to the Buyer, for the amount and upon the terms and
conditions stated in this Agreement, in a closing or closings as herein
described, 1,000,000 shares of the Company's common stock, par value $.01 per
share ("Common Stock"), an option to purchase 2,000,000 shares of Common
Stock having an exercise price of $1.25 per share and expiring December 31,
2001, and an option to purchase 1,000,000 shares of Common Stock having an
exercise price of $5.00 per share and expiring December 31, 2004. The options
are granted in separate agreements executed by the parties concurrently with
this Agreement (the "Option Agreements").

         NOW, THEREFORE, in consideration of their respective promises
contained herein and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by the parties, the Company and
the Buyer hereby agree as follows:

         SECTION 1.        PURCHASE AND SALE OF SECURITIES.

         (a) PURCHASE. The Buyer hereby agrees to purchase from the Company,
and the Company agrees to sell to the Buyer, 1,000,000 shares of Common Stock
("Stock"), an option to purchase 2,000,000 shares of Common Stock having an
exercise price of $1.25 per share and expiring December 31, 2001 ("2001
Option"), and an option to purchase 1,000,000 shares of Common Stock having
an exercise price of $5.00 per share and expiring December 31, 2004 ("2004
Option" and, together with the Stock and the 2001 Option, the "Securities").
The 2001 Option and the 2004 Option (collectively, the "Options") shall be
subject to the terms and conditions of the Option Agreements.

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         (b) PURCHASE PRICE. The purchase price for the Stock and the 2001
Option is $600,000. The purchase price for the 2004 Option is $50,000. The
aggregate purchase price for the Securities is $650,000 (the "Purchase
Price").

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         (c) THE CLOSING. The date of the Closing shall be March 20, 2000.
The Purchase Price shall be delivered to the Company by cashier's check or by
wire transfer of immediately available funds in United States Dollars. At the
Closing, the Company shall deliver certificates representing the Stock, duly
issued and executed by the authorized officers on behalf of the Company, to
the Buyer, and the Company and Buyer shall sign and the Company shall deliver
to Buyer the Option Agreements and the Registration Rights Agreement (as
defined below).

         SECTION 2.        BUYER'S REPRESENTATIONS AND WARRANTIES.

         The Buyer understands, agrees with, and represents and warrants to
the Company with respect to its purchase hereunder, that:

         (a) INVESTMENT PURPOSES; COMPLIANCE WITH 1933 ACT. The Buyer is
purchasing the Securities for its own account for investment only and not
with a view towards, or in connection with, the public sale or distribution
thereof, except pursuant to sales registered under or exempt from the 1933
Act. The Buyer is not purchasing the Securities for the purpose of covering
short sale positions in Common Stock established on or prior to the date of
the Closing. The Buyer agrees to offer, sell or otherwise transfer the
Securities only (i) in accordance with the terms of this Agreement and the
Option Agreements, as the same may be applicable, and (ii) pursuant to
registration under the 1933 Act or to a transaction for which registration
under the 1933 Act is not required. Except as set forth in Section 2(f) of
that certain Registration Rights Agreement dated as of the date hereof by and
among the Company, Buyer and Anschutz Investment Company (the "Registration
Rights Agreement") the Buyer does not by its representations contained in
this Section 2(a) agree to hold the Securities for any minimum or other
specific term and reserves the right to dispose of the Securities at any time
pursuant to a registration statement or in accordance with an exemption from
registration under the 1933 Act, in all cases in accordance with applicable
state and federal securities laws.

         (b) ACCREDITED INVESTOR STATUS. The Buyer is an "accredited
investor" as that term is defined in Rule 501(a) of Regulation D. The Buyer
has such knowledge and experience in financial and business matters that it
is capable of evaluating the merits and risks of an investment made pursuant
to this Agreement. The Buyer is aware that it may be required to bear the
economic risk of an investment made pursuant to this Agreement for an
indefinite period of time, and is able to bear such risk for an indefinite
period.

         (c) RELIANCE ON EXEMPTIONS. The Buyer understands the Securities are
being offered and sold to it in reliance on specific exemptions from the
registration requirements of the applicable United States federal and state
securities laws and that the Company is relying upon the truth and accuracy
of, and the Buyer's compliance with, the representations, warranties,
acknowledgments, understandings, agreements and covenants of the Buyer set
forth herein in order to determine the availability of such exemptions and
the eligibility of the Buyer to acquire the Securities.

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         (d) INFORMATION. The Buyer and its advisors, if any, have been
furnished with the Company's Form 10-KSB as filed with the SEC for the fiscal
year ended September 30, 1999, the Company's Form 10-QSB for the fiscal
quarter ended December 31, 1999, and the Company's private placement
memorandum dated October 12, 1999 that was not prepared for the offer and
sale of the Securities. The Buyer and its advisors, if any, have been
afforded the opportunity to ask questions of the Company and have received
complete and satisfactory answers to any such inquiries. The Buyer
understands that its investment in the Securities involves a high degree of
risk. The Buyer has sought such accounting, legal and tax advice as it has
considered necessary to an informed investment decision with respect to the
investment made pursuant to this Agreement.

         (e) NO GOVERNMENT REVIEW. The Buyer understands that no United
States federal or state agency or any other government or governmental agency
has passed on or made any recommendation or endorsement of the Securities or
the fairness or suitability of the investment in the Securities, nor have
such authorities passed upon or endorsed the merits of the offering of the
Securities.

         (f) TRANSFER OR RESALE. The Buyer understands that: (i) the
Securities have not been and are not being registered under the 1933 Act or
any state securities laws, and that the Stock may not be offered for sale,
sold, assigned or transferred unless either (x) subsequently registered
thereunder or (y) the Buyer shall have delivered to the Company, if so
requested by the Company, a legal opinion reasonably satisfactory to the
Company's outside counsel to the effect that the securities to be sold,
assigned or transferred may be sold, assigned or transferred pursuant to an
exemption from such registration, (ii) the sale, assignment or transfer of
the Options or any shares of Common Stock issuable upon the exercise thereof
are subject to certain restrictions as set forth in the Option Agreements and
(iii) except as set forth in the Registration Rights Agreement, neither the
Company nor any other person is under any obligation to register such
securities under the 1933 Act or any state securities laws or to comply with
the terms and conditions of any exemption thereunder.

         (g) LEGEND. The Buyer understands that unless the resale of the
shares of the Stock or Common Stock underlying the Options (collectively, the
"Subject Shares") has been registered under the 1933 Act or may be sold by
the Buyer pursuant to paragraph (k) of Rule 144 (as amended, or any
applicable rule which operates to replace said Rule) promulgated under the
1933 Act ("Rule 144"), the stock certificates representing the Common Stock
will bear a restrictive legend (the "Legend") in substantially the following
form:

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES LAWS, AND MAY NOT
BE PLEDGED, SOLD, OFFERED FOR SALE, TRANSFERRED, OR OTHERWISE DISPOSED OF IN
THE ABSENCE OF REGISTRATION UNDER OR EXEMPTION FROM SUCH ACT AND ALL
APPLICABLE STATE SECURITIES LAWS.

The Legend will be removed and the Company will issue certificates without
the Legend to the transferee of the applicable Subject Shares upon which the
Legend is stamped, if, unless otherwise required by state securities laws,
(a) such Subject Shares were resold pursuant to and in accordance

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with the registration of same under the 1933 Act, or (b) in connection with a
resale transaction, such holder provides the Company an opinion by counsel
reasonably acceptable to the Company's outside counsel, to the effect that a
public sale, assignment or transfer of the Common Stock may be made without
registration under the 1933 Act.

         (h) AUTHORIZATION; ENFORCEMENT. This Agreement has been duly and
validly authorized, executed and delivered by the Buyer and is a valid and
binding agreement of the Buyer enforceable against Buyer in accordance with
its terms, subject as to enforceability to general principles of equity and
to bankruptcy, insolvency, moratorium, and other similar laws affecting the
enforcement of creditors' rights generally.

         (i) NO BROKERS; NO GENERAL SOLICITATION. Buyer 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. Buyer acknowledges that no broker was
involved with respect to the transactions contemplated hereby.

         SECTION 3.        REPRESENTATIONS AND WARRANTIES OF THE COMPANY.

         The Company understands, agrees with, and represents and warrants to
the Buyer that:

         (a) ORGANIZATION AND QUALIFICATION: REPORTING COMPANY STATUS. The
Company and its subsidiaries are corporations duly organized and existing in
good standing under the laws of the respective jurisdictions in which they
are incorporated and have the requisite corporate power to own their
properties and to carry on their business as now being conducted. Each of the
Company and its subsidiaries are duly qualified as a foreign corporation to
do business and is in good standing in every jurisdiction in which the nature
of the business conducted by it makes such qualification necessary. The
Company has registered its Common Stock pursuant to Section 12 of the
Securities Exchange Act of 1934, as amended (the "1934 Act") and sales of its
Common Stock are reported by the National Quotation Bureau, Inc. on the Over
the Counter Bulletin Board.

         (b) AUTHORIZATION; ENFORCEMENT. (i) The Company has the requisite
corporate power and authority to enter into and perform this Agreement and
the other agreements contemplated hereby or referred to herein (collectively,
the "Agreements") and to issue and sell the Securities in accordance with the
terms hereof, (ii) the execution, delivery and performance of the Agreements
by the Company and the consummation by it of the transactions contemplated
hereby have been duly authorized by the Company's Board of Directors and no
further consent or authorization of the Company, its Board of Directors, or
its stockholders is required, (iii) the Agreements and, on the date of the
Closing, the Securities sold at the Closing, have been duly and validly
authorized, executed and delivered by the Company, and (iv) the Agreements
constitute the valid and binding obligations of the Company enforceable
against the Company in accordance with their respective terms, except as such
enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium, liquidation or similar laws relating to, or
affecting, generally, the enforcement of creditors' rights and remedies or by
other equitable principles of general application. The Company

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(and its legal counsel) have examined this Agreement and is satisfied in its
sole discretion that this Agreement and the accompanying Exhibits, Schedules
and the Addenda, if any, are in accordance with Regulation D.

         (c) CAPITALIZATION. As of December 31, 1999, the authorized Common
Stock of the Company consists of 100,000,000 shares of Common Stock of which
52,619,372 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 are subject to preemptive rights or any other similar rights or
any liens or encumbrances, whether or not contingent. Except as disclosed in
the Company's Form 10-KSB for the year ended September 30, 1999, and its Form
10-QSB for the fiscal quarter ended December 31, 1999, (i) there are no
outstanding options, warrants, scrip, 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 the Company or any of its
subsidiaries, or arrangements by which the Company or any of its subsidiaries
is or may become bound to issue additional shares of capital stock of the
Company or any of its subsidiaries, and (ii) there are no outstanding debt
securities. The Company has made available to the Buyer true and correct
copies of the Company's Articles of Incorporation, as amended, as in effect
on the date hereof ("Certificate of Incorporation"), and the Company's
Bylaws, as in effect on the date hereof ("Bylaws").

         (d) ISSUANCE OF SECURITIES. The Stock is all 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 the Company.

         (e) NO REGISTRATION REQUIREMENTS. Neither the Company, nor any of
its affiliates, nor any person acting on its or their behalf, has directly or
indirectly made any offers or sales of any security or solicited any offers
to buy any security under circumstances which would prevent the parties
hereto from consummating the sale contemplated hereby pursuant to an
exemption from registration under the 1933 Act and specifically in accordance
with the provisions of Regulation D. The sale contemplated hereby is exempt
from the registration requirements of the 1933 Act, assuming the accuracy of
the representations and warranties contained herein of the Buyer.

         (f) NO CONFLICTS. The execution, delivery and performance of this
Agreement by the Company and the consummation by the Company of the
transactions contemplated hereby will not (i) result in a violation of the
Articles of Incorporation or Bylaws or (ii) conflict with, or constitute a
default (or an event which with notice or lapse of time or both would become
a default) under, or give to others any rights of termination, amendment,
acceleration or cancellation of, any material agreement, indenture or
instrument to which the Company or any of its subsidiaries is a party, or
result in a violation of any law, rule, regulation, order, judgment or decree
(including federal and state securities laws and regulations) applicable to
the Company or any of its subsidiaries or by which any property or asset of
the Company or any of its subsidiaries is bound or affected. Neither the
Company nor any of its subsidiaries is in violation of its Articles of
Incorporation or other organizational documents, and neither the Company nor
any of its subsidiaries are in default (and no event has occurred which, with
notice or lapse of time or both, would put the Company or any

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of its subsidiaries in default) under, nor has there occurred any event
giving others (with notice or lapse of time or both) any rights of
termination, amendment, acceleration or cancellation of, any material
agreement, indenture or instrument to which the Company or any of its
subsidiaries is a party. The business of the Company and its subsidiaries is
not being conducted, and shall not be conducted so long as the Buyer owns any
of the Securities, in violation of any law, ordinance or regulation of any
governmental entity. Except as specifically contemplated by this Agreement
and as required under the 1933 Act and any applicable state securities laws,
the Company is not required to obtain any consent, authorization or order of,
or make any filing or registration with, any court or governmental agency in
order for it to execute, deliver or perform any of its obligations under this
Agreement, in accordance with the terms hereof.

         (g) SEC DOCUMENTS; FINANCIAL STATEMENTS. Since January 1, 1997, the
Company has timely filed all reports, schedules, forms, statements and other
documents required to be filed by it with the SEC pursuant to the reporting
requirements of the Securities Exchange Act of 1934, as amended (the "1934
Act") (all of the foregoing filed prior to the date hereof and all exhibits
included therein and financial statements and schedules hereto and documents
(other than exhibits) incorporated by reference therein, being hereinafter
referred to as the "SEC Documents"). The Company has made available to the
Buyer true and complete copies of the SEC Documents. As of their respective
dates, the SEC Documents complied in all material respects with the
requirements of the 1934 Act and the rules and regulations of the SEC
promulgated thereunder applicable to the SEC Documents. Except as set forth
in the financial statements of the Company included in the SEC Documents and
a finder's fee claim by John M. King IV, the Company has no liabilities,
contingent or otherwise, other than (i) liabilities subsequent to the date of
such financial statements incurred in the ordinary course of business and
consistent with past practice and (ii) obligations under contracts and
commitments incurred in the ordinary course of business and consistent with
past practice and not required under generally accepted accounting principles
to be reflected in such financial statements, in each case of clause (i) and
(ii) next above which, individually or in the aggregate, are not material to
the financial condition, business, operations, properties, operating results
or prospects of the Company. Except for the finder's fee claim of John M.
King IV, the SEC Documents contain a description of the general nature of all
material undischarged written and oral contracts, agreements, leases or other
instruments to which the Company or any subsidiary is a party or by which the
Company or any subsidiary is subject (each a "Contract"). None of the
Company, its subsidiaries or, to the best of the Company's knowledge, any of
the other parties thereto, is in breach or violation of any Contract. No
event, occurrence or condition exists which, with the lapse of time, the
giving of notice, or both, or the happening of any further event or
condition, would become a default by the Company or its subsidiaries
thereunder which would, individually or in the aggregate with any other such
defaults by the Company or its subsidiaries, have a Material Adverse Effect.
"Material Adverse Effect" means any material adverse effect on the
operations, properties or financial condition of the Company and its
subsidiaries taken as a whole.

         (h) ABSENCE OF CERTAIN CHANGES. Since December 31, 1999, there has
been no material adverse change and no material adverse development in the
business, properties, operation, financial condition, results of operations
or prospects of the Company.

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         (i) ABSENCE OF LITIGATION. Except as specifically disclosed in the
SEC Documents, there is no action, suit, proceeding, inquiry or investigation
before or by any court, public board or body pending or, to the knowledge of
the Company, threatened against or affecting the Company.

         (j) NO BROKERS; NO GENERAL SOLICITATION. The Company 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. The Company acknowledges that no broker
was involved with respect to the transactions contemplated hereby.

         (k) INTELLECTUAL PROPERTY. (i) As used herein, "Intellectual
Property" shall mean all inventions (whether patentable or unpatentable and
whether or not reduced to practice), all improvements thereto, and all
patents, patent applications and patent disclosures, together with all
reissuances, continuations, continuations-in-part, revisions, extensions and
reexaminations thereof, trademarks, service marks, trade dress, logos, trade
names and corporate names, together with all translations, adaptations,
derivations and combinations thereof and including all goodwill associated
therewith, and all applications, registrations and renewals in connection
therewith, copyrightable works, all copyrights and all applications,
registrations and renewals in connection therewith, mask works and all
applications, registrations and renewals in connection therewith, trade
secrets and confidential business information (including ideas, research and
development, know-how, formulas, compositions, manufacturing and production
processes and techniques, technical data, designs, drawings, specifications,
customer and supplier lists, pricing and cost information and business and
marketing plans and proposals), proprietary software, proprietary rights and
copies and tangible embodiments thereof (in whatever form or medium).

                  (ii) Except as set forth on SCHEDULE 3(k)(ii) hereto, the
Company and its subsidiaries own or are licensed or otherwise have the right
to use, without payment to any other person, the Intellectual Property used
in or necessary for each of their businesses, as presently conducted. Neither
the Company nor any of its subsidiaries has entered into any agreement that
restricts or affects its use and/or location of use of any of its
Intellectual Property.

                  (iii) Without limiting the scope of the Company's warranty
and representation in sub-paragraph (ii) above, (w) each trademark
registration included in the Intellectual Property exists and is owned by the
Company or any of its subsidiaries and has been maintained in good standing;
(x) each patent and application included in the Intellectual Property exists,
is owned by or licensed to the Company or one of its subsidiaries, and has
been maintained in good standing; (y) each copyright registration included in
the Intellectual Property exists and is owned by the Company or one of it
subsidiaries; and (z) to the Company's knowledge, no other firm, corporation,
association or person claims the right to use in connection with similar or
related goods and in any geographic area, any mark, logo, name, symbol,
device, or slogan which is identical or confusingly similar to any of the
trademarks included in the Intellectual Property or which could serve to
dilute the distinctiveness of such trademarks.

                  (iv) The Company and its subsidiaries' ownership and/or use
of Intellectual Property in their businesses, as presently conducted, does
not conflict with, or result in any violation

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of, or default (with or without notice or lapse of time or both) under, or
give rise to a right of termination, cancellation or acceleration of any
obligation, or result in any loss of a material benefit under, or the
creation of any lien in or upon any of the properties or assets of the
Company or its subsidiaries under, any contract between the Company and any
person or, to the Company's knowledge, any other intellectual property rights
of any other person, except for any such conflict, violation, default, right
of termination, cancellation acceleration, loss of material benefit or
creation of any lien which would not have a material adverse effect with
respect to the Company.

                  (v) The Company has not received any communications
alleging that the Company or one of its subsidiaries has violated or, by
conducting its business, would infringe upon the intellectual property rights
of any other person. The Company is not aware of any infringement or
misappropriation by others of any of its or its subsidiaries' Intellectual
Property.

         (l) PERMITS AND LICENSES. The Company holds all material licenses,
permits and other authorizations of any agency, public, regulatory or other
governmental authority necessary to conduct its business as now being
conducted or, under currently applicable statutes, rules, ordinances,
regulations or other laws, to continue to conduct its business as now being
conducted. Such licenses, permits and other authorizations held by the
Company are valid and in full force and effect, and there are no legal
actions pending or, to the knowledge of the Company, threatened that could
result in the termination, impairment or nonrenewal thereof.

         (m) OTHER INFORMATION. No representation or warranty of the Company
in this Agreement, nor any statement, certificate or other document furnished
or to be furnished by the Company to the Buyer pursuant to this Agreement,
nor any exhibits or schedules hereto, contains any untrue statement of a
material fact, or omits to state a material fact required to be stated
therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading.

         SECTION 4.        COVENANTS.

         (a) BEST EFFORTS. Each party shall use its best efforts timely to
satisfy each of the conditions to be satisfied by it as provided in Sections
6 and 7 of this Agreement.

         (b) SECURITIES LAWS. The Company agrees to timely file a Form D (or
equivalent form required by applicable state law) with respect to the
Securities if and as required under Regulation D and applicable state
securities laws. The Company shall, on or before the date of the Closing,
take such action as is necessary to sell the Securities being sold to the
Buyer under applicable securities laws of the United States, and shall if
specifically so requested provide evidence of any such action so taken to the
Buyer on or prior to the Closing Date.

         (c) REPORTING STATUS. So long as the Buyer beneficially owns any of
the Securities, the Company shall file all reports required to be filed with
the SEC pursuant to the 1934 Act on a timely

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basis, and the Company shall not terminate its status as an issuer required
to file reports under the 1934 Act even if the 1934 Act or the rules and
regulations hereunder would permit such termination.

         (d) USE OF PROCEEDS. The Company will use the proceeds from the sale
of the Securities for the Company's internal working capital purposes,
including costs and expenses of the Company's business operations and payment
of certain outstanding obligations of the Company, research and development,
and to the extent deemed advisable by the Company, for the purchase of new
technologies for use by the Company and its subsidiaries, and for the
purchase of additional subsidiaries and the development and marketing of
their technologies.

         (e) RESERVATION OF SHARES. The Company shall at all times have
authorized, and reserved for the purpose of issuance, a sufficient number of
shares of Common Stock to provide for the issuance of the Securities and any
Common Stock issuable upon the exercise or conversion thereof.

         (f) PROSPECTUS DELIVERY REQUIREMENT. The Buyer understands that the
1933 Act requires under certain circumstances the delivery of a prospectus
relating to the Common Stock in connection with any resale thereof, and the
Buyer shall comply with any applicable prospectus delivery requirements of
the 1933 Act in connection with any such sale.

         (g) INTENTIONAL ACTS OR OMISSIONS. Neither party shall intentionally
perform any act which if performed, or omit to perform any act which if
omitted to be performed, would prevent or excuse the performance of this
Agreement or any of the transactions contemplated hereby.

         SECTION 5.        REMOVAL OF LEGEND.

         The Legend will be removed and the Company will issue certificates
without the Legend to the transferee of the applicable Subject Shares upon
which the Legend is stamped, if, unless otherwise required by state
securities laws, (a) such Subject Shares were resold pursuant to and in
accordance with the registration of same under the 1933 Act, or (b) in
connection with a resale transaction, such holder provides the Company an
opinion by counsel reasonably acceptable to the Company's outside counsel, to
the effect that a public sale, assignment or transfer of the Common Stock may
be made without registration under the 1933 Act. The Buyer agrees that its
resale of all Common Stock, shall be made only pursuant to an effective
registration statement and to deliver a prospectus in connection with such
sale, or in a transaction in which registration is not required under the
registration requirements of the 1933 Act. In the event the Legend is removed
from any certificate for Common Stock or any Common Stock is issued without
the Legend and thereafter the effectiveness of a registration statement
covering the sales of such Common Stock is suspended or the Company
determines that a supplement or amendment thereto is required by applicable
securities laws, then upon reasonable advance notice to the holder of such
Security, the Company shall be entitled to require that the Legend be placed
upon any such Security which cannot then be sold pursuant to an effective
registration statement or with respect to which the opinion referred to in
clause (b) next above has not been rendered, which Legend shall be removed
when such Common

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Stock may be sold pursuant to an effective registration statement or at such
time as such holder provides the opinion with respect thereto described in
clause (b) next above.

         SECTION 6.        CONDITIONS TO THE COMPANY'S OBLIGATION TO SELL.

         The obligation of the Company hereunder to sell the Securities at
the Closing is subject to the satisfaction, on or before the date of the
Closing as described herein, of each of the following conditions, provided
that these conditions are for the Company's sole benefit and may be waived by
the Company at any time in its sole discretion:

         (a) The parties shall have executed this Agreement, and the parties
shall have delivered executed originals of the documents to the other party.

         (b) The Buyer shall have delivered to the Company the Purchase Price
for the Securities, as provided in this Agreement.

         (c) The representations and warranties of the Buyer shall be true
and correct in all material respects as of the date made and as of the date
of the Closing as though made at that time (except for representations and
warranties that refer to a specific date), and the Buyer shall have
performed, satisfied and complied in all material respects with the
covenants, agreements and conditions required by this Agreement to be
performed, satisfied or complied with by the Buyer at or prior to the date of
the Closing.

         (d) No statute, rule, regulation, executive order, decree, ruling or
injunction shall have been enacted, entered, promulgated or endorsed by any
court or governmental authority of competent jurisdiction or any self
regulatory organization having authority over the matters contemplated hereby
which restricts or prohibits the consummation of any of the transactions
contemplated herein.

         SECTION 7.        CONDITIONS TO THE BUYER'S OBLIGATION TO PURCHASE.

         The obligation of the Buyer to purchase the Securities is subject to
the satisfaction, on or before the date of the Closing, of each of the
following conditions, provided that these conditions are for the sole benefit
of the Buyer and may be waived by the Buyer at any time in its sole
discretion:

         (a) The parties shall have executed this Agreement and the
Registration Rights Agreement, and the parties shall have delivered executed
originals of the respective documents to the other party.

         (b) The Company shall have delivered to the Buyer the Securities
(including the Option Agreements executed on behalf of the Company), as
provided in this Agreement.

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         (c) The representations and warranties of the Company shall be true
and correct in all material respects as of the date made and as of the date
of the Closing as though made at that time (except for representations and
warranties that refer to a specific date), and the Company shall have
performed, satisfied and complied in all material respects with the
covenants, agreements and conditions required by this Agreement to be
performed, satisfied or complied with by the Company at or prior to the date
of the Closing. The Buyer may require a certificate, executed by the Chief
Executive Officer or a Vice President of the Company, dated as of the date of
the Closing, to the foregoing effect.

         (d) No statute, rule, regulation, executive order, decree, ruling or
injunction shall have been enacted, entered, promulgated or endorsed by any
court or governmental authority of competent jurisdiction or any self
regulatory organization having authority over the matters contemplated hereby
which restricts or prohibits the consummation of any of the transactions
contemplated herein.

         (e) An opinion of counsel to the Company, in form and substance
acceptable to the Buyer.

         SECTION 8.        GOVERNING LAW; MISCELLANEOUS.

         (a) GOVERNING LAW. This Agreement shall be governed by and
interpreted in accordance with the laws of the State of Colorado without
regard to the principles of conflict of laws. In the event of any litigation
regarding the interpretation or application of this Agreement, the parties
irrevocably consent to jurisdiction in any of the state or federal courts
located in the State of Colorado and waive their rights to object to venue in
any such court, regardless of the convenience or inconvenience thereof to any
party. Service of process in any civil action relating to or arising out of
this Agreement (including also all Exhibits or Addenda hereto, if any), or
the transactions contemplated herein may be accomplished in any manner
provided by law. The parties hereto agree that a final, non-appealable
judgment in any such suit or proceeding shall be conclusive and may be
enforced in other jurisdictions by suit on such judgment or in any other
lawful manner.

         (b) COUNTERPARTS. This Agreement may be executed in two or more
identical counterparts, all of which shall be considered one and the same
agreement and shall become effective when counterparts have been signed by
each party and signature pages from such counterparts have been delivered to
the other party. In the event any signature page is delivered by facsimile
transmission (which the parties agree is an acceptable form of delivery), the
party using such means of delivery shall cause two (2) additional originally
executed signature pages to be physically delivered to the other party within
three (3) business days of the execution and delivery hereof.

         (c) HEADINGS; GENDER, ETC. The headings of this Agreement are for
convenience of reference and shall not form a part of, or affect the
interpretation of this Agreement. As used herein, the masculine shall refer
to the feminine and neuter, the feminine to the masculine and neuter, and the
neuter to the masculine and feminine, as the context may require. As used
herein, unless the

                                       12
<PAGE>

context clearly requires otherwise, the words "herein," "hereunder" and
"hereby," shall refer to this entire Agreement and not only to the Section or
paragraph in which such word appears. If any date specified herein falls upon
a Saturday, Sunday or public or legal holidays, the date shall be construed
to mean the next business day following such Saturday, Sunday or public or
legal holiday. For purposes of this Agreement, a "business day" is any day
other than a Saturday, Sunday or public or legal holiday.

         (d) SEVERABILITY. If any provision of this Agreement shall be
invalid or unenforceable in any jurisdiction, such invalidity or
unenforceability shall not affect the validity or enforceability of the
remainder of this Agreement in that jurisdiction or the validity or
enforceability of any provision of this Agreement in any other jurisdiction.

         (e) ENTIRE AGREEMENT; AMENDMENTS. This Agreement and the instruments
referenced herein contain the entire understanding of the parties with
respect to the matters covered herein and therein and, except as specifically
set forth herein or therein, neither the Company nor the Buyer makes any
representation, warranty, covenant or undertaking with respect to such
matters. No provision of this Agreement may be waived or amended other than
by an instrument in writing signed by the party to be charged with
enforcement.

         (f) NOTICES. Any notices required or permitted to be given under the
terms of this Agreement shall be sent by U. S. Mail or delivered personally
or by courier or via facsimile (if via facsimile, to be followed within three
(3) business days by an original of the notice document via U.S. Mail or
courier) and shall be effective five (5) days after being placed in the mail,
if mailed, certified or registered, return receipt requested, or upon
receipt, if delivered personally or by courier or by facsimile, in each case
properly addressed to the party to receive the same. The addresses for such
communications shall be:

If to the Company:        Rentech, Inc.
                          1331 17th Street, Suite 720
                          Denver, Colorado 80202
                          Telephone: (303) 298-8008
                          Facsimile: (303) 298-8010
                          Attention: Mr. Ronald C. Butz, Vice President & COO

If to the Buyer, at the address on the signature page of this Agreement. Each
party shall provide written notice to the other party of any change in
address.

         (g) SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon and
inure to the benefit of the parties and their respective successors. Neither
party shall assign this Agreement or any rights or obligations hereunder
without the prior written consent of the other party (which consent shall not
be unreasonably withheld or delayed), except that Buyer may assign its rights
hereunder in whole or in part to (i) any entity or person that directly, or
indirectly through one or more intermediaries, is controlled by, or is under
common control with Buyer (an "Affiliate") or (ii) any director, officer,
employee, representative or agent of Buyer or any of its Affiliates. Any

                                       13
<PAGE>

assignee of the Buyer shall be an "accredited investor" as that term is
defined in Rule 501(a) of Regulation D, and no assignment shall be made by
the Buyer unless it is made in accordance with any applicable securities laws.

         (h) NO THIRD PARTY BENEFICIARIES. This Agreement is intended for the
benefit of the parties hereto and their respective permitted successors and
permitted assigns, and is not for the benefit of, nor may any provision
hereof be enforced by, any other person.

         (i) SURVIVAL. The representations and warranties of the Company and
the Buyer contained in Sections 2 and 3 and the agreements and covenants set
forth in Sections 4 shall survive the Closing of the purchase and sale of
Securities purchased and sold hereby.

         (j) FURTHER ASSURANCE. Each party shall do and perform, or cause to
be done and performed, all such further acts and things, and shall execute
and deliver all such other agreements, certificates, instruments and
documents, as the other party may reasonably request in order to carry out
the intent and accomplish the purposes of this Agreement and the consummation
of the transactions contemplated hereby.

         (k) REMEDIES. No provision of this Agreement providing for any
specific remedy to a party shall be construed to limit such party to the
specific remedy described, and any other remedy that would otherwise be
available to such party at law or in equity shall be so available. Nothing in
this Agreement shall limit any rights a party may have with any applicable
federal or state securities laws with respect to the transactions
contemplated hereby.

                            [Signature Page Follows]

                                       14
<PAGE>

         IN WITNESS WHEREOF, the Buyer and the Company have caused this Stock
Purchase Agreement to be duly executed as of the date first written above.


Rentech, Inc.                                      Forest Oil Corporation

By:/s/ Dennis L. Yakobson                          By:/s/ David H. Keyte
   ----------------------------                       --------------------------
   Dennis L. Yakobson                                 David H. Keyte
   President                                          Executive Vice President
                                                      Forest Oil Corporation
                                                      1600 Broadway, Suite 2200
                                                      Denver, Colorado  80202