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                                                                   Exhibit 10.23

METABOLIX
where nature performs(TM) [LOGO]

[LOGO]

                                         21 Erie Street
                                         Cambridge, Massachusetts 02139-4260 USA
                                         Tel: 617.492.0505 . Fax: 617-492-1996
                                         Web: www.metabolix.com


                                       August 29, 2006

Brian Igoe
44 Oak Street
Weston, MA 02493

     Re: EMPLOYMENT AGREEMENT

Dear Brian:

     This letter is to confirm our understanding with respect to your employment
by Metabolix, Inc. (the "Company"). The terms and conditions agreed to in this
letter are hereinafter referred to as the "Agreement." In consideration of the
mutual promises and covenants contained in this Agreement, and for other good
and valuable consideration, the receipt and sufficiency of which are hereby
mutually acknowledged, we have agreed as follows:

     1.  EMPLOYMENT.

         (a)    GENERAL. The Company will employ you, and you will be employed
     by the Company, as the Vice President, Chief Brand Officer, of the Company,
     reporting to the Chief Executive Officer, and you shall have the
     responsibilities, duty and authority commensurate with that position. You
     will also perform such other and/or different services for the Company as
     may be assigned to you from time to time. Your employment will commence on
     or about September 1, 2006. You agree that if your employment hereunder
     ends for any reason, you will tender your resignation to the Company of any
     office you may then hold in the Company.

         (b)    DEVOTION TO DUTIES. While you are employed hereunder, you will
     use your best efforts, skills and abilities to perform faithfully all
     duties assigned to you pursuant to this Agreement and will devote your full
     business time and energies to the business and affairs of the Company.
     While you are employed hereunder, you will not undertake any other
     employment from any person or entity without the prior written consent of
     the Company. Notwithstanding the foregoing, nothing contained herein shall
     be deemed to prohibit you from engaging in passive investment or charitable
     activities, so long as they do not interfere with the performance of your
     duties hereunder.

     2.  EMPLOYMENT AT WILL.  Your  employment  hereunder will be on an
"at-will"  basis and may be terminated by the Company or by you at any time for
any reason or for no reason.

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Brian Igoe
August 29, 2006
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     3.  COMPENSATION.

         (a)    BASE SALARY. While you are employed hereunder, the Company will
     pay you a base salary at the annual rate of $16,666.67 per month
     (annualized at $200,000.00) (the "Base Salary"). This Base Salary may be
     subject to upward (but not downward) adjustment from time to time in the
     discretion of the Company. The Company will deduct from each monthly salary
     payment all amounts required to be deducted or withheld under applicable
     law or under any employee benefit plan in which you participate.

         (b)    BONUSES.

                (i) In addition to the Base Salary, the Company shall pay you a
     signing bonus of $20,000.00, payable at the same time as your first
     paycheck after commencement of your employment.

                (ii) In addition to the foregoing, the Company on or before
     December 31, 2006, will establish a formalized bonus scheme and pay you an
     annual bonus (a "Bonus") in an amount to be determined by the Company's
     Compensation Committee. The amount will be based on several criteria,
     including the financial condition of the Company and its overall
     performance for the year, but will be strongly influenced by your
     contributions toward the achievement of established corporate goals and
     objectives, as well as other contributions that add recognizable value to
     the Company. The present target for executive bonuses is 50% of Base Salary
     (the "Target Bonus"). This Target Bonus will be subject to revision from
     time to time by the Compensation Committee. In order to receive an annual
     bonus, you must be employed at the time of a timely payment, which will be
     paid on or before March 15 of the year following the year in which it is
     earned.

         (c)    EQUITY COMPENSATION. Upon approval by the Compensation Committee
     of the Company's Board of Directors, the Company shall grant you stock
     options for the purchase of 200,000 shares of the Company's Common Stock at
     an exercise price equal to the fair market value per share of the Common
     Stock on the date of grant. Such stock options shall vest in sixteen (16)
     quarterly installments over a period of four (4) years from the date of
     commencement of your employment. Such options shall be incentive stock
     options to the extent permitted under applicable tax law and regulations.
     In addition, the Company, in the Board's sole discretion, may from time to
     time grant to you stock options, restricted stock or other forms of equity
     compensation pursuant to the Metabolix, Inc. 2005 Stock Plan or any other
     authorized stock plan in effect at the time.

         (d)    VACATION. You will be entitled to five (5) weeks paid vacation
     and paid holidays, accrued and used in accordance with the Company's
     policies as currently in effect. All vacation days will be taken at times
     mutually agreed by you and the Company and will be subject to the business
     needs of the Company.

         (e)    FRINGE BENEFITS. You will be entitled to participate in employee
     benefit plans which the Company provides or may establish for the benefit
     of its senior executives

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Brian Igoe
August 29, 2006
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     generally (for example, group life, disability, medical, dental and other
     insurance, retirement, pension, profit-sharing and similar plans)
     (collectively, the "Fringe Benefits"). Your eligibility to participate in
     the Fringe Benefits and receive benefits thereunder will be subject to the
     plan documents governing such Fringe Benefits. Nothing contained herein
     will require the Company to establish or maintain any Fringe Benefits.

     4.  TERMINATION.

         (a)    GENERAL. As an at-will employee, your employment may be
     terminated at any time for any reason or for no reason. Upon termination,
     unless otherwise specifically provided herein, you shall be eligible only
     to receive (i) the portion of your Base Salary as has accrued prior to such
     termination and has not yet been paid, (ii) an amount equal to the value of
     your accrued unused vacation days, and (iii) reimbursement for expenses
     properly incurred by you on behalf of the Company prior to such termination
     if such expenses are properly documented in accordance with Company policy
     and practice and submitted for reimbursement within thirty (30) days of the
     termination date (collectively, the "Accrued Obligations"). Such amounts
     will be paid promptly after termination in accordance with applicable law.

         (b)    TERMINATION WITHOUT CAUSE OR WITH GOOD REASON. Except as
     provided in Section 4(c) hereof, in the event that your employment is
     terminated by the Company without Cause or by you with Good Reason (each,
     as defined below), in addition to the Accrued Obligations, and contingent
     on your provision of a timely and complete release of claims against the
     Company, you shall be entitled to receive continuation of your Base Salary
     in effect at the time of termination for the period of twelve (12) months
     following the termination. To the extent required by Section 409A of the
     Internal Revenue Code of 1986, as amended (the "Code"), the first
     installment of such Base Salary in the amount of six (6) months' Base
     Salary shall be payable on the first business day following the six (6)
     month anniversary of the effective date of termination, and the remainder
     shall be payable in accordance with the Company's regular payroll
     procedures thereafter. If Section 409A of the Code is not then applicable,
     such Base Salary continuation shall commence immediately from the date of
     termination. In addition, should the award of a Bonus have become
     customary, you shall be entitled to a payment equal to the average of the
     Bonuses paid to you (if any) in the two years preceding the termination, to
     be paid (A) on the first business day following the six (6) month
     anniversary of the effective date of termination, to the extent required by
     Section 409A of the Code, or (B) if Section 409A of the Code is not then
     applicable, within thirty (30) days following the termination. In addition
     to the foregoing, you shall be entitled to receive payment of COBRA
     premiums to maintain medical and dental benefits, if any, in effect at the
     time of termination for the period of twelve (12) months following the
     termination.

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Brian Igoe
August 29, 2006
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         (c)    TERMINATION WITHOUT CAUSE OR WITH GOOD REASON BEFORE OR AFTER A
     CHANGE OF CONTROL.

                (i) In the event that your employment is terminated by the
     Company without Cause or by you for Good Reason (each, as defined below)
     within the twenty-four (24) month period immediately following or the two
     month period immediately prior to a Change of Control (as defined below),
     in addition to the Accrued Obligations, and contingent on your provision of
     a timely release of claims against the Company, you shall be entitled to
     receive:

                       (A) continuation of your Base Salary in effect at the
     time of  termination  for the period of twelve (12) months following the
     termination. To the extent required by Section 409A of the Code, the first
     installment of such Base Salary in the amount of six (6) months' Base
     Salary shall be payable on the first business day following the six (6)
     month anniversary of the effective date of termination, and the remainder
     shall be payable in accordance with the Company's regular payroll
     procedures thereafter. If Section 409A of the Code is not then applicable,
     such Base Salary continuation shall commence immediately from the date of
     termination.

                       (B) In addition, should the award of a Bonus have become
     customary, you shall be entitled to a payment equal to the average of the
     Bonuses paid to you (if any) in the two years preceding the termination, to
     be paid (A) on the first business day following the six (6) month
     anniversary of the effective date of termination, to the extent required by
     Section 409A of the Code, or (B) if Section 409A of the Code is not then
     applicable, within thirty (30) days following the termination.

                       (C) continued  payment of COBRA premiums to maintain
     medical and dental benefits, if any, in effect at the time of termination
     for the period of twelve (12) months following the termination; and

                       (D) full vesting of all options granted to you under the
     Metabolix Inc. 1995 Stock Plan, the Metabolix Inc. 2005 Stock Plan, or any
     authorized successor stock plan provided that the conditions to vesting
     other than the passage of time have been satisfied.

                (ii) You agree that the payments and benefits hereunder, and
     under all other contracts, arrangements or programs that apply to you (the
     "Company Payments"), shall be reduced to an amount that is one dollar less
     than the amount that would trigger an excise tax under Section 4999 of the
     Code, as determined in good faith by the Company's independent public
     accountants, PROVIDED, HOWEVER, that the reduction shall occur only if the
     reduced Company Payments received by you (after taking into account further
     reductions for applicable federal, state and local income, social security
     and other taxes) would be greater than the unreduced Company Payments to be
     received by you minus (i) the excise tax payable with respect to such
     Company Payments under Section 4999 of the Code; and (ii) all applicable
     federal, state and local income, social security and other

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Brian Igoe
August 29, 2006
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     taxes on such Company Payments. You and the Company agree to cooperate in
     good faith with each other in connection with any administrative or
     judicial proceedings concerning the existence or amount of golden parachute
     penalties with respect to payments or benefits that you receive.

         (d)    "CAUSE". As used herein, "Cause" shall be defined as (i) your
     conviction for, or plea of nolo contendere, to a felony or a crime
     involving moral turpitude, (ii) your commission of a material act of
     personal dishonesty or a breach of fiduciary duty, in either case,
     involving personal profit in connection with your employment by the
     Company, (iii) your commission of an act which the Board of Directors shall
     reasonably have found to have involved willful misconduct or gross
     negligence on your part in the conduct of your duties under this Agreement,
     (iv) your habitual absenteeism, (v) your material breach of any material
     provision of this Agreement continuing for thirty days after your receipt
     of written notice thereof from the Company, or (vi) the willful and
     continued failure by you to perform substantially your duties with the
     Company (other than any such failure resulting from your incapacity due to
     physical or mental illness).

         (e)    "CHANGE OF CONTROL". As used herein, a "Change of Control" shall
     occur or be deemed to have occurred only upon any one or more of the
     following events:

                (i)    a merger or consolidation of the Company other than a
         merger or consolidation which would result in the voting securities of
         the Company outstanding immediately prior thereto continuing to
         represent (either by remaining outstanding or by being converted into
         voting securities of the surviving entity or the parent of such
         corporation) at least fifty percent (50%) of the total voting power
         represented by the voting securities of the Company or such surviving
         entity or parent of such corporation outstanding immediately after such
         merger or consolidation;

                (ii)   the sale or disposition by the Company of all or
         substantially all of the Company's assets; or

                (iii)  any one person, entity or group, who is not a shareholder
         at time of execution of this Agreement, acquires ownership of capital
         stock of the Company that, together with the capital stock of the
         Company already held by such person, entity or group, constitutes more
         than 50% of the total fair market value or total voting power of the
         capital stock of the Company; provided, however, if any one person,
         entity or group is considered to own more than 50% of the total fair
         market value or total voting power of the capital stock of the Company,
         the acquisition of additional capital stock by the same person, entity
         or group shall not be deemed to be a Change of Control, and further
         provided that the foregoing shall not be deemed a Change of Control if
         the average stock price paid for each share of stock held by the
         person, entity or group is less than $8.00/share (provided that such
         price shall be adjusted as appropriate to reflect any stock

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Brian Igoe
August 29, 2006
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         dividend, stock split, or recapitalization of the Company after the
         date of this agreement).

         (f)    "Good Reason" shall be defined as, in the absence of a cure by
     the Company within 30 days after written notice by you to the Board, a (i)
     a change in title of Vice President, Chief Brand Officer, (ii) a material
     diminution of responsibilities, duties or powers, (iii) a reduction in Base
     Salary, Target Bonus, vacation or other benefits, except that benefits need
     only be substantially equivalent, or (iv) a requirement that you relocate
     your principal place of employment to (or that you travel more than 50 days
     in any calendar year to the Company's principal place of business in) a
     location more than 50 miles from its current location in Cambridge,
     Massachusetts, PROVIDED THAT you must provide the Company with at least
     thirty (30) days advance written notice of your intent to terminate your
     employment hereunder and an opportunity to cure.

     5.  NONCOMPETITION, CONFIDENTIALITY AND INVENTIONS OBLIGATIONS. As a
condition of your employment with the Company and as a condition of this
Agreement, you must execute the Employee Noncompetition, Confidentiality and
Inventions Agreement attached hereto as EXHIBIT A.

     6.  DISCLOSURE TO FUTURE EMPLOYERS. You will provide, and the Company, in
its discretion, may similarly provide, a copy of the covenants contained in the
Employee Noncompetition, Confidentiality and Inventions Agreement to any
business or enterprise which you may, directly or indirectly, own, manage,
operate, finance, join, control or in which you may participate in the
ownership, management, operation, financing, or control, or with which you may
be connected as an officer, director, employee, partner, principal, agent,
representative, consultant or otherwise.

     7.  REPRESENTATIONS. You hereby represent and warrant to the Company that
you understand this Agreement, that you enter into this Agreement voluntarily
and that your employment under this Agreement will not conflict with any legal
duty owed by you to any other party.

     8.  GENERAL.

         (a)    NOTICES. All notices, requests, consents and other
     communications hereunder which are required to be provided, or which the
     sender elects to provide, in writing, will be addressed to the receiving
     party's address set forth above or to such other address as a party may
     designate by notice hereunder, and will be either (i) delivered by hand,
     (ii) sent by overnight courier, or (iii) sent by registered or certified
     mail, return receipt requested, postage prepaid. All notices, requests,
     consents and other communications hereunder will be deemed to have been
     given either (i) if by hand, at the time of the delivery thereof to the
     receiving party at the address of such party set forth above, (ii) if sent
     by overnight courier, on the next business day following the day such
     notice is delivered to the courier service, or (iii) if sent by registered
     or certified mail, on the fifth business day following the day such mailing
     is made.

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Brian Igoe
August 29, 2006
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         (b)    ENTIRE AGREEMENT. This Agreement, together with any Stock Option
     Agreements executed by you and the Company (either prior to or in
     conjunction with this Agreement), the Employee Noncompetition,
     Confidentiality and Inventions Agreement and the other agreements
     specifically referred to herein, embodies the entire agreement and
     understanding between the parties hereto with respect to the subject matter
     hereof and supersedes all prior oral or written agreements and
     understandings relating to the subject matter hereof. No statement,
     representation, warranty, covenant or agreement of any kind not expressly
     set forth in this Agreement will affect, or be used to interpret, change or
     restrict, the express terms and provisions of this Agreement.

         (c)    MODIFICATIONS AND AMENDMENTS. The terms and provisions of this
     Agreement may be modified or amended only by written agreement executed by
     the parties hereto.

         (d)    WAIVERS AND CONSENTS. The terms and provisions of this Agreement
     may be waived, or consent for the departure therefrom granted, only by
     written document executed by the party entitled to the benefits of such
     terms or provisions. No such waiver or consent will be deemed to be or will
     constitute a waiver or consent with respect to any other terms or
     provisions of this Agreement, whether or not similar. Each such waiver or
     consent will be effective only in the specific instance and for the purpose
     for which it was given, and will not constitute a continuing waiver or
     consent.

         (e)    ASSIGNMENT. The Company may assign its rights and obligations
     hereunder to any person or entity that succeeds to all or substantially all
     of the Company's business or that aspect of the Company's business in which
     you are principally involved or to any Company Affiliate. You may not
     assign your rights and obligations under this Agreement without the prior
     written consent of the Company and any such attempted assignment by you
     without the prior written consent of the Company will be void.

         (f)    GOVERNING LAW. This Agreement and the rights and obligations of
     the parties hereunder will be construed in accordance with and governed by
     the law of Massachusetts, without giving effect to the conflict of law
     principles thereof.

         (g)    JURISDICTION, VENUE AND SERVICE OF PROCESS. Any legal action or
     proceeding with respect to this Agreement will be brought in the courts of
     Massachusetts or of the United States of America for the District of
     Massachusetts. By execution and delivery of this Agreement, each of the
     parties hereto accepts for itself and in respect of its property, generally
     and unconditionally, the exclusive jurisdiction of the aforesaid courts.

         (h)    SEVERABILITY. The parties intend this Agreement to be enforced
     as written. However, if any portion or provision of this Agreement is to
     any extent declared illegal or unenforceable by a duly authorized court
     having jurisdiction, then the remainder of this Agreement, or the
     application of such portion or provision in circumstances other than those
     as to which it is so declared illegal or unenforceable, will not be
     affected thereby, and each

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Brian Igoe
August 29, 2006
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     portion and provision of this Agreement will be valid and enforceable to
     the fullest extent permitted by law.

         (i)    HEADINGS AND CAPTIONS. The headings and captions of the various
     subdivisions of this Agreement are for convenience of reference only and
     will in no way modify or affect the meaning or construction of any of the
     terms or provisions hereof.

         (j)    ACKNOWLEDGMENTS. You hereby acknowledge and recognize that the
     enforcement of any of the provisions in this Agreement and the
     Noncompetition, Confidentiality and Inventions Agreement may potentially
     interfere with your ability to pursue a proper livelihood. You represent
     that you are knowledgeable about the business of the Company and further
     represent that you are capable of pursuing a career in other industries
     other than the field of noncompetition as set forth in the Noncompetition,
     Confidentiality and Inventions Agreement to earn a proper livelihood. You
     recognize and agree that the enforcement of the Noncompetition,
     Confidentiality and Inventions Agreement is necessary to ensure the
     preservation, protection and continuity of the business, trade secrets and
     goodwill of the Company. You agree that, due to the proprietary nature of
     the Company's business, the restrictions set forth in the Noncompetition,
     Confidentiality and Inventions Agreement are reasonable as to time and
     scope.

         (k)    TAXES. All payments required to be made by the Company to you
     under this Agreement shall be subject to the withholding of such amounts
     for taxes and other payroll deductions as the Company may reasonably
     determine it should withhold pursuant to any applicable law or regulation.
     To the extent applicable, it is intended that this Agreement comply with
     the provisions of Section 409A of the Code, and this Agreement shall be
     construed and applied in a manner consistent with this intent. In the event
     that any severance payments or benefits hereunder are determined by the
     Company to be in the nature of nonqualified deferred compensation payments,
     you and the Company hereby agree to take such actions as may be mutually
     agreed to ensure that such payments or benefits comply with the applicable
     provisions of Section 409A of the Code and the official guidance issued
     thereunder. Notwithstanding the foregoing, the Company does not guarantee
     the tax treatment or tax consequences associated with any payment or
     benefit arising under this Agreement.

         (l)    COUNTERPARTS. This Agreement may be executed in two or more
     counterparts, and by different parties hereto on separate counterparts,
     each of which will be deemed an original, but all of which together will
     constitute one and the same instrument.

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Brian Igoe
August 29, 2006
Page 9

     If the foregoing accurately sets forth our agreement, please so indicate by
signing and returning to us the enclosed copy of this Agreement.

                                                   Very truly yours,

                                                   Metabolix, Inc.


                                                   By: /s/ JAMES J. BARBER
                                                      -------------------------
                                                   Name: James J. Barber
                                                   Title: President and CEO


ACCEPTED AND APPROVED:


/s/ BRIAN IGOE                                     8/29/06
- ------------------------------                     ------------------
Brian Igoe                                         Date


ATTACHMENT: Exhibit A (Noncompetition, Confidentiality and Inventions Agreement)