**EXHIBIT 31.2**

 

**CERTIFICATION**

 

I, Joseph D. Hill certifythat:

 

1.     I have reviewed thisquarterly report on Form 10-Q of Metabolix, Inc.;

 

2.     Based on my knowledge, thisreport does not contain any untrue statement of a material fact  or omit to state a material fact necessary tomake the statements made, in light of the circumstances under which suchstatements were made, not misleading with respect to the period covered by thisreport;

 

3.     Based on my knowledge, thefinancial statements, and other financial information included in this report,fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periodspresented in this report;

 

4.     The registrant’s othercertifying officer(s) and I are responsible for establishing andmaintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) and internal control over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant andhave:

 

(a)   Designed such disclosurecontrols and procedures, or caused such disclosure controls and procedures tobe designed under our supervision, to ensure that material information relatingto the registrant, including its consolidated subsidiaries, is made known to usby others within those entities, particularly during the period in which thisreport is being prepared;

 

(b)   Designed such internalcontrol over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles;

 

(c)   Evaluated the effectivenessof the registrant’s disclosure controls and procedures and presented in thisreport our conclusions about the effectiveness of the disclosure controls andprocedures, as of the end of the period covered by this report based on suchevaluation; and

 

(d)   Disclosed in this report anychange in the registrant’s internal control over financial reporting thatoccurred during the registrant’s most recent fiscal quarter (the registrant’sfourth fiscal quarter in the case of an annual report) that has materiallyaffected, or is reasonably likely to materially affect, the registrant’sinternal control over financial reporting; and

 

5.     The registrant’s othercertifying officer(s) and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the registrant’sauditors and the audit committee of the registrant’s board of directors (orpersons performing the equivalent functions):

 

(a)   All significant deficienciesand material weaknesses in the design or operation of internal control overfinancial reporting which are reasonably likely to adversely affect theregistrant’s ability to record, process, summarize and report financialinformation; and

 

(b)   Any fraud, whether or notmaterial, that involves management or other employees who have a significantrole in the registrant’s internal control over financial reporting.

 

 
| Date: May 7, 2009 | /s/   JOSEPH D.  HILL |
|------------------------|---------------------------------|
|                   | Name:                           | Joseph D. Hill |
|                   | Title:                          | *Chief Financial Officer  (Principal Financial and Accounting Officer)* |

 

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