**Exhibit 31.2**

**CATALYTICA ENERGY SYSTEMS, INC.**

**CERTIFICATION OF CHIEF FINANCIAL OFFICERPURSUANT TORULE 13a-14(a) / 15d-14(a) OF THE SECURITIES EXCHANGE ACTOF 1934**

I, Robert W. Zack,certify that:

1.                I have reviewedthis annual report on Form 10-K of Catalytica Energy Systems, Inc.;

2.                Based on myknowledge, this annual report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

3.                Based on myknowledge, the financial statements, and other financial information includedin this report, fairly present in all material respects the financial condition,results of operations and cash flows of the Registrant as of, and for, theperiods presented in this report;

4.                The Registrant’sother certifying 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)) for the Registrant and have:

(a)    Designedsuch disclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that materialinformation relating to the Registrant, including its consolidatedsubsidiaries, is made known to us by others within those entities, particularlyduring the period in which this report is being prepared;

(b)   Evaluatedthe effectiveness of the Registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thisreport based on such evaluation; and

(c)    Disclosedin this report any change in the Registrant’s internal control over financialreporting that occurred during the Registrant’s most recent fiscal quarter (theRegistrant’s fourth fiscal quarter in the case of an annual report) that hasmaterially affected, or is reasonably likely to materially affect, theRegistrant’s internal control over financial reporting; and

5.                The Registrant’sother certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the Registrant’sauditors and the audit committee of Registrant’s board of directors (or personsperforming the equivalent functions):

(a)    Allsignificant deficiencies and material weaknesses in the design or operation ofinternal control over financial reporting which are reasonably likely toadversely affect the Registrant’s ability to record, process, summarize andreport financial information; and

(b)   Any fraud, whether or not material, that involves management orother employees who have a significant role in the Registrant’s internalcontrol over financial reporting.

| Date:  March 30, 2006 |        | ** ** | ** **                |
|----------------------------|--------|------------|---------------------------|
|                       | By:    |       | /s/ ROBERT W.  ZACK       |
|                       | Name:  |       | Robert W. Zack            |
|                       | Title: |       | *Chief Financial Officer* |

 

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