**Exhibit 31.2**

**CATALYTICAENERGY 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.                Ihave reviewed this annual report on Form 10-K of Catalytica EnergySystems, Inc.;

2.                Basedon my knowledge, 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.                Basedon my knowledge, the financial statements, and other financial informationincluded in this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the Registrant as of, andfor, the periods presented in this report;

4.                TheRegistrant’s other certifying officer(s) and I are responsible forestablishing and maintaining disclosure controls and procedures (as defined inExchange Act Rules 13a-15(e) and 15d-15(e)) and internalcontrol over financial reporting (as defined in Exchange ActRules 13a-15(f) and 15d-15(f)) for the Registrant and have:

(a)    Designed such disclosure controls and procedures, or caused suchdisclosure controls and procedures to be designed under our supervision, toensure that material information relating to the Registrant, including itsconsolidated subsidiaries, is made known to us by others within those entities,particularly during the period in which this report is being prepared;

(b)   Designed such internal control over financial reporting, or causedsuch internal control over financial reporting to be designed under oursupervision, to provide reasonable assurance regarding the reliability offinancial reporting and the preparation of financial statements for externalpurposes in accordance with generally accepted accounting principles;

(c)    Evaluated the effectiveness of the Registrant’s disclosurecontrols and procedures and presented in this report our conclusions about theeffectiveness of the disclosure controls and procedures, as of the end of theperiod covered by this report based on such evaluation; and

(d)   Disclosed in this report any change in the Registrant’s internalcontrol over financial reporting that occurred during the Registrant’s mostrecent fiscal quarter (the Registrant’s fourth fiscal quarter in the case of anannual report) that has materially affected, or is reasonably likely tomaterially affect, the Registrant’s internal control over financial reporting;and

5.                TheRegistrant’s other certifying officer(s) and I have disclosed, based onour most recent evaluation of internal control over financial reporting, to theRegistrant’s auditors and the audit committee of Registrant’s board ofdirectors (or persons performing the equivalent functions):

(a)    All significant deficiencies and material weaknesses in thedesign or operation of internal control over financial reporting which arereasonably likely to adversely affect the Registrant’s ability to record,process, summarize and report financial information; and

(b)   Any fraud, whether or not material, thatinvolves management or other employees who have a significant role in theRegistrant’s internal control over financial reporting.
| Date: March 30, 2005 |
|---------------------------|
|                      | By: | /s/ ROBERT W. ZACK |   |
|                      | Name: | Robert W. Zack |
|                      | Title: | *Vice President of Finance  and Chief Financial Officer* |

 

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