Lime Energy (LMEC) 10-Q 2012 Q1 Quarterly report

Exhibit 32.1

CERTIFICATION PURSUANT TO SECTION 1350 OF CHAPTER 63

OF TITLE 18 OF THE UNITED STATES CODE

I, John O’Rourke, the Chief Executive Officer of Lime Energy Co., certify pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge and belief:

1.The Quarterly Report Under Section 13(a) or 15(d) of the Securities Exchange Act of 1934 on Form 10-Q for the Quarterly Period ended March 31, 2012 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2.The information contained in the Quarterly Report Under Section 13 or 15(d) of the Securities Exchange Act of 1934 on Form 10-Q for the Quarterly Period ended March 31, 2012 fairly presents, in all material respects, the financial condition and results of operations of Lime Energy Co. and its subsidiaries.

/s/ John O’Rourke

John O’Rourke

President and Chief Executive Officer

May 10, 2012