FIRST AMENDMENT TO CHEMICALS, EQUIPMENT, AND TECHNICALENGINEERING SERVICES SUPPLY AGREEMENT

Exhibit 10.66

FIRST AMENDMENT TO CHEMICALS, EQUIPMENT,

AND TECHNICAL ENGINEERING SERVICES SUPPLY AGREEMENT

THIS FIRST AMENDMENT TO CHEMICALS, EQUIPMENT, AND TECHNICAL ENGINEERING SERVICES SUPPLY AGREEMENT (this “Amendment”), is effective as of this 26th day of October, 2009 (the “Effective Date”), and is by and between ADA-ES, Inc., a Colorado corporation (“ADA”) and Clean Coal Solutions, LLC, a Colorado limited liability company (formerly known as “ADA-NexCoal, LLC”) (the “Company”). ADA and the Company are sometimes herein collectively referred to as the “parties” and each individually as a “party.”

RECITALS

A. ADA and the Company are parties to that certain Chemicals, Equipment, and Technical Engineering Services Supply Agreement, dated as of November 3, 2006 (the “Agreement”).

B. The parties wish to amend the Agreement to amend the cost of certain Chemicals and Additives as set forth in the amended Schedule A to the Agreement.

C. Capitalized terms not otherwise defined herein shall have the meanings ascribed to such terms in the Agreement.

AGREEMENT

NOW, THEREFORE, in consideration of the premises and of the mutual covenants hereinafter set forth and for other good and valuable consideration, the receipt and sufficiency of which the parties hereby acknowledge, the parties do hereby agree as follows:

1. Amendments.

a. Section 4.1 to the Agreement is hereby amended, restated and replaced in its entirety to read as follows:

“4.1 Prices. The price to the Company for the Chemicals and Additives, Equipment and Technical Engineering Services shall be as set forth on Schedule A and Schedule B, respectively. The prices charged by ADA to the Company shall be no less favorable to the Company than the prices charged by ADA to customers who, during the term of this Agreement as set forth in Article IX, purchase similar volumes of substantially similar Chemicals and Additives, Equipment and Technical Engineering Services. Except as set forth on Schedule A as it relates to the pricing of the mercury control halogen additive and the iron mineralizer additive, ADA may change the prices of any Chemicals and Additives, Equipment and Technical Engineering Services supplied hereunder upon thirty (30) days advance written notice to the Company.”

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b. Schedule A to the Agreement shall be deleted in its entirety and is hereby replaced with the following Schedule A:

“Schedule A to

Chemicals, Equipment and

Technical Engineering Services Supply Agreement

Chemicals and Additives and Equipment Terms List

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2. Entire Agreement. The terms and conditions of this Amendment shall be incorporated by reference in the Agreement as though set forth in full therein. In the event of any inconsistency between the provisions of this Amendment and any other provision of the Agreement, the terms and provisions of this Amendment shall govern and control. Except to the extent specifically amended or superseded by the terms of this Amendment, all of the provisions of the Agreement shall remain in full force and effect to the extent in effect on the date hereof. The Agreement, as modified by this Amendment, constitutes the complete agreement between the parties and supersedes any prior written or oral agreements, writings, communications or understandings of the parties with respect to the subject matter hereof.

3. Miscellaneous.

a. Counterparts. This Amendment may be executed in identical counterpart copies, each of which shall be an original, but all of which shall constitute one and the same agreement. Delivery of an executed counterpart of a signature page to this Amendment by facsimile transmission shall be effective as delivery of a manually executed counterpart thereof.

b. Headings. Section headings used herein are for convenience of reference only, are not part of this Amendment, and are not to be taken into consideration in interpreting this Amendment.

c. Effect. Upon the effectiveness of this Amendment, from and after the date hereof, each reference in the Agreement to “this Agreement,” “hereunder,” “hereof,” or words of like import or references to schedules or exhibits to the Agreement shall mean and be a reference to the Agreement or the schedules or exhibits thereto as amended hereby, and each reference in any other document to the Agreement, “thereunder,” “thereof,” or words of like import or references to schedules or exhibits to the Agreement shall mean and be a reference to the Agreement or the schedules or exhibits thereto as amended hereby.

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d. No Novation. Except as and to the extent provided for or specifically resulting from the execution, delivery and effectiveness of this Amendment, this Amendment shall not (i) limit, impair, constitute a waiver of, or otherwise affect any right, power, or remedy of any party under the Agreement, (ii) constitute a waiver of any provision in the Agreement, or (iii) alter, modify, amend or in any way affect any of the terms, conditions, obligations, covenants, or agreements contained in the Agreement, all of which are ratified and affirmed in all respects and shall continue in full force and effect as amended by this Agreement.

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IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly executed as of the Effective Date.

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