Exhibit 10.47

Execution Version

AMENDMENT

TO

AGREEMENT TO LEASE

THIS AMENDMENT TO AGREEMENT TO LEASE (this “Amendment”), dated as of May 9,
2011, is by and among Clean Coal Solutions, LLC, a Colorado limited liability
company “(“CCS”), AEC-NM, LLC, a Colorado limited liability company (“AEC-NM”),
AEC-TH, LLC, a Colorado limited liability company (“AEC-TH”), and GS RC
INVESTMENTS LLC, a Delaware limited liability company (“GS RC”). CCS, AEC-NM,
AEC-TH and GS RC are sometimes referred to herein, collectively, as the
“Parties” and, individually, as a “Party.”

WHEREAS, CCS, AEC-NM, AEC-TH and GS RC entered into that certain Agreement to
Lease, dated as of June 29, 2010 and as amended on August 10, 2010 (the
“Agreement to Lease”); and

WHEREAS, Goldman, Sachs & Co. (“Goldman Sachs”) and CCS have entered into an
Indicative Term Sheet, dated May 5, 2011, pursuant to which, among other things,
Goldman Sachs has agreed to cause GS RC to amend the Agreement to Lease as set
forth herein.

NOW, TEHREFORE, in consideration of the premises and of the mutual promises,
covenants and agreements contained herein, and for other valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the Parties agree
as follows:

1. Amendments to Agreement to Lease. The Parties hereby agree to amend the
Agreement to Lease as follows:

 

  (a) Paragraph C in the Recitals of the Agreement to Lease is hereby deleted in
its entirety.

 

  (b) Section 2.4 of the Agreement to Lease is hereby deleted in its entirety
and the following is substituted in lieu thereof:

“[Reserved]”

 

  (c) Section 9.15(b) of the Agreement to Lease is hereby deleted in its
entirety and the following is substituted in lieu thereof:

“Lessee may, without the need for consent from Lessor, make an Assignment of
this Agreement to any Person (i) succeeding to all or substantially all of its
assets, provided such Person has, or its obligations under this Agreement are
guaranteed by a Person who has, an Investment Grade rating, or (ii) after
December 31, 2019 if the Section 45 Credit for Refined Coal produced by the
Facilities has been extended beyond such date; and”

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  (d) Each of the following definitions is hereby deleted in its entirety from
Annex I of the Agreement to Lease:

“Acceptance Period” has the meaning set forth in Section 2.4.

“Offer Notice” has the meaning set forth in Section 2.4.

“Offer Date” has the meaning set forth in Section 2.4.

“Purchase Notice” has the meaning set forth in Section 2.4.

“Refined Coal Investor” means any Person other than an entity whose primary
business, taking into account the business of its Affiliates, is the generation,
transmission and sale of electric power and that is regulated as to rate by the
public utility commission of any applicable state or jurisdiction.

 

  (e) Schedule 2.4 to the Agreement to Lease, and all references thereto
contained in the Agreement to Lease, is hereby deleted in its entirety.

2. The provisions of the Agreement to Lease, as amended hereby, shall remain in
full force and effect and the Parties hereby ratify, confirm and adopt all the
terms and provisions of the Agreement to Lease, as amended hereby.

3. This Amendment shall constitute the entire agreement between the Parties
relating to the amendment of the Agreement to Lease. No modification of this
Amendment or waiver of any provision hereof shall be binding unless the
modification or waiver shall be in writing and signed by the Parties to be
bound.

4. This Amendment may be executed and delivered (including by facsimile or
electronic mail transmission) in one or more counterparts, all of which shall be
considered one and the same agreement and shall become effective when one or
more counterparts have been signed by each of the Parties and delivered to the
other Parties, it being understood that all Parties need not sign the same
counterpart.

[SIGNATURE PAGES FOLLOW]

 

2

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IN WITNESS WHEREOF, this Amendment has been signed by each of the Parties as of
the date first above written.

 

CLEAN COAL SOLUTIONS, LLC By:   /s/ Brian C. Humphrey Name:   Brian C. Humphrey
Title:   Manager AEC-NM, LLC By:  

Clean Coal Solutions, LLC,

its managing member

By:   /s/ Brian C. Humphrey Name:   Brian C. Humphrey Title:   Manager AEC-TH,
LLC By:  

Clean Coal Solutions, LLC,

its managing member

By:   /s/ Brian C. Humphrey Name:   Brian C. Humphrey Title:   Manager

[SIGNATURE PAGE TO AMENDMENT TO AGREEMENT TO LEASE]

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GS RC INVESTMENTS LLC By:  

GSFS INVESTMENTS I CORP.,

its sole member

By:   /s/ Albert Dombrowski Name:   Albert Dombrowski Title:   Authorized
Signatory

[SIGNATURE PAGE TO AMENDMENT TO AGREEMENT TO LEASE]