Exhibit 10.15

FIRST AMENDMENT TO

STOCKHOLDER AGREEMENT

This First Amendment (this “Amendment”) to the Stockholder Agreement of REG
Newco, Inc. (now known as Renewable Energy Group, Inc.), a Delaware corporation
(the “Company”), is made and entered into effective as of June 29, 2010.
Capitalized terms used but not otherwise defined in this Amendment shall have
the respective meanings assigned to such terms in the Stockholder Agreement (as
defined below).

WHEREAS, the Company, NGP Energy Technology Partners L.P., a Delaware limited
partnership (“NGP Energy”), Natural Gas Partners, VIII, L.P., a Delaware limited
partnership (collectively with NGP Energy, “NGP”) and certain other Stockholders
entered into that certain Stockholder Agreement of the Company, dated as of
February 26, 2010 (the “Stockholder Agreement”);

WHEREAS, pursuant to Section 2(a)(ii) of the Stockholder Agreement, subject to
certain conditions, NGP is entitled to nominate and elect two representatives to
the Company’s Board of Directors; and

WHEREAS, it is the desire of the undersigned to amend the Stockholder Agreement
to modify the number of directors of the Company to be nominated and elected by
NGP, and to provide NGP with an observer right with respect to Board meetings,
upon the terms and conditions set forth herein.

NOW, THEREFORE, in consideration of the mutual promises of the parties, the
parties agree and acknowledge as follows:

Section 1. Amendments.

(a) The Stockholder Agreement is amended, as of the date hereof, by replacing
the existing Section 2(a)(ii) of the Stockholder Agreement with the following
provision:

“(ii) the nomination and election to the Board of (A) for so long as NGP holds
at least 2,105,263 shares of Series A Preferred Stock (and/or Common Stock
issued or issuable upon conversion of such Series A Preferred Stock) (subject to
appropriate adjustments in the event of any stock dividend, stock split,
combination or other similar recapitalization affecting such shares), one
(1) representative designated by NGP, which number may be increased at any time
in the sole discretion of NGP to two (2) representatives effective upon the
written request of NGP, (B) for so long as Westway holds at least 657,895 shares
of Series A Preferred Stock (and/or Common Stock issued or issuable upon
conversion of such Series A Preferred Stock) (subject to appropriate adjustments
in the event of any stock dividend, stock split, combination or other similar
recapitalization affecting such shares), one (1) representative designated by
Westway, (C) for so long as Bunge holds at least 526,316 shares of Series A
Preferred Stock (and/or Common Stock issued or issuable upon conversion of such
Series A Preferred Stock) (subject to appropriate adjustments in the event of
any stock dividend, stock split,

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combination or other similar recapitalization affecting such shares), one
(1) representative designated by Bunge and (D) for so long as the members of the
USBG Group collectively hold at least 1,277,167 shares of Series A Preferred
Stock (and/or Common Stock issued or issuable upon conversion of such Series A
Preferred Stock) (subject to appropriate adjustments in the event of any stock
dividend, stock split, combination or other similar recapitalization affecting
such shares), one (1) representative designated by the members of the USBG Group
holding a majority of the shares of Series A Preferred Stock (and/or Common
Stock issued or issuable upon conversion of the shares of such Series A
Preferred Stock) held by members of the USBG Group (Westway, Bunge and the USBG
Group are collectively referred to herein as the “Strategic Investors”);
provided, however, in the event any of NGP, Westway, Bunge or USBG Group has
elected to have all of its shares of Series A Preferred Stock redeemed by the
Company pursuant to the Series A Certificate of Designation (a “Redeeming
Stockholder”), and the Company is not able to redeem all the shares of Series A
Preferred Stock held by the Redeeming Stockholder, then the Redeeming
Stockholder shall not lose the right to have its representative(s) nominated and
elected to the Board pursuant to this Subsection 2(a)(ii) until such redemption
is complete.”

(b) The Stockholder Agreement is amended, as of the date hereof, by replacing
the existing Section 7(c) of the Stockholder Agreement with the following
provision:

“(c) Observer Rights. The Company shall permit up to four (4) non-voting
observers to attend each meeting of the Board and of any committees of the
Board, consisting of the President of the Company, an observer appointed by West
Central, an observer appointed by Energy Technology Partners, L.L.C. and, for so
long as only (1) director has been appointed to the Board by NGP as contemplated
in Section 2(a)(ii) above, an observer appointed by NGP; provided however that
NGP shall not have the right to appoint an observer pursuant to this Section 7
during the period in which NGP has appointed two (2) directors to the Board as
contemplated in Section 2(a)(ii) above. Such observers shall receive advance
notice of all such meetings and all materials provided to the directors before
and during such meetings. The Company may remove or exclude such observers from
any meeting of the Board and of any committees of the Board when such observers’
presence would reasonably be expected to compromise attorney-client
confidentiality, would be reasonably necessary to protect highly confidential
information or for other similar bona fide corporate reasons. The decision of
the Board with respect to the privileged or confidential nature of such
information shall be final and binding.”

Section 2. Effect. This Amendment constitutes an amendment to the Stockholder
Agreement. The terms and provisions of the Stockholder Agreement and all other
documents and instruments relating and pertaining to the Stockholder Agreement
shall continue in full force and effect, as amended hereby. In the event of any
conflict between the provisions of the Stockholder Agreement and the provisions
of this Amendment, the provisions of this Amendment shall control.

 

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Section 3. Counterparts. This Amendment may be executed in any number of
counterparts, each of which shall for all purposes be deemed to be an original,
and all such counterparts shall together constitute but one and the same
instrument.

[Signature Page Follows]

 

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IN WITNESS WHEREOF, the parties hereto have executed this Amendment effective as
of the day first above written.

 

COMPANY: RENEWABLE ENERGY GROUP, INC. By:   /s/ Jeffrey Stroburg Name:   Jeffrey
Stroburg Title:   Chairman / CEO COMMON STOCKHOLDERS: WEST CENTRAL COOPERATIVE
By:  

/s/ Jeffrey Stroburg

Name:   Jeffrey Stroburg Title:   President / CEO BLUE MARBLE INVESTORS LLC By:
  /s/ Kendell Enebrit Name:   Kendell Enebrit Title:   Secretary WEST CENTRAL
BIODIESEL INVESTORS, LLC By:   /s/ Susan Tronchetti Name:   Susan Tronchetti
Title:   Manager ENERGY TECHNOLOGY PARTNERS, L.L.C. By:   /s/ Chris Sorrells
Name:   Chris Sorrells Title:   Managing Director

FIRST AMENDMENT TO STOCKHOLDER AGREEMENT

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BUNGE NORTH AMERICA, INC. By:   /s/ Eric Hakmiller Name:   Eric Hakmiller Title:
  Vice-President Bunge Biofuels BIOFUELS COMPANY OF AMERICA, LLC By:   /s/ Mark
A. Barke Name:   Mark A. Barke Title:   President GATX CORPORATION By:   /s/
Eric P. Herkness Name:   Eric P. Herkness Title:   Vice President TODD &
SARGENT, INC. By:   /s/ Lee Sargent Name:   Lee Sargent Title:   CEO & Chair
SARGECO, INC. By:   /s/ Lee Sargent Name:   Lee Sargent Title:   President

FIRST AMENDMENT TO STOCKHOLDER AGREEMENT

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NATURAL GAS PARTNERS VIII, L.P. By: G.F.W. Energy VIII, L.P., General Partner
By: GFW VIII, L.L.C., General Partner By:   /s/ William J. Quinn Name:   William
J. Quinn  

Authorized Member

E D & F MAN HOLDINGS BV By:   /s/ Paul Chatterton Name:  

Paul Chatterton

Title:   Appointed Representative USBG MEMBERS:   USRG HOLDCO V, LLC   By:   /s/
Jonathan Koch   Name:  

Jonathan Koch

  Title:       OHANA HOLDINGS, LLC   By:   /s/ Jonathan Koch   Name:  

Jonathan Koch

  Title:       JYCO, LLC   By:   /s/ Jonathan Koch   Name:  

Jonathan Koch

  Title:    

FIRST AMENDMENT TO STOCKHOLDER AGREEMENT

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SUPREME OIL COMPANY, INC. By:   /s/ Jonathan Koch Name:   Jonathan Koch Title:  
  PADMA RAG DATTA TRUST By:   /s/ Lois-Ellin G. Datta Name:   Lois-Ellin G.
Datta Title:   Trustee JANE SU AND RICHARD CHOW REVOCABLE TRUST By:   /s/
Richard Chow Name:   Richard Chow Title:   Trustee

FIRST AMENDMENT TO STOCKHOLDER AGREEMENT

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SERIES A STOCKHOLDERS: NGP ENERGY TECHNOLOGY PARTNERS, L.P. By NGP ETP, L.L.C.,
its General Partner By:   /s/ Chris Sorrells Name:   Chris Sorrells Title:  
Managing Director NATURAL GAS PARTNERS VIII, L.P. By: G.F.W. Energy VIII, L.P.,
General Partner By: GFW VIII, L.L.C., General Partner By:   /s/ William J. Quinn
Name:   William J. Quinn   Authorized Member E D & F MAN HOLDINGS BV By:   /s/
Paul Chatterton Name:   Paul Chatterton Title:   Appointed Representative BUNGE
NORTH AMERICA, INC. By:   /s/ Eric Hakmiller Name:   Eric Hakmiller Title:  
Vice-President Bunge Biofuels WEST CENTRAL COOPERATIVE By:   /s/ Jeffrey
Stroburg Name:   Jeffrey Stroburg Title:   President / CEO

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USBG MEMBERS:   USRG HOLDCO V, LLC   By:   /s/ Jonathan Koch   Name:   Jonathan
Koch   Title:   Manager   OHANA HOLDINGS, LLC   By:   /s/ Jonathan Koch   Name:
  Jonathan Koch   Title:   Manager   JYCO, LLC   By:   /s/ Jonathan Koch   Name:
  Jonathan Koch   Title:   Manager   SUPREME OIL COMPANY, INC.   By:   /s/
Jonathan Koch   Name:   Jonathan Koch   Title:   Manager   PADMA RAG DATTA TRUST
  By:   /s/ Lois-Ellin G. Datta   Name:   Lois-Ellin G. Datta   Title:  

Trustee

  JANE SU AND RICHARD CHOW REVOCABLE TRUST   By:   /s/ Richard Chow   Name:  
Richard Chow   Title:   Trustee

FIRST AMENDMENT TO STOCKHOLDER AGREEMENT

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