As filed with the Securities and Exchange Commission on October 26, 2011

Registration No. 333-175627

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Amendment No. 5

to

Form S-1

REGISTRATION STATEMENT

Under

THE SECURITIES ACT OF 1933

RENEWABLE ENERGY GROUP, INC.

(Exact name of registrant as specified in its charter)

416 South Bell Avenue

Ames, Iowa 50010

(515) 239-8000

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Jeffrey Stroburg

Chief Executive Officer

416 South Bell Avenue

Ames, Iowa 50010

(515) 239-8000

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box.  ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

Part II

Information not required in prospectus

Item 13. Other Expenses of Issuance and Distribution

The following table sets forth the various expenses expected to be incurred by Renewable Energy Group, Inc. (the “Registrant”) in connection with the sale and distribution of the securities being registered hereby, other than underwriting discounts and commissions. All amounts are estimated except the United States Securities and Exchange Commission, or SEC, registration fee and the Financial Industry Regulatory Authority filing fee.

Item 14. Indemnification of Directors and Officers

Section 102 of the Delaware General Corporation Law, or DGCL, allows a corporation to eliminate the personal liability of directors of a corporation to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, except where the director breached the duty of loyalty, failed to act in good faith, engaged in intentional misconduct or knowingly violated a law, authorized the payment of a dividend or approved a stock repurchase in violation of the DGCL or obtained an improper personal benefit.

Section 145 of the DGCL provides, among other things, that we may indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding—other than an action by or in the right of the Registrant—by reason of the fact that the person is or was a director, officer, agent or employee of the Registrant, or is or was serving at our request as a director, officer, agent or employee of another corporation, partnership, joint venture, trust or other enterprise against expenses, including attorneys’ fees, judgments, fines and amounts paid in settlement actually and reasonably incurred by the person in connection with such action, suit or proceeding. The power to indemnify applies (a) if such person is successful on the merits or otherwise in defense of any action, suit or proceeding, or (b) if such person acting in good faith and in a manner he or she reasonably believed to be in the best interest, or not opposed to the best interest, of the Registrant, and with respect to any criminal action or proceeding had no reasonable cause to believe his or her conduct was unlawful. The power to indemnify applies to actions brought by or in the right of the Registrant as well but only to the extent of defense expenses, including attorneys’ fees but excluding amounts paid in settlement, actually and reasonably incurred and not to any satisfaction of judgment or settlement of the claim itself, and with the further limitation that in such actions no indemnification shall be made in the event of any adjudication of liability to the Registrant, unless the court believes that in light of all the circumstances indemnification should apply.

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Information not required in prospectus

Section 174 of the DGCL provides, among other things, that a director, who willfully or negligently approves of an unlawful payment of dividends or an unlawful stock purchase or redemption, may be held liable for such actions. A director who was either absent when the unlawful actions were approved or dissented at the time, may avoid liability by causing his or her dissent to such actions to be entered in the books containing minutes of the meetings of the Board of Directors at the time such action occurred or immediately after such absent director receives notice of the unlawful acts.

The Registrant’s amended and restated bylaws provide that the Registrant shall indemnify its directors and executive officers to the fullest extent not prohibited by the DGCL or any other applicable law. In addition, the Registrant has entered into separate indemnification agreements, with its directors and officers which would require the Registrant, among other things, to indemnify them against certain liabilities which may arise by reason of their status or service as directors or officers to the fullest extent not prohibited by law. These indemnification provisions and the indemnification agreements may be sufficiently broad to permit indemnification of the Registrant’s officers and directors for liabilities, including reimbursement of expenses incurred, arising under the Securities Act of 1933, as amended, which we refer to as the Securities Act. The Registrant also maintains director and officer liability insurance.

The form of Underwriting Agreement, to be attached as Exhibit 1.1 hereto, provides for indemnification by the Underwriters of us and our officers and directors for certain liabilities, including liabilities arising under the Securities Act, and affords certain rights of contribution with respect thereto.

Item 15. Recent Sales of Unregistered Securities

WestLB Revolving Credit Agreement

On April 8, 2010, REG Seneca LLC, a wholly-owned subsidiary of the Registrant, agreed to lease and operate a biodiesel production facility in Seneca, Illinois. Concurrently with the execution of the lease, certain subsidiaries of the Registrant entered into a Revolving Credit Agreement with WestLB, AG, under which the Registrant issued 500,000 shares of its common stock to WestLB, AG. See “Certain Relationships and Related Party Transactions” on page 112 for a full discussion of the transaction.

Tellurian Biodiesel, Inc. and American BDF, LLC Acquisition

On July 16, 2010, the Registrant issued 598,295 shares of its common stock for certain assets of Tellurian Biodiesel, Inc. and American BDF, LLC with ongoing obligations to issue up to an additional 731,250 shares of common stock, in accordance with the asset purchase agreement.

Clovis Biodiesel, LLC Acquisition

On September 21, 2010, the Registrant issued 2,150,000 shares of its common stock to ARES Corporation in exchange for the assets of Clovis Biodiesel, LLC, a wholly owned subsidiary of the ARES Corporation, and $8.0 million cash.

SoyMor Acquisition

On July 1, 2011, the Registrant issued 80,000 and 1,770,000 shares of its common stock to SoyMor Cooperative and SoyMor Biodiesel, LLC, respectively, in exchange for substantially all the assets of SoyMor Biodiesel, LLC and SoyMor Cooperative’s soy lecithin assets.

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Information not required in prospectus

Since February 26, 2010, the Registrant has issued warrants to purchase an aggregate of 335,924 shares of its common stock at exercise prices ranging from $2.23 to $4.47.

Unless otherwise stated, the sales of the above securities were deemed to be exempt from registration under the Securities Act in reliance upon Section 4(2) of the Securities Act (or Regulation D or Regulation S promulgated thereunder), or Rule 701 promulgated under Section 3(b) of the Securities Act as transactions by an issuer not involving any public offering or pursuant to benefit plans and contracts relating to compensation as provided under Rule 701. The recipients of the securities in each of these transactions represented their intentions to acquire the securities for investment only and not with a view to or for sale in connection with any distribution thereof, and appropriate legends were placed upon the stock certificates issued in these transactions. All recipients had adequate access, through their relationships with the Registrant, to information about the Registrant. The sales of these securities were made without any general solicitation or advertising.

Item 16. Exhibits and Financial Statement Schedules

The following exhibits are included herein or incorporated herein by reference:

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Information not required in prospectus

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Information not required in prospectus

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Information not required in prospectus

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Information not required in prospectus

Financial statement schedule I is included on page F-64. All other schedules are omitted because they are not required, or not applicable or the information is included in the consolidated financial statements or notes thereto.

Item 17. Undertakings

Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission

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such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

The undersigned registrant hereby undertakes that:

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized in the City of Ames, State of Iowa, on October 26, 2011.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

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Signatures

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Exhibit index

Exhibit index

Exhibit index

Exhibit index

Exhibit index

Financial statement schedule I is included on page F-64. All other schedules are omitted because they are not required, or not applicable or the information is included in the consolidated financial statements or notes thereto.