Exhibit 5.1

[LETTERHEAD OF DAVENPORT, EVANS, HURWITZ & SMITH, L.L.P.]

August 13, 2008

VeraSun Energy Corporation

100 22nd Avenue

Brookings, South Dakota 57006

Re: VeraSun Energy Corporation Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as special South Dakota counsel to VeraSun Energy Corporation, a South Dakota corporation (the “Company”), US BioEnergy Corporation, a South Dakota corporation (“US Bio”), and VeraSun Aurora Corporation, a South Dakota corporation (“VAC”), in connection with the registration statement on Form S-3 (the “Registration Statement”) to be filed on the date hereof by the Company and each of the Company’s subsidiaries, including VAC, listed on Schedule I hereto (the “Additional Registrants”) with the U.S. Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”). The Registration Statement relates to the issuance and sale from time to time, pursuant to Rule 415 of the General Rules and Regulations of the Commission promulgated under the Act, of the following securities with an aggregate offering price of up to $750,000,000: (a) by the Company, (i) shares of Common Stock of the Company, par value $0.01 per share (the “Common Stock”); (ii) shares of Preferred Stock of the Company, par value $0.01 per share, to be issued in one or more series (the “Preferred Stock”); (iii) interests in shares of Preferred Stock represented by depositary shares (the “Depositary Shares”) evidenced by depositary receipts (the “Receipts”), which may be issued pursuant to one or more deposit agreements (each, a “Deposit Agreement”) proposed to be entered into between the Company and one or more depositaries to be named in the applicable Deposit Agreements (each, a “Depositary”); (iv) debt securities of the Company which may be secured or unsecured, senior, subordinated or junior subordinated or convertible (the

VeraSun Energy Corporation

August 13, 2008

Page 2

“Debt Securities”), to be issued in one or more series under the indenture proposed to be entered into between the Company and a trustee that has been or will be appointed prior to the issuance of the Debt Securities (the “Trustee”), the form of which is being filed as an exhibit to the Registration Statement (the “Indenture”); (v) warrants (the “Warrants”) to purchase debt or equity securities of the Company as shall be designated by the Company at the time of the offering issued pursuant to one or more warrant agreements (each, a “Warrant Agreement”) proposed to be entered into between the Company and one or more warrant agents to be named in the applicable Warrant Agreements (each, a “Warrant Agent”); (vi) subscription rights (the “Subscription Rights”) to purchase Common Stock, Preferred Stock, Debt Securities or other securities of the Company which may be issued under one or more subscription rights certificates (each, a “Subscription Rights Certificate”) and/or pursuant to one or more subscription rights agreements (each, a “Subscription Rights Agreement”) proposed to be entered into between the Company and one or more subscription agents to be named in the applicable Subscription Rights Agreements (each, a “Subscription Agent”); (vii) purchase contracts (the “Purchase Contracts”) entitling or obligating the holders thereof to purchase from or sell to the Company, and the Company to sell to or purchase from such holders, debt or equity securities issued by the Company or by third parties at a future date or dates, which may be issued under one or more purchase contract agreements (each, a “Purchase Contract Agreement”) proposed to be entered into by the Company and one or more purchase contract agents to be named in the applicable purchase contract agreements (each, a “Purchase Contract Agent”); (viii) purchase units (the “Purchase Units”), each consisting of a Purchase Contract and Debt Securities or debt obligations of third parties, including U.S. Treasury securities, or other securities (or any combination of the foregoing), securing the holders’ obligations to purchase or to sell the securities under the applicable Purchase Contracts; and (ix) such indeterminate amount and number of each class or series of the foregoing securities as may be issued upon conversion, exchange, exercise or settlement, as applicable, of any other securities that provide for such conversion, exchange, exercise or settlement (collectively, “Indeterminate Securities”); and (b) by one or more of the Additional Registrants, guarantees of Debt Securities, including Indeterminate Securities constituting Debt Securities (the “Guarantees”). The Common Stock, the Preferred Stock, the Depositary Shares, the Debt Securities, the Guarantees, the Warrants, the Subscription Rights, the Purchase Contracts, the Purchase Units and the Indeterminate Securities are collectively referred to herein as the “Offered Securities.”

This opinion is being delivered in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Act.

In connection with this opinion, we have examined originals or copies, certified or otherwise identified to our satisfaction, of (i) the Registration Statement, (ii) the Articles

VeraSun Energy Corporation

August 13, 2008

Page 3

of Incorporation of the Company, as currently in effect, (iii) the Amended and Restated Bylaws of the Company, as currently in effect, (iv) the Second Amended and Restated Articles of Incorporation of VAC, as currently in effect, (v) the Bylaws of VAC, as currently in effect, (vi) the Third Amended and Restated Articles of Incorporation of US Bio, as currently in effect, (vii) the By-Laws of US Bio, as currently in effect, (viii) the form of Indenture being filed as an exhibit to the Registration Statement, (ix) a specimen certificate evidencing the Common Stock and (x) certain resolutions of the board of directors of the Company (the “Board of Directors”), the board of directors of US Bio (the “US Bio Board”) and the board of directors of VAC (the “VAC Board”) relating to the registration of the Offered Securities and related matters. We have also examined originals or copies, certified or otherwise identified to our satisfaction, of such records of the Company, US Bio and VAC and such agreements, certificates and receipts of public officials, certificates of officers or other representatives of the Company, US Bio and VAC and others, and such other documents, certificates and records as we have deemed necessary or appropriate as a basis for the opinions set forth below.

In our examination, we have assumed the legal capacity of all natural persons, the genuineness of all signatures, including endorsements, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as facsimile, electronic, certified, conformed or photostatic copies, and the authenticity of the originals of such copies. In making our examination of executed documents or documents to be executed, we have assumed that the parties thereto, other than the Company, US Bio and VAC, had or will have the power, corporate or other, to enter into and perform all obligations thereunder and have also assumed the due authorization by all requisite action, corporate or other, and the execution and delivery by such parties of such documents and the validity and binding effect thereof on such parties. We have assumed that each of the Additional Registrants, other than VAC and US Bio, is and has been duly organized and is and will continue to be validly existing in good standing, and has and will continue to have the requisite legal status and legal capacity, under the laws of the state of its incorporation or formation, as the case may be, and that the Company and each of the Additional Registrants has complied and will comply with all aspects of applicable laws of jurisdictions other than the State of South Dakota in connection with the transactions contemplated by the Indenture, any supplemental indenture thereto, the Warrant Agreements, the Deposit Agreements, the Subscription Rights Agreements, the Purchase Contract Agreements, the Purchase Contracts, the Purchase Units and the Registration Statement. We have also assumed that the Indenture and any supplemental indenture thereto and each Deposit Agreement, Warrant Agreement, Subscription Rights Agreement, Purchase Contract Agreement and Purchase Unit will be duly authorized, executed and delivered by the applicable Trustee, Depositary, Warrant Agent, Subscription Agent or Purchase Contract Agent, as the case may be, and, in the case of the Indenture, in substantially the form reviewed by us, and

VeraSun Energy Corporation

August 13, 2008

Page 4

that each Receipt, Debt Security, Guarantee, Warrant, Subscription Rights Certificate, Purchase Contract or Purchase Unit that may be issued will be manually authenticated, signed or countersigned, as the case may be, by duly authorized officers of the applicable Depositary, Trustee, Warrant Agent, Subscription Agent or Purchase Contract Agent, as the case may be. We have assumed that the choice of New York law to govern the Indenture and any supplemental indenture thereto is a valid and legal provision. We have also assumed that New York law will be chosen to govern the Warrant Agreements, the Deposit Agreements, the Receipts, the Subscription Rights Agreements, the Purchase Contract Agreements, the Purchase Contracts and the Purchase Units and that such choice in each case is a valid and legal provision. As to any facts material to the opinions expressed herein which were not independently established or verified, we have relied upon oral or written statements and representations of officers and other representatives of the Company, US Bio and VAC and others and of public officials. We have relied as to matters of New York law on the opinion of Skadden, Arps, Slate, Meagher & Flom LLP of even date herewith and to be filed as Exhibit 5.2 to the Registration Statement.

Members of our firm are admitted to the bar in the State of South Dakota, and we do not express any opinion as to the effect of any laws, other than the laws of the State of South Dakota, on the opinions stated herein. The Offered Securities may be issued from time to time on a delayed or continuous basis, and this opinion is limited to the laws, including the rules and regulations, as in effect on the date hereof, which laws are subject to change with possible retroactive effect.

Based upon and subject to the foregoing, and the limitations, qualifications, exceptions, and assumptions set forth herein, we are of the opinion that:

1. With respect to any shares of Common Stock to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting Common Stock (the “Offered Common Stock”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act, (ii) an appropriate prospectus supplement with respect to the Offered Common Stock has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Common Stock is to be sold pursuant to a firm commitment underwritten offering, the underwriting agreement with respect to the Offered Common Stock has been duly authorized, executed and delivered by the Company and the other parties thereto, (iv) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance of the Offered Common Stock and related matters, (v) terms of the issuance of the Offered Common Stock have been duly established and are then in conformity with the Articles so as not to violate any applicable law, the articles of incorporation of the Company, as

VeraSun Energy Corporation

August 13, 2008

Page 5

then in effect (the “Articles”) or the bylaws of the Company as then in effect (the “Bylaws”), or result in a default under or breach of any agreement or instrument binding upon the Company, and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company and (vi) certificates representing the Offered Common Stock substantially in the form of the specimen certificate examined by us have been manually signed by an authorized officer of the transfer agent and registrar for the Offered Common Stock and registered by such transfer agent and registrar, and have been delivered upon payment in full of the consideration payable with respect to the Offered Common Stock as determined by the Board of Directors in accordance with applicable law, at a price per share not less than the per share par value of the Common Stock and as contemplated by any applicable underwriting agreement, the Offered Common Stock will be validly issued, fully paid and nonassessable.

2. With respect to any series of Preferred Stock to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting shares of Preferred Stock of such series (the “Offered Preferred Stock”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act, (ii) an appropriate prospectus supplement with respect to the Offered Preferred Stock has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Preferred Stock is to be sold pursuant to a firm commitment underwritten offering, the underwriting agreement with respect to the Offered Preferred Stock has been duly authorized, executed and delivered by the Company and the other parties thereto, (iv) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance and terms of the Offered Preferred Stock and related matters, (v) the terms of the Offered Preferred Stock and of their issuance and sale have been duly established and are then in conformity with the Articles, so as not to violate any applicable law, the Articles or the Bylaws, or result in a default under or breach of any agreement or instrument binding upon the Company, and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company, and (vi) certificates (in a form in compliance with any applicable provision of South Dakota corporate law and the Articles or the Bylaws) representing shares of the Preferred Stock have been manually signed by an authorized officer of the transfer agent and registrar for the Offered Preferred Stock and registered by such transfer agent and registrar, and have been delivered upon payment in full of the consideration payable with respect to the Offered Preferred Stock as determined by the Board of Directors in accordance with applicable law, at a price per share not less than the per share par value of the Common Stock and as contemplated by any applicable underwriting agreement, the Offered Preferred Stock will be validly issued, fully paid and nonassessable.

VeraSun Energy Corporation

August 13, 2008

Page 6

3. With respect to any series of Debt Securities to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting Debt Securities of such series (the “Offered Debt Securities”), and any Guarantees of the Offered Debt Securities to be offered by VAC and US Bio (the “Offered Guarantees”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act and the Indenture has been qualified under the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”), (ii) an appropriate prospectus supplement with respect to the Offered Debt Securities and the Offered Guarantees has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Debt Securities and the Offered Guarantees are to be sold pursuant to a firm commitment underwritten offering, the underwriting agreement with respect to the Offered Debt Securities and the Offered Guarantees has been duly authorized, executed and delivered by the Company and VAC, US Bio and the other parties thereto, (iv) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance and terms of the Offered Debt Securities, the Indenture and any applicable supplemental indenture thereto and related matters, (v) the US Bio Board, including any appropriate committee appointed thereby, and appropriate officers of US Bio have taken all necessary action to approve the issuance and terms of the Offered Guarantees, the Indenture and any applicable supplemental indenture thereto and related matters, (vi) the VAC Board, including any appropriate committee appointed thereby, and appropriate officers of VAC have taken all necessary action to approve the issuance and terms of the Offered Guarantees, the Indenture and any applicable supplemental indenture thereto and related matters, (vii) the Indenture and any supplemental indenture in respect of the Offered Debt Securities and Offered Guarantees have been duly authorized, executed and delivered by each party thereto, (viii) the terms of the Offered Debt Securities and the Offered Guarantees and of their issuance and sale have been duly established in conformity with the Indenture and any supplemental indenture to be entered into in connection with the issuance of the Offered Debt Securities and Offered Guarantees so as not to violate any applicable law, the Articles, the Bylaws, the articles of incorporation of US Bio or VAC as then in effect or the bylaws of US Bio or VAC as then in effect, or result in a default under or breach of any agreement or instrument binding upon the Company, US Bio or VAC, and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company, US Bio or VAC, and (ix) the Offered Debt Securities and the Offered Guarantees have been issued in a form that complies with the Indenture and have been duly executed and authenticated in accordance with the provisions of the Indenture and any supplemental indenture to be entered into in connection with the issuance of the Offered Debt

VeraSun Energy Corporation

August 13, 2008

Page 7

Securities and Offered Guarantees and duly delivered to the purchasers thereof upon payment of the agreed-upon consideration therefor, the Offered Debt Securities and the Offered Guarantees, when issued and sold in accordance with the Indenture and any supplemental indenture to be entered into in connection with the issuance of the Offered Debt Securities and the Offered Guarantees and the applicable underwriting agreement, if any, or any other duly authorized, executed and delivered valid and binding purchase or agency agreement, will be valid and binding obligations of (X) the Company and (Y) US Bio and VAC, respectively, enforceable against (X) the Company and (Y) US Bio and VAC, respectively, in accordance with their respective terms, except to the extent that enforcement thereof may be limited by (a) bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to creditors’ rights generally, (b) general principles of equity (regardless of whether enforceability is considered in a proceeding at law or in equity), (c) public policy considerations which may limit the rights of parties to obtain remedies, (d) waivers of any usury defense contained in the Indenture or Offered Debt Securities or Offered Guarantees which may be unenforceable, (e) requirements that a claim with respect to any Offered Debt Securities denominated in a currency, currency unit or composite currency other than United States dollars (or a judgment denominated other than in United States dollars in respect of such claim) be converted into United States dollars at a rate of exchange prevailing on a date determined pursuant to applicable law and (f) governmental authority to limit, delay or prohibit the making of payments outside the United States or in foreign currencies, currency units or composite currencies.

4. With respect to any series of Warrants to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting Warrants of such series (the “Offered Warrants”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act, (ii) an appropriate prospectus supplement with respect to the Offered Warrants has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Warrants are to be sold pursuant to a firm commitment underwritten offering, the underwriting agreement with respect to the Offered Warrants has been duly authorized, executed and delivered by the Company and the other parties thereto, (iv) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance and terms of the Offered Warrants, the Warrant Agreement and related matters, (v) the terms of the Offered Warrants and of their issuance and sale have been duly established in conformity with the applicable Warrant Agreement so as not to violate any applicable law, the Articles or the Bylaws or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company and the applicable

VeraSun Energy Corporation

August 13, 2008

Page 8

Warrant Agent, (vi) the Common Stock or the Preferred Stock relating to such Offered Warrants have been duly authorized for issuance, (vii) the Debt Securities relating to such Offered Warrants have been duly executed and authenticated in accordance with the provisions of the Indenture and any applicable supplemental indenture thereto and duly delivered to the purchasers thereof upon exercise of the Offered Warrants and payment of the agreed-upon consideration therefor, and (viii) the Offered Warrants have been duly executed, delivered, countersigned, issued and sold in accordance with the provisions of the applicable Warrant Agreement to be filed on a Current Report on Form 8-K in the manner contemplated in the Registration Statement or any prospectus supplement relating thereto, the Offered Warrants (including any Warrants duly issued upon conversion, exchange or exercise of any Debt Securities or Preferred Stock), when issued and sold in accordance with the applicable Warrant Agreement and the applicable purchase agreement or any other duly authorized, executed and delivered valid and binding purchase or agency agreement, will be valid and binding obligations of the Company, enforceable against the Company in accordance with their respective terms, except to the extent that enforcement thereof may be limited by (a) bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to creditors’ rights generally, (b) general principles of equity (regardless of whether enforceability is considered in a proceeding at law or in equity) and (c) public policy considerations which may limit the rights of parties to obtain remedies.

5. With respect to Depositary Shares to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting Depositary Shares (the “Offered Depositary Shares”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act, (ii) an appropriate prospectus supplement with respect to the Offered Depositary Shares has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Depositary Shares are to be sold pursuant to a firm commitment underwritten offering, the underwriting agreement with respect to the Offered Depositary Shares has been duly authorized, executed and delivered by the Company and the other parties thereto, including the adoption of articles of amendment for such related series of Preferred Stock in the form required by South Dakota law, (iv) such articles of amendment have been duly filed with the Secretary of State of South Dakota, (v) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance and terms of the Offered Depositary Shares and the related series of Preferred Stock, the applicable Deposit Agreement and related matters, (vi) the terms of the Offered Depositary Shares and related Receipts and of their issuance and sale have been duly established in conformity with the applicable Deposit Agreement so as not to violate any applicable law, the Articles or the Bylaws or result in a default under or breach of any agreement or

VeraSun Energy Corporation

August 13, 2008

Page 9

instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company and the applicable Depositary, (vii) the shares of Preferred Stock relating to such Offered Depositary Shares have been duly authorized for issuance and have been duly issued and paid for in the manner contemplated in the Registration Statement or any prospectus relating thereto, (viii) the applicable Deposit Agreement has been duly executed and delivered, (ix) the Offered Depositary Shares have been duly executed, delivered, countersigned, issued and sold in accordance with the provisions of the applicable Deposit Agreement to be filed on a Current Report on Form 8-K in the manner contemplated in the Registration Statement or any prospectus supplement relating thereto, and the Offered Depositary Shares have been delivered to the Depositary for deposit in accordance with the applicable Deposit Agreement, and (x) the Receipts evidencing the Offered Depositary Shares have been duly issued against deposit of the related shares of Preferred Stock with the Depositary in accordance with the applicable Deposit Agreement, such Receipts will be validly issued and will entitle the holders thereof to the rights specified therein and in the Deposit Agreement, and the Offered Depositary Shares, when issued and sold in accordance with the applicable Deposit Agreement and the applicable purchase agreement or any other duly authorized, executed and delivered valid and binding purchase or agency agreement, will be valid and binding obligations of the Company, enforceable against the Company in accordance with their respective terms, except to the extent that enforcement thereof may be limited by (a) bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to creditors’ rights generally, (b) general principles of equity (regardless of whether enforceability is considered in a proceeding at law or in equity) and (c) public policy considerations which may limit the rights of parties to obtain remedies.

6. With respect to Subscription Rights to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting Subscription Rights (the “Offered Subscription Rights”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act, (ii) an appropriate prospectus supplement with respect to the Offered Subscription Rights has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Subscription Rights are to be sold pursuant to a firm commitment underwritten offering, the underwriting agreement with respect to the Offered Subscription Rights has been duly authorized, executed and delivered by the Company and the other parties thereto, (iv) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance and terms of the Offered Subscription Rights, the Subscription Rights Agreement and related matters, including setting forth the

VeraSun Energy Corporation

August 13, 2008

Page 10

terms of the Subscription Rights in a Subscription Rights Certificate, (v) the terms of the Offered Subscription Rights and of their issuance and sale have been duly established by the Company and the applicable Subscription Agent in conformity with the applicable Subscription Rights Agreement and Subscription Rights Certificate so as not to violate any applicable law, the Articles or the Bylaws or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company and the applicable Subscription Agent, (vi) the Common Stock relating to such Offered Subscription Rights has been duly authorized for issuance, and (vii) the Offered Subscription Rights have been duly executed, delivered, countersigned, issued and sold in accordance with the provisions of the applicable Subscription Rights Agreement and Subscription Rights Certificate to be filed on a Current Report on Form 8-K in the manner contemplated in the Registration Statement or any prospectus supplement relating thereto, the Offered Subscription Rights, when issued and sold in accordance with the applicable Subscription Rights Agreement and Subscription Rights Certificate and the applicable purchase agreement or any other duly authorized, executed and delivered valid and binding purchase or agency agreement, will be valid and binding obligations of the Company, enforceable against the Company in accordance with their respective terms, except to the extent that enforcement thereof may be limited by (a) bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to creditors’ rights generally, (b) general principles of equity (regardless of whether enforceability is considered in a proceeding at law or in equity) and (c) public policy considerations which may limit the rights of parties to obtain remedies.

7. With respect to any Purchase Contracts to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting Purchase Contracts (the “Offered Purchase Contracts”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act, (ii) an appropriate prospectus supplement with respect to the Offered Purchase Contracts has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Purchase Contracts are to be sold pursuant to firm commitment underwritten offering, the underwriting agreement with respect to the Offered Purchase Contracts has been duly authorized, executed and delivered by the Company and the other parties thereto, (iv) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance and terms of the Offered Purchase Contracts and related matters, (v) the terms of the Offered Purchase Contracts and of their issuance and sale have been duly established with the applicable Purchase Contract Agreement so as not to violate any applicable law, the Articles or the Bylaws, or result in a default under

VeraSun Energy Corporation

August 13, 2008

Page 11

or breach of any agreement or instrument binding upon the Company, and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company and the applicable Purchase Contract Agent, and (vi) the applicable Offered Purchase Contracts have been duly executed and delivered and duly issued and sold in the applicable form to be filed as an exhibit to a Current Report on Form 8-K in the manner contemplated in the Registration Statement or any prospectus supplement relating thereto, the Offered Purchase Contracts, when issued and sold in accordance with the applicable Purchase Contract Agreement and the applicable underwriting agreement or any other duly authorized, executed and delivered valid and binding agreement, will be valid and binding obligations of the Company, enforceable against the Company in accordance with their respective terms, except to the extent that enforcement thereof may be limited by (a) bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to creditors’ rights generally, (b) general principles of equity (regardless of whether enforceability is considered in a proceeding at law or in equity) and (c) public policy considerations which may limit the rights of parties to obtain remedies.

8. With respect to any Purchase Units to be offered by the Company pursuant to the Registration Statement, including any Indeterminate Securities constituting Purchase Units (the “Offered Purchase Units”), when (i) the Registration Statement, as finally amended (including all necessary post-effective amendments), has become effective under the Act, (ii) an appropriate prospectus supplement with respect to the Offered Purchase Units has been prepared, delivered and filed in compliance with the Act and the applicable rules and regulations thereunder, (iii) if the Offered Purchase Units are to be sold pursuant to a firm commitment underwritten offering, the underwriting agreement with respect to the Offered Purchase Units has been duly authorized, executed and delivered by the Company and the other parties thereto, (iv) the Board of Directors, including any appropriate committee appointed thereby, and appropriate officers of the Company have taken all necessary corporate action to approve the issuance and terms of the Offered Purchase Units and related matters, (v) the terms of the Offered Purchase Units and the related Offered Purchase Contracts and of their issuance and sale have been duly established in conformity with the applicable Purchase Contract Agreement so as not to violate any applicable law, the Articles or the Bylaws, or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company and the applicable Purchase Contract Agent, (vi) any Purchase Contracts and Debt Securities or debt obligations of third parties, including U.S. Treasury securities, or other securities (or any combination of the foregoing) included in such Offered Purchase Units have been duly issued and paid for in the manner contemplated in the Registration Statement and any prospectus supplement relating thereto, and (vii) the Offered Purchase Units have been duly executed, delivered,

VeraSun Energy Corporation

August 13, 2008

Page 12

countersigned, issued and sold in accordance with the provisions of the applicable Purchase Contract Agreement in the applicable form to be filed on a Current Report on Form 8-K in the manner contemplated in the Registration Statement or any prospectus supplement relating thereto, the Offered Purchase Units, when issued and sold in accordance with the applicable Purchase Contract Agreement and the applicable purchase agreement or any other duly authorized, executed and delivered valid and binding agreement, will be valid and binding obligations of the Company, enforceable against the Company in accordance with their respective terms, except to the extent that enforcement thereof may be limited by (a) bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium or other similar laws now or hereafter in effect relating to creditors’ rights generally, (b) general principles of equity (regardless of whether enforceability is considered in a proceeding at law or in equity) and (c) public policy considerations which may limit the rights of parties to obtain remedies.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement. We also hereby consent to the reference to our firm under the heading “Legal Matters” in the prospectus which forms a part of the Registration Statement. In giving this consent, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission. This opinion is expressed as of the date hereof unless otherwise expressly stated, and we disclaim any undertaking to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable laws.

Respectfully submitted,

/s/ Davenport, Evans, Hurwitz & Smith, L.L.P.

DAVENPORT, EVANS, HURWITZ & SMITH, L.L.P.

Schedule I

US BioEnergy Corporation, a South Dakota corporation

VeraSun Aurora Corporation, a South Dakota corporation

VeraSun Biodiesel, LLC, a Delaware limited liability company

VeraSun Charles City, LLC, a Delaware limited liability company

VeraSun Fort Dodge, LLC, a Delaware limited liability company

VeraSun Granite City, LLC, a Delaware limited liability company

VeraSun Hartley, LLC, a Delaware limited liability company

VeraSun Litchfield, LLC, a Delaware limited liability company

VeraSun Marketing, LLC, a Delaware limited liability company

VeraSun Reynolds, LLC, a Delaware limited liability company

VeraSun Tilton, LLC, a Delaware limited liability company

VeraSun Welcome, LLC, a Delaware limited liability company