MEMBERSHIP INTEREST PURCHASE AGREEMENT

EXHIBIT 10.1

MEMBERSHIP INTEREST PURCHASE AGREEMENT

This MEMBERSHIP INTEREST PURCHASE AGREEMENT (this “Agreement”) is made and entered into as of April 30, 2006, by, between and among US BioEnergy Corporation, a South Dakota corporation (“Buyer”), and each of the persons identified on Schedule A attached hereto (collectively referred to herein as the “Sellers” and individually as a “Seller”). Val-E Ethanol, LLC, a Nebraska limited liability company (“Val-E”), has also executed this Agreement and is a party to this Agreement solely for the purpose of acknowledging agreement to the specific provisions identified with respect to Val-E on the signature page of this Agreement. Buyer, Sellers and Val-E (limited as stated) are herein referred to as “Parties” and individually as a “Party” to this Agreement.

RECITALS

NOW, THEREFORE, in consideration of the premises and the mutual promises herein made, and in consideration of the representations, warranties and covenants herein contained, the Parties agree as follows:

ARTICLE I

PURCHASE AND SALE OF MEMBERSHIP INTERESTS

Section 1.1. Purchase and Sale Transaction.

Subject to the terms and conditions set forth in this Agreement and the consummation of the transactions contemplated by this Agreement, on the closing date (as defined in Section 1.3 and hereinafter referred to as the “Closing Date”) and for the consideration specified in Section 1.2, Buyer shall purchase from Sellers, and Sellers shall sell, transfer, assign and convey to

Buyer, free and clear of any and all liens, claims, encumbrances, security interests or options whatsoever, all of Sellers’ right, title and interest in and to all of their respective Membership Interests in Val-E, as set forth on Schedule A to this Agreement, constituting in the aggregate 49.82% of the outstanding Membership Interests in Val-E, including all of Sellers’ rights and other benefits to which holders of Membership Interests in Val-E may be entitled under the Operating Agreement of Val-E dated December 28, 2005 (the “Operating Agreement”) or otherwise, including, without limitation, (i) Sellers’ shares of the profits and losses of Val-E, (ii) all rights of Sellers to receive distributions of Val-E’s monies and other property or assets due and to become due to Sellers under or pursuant to the Operating Agreement or applicable law (regardless of the source of those distributions or payments or when the same was earned or received by Val-E), (iii) all rights of Sellers to vote on or participate in the management of Val-E, (iv) all rights of Sellers to information concerning the business and affairs of Val-E, (v) all claims of Sellers for damages arising out of or for any breach of or default under the Operating Agreement, and (vi) all rights of Sellers to act under the Operating Agreement and to compel performance and otherwise exercise remedies under the Operating Agreement (all of the foregoing collectively referred to herein as the “Purchased Membership Interests”).

Section 1.2. Purchase Price; Exchanged Shares.

As consideration for the sale, transfer and assignment of the Purchased Membership Interests and for the covenants of the Sellers herein, Buyer agrees to pay Sellers at the Closing consideration in the form of an aggregate of 6,205,000 shares of Class A common stock of the Buyer (the “Purchase Price” or “Exchanged Shares”), such Exchanged Shares to be divided among and issued to the respective Sellers as set forth on Schedule A to this Agreement. The sale, transfer and assignment of the Purchased Membership Interests and registration and delivery of the Exchanged Shares to Sellers contemplated by this Agreement are herein referred to as the “Purchase Transaction.” The number of Exchanged Shares shall be adjusted for any stock splits, recapitalizations or other actions which affect the fundamental terms of the Class A common stock of Buyer prior to the Closing.

Section 1.3. The Closing.

The closing of the Purchase Transaction (the “Closing”) shall take place at the place and time specified for the closing of Buyer’s acquisition of PVFE pursuant to the PVFE Transaction Agreement (the “PVFE Transaction”), which is scheduled to take place by fax transmissions on April 26, 2006, or at such other place or such other time after the closing of the PVFE Transaction and following the satisfaction or waiver of all conditions to the obligations of the Parties to consummate the Purchase Transaction (other than conditions with respect to actions the respective parties will take at the Closing itself) as Buyer and Sellers may mutually determine (the “Closing Date”), but in no event later than ten (10) days following the closing of the PVFE Transaction.

Section 1.4. Deliveries at the Closing.

At the Closing, (a) Sellers shall deliver to Buyer the various certificates, instruments, agreements and documents referred to in Section 5.1 below, (b) Buyer shall deliver to Sellers the various certificates, instruments and documents referred to in Section 5.2 below, (c) Sellers shall deliver to Buyer Sellers all necessary certificates, instruments and documents to effect a transfer

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of the Purchased Membership Interests to Buyer on the terms and conditions provided in this agreement, including, without limitation, the certificates or other instruments, if any, representing the Purchased Membership Interests, endorsed in blank or accompanied by duly executed assignment documents, including assignments of the Purchased Membership Interests (the “Assignments”) in the form set forth as Exhibit A to this Agreement, together with any other documents or certificates necessary in accordance with the Operating Agreement to effect the transfer of the Purchased Membership Interests, (d) Sellers shall deliver to Buyer evidence that Buyer’s name and address and the transfer of the Purchased Membership Interests are reflected in the records of Val-E effective as of the Closing Date, and (e) Buyer shall deliver to Sellers the Exchanged Shares described in Section 1.2 hereof in the amount for each Seller as set forth on Schedule A to this Agreement.

Section 1.5. Effects of the Transaction.

The purchase and sale of the Purchased Membership Interests shall be effective as of April 30, 2006 (the “Effective Date”), and Val-E will recognize the transfer of the Purchased Membership Interests as of the Effective Date. From and after the Effective Date, the portion of profits or losses of Val-E and the portions of all other items of income, gain, loss, deduction or credit allocable to the Purchased Membership Interests on or after such Effective Date shall be credited or charged, as the case may be, to Buyer and not to Sellers. From and after the Effective Date, Sellers shall not be entitled to any distributions or payments in respect of the Purchased Membership Interests, and Buyer shall be entitled to all distributions or payments in respect of the Purchased Membership Interests made on or after the Effective Date, regardless of the source of those distributions or payments or when the same were earned or received by Val-E. All profits, losses, each item thereof, and other items of income, gain, loss, deduction or credit allocable to the Purchased Membership Interests and attributable to any period before the Effective Date shall be allocated to Sellers, and shall be computed by Val-E on the basis of an interim closing of the books as of the Effective Date in accordance with the Operating Agreement and applicable law and in a manner consistent with its past accounting and allocation practices. From and after the Closing Date, Sellers will no longer be parties to the Operating Agreement, will no longer be members of Val-E, will have no right to vote on or participate in the management of Val-E and will have no right to any information concerning the business and affairs of Val-E.

ARTICLE II

REPRESENTATIONS AND WARRANTIES CONCERNING THE PARTIES AND THE TRANSACTION

Section 2.1. Representations and Warranties of Sellers.

Each Seller hereby represents and warrants to Buyer that the statements contained in this Section 2.1 are correct and complete as of the date of this Agreement and shall be correct and complete as of the Closing Date and as of the Effective Date (as though made at the Closing Date and Effective Date and as if the Closing Date and Effective Date were substituted for the date of this Agreement throughout this Section 2.1).

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(a) If such Seller is an entity, such Seller is duly organized, validly existing and in good standing under the laws of the jurisdiction of its organization and in any jurisdiction in which the failure to be qualified would impair its ability to enter into this Agreement or adversely affect the enforceability of this Agreement.

(b) Such Seller has full power and authority to execute and deliver this Agreement and to perform its obligations hereunder.

(c) Neither the execution and delivery of this Agreement nor the consummation of the transactions contemplated hereby will (i) violate any constitution, statute, regulation, rule, injunction, judgment, order, decree, ruling, charge or other restriction of any government, governmental agency or court to which such Seller is subject, or any provision of such Seller’s articles of organization or incorporation, operating agreement or bylaws, or (ii) conflict with, result in a breach of or constitute a default under (upon the giving of notice or lapse of time or both), result in the acceleration of, or create in any party the right to accelerate, terminate, modify or cancel, or require any notice under, any agreement, contract, lease, license, instrument or other arrangement to which such Seller is a party or by which such Seller is bound or to which the Purchased Membership Interest of such Seller is subject.

(d) Such Seller has no liability or other obligation to pay any fees or commissions to any broker, finder or agent with respect to the transactions contemplated by this Agreement for which the Buyer could become liable.

(e) Such Seller holds of record and is the sole beneficial owner of the Purchased Membership Interest of such Seller, as described on Schedule A to this Agreement, which Purchased Membership Interest is a validly issued, fully paid and non-assessable Membership Interest in Val-E, and is free and clear of any restrictions on transfer (other than any restrictions under federal or state securities laws and the Operating Agreement), liens, claims, encumbrances, security interests, options, warrants, purchase rights, rights of first refusal or other demands. Such Seller is not a party to any option, warrant, purchase right, right of first refusal or other contract or commitment that could require Seller to sell, transfer or otherwise dispose of such Purchased Membership Interest (other than this Agreement and the Operating Agreement). Such Seller has good and marketable title to such Purchased Membership Interest, such Purchased Membership Interest represents such Seller’s entire interest and investment in Val-E and such Purchased Membership Interest represents the percentage ownership of Val-E stated on Schedule A to this Agreement.

(f) Such Seller purchased such Seller’s Purchased Membership Interest for the amount stated on Schedule A to this Agreement, which amount has been paid in full to Val-E and no portion of which is unpaid or outstanding by promissory note or otherwise.

(g) Other than its ordinary obligations as a member of Val-E under the Operating Agreement, such Seller has no obligations or liabilities owed to Val-E or any other person for which Buyer would or will become responsible following the effective date of the transfer of the Purchased Membership Interests.

(h) Such Seller (i) is an “accredited investor” as defined in Regulation D of the Securities and Exchange Commission under the Securities Act of 1933, as amended (the “Act”)

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for purposes of the acquisition of the Exchanged Shares, (ii) is acquiring the Exchanged Shares solely for such Seller’s own account, for investment purposes only and, with no present intention of distributing, selling or otherwise disposing of the Exchanged Shares in connection with a distribution as such term is understood under the Act, (iii) understands that the Exchanged Shares may not be sold, transferred or otherwise disposed of without registration under the Act and applicable state securities laws, or the availability of exemptions thereunder, and (iv) agrees that Buyer may place restrictive legends on certificates representing the Exchanged Shares to evidence the restrictions on transfer thereof imposed by federal and state securities laws and may place a stop transfer order in its stock records or with its stock transfer agent and registrar with respect to the Exchanged Shares.

Section 2.2. Representations and Warranties of Buyer .

Buyer represents and warrants to Sellers that the statements contained in this Section 2.2 are correct and complete as of the date of this Agreement and shall be correct and complete as of the Closing Date and as of the Effective Date (as though made at the Closing Date and Effective Date and as if the Closing Date and Effective Date were substituted for the date of this Agreement throughout this Section 2.2).

(a) Buyer is duly organized, validly existing and in good standing under the laws of the state of South Dakota and in any jurisdiction in which the failure to be qualified would impair its ability to enter into this Agreement or adversely affect the enforceability of this Agreement.

(b) Buyer has full power and authority to execute and deliver this Agreement and to perform its obligations hereunder.

(c) Neither the execution and delivery of this Agreement nor the consummation of the transactions contemplated hereby will (i) violate any constitution, statute, regulation, rule, injunction, judgment, order, decree, ruling, charge or other restriction of any government, governmental agency or court to which Buyer is subject, or any provision of Buyer’s articles of incorporation or bylaws or (ii) conflict with, result in a breach of or constitute a default under (upon the giving of notice or lapse of time or both), result in the acceleration of, or create in any party the right to accelerate, terminate, modify or cancel, or require any notice under, any agreement, contract, lease, license, instrument or other arrangement to which Buyer is a party or by which Buyer is bound.

(d) When issued at the Closing in accordance with the terms of this Agreement, the Exchanged Shares will be validly issued, fully paid and non-assessable shares of Class A common stock of the Buyer, subject only to the terms of Article VII of this Agreement and the Purchase Escrow Agreement and Instructions provided for therein.

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ARTICLE III

PRE-CLOSING COVENANTS

The Parties agree as follows with respect to the period between the execution of this Agreement and the Closing:

Section 3.1 General.

Each of the Parties will use its reasonable best efforts to take all actions and to do all things necessary, proper or advisable in order to consummate and make effective the transactions contemplated by this Agreement (including satisfaction, but not waiver, of the closing conditions set forth in Article V below).

Section 3.2 Access to Information.

Val-E will give Buyer and its management personnel, counsel, accountants, financial advisors and all other reasonable representatives of Buyer (“Representatives”) full access and opportunity, during normal business hours, to examine Val-E’s assets, books and records and shall afford Buyer and Representatives full and complete access to examine all assets, contracts, facilities and information used in connection with Val-E’s development and intended operations.

Section 3.3 Notices and Consents.

Val-E agrees to give, and Sellers will use their best efforts to cause Val-E to give, any notices to third parties, and Val-E agrees to use, and Sellers will use their best efforts to cause Val-E to use, reasonable commercial efforts to obtain any third party consents that Buyer may reasonably request in connection with or to effect the transactions contemplated by this Agreement. Each of the Parties will give any notices to, make any filings with, and use its reasonable commercial efforts to obtain any authorizations, consents and approvals of governments and governmental agencies, known to be required in connection with the matters referred to in Section 2.1(c) and Section 2.2(c).

Section 3.4 Operation of Val-E Business.

Val-E agrees, and Sellers shall use their best efforts to cause Val-E, to operate its business and conduct its affairs in the ordinary course of business and as set forth in the Operating Agreement, except as otherwise provided in Article VI of this Agreement. Val-E shall not make any distribution with respect to any ownership interest in Val-E, including specifically the Purchased Membership Interests, until after Buyer’s purchase and complete redemption of the Purchased Membership Interests hereunder.

Section 3.5 Notice of Developments.

Each Party will give prompt written notice to the others of any development causing a breach of any of its own representations and warranties in Article II above. However, no disclosure by any Party pursuant to this Section 3.5 shall be deemed to prevent or cure any misrepresentation, breach of warranty or breach of covenant.

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ARTICLE IV

POST-CLOSING COVENANTS

The Parties agree as follows with respect to the period following the Closing:

Section 4.1 Additional Instruments and Further Assurances.

The Parties agree to cooperate at all times from and after the Closing with respect to any of the matters described herein, and to execute such further deeds, bills of sale, assignments, releases, assumptions, notifications and other documents or instruments as may be reasonably requested for the purpose of giving effect to, evidencing or giving notice of the transactions contemplated by this Agreement or the agreements of the Parties under this Agreement.

Section 4.2 Confidentiality.

The confidentiality and nondisclosure obligations of the Parties with respect to information exchanged between the Parties shall continue to be governed by the terms of the Mutual Confidentiality Agreement between Buyer and Val-E dated April 26, 2006

Section 4.3 Post-Closing Events.

The Sellers and the Buyer understand and agree that this Agreement is made in contemplation of the following post-Closing events, as to which Sellers and Buyer agree to use their reasonable best efforts to cause to occur:

(a) On and following the Effective Date, Buyer, either directly or indirectly through PVFE, will own 100% of the Membership Interests; and Buyer, subject to confirmation of accounting treatment of the acquisition satisfactory to Buyer, will cause PVFE to distribute its 50.18% Membership Interest in Val-E to Buyer, resulting in Val-E becoming and being a wholly-owned, single-member, first-tier subsidiary of Buyer.

(b) All real and personal property (including contract rights and other intangibles) of Val-E immediately prior to the acquisition will remain vested in and continue with Val-E following the acquisition. The existence of Val-E will continue without dissolution for state law purposes. As of the Effective Date, the existence of Val-E will terminate for tax purposes, and Val-E will become a disregarded entity for tax purposes. As sole member, Buyer will cause Val-E to file its final tax return for the period from its most recent fiscal year end to the Effective Date.

(c) As of the Effective Date, the Operating Agreement will be replaced and superseded by a single-member operating agreement and, if necessary, the Val-E articles of organization will be amended and restated to reflect the single-member ownership. Following the Effective Date, Val-E will continue to be a manager-managed entity, the members of the Executive Committee of Buyer will serve as the managers of Val-E, and each of the then current managers of Val-E will serve on the initial Board of Managers of Val-E, which Board of Managers will be a local board similar in nature and function to the local boards of other Buyer subsidiaries.

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(d) The acquisition transaction may constitute an exchange transaction within Section 351 of the Internal Revenue Code for tax purposes, although Sellers and Buyer understand that the cost basis of each Seller in its Membership Interest equals approximately the value of the Exchanged Shares that it will receive in the Purchase Transaction.

ARTICLE V

CONDITIONS TO OBLIGATION TO CLOSE

Section 5.1 Conditions to Obligation of the Buyer.

The obligation of the Buyer to purchase the Purchased Membership Interests and to consummate the transactions to be performed by it in connection with the Closing with respect to any and all of the Sellers, regardless of which Seller or Sellers may be responsible for the failure of any condition herein, is subject to satisfaction of each of the following conditions:

(a) Buyer shall have completed its due diligence review of Val-E and the Purchase Transaction to Buyer’s satisfaction, such due diligence review to include, without limitation, the following:

(i) The satisfactory review and verification by Buyer of all business and accounting records and financial statements of Val-E;

(ii) Identification and inspection of all development agreements, option agreements, permits, applications, letters of intent, grants, incentive packages or payments in Nebraska and contracts of Val-E, including all material contracts relating to the construction of the Val-E ethanol plant in Ord, Nebraska and verification that all such contracts and relationships will survive the completion of the Purchase Transaction;

(iii) Satisfactory completion of a due diligence review by Buyer of Val-E’s assets, liabilities and prospects, including state incentive packages; and

(iv) Determination that the transactions contemplated herein comply with all applicable laws and regulations.

(b) Each of the representations and warranties of each of the Sellers set forth in Section 2.1 above shall be true and correct in all material respects at and as of the Closing Date.

(c) Each of the Sellers shall have performed and complied with all of its covenants hereunder in all material respects through the Closing.

(d) The closing of the PVFE Transaction shall have been completed.

(e) Buyer shall be satis