<Page>

                                                                    Exhibit 10.4

<Table>
                                                                          
PD: $30.50                                                                      Reg ______
                                                                                Index______
                                                                                G. Index____
WHEN RECORDED RETURN TO:                State of Nebraska, County of Fillmore   RE Cards___
Michael J. Green                        Filed for Record On April 27 2005       C. Map____
Regency West 5                          At 4:11 O'Clock P M And Record in       MF ______
4500 Westown Parkway, Suite 277         Book 48 Of Misc On Page 391             Xerox ____
West Des Moines, Iowa  50266            Carol Vejraska County Clerk             Paged ____
</Table>

<Table>
                                                                             
PREPARER
INFORMATION Michael J. Green     4500 Westown Pkwy., Ste. 277 West Des Moines, IA  (515) 242-2431
            ---------------------------------------------------------------------  --------------
            Individual's Name           Street Address             City                 Phone
</Table>

________________________________________________________________________________
                                           SPACE ABOVE THIS LINE FOR RECORDER

                          REAL ESTATE OPTION AGREEMENT

     THIS AGREEMENT is made this 13th day of April, 2005, by and between L & K
Land, Inc., a Nebraska corporation, (hereinafter referred to as "Optionor") and
Advanced BioEnergy, LLC, a Delaware limited liability company (hereinafter
referred to as "Optionee").

                              W I T N E S S E T H:

     WHEREAS, Optionor is the owner of real estate described in full at
paragraph 1 below and is desirous of securing a future purchaser of said real
property under defined terms; and

     WHEREAS, Optionee desires to acquire said property from Optionor in
accordance with the terms and conditions set forth hereafter.

     IN CONSIDERATION of the covenants and promises contained hereafter, it is
agreed:

     1.   PREMISES: That Optionor hereby grants to Optionee the exclusive option
          to purchase real property, together with all improvements thereon, if
          any, in Fillmore County, Nebraska, more specifically described as
          follows:

          North half of the Northeast quarter of Section 26-8-3, approximately
          103 acres, Fillmore County, Nebraska.

     2.   OPTION CONSIDERATION: As consideration for the option grant provided
          in paragraph 1 above, Optionee agrees to pay to Optionor at the time
          of the execution of this Option Agreement the sum of $5,000.00. The
          parties agree that there is valid and sufficient consideration for
          this Agreement based on this sum, the mutual obligations herein
          contained and other good and valuable consideration. In addition,
          Optionor

                                                                       391 - 1/6

<Page>

          agrees not to enter into any other Purchase, Lease or Agreement of any
          kind with any other party relating to the subject property while this
          Option Agreement is in place.

     3.   TERM: This option shall commence on the date of the execution of this
          Option Agreement and continue to the 1st day of August, 2006, at 12:00
          midnight at which time it expires and is null and void if not
          exercised.

     4.   PURCHASE TERMS: Pursuant to the terms of this option, Optionor agrees
          to sell and Optionee agrees to purchase the above-described real
          property with improvements thereon under the following terms and
          conditions:

          a.   PURCHASE PRICE: The purchase price shall be: $566,500.00.

               The Optionee agrees to pay in cash at closing the relevant amount
               as set forth above. Optionee shall be credited against said
               purchase price with the full amount paid in cash as the option
               consideration hereunder.

          b.   ABSTRACT: Optionor shall promptly after receipt of notice of
               exercise of option provide a title commitment showing title to be
               marketable in accordance with this Agreement, the land title laws
               of the State of Nebraska and the Nebraska Title Standards of the
               Nebraska State Bar Association. If closing is delayed due to
               Optionor's inability to provide marketable title, then Optionee
               may rescind this Agreement after giving 14 days written notice to
               the other party and the broker if any. Cost of title insurance
               split one-half to the Optionor and one-half to the Optionee.

          c.   WARRANTY DEED: At closing, upon receipt of the full purchase
               price set forth above, Optionor shall execute and deliver to
               Optionee an appropriate Warranty Deed, Declaration of Value and
               Hazard Statement for recording by Optionee.

          d.   TAXES: Optionor shall pay all real estate taxes prorated to the
               date of closing. If the amount of any such tax to be prorated
               cannot be ascertained, proration shall be computed on the amount
               for the preceding year.

          e.   SPECIAL ASSESSMENTS: The Optionor shall pay all special
               assessments which are a lien and due and payable on said property
               and can be paid as of the date of closing.

          f.   EMINENT DOMAIN: In the event the property or any part thereof is
               taken or threatened to be taken pursuant to eminent domain after
               the notice of exercise of the above option, but prior to closing,
               the Optionee shall have the right at its election to cancel and
               terminate this agreement or to complete the purchase as set forth
               above with the Optionee being entitled to receive all
               condemnations proceeding against the real property.

                                                                       391 - 2/6

                                        2
<Page>

          g.   CLOSING: Closing shall be held on a date agreeable to the parties
               not later than 90 days from the date of the notice of demand to
               close.

          h.   DEFAULT: In the event Optionor has fulfilled all of its
               obligations hereunder and all conditions precedent and concurrent
               to closing for which it is responsible and Optionee fails to
               fulfill its obligations hereunder and continues to fail and
               refuses to fulfill its obligations hereunder for more than 30
               days after receipt of written notice of such default from
               Optionor may either: 1) terminate this Agreement in which event
               it shall be entitled to retain the option money deposits and any
               other monies paid hereunder and such termination and retainage
               shall be the sole remedy and damages available to the Optionee;
               or 2) pursue any legal and/or equitable remedy available to it.
               In the event Optionee fulfills all of its obligations hereunder
               and meets all conditions precedent and concurrent to closing for
               which it is responsible and Optionor is unable, fails or refuses
               to meet its obligations hereunder for more than 30 days after
               receipt of written notice of such default, Optionee may either:
               1) terminate this Agreement in which event it shall be entitled
               to receive refund of all of its option money deposits and any
               other monies paid hereunder and such termination and refund shall
               be the sole remedy and damages available to the Optionee; or 2)
               pursue any legal and/or equitable remedy available to it.

          i.   PERSONAL PROPERTY: Optionor understands and agrees that Optionee
               shall have the right under the Purchase Agreement to retain the
               well, pump, engine, gearbox, water rights and any other equipment
               necessary to get water out of the ground on the subject property.
               Optionee further agrees that Optionor shall have the right to
               retain the pivot located on the property and shall have a
               reasonable time period for removal of the same at Optionor's
               expense.

          j.   CROP DAMAGE: In the event that Optionee's due diligence and/or
               closing and conveyance of the Property to Optionee shall occur
               after Optionor plants crops, but before harvest of those crops,
               the parties hereto mutually agree that Optionor shall have the
               right, upon notice to the Optionee and at the Optionee's
               convenience, to harvest any crops not destroyed by the Optionee
               in the process of its due diligence and/or its constructing of
               the ethanol plant and related improvements thereto. The Optionee
               shall have no duty to preserve any of such crops, and the
               Optionor accepts as liquidated damages (in lieu of any and all
               other damages) an amount equal to 120% of the University of
               Nebraska estimated per acre crop input cost for Fillmore County,
               Nebraska for the applicable crop year multiplied by the number of
               acres, or fractional acres, of crop destroyed on the Property by
               the Optionee prior to the harvest of such crop acres by the
               Optionor. The number of such acres destroyed shall be measured by
               a third-party as the parties hereto may mutually identify.

     5.   RECORDING OF OPTION: The parties hereto agree that this Option
          Agreement shall be recorded.

                                                                       391 - 3/6

                                        3
<Page>

     6.   INSPECTION RIGHTS: Optionee shall, during the term of this Option
          Agreement, have the unrestricted rights to enter upon the subject
          property for purposes of performing any and all due diligence
          necessary to Optionee's determination to purchase the subject property
          including, but not limited to, the taking of soil samples. Optionee
          understands and agrees that during the term of this Option Agreement
          Optionor shall have the full and unrestricted right to plant irrigated
          corn or soybeans on the subject property. Should Optionee, as a part
          of its inspection, damage any of the growing crops on the subject
          property, Optionee shall be responsible for the payment of the fair
          market value thereof to Optionor.

     7.   NOTICES: Any notice, demand or other document which either party is
          required or may desire to give or deliver to or make upon the other
          party shall be given in writing and served either personally or given
          by prepaid United States certified mail, return receipt requested, and
          addressed to the following addresses:

          If to Optionor:          L & K Land, Inc.
                                   c/o Stanley L. Schepers
                                   745 Turtle Beach
                                   Marquette, Nebraska 68854

          If to Optionee:          Advanced BioEnergy, LLC
                                   c/o Brown, Winick, Graves, Gross, Baskerville
                                   and Schoenebaum, P.L.C.
                                   Attn:  William E. Hanigan
                                   666 Grand Avenue, Suite 2000
                                   Des Moines, Iowa 50309-2510

          Either party hereto may designate a different address for itself, or
          additional persons to whom copies thereof are to be sent, by notice
          similarly given.

     8.   REAL ESTATE BROKERS: The parties hereto represent that, absent
          specific disclosure in writing, no real estate brokers have been
          employed, utilized or relied upon by either party as a result of the
          grant of this option or the real estate sale contemplated therein.

     9.   TIME: Time is of the essence as to the performance of all of the terms
          and conditions of this Agreement.

     10.  ATTORNEY FEES: Any action required of the Optionor hereunder to
          enforce its rights to this Agreement shall entitle the Optionor to the
          recovery of its reasonable attorney fees, costs and expenses incurred
          and necessary to the enforcement of said rights.

                                                                       391 - 4/6

                                        4
<Page>

     11.  GENERAL: This Agreement shall be deemed to have been made and shall be
          construed and interpreted in accordance with the laws of the State of
          Nebraska. This Agreement shall be binding upon and inure to the
          benefit of the respective parties hereto and their successors and
          assigns. The captions and titles herein are for reference only and are
          not to be considered a part of this Agreement or in the interpretation
          hereof. This Agreement shall not be valid until signed by both
          parties. The phrase "execution and delivery hereof," as used above,
          shall be the date the last party hereto signs this Agreement and
          serves it upon the other party in the same manner as set forth for
          notices. Time is of the essence.

     IN WITNESS WHEREOF, said parties hereto subscribe their names.

OPTIONOR:                                     OPTIONEE:

L & K LAND, INC.                              ADVANCED BIOENERGY, LLC


By   /s/Stanley L. Schepers, President        By   /s/Revis L. Stephenson III
  ---------------------------------------       --------------------------------
     Stanley L. Schepers, President                Revis L. Stephenson III,
Chairman

By   /s/Kathryn J. Schepers, Secretary
  ---------------------------------------
     Kathryn J. Schepers, Secretary

STATE OF  Nebraska     )
                       )SS:
COUNTY OF   Menrick    )

     On this 13th day of April, 2005, before me, the undersigned, a Notary
Public in and for said County and State, personally appeared Stanley L. Schepers
and Kathryn J. Schepers, to me personally known, who, being by me duly sworn,
did say that they are the President and Secretary, respectively, of said
corporation executing the within and foregoing instrument; that said instrument
was signed on behalf of said corporation by authority of its Board of Directors;
and that the said President and Secretary as such officers acknowledged the
execution of said instrument to be the voluntary act and deed of said
corporation, by it and by them voluntarily executed.

[NOTARY SEAL]                                           /s/Ina Cotner
                                                --------------------------------
                                 Notary Public in and for the State of Iowa


                                                                       391 - 5/6

                                        5
<Page>

STATE OF  Minnesota    )
                       )SS:
COUNTY OF   Hennepin   )

     On this 26th day of April, 2005, before me, the undersigned, a Notary
Public in and for the State of Minnesota, personally appeared Revis L.
Stephenson III to me personally known, who being by me duly sworn, did say that
he is the Chairman of Advanced BioEnergy, LLC, a limited liability company,
executing the within and foregoing instrument; that no seal has been procured by
the said limited liability company; that said instrument was signed on behalf of
the limited liability company by authority of its members; and that Revis L.
Stephenson III, as Chairman, acknowledged the execution of the foregoing
instrument to be the voluntary act and deed of the limited liability company, by
it and by him voluntarily executed.


[NOTARY SEAL]                                /s/Marie DeVoe White
                                   ---------------------------------------------
                                   Notary Public in and for the State of MN


                                                                       391 - 6/6

                                        6