**Exhibit 10.21**

FIFTH AMENDED AND RESTATEDIRREVOCABLE STANDBY LETTER OF CREDIT

Letter of Credit No. 1158

Dateof Issuance:    February 16, 2007
| Issuer: |   | Home Federal Bank                 |
|---------|--------|-----------------------------------|
|    |   | 225 South Main Avenue             |
|    |   | Sioux Falls, SD 57104             |
|    |   |                              |
| To:     |   | Northwestern Services Corporation |
|    |   | 125 S. Dakota Avenue, Suite 1100  |
|    |   | Sioux Falls, SD 57104-6403        |

 

This Fifth Amended and Restated Irrevocable Standby Letter of Creditamends, restates and replaces that certain Fourth Amended and RestatedIrrevocable Standby  Letter of Creditdated February 16, 2006 by Home Federal Bank (Letter of Credit No. 1158).

1.             Home Federal Bank (the “Bank”) herebyestablishes in favor of NorthWestern Services Corporation (“NSC,” successor bymerger to NorthWestern Energy Corporation) an Irrevocable Standby Letter ofCredit (the “Letter of Credit”) at the request and for the account of GreatPlains Ethanol, LLC, a South Dakota limited liability company (“Great Plains”),whereby the Bank, subject to the terms and conditions contained herein,authorizes NSC to draw on it at any time or times before the Expiration Date(as defined below), by its draft (the “Draft”), in the form of Appendix 1hereto, an amount up to an aggregate amount of $780,000.00, as set forth on anaccompanying certificate (the “Draw Certificate”), in the form of Appendix 2hereto.

2.             This Letter of Credit shall expire at theclose of business on March 1, 2008 (the “Expiration Date”), unless extended.

3.             This Letter of Credit is issued in conjunctionwith a Natural Gas Distribution Delivery Agreement between NorthWestern EnergyCorporation and Great Plains dated September 2, 2002 (the “Agreement”), underwhich Great Plains agreed to transport a minimum quantity of natural gas to itsplant at a fixed price for delivery through a pipeline constructed to serve theplant and the obligations of Great Plains

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under the Agreement. The terms and conditions of the Agreement areincorporated herein by reference.

4.             Funds under this Letter of Credit are availableto NSC in accordance with and against its Draft and Draw Certificate, eachdated the date of presentation and executed by an officer of NSC, referring tothe number of this Letter of Credit and presented along with the originalLetter of Credit at our office at 225 South Main Avenue, Sioux Falls, SouthDakota 57104 during normal banking hours on or prior to the Expiration Date orany extension thereof. NSC warrants and represents to the Bank that it hasassigned or will assign its rights to the proceeds of this Letter of Credit toTetra Financial Group. Within 48 hours following presentation of the Draft,Draw Certificate and original Letter of Credit, the funds drawn shall bepayable jointly by the Bank to NSC and Tetra Financial Group.

5.             This Letter of Credit sets forth in full theterms of our undertaking, and such undertaking shall not in any way be modifiedor amended, without the consent of the Bank, except as to the completion of theDraft and Draw Certificates referred to herein.
|                                                                                                  | HOME  FEDERAL BANK |
|-------------------------------------------------------------------------------------------------------|--------------------|
|                                                                                                  |               |
|                                                                                                  |               |
|                                                                                                  | By                 | /s/ David Brown |
|                                                                                                  | Its                | Senior Vice President |
|                                                                                                  |
|                                                                                                  |
| AGREED AND ACCEPTED                                                                                   |
| this               day of February, 2007. |
|                                                                                                  |
| NORTHWESTERN SERVICES CORPORATION                                                                     |
|                                                                                                  |
|                                                                                                  |
| By                                                                                                    | /s/ Paul Evans     |   |
| Its                                                                                                   | Treasurer          |   |
|                                                                                                       |                    |  |  |  |

 

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Appendix 1

**DRAFT**

Date:
| To:    |   | Home Federal Bank     |
|--------|--------|-----------------------|
|   |   | 225 South Main Avenue |
|   |   | Sioux Falls, SD 57104 |

 

Within 48 hours of presentation of this Draft, a signed and completedDraw Certificate and the original Letter of Credit, PAY JOINTLY TO THE ORDER OFNorthWestern Services Corporation (successor by merger to NorthWestern EnergyCorporation) and Tetra Financial Group the sum of $                under that certain Natural Gas Distribution Delivery Agreement betweenNorthWestern Energy Corporation and Great Plains Ethanol, LLC dated September2, 2002.

Drawn under Fifth Amended and Restated Irrevocable Standby Letter ofCredit No. 1158 dated February 16, 2007.
|   | NORTHWESTERN SERVICES |
|--------|-----------------------|
|   | CORPORATION           |
|   |                  |
|   |                  |
|   | By                    |   |
|   | Its                   |   |

 

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Appendix 2

**DRAW CERTIFICATE**

Letter of Credit No. 1158

Date:
| To:    |   | Home Federal Bank     |
|--------|--------|-----------------------|
|   |   | 225 South Main Avenue |
|   |   | Sioux Falls, SD 57104 |

 

The undersigned, a duly authorized officer of NorthWestern ServicesCorporation (“NSC,” successor by merger to NorthWestern Energy Corporation),certifies to Home Federal Bank that:

1.             NSC is making a draw under the Fifth Amendedand Restated Irrevocable Standby Letter of Credit No. 1158 dated February 16,2007 with respect to (check the applicable box):

o            afailure by Great Plains to meet the Minimum Annual Obligation for 20    established under the Natural Gas Distribution Delivery Agreement betweenNorthWestern Energy Corporation and Great Plains dated September 2, 2002 (the“Agreement”),

o            afailure by Great Plains to meet the Minimum Total Obligation established underthe Agreement, or

o            thetermination of the Agreement by Great Plains for any reason other than forNSC’s refusal to perform its obligations under the Agreement.

2.             The amount of the Draft accompanying thisCertificate is $                   ,such sum being (check the applicable box):

o            theremaining Minimum Annual Obligation for 20     , or

o            Ithe entire outstanding balance of Great Plains’ Minimum Total Obligation

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in accordance with the termsof the Agreement.

3.             The amount of the Draft accompanying thisCertificate was computed in accordance with the terms and conditions of theAgreement and does not exceed, when combined with any prior amount drawn byNSC, the amount available to be so drawn.
|   | NORTHWESTERN SERVICES |
|--------|-----------------------|
|   | CORPORATION           |
|   |                  |
|   |                  |
|   | By                    |   |
|   | Its                   |   |

 

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