Document:

AMENDMENT NO. 9 TO INDEMNIFICATION AGREEMENT

            THIS AMENDMENT NO. 9 to the Indemnification Agreement is made as of
the 11th day of July, 2003 (as supplemented or modified from time to time, this
"Agreement") by and among AJG Financial Services, Inc., by its Vice President,
General Counsel, as agent (the "Major Shareholder Agent") for Bernard J. Zahren,
Finova Mezzanine Capital Corp., AJG Financial Services, Inc., ("AJG")
Environmental Opportunities Fund (for itself and as successor to) Environmental
Opportunities Fund Cayman, Fredric Rose, M&R Associates, Martin F. Laughlin,
Richard J. Augustine and Michael J. Carolan (each, an "Initial Major
Shareholder"), Stephen Rosenberg, US Energy Biogas Corp. (formerly known as
Zahren Alternative Power Corporation), a Delaware corporation ("ZAPCO "), U.S.
Energy Systems, Inc., a Delaware corporation ("USE"), and Cinergy Energy
Solutions, Inc., a Delaware corporation ("CES"). Unless indicated otherwise,
capitalized terms shall have the same meanings herein as they have in the
Indemnification Agreement (as defined below).

                              W I T N E S S E T H:

            WHEREAS, the parties hereto, the Initial Major Shareholders and USE
Acquisition Corp, which was merged into ZAPCO, have previously entered into that
certain Indemnification Agreement dated as of November 28, 2000 (as amended by
Amendment No. 1 dated as of May 11, 2001, Amendment No. 2 dated as of November
1, 2002, Amendment No. 3 dated as of February 10, 2003, Amendment No. 4 dated as
of March 13, 2003, Amendment No. 5 dated as of April 15, 2003, Amendment No. 6
dated as of May 14, 2003, and Amendment No. 7 dated as of June 11, 2003 and
Amendment No. 8 dated as of June 27, 2003, the "Indemnification Agreement");

            WHEREAS, the parties hereto now wish to amend the Indemnification
Agreement:

            NOW, THEREFORE, in consideration of $10.00 and other consideration,
the receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

            1.    Section 4(a)(i) of the Indemnification Agreement is hereby
                  amended by deleting the existing section in its entirety and
                  inserting in its place the following section:

                  i. unless a Notice of Claim (as defined herein) has been
            delivered to the Major Shareholders, on or prior to July 31, 2003
            provided that notwithstanding anything to the contrary in this
            Section 4(a)(i) Notices of Claim arising from or relating to
            breaches of Section 3.10, 3.17 and 3.20 of the Merger Agreement may
            be delivered prior to the sixth anniversary of the Closing Date;

            2.    Clause (i) in Section 4(a) of the Indemnification Agreement
                  following "The ZAPCO Indemnitees shall not be entitled to
                  recover under Section 3(b):" is hereby amended by deleting the
                  existing clause in its entirety and inserting

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<PAGE>

                  in its place the following clause:

                  i. unless a Notice of Claim (as defined herein) has been
            delivered to the Beneficiaries, on or prior to July 31, 2003 except
            that Notices of Claim arising from or relating to the breaches of
            Sections 4.09, 4.15 and 4.18 of the Merger Agreement may be
            delivered prior to the sixth anniversary of the Closing Date;

            3.    Except as amended hereby, the Indemnification Agreement is
                  hereby ratified and confirmed and, as so amended, remains in
                  full force and effect on the date hereof.

            IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be Executed as of the date first written above.

                                        US ENERGY BIOGAS CORP:

                                        By: ____________________________________
                                            Name:
                                            Title:

                                        MAJOR SHAREHOLDER AGENT:
                                        AJG FINANCIAL SERVICES, INC.

                                        By: ____________________________________
                                            Name:
                                            Title:

                                        CINERGY ENERGY SOLUTIONS, INC.:

                                        By: ____________________________________
                                            Name:
                                            Title:

                                        U.S. ENERGY SYSTEMS, INC.:

                                        By: ____________________________________
                                            Name:
                                            Title:

                                       2AMENDMENT NO. 10 TO INDEMNIFICATION AGREEMENT

            THIS AMENDMENT NO. 10 to the Indemnification Agreement is made as of
the 28th day of July, 2003 (as supplemented or modified from time to time, this
"Agreement") by and among AJG Financial Services, Inc., by its Vice President,
General Counsel, as agent (the "Major Shareholder Agent") for Bernard J. Zahren,
Finova Mezzanine Capital Corp., AJG Financial Services, Inc., ("AJG")
Environmental Opportunities Fund (for itself and as successor to) Environmental
Opportunities Fund Cayman, Fredric Rose, M&R Associates, Martin F. Laughlin,
Richard J. Augustine and Michael J. Carolan (each, an "Initial Major
Shareholder"), Stephen Rosenberg, US Energy Biogas Corp. (formerly known as
Zahren Alternative Power Corporation), a Delaware corporation ("ZAPCO "), U.S.
Energy Systems, Inc., a Delaware corporation ("USE"), and Cinergy Energy
Solutions, Inc., a Delaware corporation ("CES"). Unless indicated otherwise,
capitalized terms shall have the same meanings herein as they have in the
Indemnification Agreement (as defined below).

                              W I T N E S S E T H:

            WHEREAS, the parties hereto, the Initial Major Shareholders and USE
Acquisition Corp, which was merged into ZAPCO, have previously entered into that
certain Indemnification Agreement dated as of November 28, 2000 (as amended by
Amendment No. 1 dated as of May 11, 2001, Amendment No. 2 dated as of November
1, 2002, Amendment No. 3 dated as of February 10, 2003, Amendment No. 4 dated as
of March 13, 2003, Amendment No. 5 dated as of April 15, 2003, Amendment No. 6
dated as of May 14, 2003, and Amendment No. 7 dated as of June 11, 2003,
Amendment No. 8 dated as of June 27, 2003 and Amendment No. 9 dated July 11,
2003, the "Indemnification Agreement");

            WHEREAS, the parties hereto now wish to amend the Indemnification
Agreement:

            NOW, THEREFORE, in consideration of $10.00 and other consideration,
the receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

            1.    Section 4(a)(i) of the Indemnification Agreement is hereby
                  amended by deleting the existing section in its entirety and
                  inserting in its place the following section:

                  i. unless a Notice of Claim (as defined herein) has been
            delivered to the Major Shareholders, on or prior to August 15, 2003
            provided that notwithstanding anything to the contrary in this
            Section 4(a)(i) Notices of Claim arising from or relating to
            breaches of Section 3.10, 3.17 and 3.20 of the Merger Agreement may
            be delivered prior to the sixth anniversary of the Closing Date;

            2.    Clause (i) in Section 4(a) of the Indemnification Agreement
                  following "The ZAPCO Indemnitees shall not be entitled to
                  recover under Section 3(b):" is hereby amended by deleting the
                  existing clause in its entirety and inserting in

                                       1
<PAGE>

                  its place the following clause:

                  i. unless a Notice of Claim (as defined herein) has been
            delivered to the Beneficiaries, on or prior to August 15, 2003
            except that Notices of Claim arising from or relating to the
            breaches of Sections 4.09, 4.15 and 4.18 of the Merger Agreement may
            be delivered prior to the sixth anniversary of the Closing Date;

            3.    Except as amended hereby, the Indemnification Agreement is
                  hereby ratified and confirmed and, as so amended, remains in
                  full force and effect on the date hereof.

            IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be Executed as of the date first written above.

                                        US ENERGY BIOGAS CORP:

                                        By: ____________________________________
                                            Name:
                                            Title:

                                        MAJOR SHAREHOLDER AGENT:
                                        AJG FINANCIAL SERVICES, INC.

                                        By: ____________________________________
                                            Name:
                                            Title:

                                        CINERGY ENERGY SOLUTIONS, INC.:

                                        By: ____________________________________
                                            Name:
                                            Title:

                                        U.S. ENERGY SYSTEMS, INC.:

                                        By: ____________________________________
                                            Name:
                                            Title:

                                       2Robocom Systems International Inc.                                  Exhibit 10.7

                              AMENDED AND RESTATED
                                 PROMISSORY NOTE

US$ 58,020                                        Massapequa, New York
                                                  May 30, 2003
                                                  Originally dated May 30, 2002

      FOR VALUE RECEIVED, the undersigned maker, ROBOCOM SYSTEMS INTERNATIONAL
INC., a New York corporation (the "Borrower"), hereby unconditionally promises
to pay to order of Irwin Balaban, an individual residing at 17 Fairbanks Blvd.,
Woodbury, NY 11797 (the "Lender"), the outstanding principal amount of
Fifty-eight Thousand Twenty Dollars ($58,020), in same day funds in a single
installment on June 30, 2005 (the "Maturity Date").

      Interest shall accrue on the unpaid principal amount of this Note from the
date of this Note until such principal amount is paid in full at the per annum
rate equal to 3.0%. Interest shall be calculated on the basis of a 360-day year
for the actual number of days elapsed and shall be paid on the Maturity Date.

      Whenever any payment on this Note shall be stated to be due on a day which
is not a business day, such payment shall be made on the next succeeding
business day and such extension of time shall be included in the computation of
the payment of interest on this Note.

      Each payment received by the Lender shall be applied first, against all
costs and expenses of the Lender incurred in connection with this Note, second,
against accrued and unpaid interest on the outstanding principal balance of this
Note, and third, the balance of each such payment shall be applied against the
principal hereof.

      If at any time (i) there occurs a default in the payment by the Borrower
of principal or interest pursuant to this Note, (ii) the Borrower is dissolved,
becomes insolvent under any law, suspends its present business, or agrees to a
merger, bulk sale or transfer of all or substantially all of its assets, (iii)
the Borrower commences or has commenced against it any bankruptcy or insolvency
proceeding or has a trustee or receiver appointed for it or its assets, or (iv)
there occurs a default in the performance of any other obligation of the
Borrower under this Note, (collectively, a "Default"), the Lender shall give
written notice thereof to the Borrower; provided, however, that, upon the
occurrence of an event specified in clauses (i), (ii) or (iii) above, no notice
shall be required. Immediately upon the occurrence of an event specified in
clauses (i), (ii) or (iii) above, or immediately upon the Lender giving the
Borrower notice regarding the occurrence of an event specified in clause (iv)
above, the Lender shall be entitled to retain any and all payments previously
made pursuant to this Note and all amounts owing pursuant to this Note shall
immediately become due and payable.

<PAGE>

      All rights and remedies of the Lender under applicable law and this Note
are cumulative and not exclusive. No single, partial or delayed exercise by the
Lender of any right or remedy shall preclude full and timely exercise by the
Lender at any time of any right or remedy of the Lender without notice. No
waiver shall be effective unless made specifically in writing by the Lender.

      The Borrower promises to pay all costs and expenses, including all
reasonable attorneys' fees and disbursements, incurred in the preparation,
administration, collection and enforcement of this Note. The Borrower hereby
waives diligence, presentment, protest, demand and notice of every kind and, to
the fullest extent permitted by law, the right to plead any statute of
limitations as a defense to any demand hereunder. The non-exercise by the Lender
of any of its rights under this Note in any particular instance shall not
constitute a waiver hereof in that or any subsequent instance.

      This Note may not be changed or terminated orally. This Note shall bind
the successors and assigns of the undersigned and shall enure to the benefit of
the Lender and his heirs, legal representatives, successors and assigns.

      Each provision of this Note shall survive until all amounts due are paid
to Lender's satisfaction and are not subject to any preference period, shall be
interpreted as consistent with existing law and shall be deemed amended to the
extent necessary to comply with any conflicting law. If a court deems any
provision invalid, the remainder of this Note shall remain in effect. Singular
number includes plural and neuter gender includes masculine and feminine as
appropriate.

      This Note shall be governed by, and construed an interpreted in accordance
with, the laws of the State of New York, without regard to its conflicts of law
provisions.

      IN WITNESS WHEREOF, the Borrower has caused this Note to be executed and
delivered as of the day and year and at the place first above written.

                                 ROBOCOM SYSTEMS INTERNATIONAL INC.

                                 By: /s/ Irwin Balaban
                                     ------------------------------------------
                                     Name:  Irwin Balaban
                                     Title: President & Chief Executive Officer

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