EXHIBIT 2.2

                       This Note and the indebtedness evidenced hereby
                  are subordinate in the manner and extent set forth in
                  that certain Subordination Agreement dated as of
                  October 10, 1997 among Thermo TerraTech Inc., Comerica
                  Bank and Holcroft L.L.C. to the indebtedness owed by
                  Holcroft L.L.C. to Comerica Bank, and each holder of
                  this Note, by its acceptance hereof, shall be bound by
                  the provisions of the Subordination Agreement.


                             SECURED PROMISSORY NOTE



        $2,218,000.00                                    October 10, 1997


             This Secured Promissory Note (hereinafter "this Note") is
        made as of the date stated hereinabove by HOLCROFT L.L.C., a
        Delaware limited liability company ("Borrower"), with a mailing
        address at 12068 Market Street, Livonia, Michigan 48150, to the
        order of THERMO TERRATECH INC., a Delaware corporation
        ("Lender"), with an office at 81 Wyman Street, Waltham,
        Massachusetts 02254-9046.


                                        I

                                     PAYMENT

             For Value Received, Borrower hereby irrevocably and
        unconditionally promises to pay to the order of Lender, at
        Lender's office at the address stated hereinabove or such other
        place as Lender may from time to time designate in writing to
        Borrower, the principal amount of TWO MILLION TWO HUNDRED
        EIGHTEEN THOUSAND DOLLARS AND NO/100THS ($2,218,000.00) (the
        "Loan") or so much thereof as may now or hereafter be disbursed
        by Lender to or for the benefit of Borrower, together with
        interest as provided hereinbelow, all in lawful money of the
        United States of America, as follows:

             1.1  Interest in Installments.  Interest only on the unpaid
        principal balance of the Loan from time to time, shall accrue at
        an annual interest rate (the "Interest Rate") equal to nine and
        one-quarter percent (9.25%), from and including the date hereof
        until October 10, 2002 (the "Maturity Date").  Interest shall be
        due and payable quarterly in arrears commencing on January 1,
        1998.  Interest hereunder shall be calculated on the basis of the
        actual number of days elapsed during the period for which
        interest is being charged hereunder, predicated on a year
        consisting of three hundred and sixty-five (365) days.
PAGE

             1.2  Payments.  The principal balance of the Loan shall be
        payable in 4 consecutive annual installments of $443,600 on each
        annual anniversary of the date hereof commencing with the year
        beginning October 10, 1998.  The remaining principal balance, as
        well as all accrued and unpaid interest, shall be due and payable
        on the Maturity Date.

             1.3  Method of Payment.  On the date a payment is due under
        Paragraphs 1.1 or 1.2 above, Borrower shall pay the amount of
        such payment to Lender in immediately available funds at the
        address of Lender specified above. 

             1.4  Application of Payments Prior to Default.  All monies
        paid by Borrower to Lender shall be applied in the following
        order of priority:  (a) first, toward payment of interest which
        has accrued on the outstanding principal balance of the Loan and
        which is due and payable; and (b) last, toward payment of the
        outstanding principal balance of the Loan.

             1.5  Prepayments.  This Note may be prepaid, in whole or in
        part, at any time, without premium or penalty.  Any payment made
        under this paragraph shall be applied as set forth in Paragraph
        1.4.

             1.6  Certain Waivers.  The Borrower hereby waives
        presentment, demand, notice of prepayment, protest and all other
        demands and notices in connection with the delivery, acceptance,
        performance, default or enforcement of this Note.  The Borrower
        hereby assents to any extension of time for payment of any
        indebtedness evidenced hereby granted or permitted by the Lender.
        The Borrower hereby waives the right to a jury trial and waives
        the right to exercise any counterclaim or setoff of any kind
        whatsoever.


                                       II

                        SECURITY, DEFAULTS, AND REMEDIES

             2.1  Security for Payment.  Payment of this Note is secured
        by a Security Agreement dated of even date herewith between
        Borrower and Lender (the "Security Agreement") (this Note, the
        Security Agreement and all other documents and instruments
        executed in connection with the Note or the Security Agreement
        hereinafter are referred to as the "Loan Documents").

             2.2  Events of Default.  Any event of default shall exist
        upon the occurrence of any of the following events (an "Event of
        Default"):

                  (a)  The failure of the Borrower to pay any sum due and
             payable hereunder, including without limitation, interest or

                                        2PAGE

             principal or both and either as an installment or on the
             Maturity Date;

                  (b)  The failure of the Borrower to observe or perform
             any of its agreements, obligations, warranties or
             representations in that certain Asset Purchase Agreement of
             even date herewith between the Borrower and the Lender (the
             "Purchase Agreement") or in any agreement with the Lender or
             with any other person or organization for borrowed money,
             including all obligations to Comerica Bank;

                  (c)  Any warranty, representation, or statement made or
             furnished to the Lender by or on behalf of the Borrower in
             the Purchase Agreement proves to have been false in any
             material respect when made;

                  (d)  The liquidation, termination of existence,
             dissolution, insolvency or business failure of the Borrower,
             or the appointment of a receiver or custodian for the
             Borrower or any part of its property if such appointment is
             not terminated or dismissed within 30 days;

                  (e)  The sale by the Borrower of all or substantially
             all of its assets;

                  (f)  The merger or consolidation of the Borrower with
             or into any other corporation in a transaction in which the
             Borrower is not the surviving entity;

                  (g)  The institution against the Borrower of any
             proceedings under the United States Bankruptcy Code or any
             other federal or state bankruptcy, reorganization,
             receivership, insolvency or other similar law affecting the
             rights of creditors, generally, which proceeding is not
             dismissed within 30 days after filing of such proceeding;

                  (h)  The institution by the Borrower of any proceedings
             under the United States Bankruptcy Code or any other federal
             or state bankruptcy, reorganization, receivership,
             insolvency or other similar law affecting the rights of
             creditors generally or the making by the Borrower of a
             composition or an assignment or trust mortgage for the
             benefit of creditors; or

                  (i)  The suspension of the transaction of the usual
             business of the Borrower.

             2.3  Acceleration of Maturity.  At any time during the
        existence of any Event of Default (other than Events of Default
        under Paragraphs 2.2(b) or (c) above), and at the option of
        Lender, the entire unpaid principal balance under this Note,
        together with interest accrued thereon and all other sums due

                                        3PAGE

        from Borrower hereunder or under any of the other Loan Documents,
        shall become immediately due and payable without notice or
        demand.  If an Event of Default occurs under Paragraphs 2.2(b) or
        (c) above, Lender shall provide Borrower notice of such Event of
        Default and Borrower shall have ten (10) days after receipt of
        such notice to cure such Event of Default.  If such Event of
        Default is not cured, the entire unpaid principal balance under
        this Note, together with interest accrued thereon and all other
        sums due from Borrower hereunder or under any of the other Loan
        Documents shall become immediately due and payable.  After the
        occurrence and during the continuance of an Event of Default
        which has not been cured, the principal balance together with
        accrued and unpaid interest of this Note shall bear interest at
        the Interest Rate plus two and one half percent (2.50%).  After
        the occurrence and during the continuance of an Event of Default,
        Borrower shall be liable for all costs of collection, including
        reasonable attorneys' fees.

             2.4  Nature of Remedies.  Lender's remedies under this Note
        and all of the other Loan Documents shall be cumulative and
        concurrent and may be pursued singly, successively, or together
        against Borrower and any other "Obligors" (as that term is
        hereinafter defined), the Collateral (as defined in the Security
        Agreement), and any other security described in the Loan
        Documents or any portion or combination of such security, and
        Lender may resort to every other right or remedy available at law
        or in equity without first exhausting the rights and remedies
        contained herein, all in Lender's sole discretion.  Failure of
        Lender, for any period of time or on more than one occasion, to
        exercise its option to accelerate the Maturity Date shall not
        constitute a waiver of the right to exercise the same at any time
        during the continued existence of the Event of Default or in the
        event of any subsequent Event of Default.  Lender shall not by
        any other omission or act be deemed to waive any of its rights or
        remedies hereunder unless such waiver is in writing and signed by
        Lender, and then only to the extent specifically set forth
        therein.  A waiver in connection with one event shall not be
        construed as continuing or as a bar to or as a waiver of any
        right or remedy in connection with a subsequent event.


                                       III

                                  OTHER MATTERS

             3.1  Notices.  Any notices, consents or other communications
        required to be sent or given hereunder shall in every case be in
        writing and shall be deemed properly served if (a) delivered
        personally, (b) sent by registered or certified mail, in all such
        cases with first class postage prepaid, return receipt requested,
        (c) delivered by a recognized overnight courier service or (d)
        sent by facsimile transmission to Borrower at (313) 591-6443, or

                                        4PAGE

        to Lender at (781) 622-1283.  The date of service of such notice
        shall be (a) the date such notice is personally delivered, (b)
        three days after the day of mailing if sent by certified or
        registered mail, (c) one day after date of delivery to the
        overnight courier if sent by overnight courier or (d) when
        receipt of such transmission is acknowledged, if sent by
        facsimile transmission.  All such notices and other
        communications to a party shall be addressed to such party at the
        address set forth on the initial page hereof or to such other
        address as such party may designate for itself in a notice to the
        other party given in accordance with this section.

             3.2  Governing Law.  THIS NOTE AND THE TRANSACTIONS
        EVIDENCED HEREBY SHALL BE GOVERNED BY AND CONSTRUED UNDER THE
        INTERNAL LAWS OF THE STATE OF MICHIGAN, WITHOUT REGARD TO
        PRINCIPLES OF CONFLICTS OF LAWS, AS THE SAME MAY FROM TIME TO
        TIME BE IN EFFECT, INCLUDING, WITHOUT LIMITATION, THE UNIFORM
        COMMERCIAL CODE AS IN EFFECT IN SUCH STATE.

             3.3  Interpretation.  The headings of sections and
        paragraphs in this Note are for convenience only and shall not be
        construed to limit or define the content, scope, or intent of the
        provisions hereof.  As used in this Note, the singular shall
        include the plural, and masculine, feminine, and neuter pronouns
        shall be fully interchangeable, where the context so requires.
        If any provision of this Note, or any paragraph, sentence,
        clause, phrase, or word, or the application thereof, in any
        circumstances, is adjudicated to be invalid, the validity of the
        remainder of this Note shall be construed as if such invalid part
        were never included herein.  Time is of the essence of this Note.

             3.4  Subsequent Holders.  Upon any endorsement, assignment,
        or other transfer of this Note by Lender or by operation of law,
        the term "Lender," as used herein, shall mean the endorsee,
        assignee, or other transferee or successor to Lender then
        becoming the holder of this Note.

             3.5  Subsequent Obligors.  This Note and all provisions
        hereof shall be binding on all persons claiming under or through
        Borrower.  The terms "Borrower" and "Obligors," as used herein,
        shall include the respective successors, assigns, legal and
        personal representatives, executors, administrators, devisees,
        legatees, and heirs of Borrower and any other Obligors.

                            [signature page follows]

                                        5PAGE

             In Witness Whereof, Borrower has caused this Note to be
        executed as of the date first written hereinabove.



                                      HOLCROFT L.L.C.

                                      By:  Holcroft Technologies L.P.,
                                           Sole Member of Holcroft L.L.C.

                                      By:  Holcroft Management, Inc.,
                                           General Partner of Holcroft
                                           Technologies L.P.

                                      By:   /s/ Scott M. Murray         
                                      Name: Scott M. Murray
                                      Title:President