Exhibit 3



                      RESTATED CERTIFICATE OF INCORPORATION

                                       OF

                           THERMO PROCESS SYSTEMS INC.


        Thermo Process Systems Inc., a corporation organized and existing
        under the laws of the State of Delaware, hereby certifies as
        follows:  The date of filing of its original Certificate of
        Incorporation with the Secretary of the State of Delaware was May
        30, 1986.  This Restated Certificate of Incorporation restates
        and integrates all amendments to the Restated Certificate of
        Incorporation of this corporation, filed with the Secretary of
        State of Delaware on June 23, 1986, and has been duly adopted by
        the written consent of the sole stockholder of this corporation
        in accordance with Sections 228, 242 and 245 of the General
        Corporation Law of the State of Delaware.

        FIRST.    The name of the corporation is Thermo Process Systems
                  Inc.

        SECOND.   The address of its registered office in the State of
                  Delaware if No. 1209 Orange Street, in the City of
                  Wilmington 19805, County of New Castle.  The name of
                  its registered agent at such address is Corporation
                  Trust Company.

        THIRD.    The purpose of the corporation is to engage in any
                  lawful act or activity for which corporations may be
                  organized under the General Corporation Law of the
                  State of Delaware.

        FOURTH.   The total number of shares of stock which the
                  corporation shall have the authority to issue is Ten
                  Million (10,000,000), and the par value of each of such
                  shares is Ten Cents ($0.10), amounting in the aggregate
                  to One Million and No/100 Dollars ($1,000,000).

        FIFTH.    The Board of Directors shall have the power to adopt,
                  amend or repeal the By-Laws.

        SIXTH.    No director shall be personally liable to the
                  corporation or its stockholders for monetary damages
                  for any breach of fiduciary duty by such director as a
                  director.  Notwithstanding the foregoing sentence, a
                  director shall be liable to the extent provided by
                  applicable law (i) for breach of the director's duty of
                  loyalty to the corporation or its stockholders, (ii)
                  for acts or omissions not in good faith or which
PAGE






                  involve intentional misconduct or a knowing violation
                  of law, (iii) pursuant to Section 174 of the Delaware
                  General Corporation Law or (iv) for any transaction
                  from which the director derived an improper personal
                  benefit.  No amendment to or repeal of this Article
                  SIXTH shall apply to or have any effect on the
                  liability or alleged liability of any director of the
                  corporation for or with respect to any acts or
                  omissions of such director occurring prior to such
                  amendment.

        IN WITNESS WHEREOF, this Restated Certificate of Incorporation
        has been executed on behalf of the undersigned corporation by its
        duly authorized officer and attested to by its duly authorized
        Secretary this 23rd day of July, 1986.

                                           THERMO PROCESS SYSTEMS INC.



                                           By: /s/ Peter G. Pantazelos
                                               --------------------------
                                               Peter G. Pantazelos
                                               Vice President and Chief
                                               Financial Officer

        ATTEST:



        By:  /s/ Paul F. Ferrari
           -----------------------------
              Paul F. Ferrari
              Secretary
PAGE









                            CERTIFICATE OF AMENDMENT 

                                       OF

                      RESTATED CERTIFICATE OF INCORPORATION

                                       OF 

                           THERMO PROCESS SYSTEMS INC.



             Thermo Process Systems Inc. (the "Corporation"), a

        corporation organized and existing under the laws of the State of

        Delaware, hereby certifies as follows, pursuant to Section 242 of

        the General Corporation Law of the State of Delaware:



             1.   That Article FOURTH of the Restated Certificate of

        Incorporation of the Corporation, as restated on July 24, 1986,

        is hereby amended to increase the number of authorized shares of

        the Corporation's Common Stock, $0.10 par value per share, from

        10,000,000 shares to 20,000,000 shares and that such amendment is

        hereby effected by deleting said Article in its entirety and

        inserting the following in substitution therefor:

             "FOURTH:  The total number of shares of stock which the
        Corporation shall have authority to issue is Twenty Million
        (20,000,000) and the par value of each share is Ten Cents
        ($0.10)."


             2.   That the Board of Directors of the Corporation at a

        meeting held on May 26, 1988, duly adopted the following

        resolution:

        RESOLVED:      That the Board of Directors recommend to the
                       Stockholders the approval of an amendment to the
                       Corporation's Restated Certificate of
PAGE






                       Incorporation to increase the Corporation's
                       authorized voting Common Stock, $.10 par value
                       from 10,000,000 to 20,000,000 shares.


             3.   That the amendment to the Corporation's Restated

        Certificate of Incorporation was duly adopted by affirmative vote

        of Stockholders of the Corporation holding in excess of 50% of

        the shares of Common Stock, $0.10 par value per share, of the

        Corporation in accordance with the provisions of Section 242 of

        the General Corporation Law of the State of Delaware.



             IN WITNESS WHEREOF, Thermo Process Systems Inc. has caused

        this Certificate of Amendment to be signed by Walter J.

        Bornhorst, its Chairman of the Board of Directors, Chief

        Executive Officer and President, and attested by Paul F. Ferrari,

        its Secretary, this 26th day of September, 1988.

                                           THERMO PROCESS SYSTEMS INC.



                                      By:  /s/ Walter J. Bornhorst
                                           -----------------------
                                           Walter J. Bornhorst,
                                           Chairman of the Board,
                                           Chief Executive Officer
                                           and President

        ATTEST:



        By:  /s/ Paul F. Ferrari
             -------------------
             Paul F. Ferrari,
             Secretary
PAGE






                            CERTIFICATE OF AMENDMENT
                                       OF
                      RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                           THERMO PROCESS SYSTEMS INC.




             Thermo Process Systems Inc. (the "Corporation"), a

        corporation organized and existing under the laws of the State of

        Delaware, hereby certifies as follows, pursuant to Section 242 of

        the General Corporation Law of the State of Delaware:

             1.   That Article FIRST of the Restated Certificate of

                  Incorporation of the Corporation, as restated on July

                  24, 1986 and amended on September 29, 1988 and on

                  October 19, 1989, is hereby amended to change the name

                  of the Corporation to Thermo TerraTech Inc. and that

                  such amendment is hereby effected by deleting said

                  Article in its entirety and inserting the following in

                  substitution therefor:

                       "Article FIRST:     The name of the Corporation
       
                  is: Thermo TerraTech Inc."

             2.   That the Board of Directors of the Corporation at a

                  meeting held on December 13, 1995 duly adopted the

                  following resolution:

                  RESOLVED: That the Directors recommend that the

                            Shareholders of the Corporation approve an

                            amendment to the Corporation's Certificate of

                            Incorporation changing the name of the

                            Corporation to Thermo TerraTech Inc.
PAGE







             3.   That the amendment to the Corporation's Restated

                  Certificate of Incorporation was duly adopted by the

                  affirmative vote of Stockholders of the Corporation

                  holding in excess of 50% of the shares of Common Stock,

                  $.10 par value per share, of the Corporation in

                  accordance with the provisions of Section 242 of the

                  General Corporation Law of the State of Delaware.

             IN WITNESS WHEREOF, Thermo Process Systems Inc. has caused

        this Certificate of Amendment to be signed by John P. Appleton  

        its President and Chief Executive Officer and attested to by

        Sandra L. Lambert, its Secretary, this 13th day of December,

        1995.



                                           Thermo Process Systems Inc.



                                           By:   /s/John P. Appleton
                                                 -------------------
                                                 John P. Appleton
                                                 President and Chief
                                                 Executive Officer


        Attest:



        By: /s/ Sandra L. Lambert
            ---------------------
            Sandra L. Lambert, Secretary