Document:

Exhibit 4.6

Exhibit 4.6

     THESE SECURITIES HAVE NOT BEEN REGISTERED WITH THE UNITED STATES SECURITIES
AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE. THE
SECURITIES MAY NOT BE RESOLD OR TRANSFERRED EXCEPT AS PERMITTED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), PURSUANT TO REGISTRATION OR AN
EXEMPTION THEREFROM.

No. ___1___                                                 US$1,000,000

                              EARTH SCIENCES, INC.
                              AMENDED AND RESTATED
                 10% CONVERTIBLE DEBENTURE DUE SEPTEMBER 8, 2003

     THIS DEBENTURE is one of a duly authorized issue of Debentures of Earth
Sciences, Inc., a corporation duly organized and existing under the laws of the
State of Colorado (the "Company"), designated as its 10% Convertible Debenture
Due September 8, 2003, in an aggregate principal amount not exceeding US$
1,000,000 (herein, the "Debentures"). This Debenture is issued as a replacement
of and contains modifications to the Company's previous debenture due on March
31, 2000 (as amended) in the principal amount of $1,000,000 issued to the Holder
(the "Prior Debenture"). The Holder's acceptance of this Debenture and
concurrent relinquishment and cancellation of the Prior Debenture is expressly
conditioned upon the Company's payment of all outstanding attorneys' fees,
accrued and unpaid interest, and other charges owing on the Prior Debenture as
of the date of this Debenture.

     FOR VALUE RECEIVED, the Company promises to pay to Tectonic Construction
Co., the registered holder hereof (the "Holder"), the principal sum of US$
1,000,000.00, on September 8, 2003 (the "Maturity Date") together with interest
on the principal sum outstanding from time to time at the annual rate equal to
the greater of (i) the prime rate as reported by Bank One, Denver, Colorado
("Prime Rate") plus two percent (2%), or (ii) ten percent (10%), adjusted
quarterly and computed on the basis of the actual number of days elapsed in a
365-day year. All accrued interest shall be payable in arrears, and shall be due
and payable at the end of each calendar quarter or, if earlier, on the
Conversion Date (as hereinafter defined). Accrual of interest shall commence on
the date hereof and shall continue until payment in full of the principal sum
has been made or duly provided for. All accrued and unpaid interest so payable,
together with any and all other amounts payable hereunder, less any amounts
required by law to be deducted or withheld, will be paid on the Maturity Date
or, if earlier, on the Conversion Date, and shall be paid to the person in whose
name this Debenture (or one or more predecessor Debentures) is registered on the
records of the Company regarding registration and transfers of the Debentures
(the "Debenture Register") on the Conversion Date or tenth day prior to the
Maturity Date, as the case may be; provided, however, that the Company's
obligation to a transferee of this Debenture arises only if such transferee
executes a subscription agreement and investment agreement as the Company may
reasonably require. The principal of, and interest on, this Debenture are
payable in such coin or currency of the United States of America as at the time
of payment is legal tender for payment of public and private debts, at the
address last appearing on the Debenture Register of the Company as designated in
writing by the Holder from time to time. The Company may prepay a portion or all
of the Debentures at any time. The Company shall provide the Holder with no less
than 30 days written notice of any prepayment. The forwarding of the Company's
check shall, subject to collection, constitute a payment of interest and
principal hereunder and shall satisfy and discharge the liability for principal
and interest on this Debenture to the extent of the sum represented by such
check. Any payments received by Holder will be applied in the following order:
(i) any collection and other costs, including, without limitation, attorneys'
fees, which the Holder may have incurred in procuring the Company's performance
hereunder, (ii) any charges assessed by the Holder, (iii) payment of the
interest then accrued and due on the unpaid interest and unpaid principal
balance of this Debenture, and (iv) principal.

     The Holder may, in its sole discretion, with at least ninety (90) days'
advance written notice to the Company, demand payment of principal, which
payment shall be applied in the same order described above. The combined total

<PAGE>

amount of quarterly principal which the Holder may demand pursuant to this
Debenture and pursuant to the $250,000 Promissory Note of even date herewith
issued by the Company to the Holder (the "Note") shall not exceed $100,000 in
any quarter. The first quarterly payment of principal shall not be due earlier
than January 1, 2001, provided that the Holder demands same in writing by no
later than October 1, 2000.

     This Debenture is subject to the following additional provisions:

     1. This Debenture is exchangeable for an equal aggregate principal amount
of Debentures of different authorized denominations, as requested by the Holders
surrendering the same. No service charge will be made for such registration or
transfer or exchange.

     2. This Debenture has been issued subject to investment representations of
the original purchaser hereof and may be transferred or exchanged only in
compliance with the Securities Act of 1933, as amended (the "Act") and the terms
of the Subscription Agreement. Prior to due presentment for transfer of this
Debenture, the Company and any agent of the Company may treat the person in
whose name this Debenture is duly registered on the Debenture Register as the
owner hereof for the purpose of receiving payment as herein provided and for all
other purposes, whether or not this Debenture be overdue, and neither the
Company nor any such agent shall be affected by notice to the contrary.

     3. The Holder of this Debenture shall be entitled, at any time during the
period commencing on and after September 8, 2000 and expiring on the Maturity
Date, to convert up to the entire outstanding principal amount on this
Debentures into shares of common stock, par value $.0l per share (the "Common
Stock"), of the Company at a conversion price for each share of the Common Stock
of the lesser of $.21 or the average trading price per share of Common Stock on
the Conversion Date. Nevertheless, the aggregate combined number of shares of
Common Stock into which this Debenture and the Note may be converted shall not
exceed 1,000,000. Such conversion shall be effectuated by surrendering the
Debenture to the Company with the form of conversion notice attached hereto as
Exhibit A, executed by the Holder evidencing its intent to convert the
Debenture. The amount of accrued but unpaid interest as of the Conversion Date
shall not be subject to conversion but shall be paid in cash as of the
Conversion Date. No fraction of shares of the Common Stock or scrip representing
fractions of shares will be issued on conversion, but the number of shares of
the Common Stock issuable shall be rounded to the nearest whole share. The date
on which notice of conversion is given shall be deemed to be the date on which
the Holder has delivered this Debenture, with the conversion notice duly
executed, to the Company, or if earlier, the date set forth in such notice of
conversion if the Debenture is received by the Company within three business
days thereafter. Such date is referred to herein as the "Conversion Date."
Facsimile delivery of the conversion notice shall be accepted by the Company.
Certificates representing Common Stock upon conversion will be delivered to the
Holder within five (5) business days from the date the notice of conversion is
delivered to the Company. The Common Stock issuable upon conversion will not
have been registered under the Securities Act of 1933, and will be issued in
reliance upon exemptions from the registration requirements of the Securities
Acts of 1933, and the transfer of such Common Stock will be subject to
restrictions imposed by applicable securities laws. A legend restricting the
transfer of the Commons Stock may be placed on any Certificate representing the
Common Stock. If the Holder converts less than then entire outstanding principal
amount of this Debenture, the Company shall execute and issue to the Holder a
substitute debenture for the remaining unpaid and unconverted principal amount,
and shall deliver same to the Holder together with the stock certificate(s).

     4. Any of the following shall constitute an "Event of Default":

          a. The Company defaults in the payment of principal or interest on
          this Debenture as and when the same is due and payable and such
          default continues for five (5) business days after the receipt of
          written notice that the Company is in default hereunder; or

          b. Any of the representations or warranties made by the Company
          herein, in the Subscription Agreement, or in any certificate or
          financial or other written statements heretofore or hereafter
          furnished by or on behalf of the Company in connection with the
          execution and delivery of this Debenture or the Subscription Agreement
          is false or misleading in any material respect at the time made; or

<PAGE>

          c. The Company fails to perform or observe, in any material respect,
          any other covenant, term, provision, condition, agreement or
          obligation of the Company under this Debenture, or under the
          Subscription Agreement, or under any related agreement, or under any
          document or instrument granting security for amounts owing under this
          Debenture including, without limitation, any of the following
          documents: Subscription Agreement and Investment Agreement of Earth
          Sciences, Inc.; Subordination Agreement among Tectonic Construction
          Co., Yankee Atomic Electric Company, Vermont Yankee Nuclear Power
          Corporation, and ESI Resources Limited dated June 12, 1997, Guarantee
          Agreement dated June 12, 1997 by Earth Sciences Extraction Company
          ("ES Extraction") in favor of Tectonic Construction Co.; and Guarantee
          Agreement dated June 12, 1997 by ESI Resources Limited, in favor of
          Tectonic Construction Co. (collectively referred to herein as the
          "Loan Documents"), and such failure continues uncured for a period of
          five (5) business days after the receipt of written notice that the
          Company is in default hereunder (it being understood that in the case
          of defaults which can not reasonably be cured within a 5-day period no
          grace period shall be necessary as a precondition to the failure to
          perform such covenant constituting an Event of Default); or

          d. The Company (1) makes an assignment for the benefit of creditors or
          commence proceedings for its dissolution; or (2) applies for or
          consents to the appointment of a trustee, liquidator or receiver for
          its or for a substantial part of its property or business; or

          e. A trustee, liquidator or receiver is appointed for the Company or
          for a substantial part of its property or business without its
          consent, and is not discharged within sixty (60) days after such
          appointment; or

          f. Bankruptcy, reorganization, insolvency or liquidation proceedings
          or other proceedings for relief under any bankruptcy law or any law
          for the relief of debtors is instituted by or against the Company and,
          if instituted against the Company, is not dismissed within sixty (60)
          days after such institution or the Company by any action or answer
          approves of, consents to, or acquiesces in any such proceeding or
          admits the material allegations of, or defaults in answering a
          petition filed in any such proceeding; or

          g. The Company fails to make any required material payments, fees,
          taxes, costs, insurance premiums when due beyond any applicable grace
          period; or

          h. The Company defaults on the payment of any material indebtedness,
          except for the Company's current indebtedness to the Bank of Hong
          Kong, for borrowed money beyond any applicable grace period; or

          i. Any judgment, levy or attachment is rendered against the Company or
          any of its assets or properties in an amount in excess of $50,000 and
          such judgment, levy or attachment is not dismissed, stayed, bonded or
          discharge within thirty (30) days of the date of entry thereof, or

          j. The control of the Company, ESI Resources Limited, ES Extraction,
          ADA-ES, Inc. or ADA -Environmental Solutions, LLC ("ADA ES"), is
          changed by reason of merger or acquisition of shares of either
          company, or sale of substantially all assets of either company; or

          k. The Company allows any of the following conditions without the
          prior written waiver of the Holder:

             i. the declaration of a dividend to holders of the Common Stock;
             ii. the declaration of a distribution to the Company by ADA ES or
             ADA-ES, Inc.;
             iii. capital expenditures in any calendar quarter exceeding
             $100,000; or
             iv. diminution by more than $100,000 of consolidated working
             capital at any calendar quarter end date, irrespective of this or
             any other convertible debenture, of less than the current
             consolidated working capital of the Company as of June 30, 2000,
             which was a deficit of $766,000.

<PAGE>

Upon the occurrence of any Event of Default or at any time thereafter, and in
each and every such case, unless such Event of Default has been waived in
writing by the Holder (which waiver shall not be deemed to be a waiver of any
subsequent Event of Default) at the option of the Holder and in the Holder's
sole discretion, then or at any time thereafter, the whole of said principal sum
then remaining unpaid hereunder, together with all interest accrued thereon, and
all other sums owing hereunder or under the Loan Documents, shall immediately
become due and payable upon the Company's receipt of the Holder's written notice
of acceleration ("Acceleration") and the liens given to secure the payment of
this Debenture may be foreclosed and the Holder may pursue all rights and
remedies available under this Debenture, or under the Loan Documents, or
otherwise available at law or in equity. If an Event of Default occurs due to
non-payment of this Debenture or the Note and the Holder does not deliver to the
Company a written notice of default and Acceleration, then the Maturity Date
shall automatically and without notice to the Holder be changed to the next
September 8 following the date of the Company's first missed payment hereunder.

     6. Following the occurrence of an Event of Default due to non-payment of
this Debenture or the Note, and so long as any such Event of Default remains
outstanding and uncured, if the Holder does not declare this Debenture in
default and provide the Company with a written notice of Acceleration, without
notice to the Company all unpaid principal and all other interest and charges
payable hereunder shall accrue interest at the annual rate equal to the greater
of (i) Prime Rate plus five percent (5%), or (ii) fifteen percent (15%).
Following the occurrence of an Event of Default, and for so long as any such
Event of Default shall remain outstanding and uncured, and upon the Holder's
written notice of such Event of Default and Acceleration, the Company promises
to pay interest on the outstanding principal balance of this Debenture, and on
any and all other amounts then outstanding, at an annual rate of interest equal
to the greater of (i) Prime Rate plus five percent (5%), or (ii) eighteen
percent (18%) per annum, provided that any interest which has accrued at the
default rate shall be paid at the time of, and as a condition precedent to the
curing of any default under any statutory right to cure. The fluctuating default
rates at which interest accrues shall be adjusted simultaneously, at each
announced change of the Prime Rate. Failure to exercise such option or charge of
such increased interest shall not be a waiver of the right to do so at any
future time or with respect to any other default.

     7. No provision of this Debenture shall alter or impair the obligation of
the Company which is absolute and unconditional, to pay the principal of, and
interest on, this Debenture at the time, place, and rate, and in the coin or
currency, herein prescribed. This Debenture and all other Debentures now or
hereafter issued of similar terms are direct obligations of the Company. The
Company shall pay all costs and expenses, including reasonable attorneys' fees,
which the Holder may incur in connection with any effort or action to collect
amounts due under this Debenture.

     8. No recourse shall be had for the payment of the principal of, or the
interest on, this Debenture, or for any claim based hereon, or otherwise in
respect hereof, against any incorporator, shareholder, officer or director, as
such, past, present or future, of the Company or any successor corporation,
whether by virtue of any constitution, statute or rule of law, or by the
enforcement of any assessment or penalty or otherwise, all such liability being,
by the acceptance hereof and as part of the consideration for the issue hereof,
expressly waived and released.

     9. The rights or remedies of the Holder as provided in this Debenture and
the Loan Documents shall be cumulative and concurrent and may be pursued singly,
successively, or together against the Company, the property described in the
Loan Documents, and any other funds, property or security held by the Holder for
the payment hereof or otherwise at the sole discretion of the Holder. The
failure to exercise any such right or remedy shall in no event be considered as
a waiver or release of such rights or remedies or the right to exercise them at
any later time.

     10. In the event the interest provisions hereof or any exactions provided
for herein, or in the Loan Documents or any other instrument securing this
Debenture shall result, because of any reduction of principal, or for any reason
at any time during the life of this loan, in any effective rate of interest
which, for any month, transcends the limit of the usury or any other law
applicable to the obligation evidenced hereby, all sums in excess of those
lawfully collectible as interest for the period in question shall, without
further agreement or notice between or by any party hereto, be applied upon
principal immediately upon receipt of such moneys by Holder, with the same force
and effect as though the payor had specifically designated such extra sums to be
so applied to principal and Holder had agreed to accept such extra payment as a

<PAGE>

premium-free prepayment. In no event shall any agreed to or actual exaction as
consideration for this obligation transcend the limits imposed or provided by
the laws applicable to this transaction or the Company hereof in the
jurisdiction in which any of the security herefor is located for the use or
detention of money or for forbearance in seeking its collection.

     11. The Company and all endorsers, guarantors and all persons liable or to
become liable on this Debenture waive presentment, protest and demand, notice of
protest, demand and dishonor and nonpayment of this Debenture, and consent to
any and all renewals and extensions in the time of payment hereof, and agree,
further, that at any time and from time to time without notice, the terms of
payment herein may be modified or the security described in the Loan Documents
released in whole or in part or increased, changed or exchanged by agreement
between the Holder hereof and any owner of the property affected by said Loan
Documents without in anywise affecting the liability of any party to this
instrument or any person liable or to become liable with respect to any
indebtedness evidenced hereby. The right to plead any and all statues of
limitation as a defense to any demand on this Debenture, or any guaranty hereof,
or any agreement to pay the same, or any demand secured by the Loan Documents,
or any and all obligations or liabilities arising out of or in connection with
this Debenture or in the Loan Documents, is expressly waived by each and every
of the Company, endorsers, or guarantors to the fullest extent permitted by law.

     12. Any forbearance of Holder in exercising any right or remedy hereunder
or under the Loan Documents, or otherwise, afforded by applicable law, shall not
be a waiver of or preclude the exercise of any right or remedy. The acceptance
by Holder of payment of any sum payable, hereunder after the due date of such
payment shall not be a waiver of Holder's right to either require prompt payment
when due of all other sums payable hereunder or to declare a default for failure
to make prompt payment. Holder shall at all times have the right to proceed
against any portion of the security held herefor in such order and in such
manner as Holder may deem fit, without waiving any rights with respect to any
other security. No delay or omission on the part of Holder in exercising any
right hereunder shall operate as a waiver of such right or of any other right
under this Debenture.

     13. This Debenture shall be governed by and construed in accordance with
the laws of the State of Colorado without regard to the choice of law provisions
thereof, and in the event this Debenture is placed in the hands of any attorney
for collection or is collected through any legal proceedings, the undersigned
promises to pay (in addition to costs and disbursements otherwise allowed), to
the extent permitted by law, reasonable attorneys' fee and legal costs (whether
or not suit is commenced and whether or not incurred in connection with appeal
of a lower court judgment or order or in collecting any judgment entered
therein),and if foreclosure is made by any public official, reasonable
attorneys' fees and legal costs shall be added by such public official to the
cost of foreclosure. The undersigned hereby represents that the proceeds of the
loan evidenced by this Debenture will be used for a commercial or business
purpose.

     14. Time is of the essence with regard to the performance of the
obligations of the Company in this Debenture and each and every term, covenant
and condition herein by or applicable to the Company.

     15. This Debenture is guaranteed by three separate guarantees executed by
ADA ES, ESI Resources Limited, and ES Extraction, each wholly owned subsidiaries
or affiliates of the Company and each of which guaranties are secured by
corresponding security agreements (the "Security Agreements").

     16. The Company hereby irrevocably waives, to the fullest extent permitted
by law, any and all right to trial by jury in any legal proceeding arising out
of or relating to this Debenture and the other Loan Documents or the
transactions contemplated thereby. In any action which may be brought under this
Debenture, Holder hereby irrevocably consents to the personal jurisdiction of
any State District Court or Federal Court located in the State of Colorado, and
further stipulates and agrees that venue shall be proper in the State of
Colorado for any such actions and further agrees not to seek a change of venue
to any court outside the State of Colorado without the consent of Holder.

     17. All notices required or permitted to be given pursuant to the terms
hereof shall be in writing and shall be delivered either by (a) certified mail,
return receipt requested, in which case notice shall be deemed received three
(3) business days after deposit, postage prepaid in the U.S. mail, (b) a
reputable messenger service or a nationally-recognized overnight courier, in

<PAGE>

which case notice shall be deemed received one (1) business day after deposit
with such messenger or courier, (c) facsimile or other telecopy transmission
(followed with "hard copy" sent by a nationally-recognized overnight courier or
mail as aforesaid), in which case notice shall be deemed received when the
facsimile or other telecopy transmission is received, provided such receipt
occurs before 5:00 p.m. recipient's local time on a business day, otherwise at
8:30 a.m. recipient's local time on the next business day or (d) personal
delivery with receipt acknowledged in writing, in which case notice shall be
deemed received upon delivery. Notices shall be deemed given or sent upon
deposit in the U.S. mail in the case of clause (a) above, or upon deposit with a
reputable messenger or courier in the case of clause (b) above. Notices shall be
deemed given or sent upon receipt of electronic confirmation in the case of
clause (c) above or upon receipt in the case of clause (d). All such notices
shall be addressed as follows:

                           To Maker:

                           Earth Sciences, Inc.
                           Attn:  Mark McKinnies
                           8100 Southpark Way #B-2
                           Littleton, CO  80120
                           Fax:  303-734-0330

                           To Holder:

                           Tectonic Construction Co.
                           100 Cherry
                           Denver, CO  80220
                           Fax:  303-394-9822

                           With a Copy To:

                           Gorsuch Kirgis LLP
                           Attn:  Stephen A. Weinstein, Esq.
                           Tower I, Suite 1000
                           1515 Arapahoe Street
                           Denver, CO  80202
                           Fax:  303-376-5001

     IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed by an officer thereunto duly authorized. EARTH SCIENCES, INC.

                                            By: /s/ Mark H. McKinnies
                                            -------------------------------
                                            Name: Mark H. McKinnies
                                            Title: President

<PAGE>

                                    EXHIBIT A

                              NOTICE OF CONVERSION

                    (To be Executed by the Registered Holder
                       in order to Convert the Debenture)

     The undersigned hereby irrevocably elects to convert the above Debenture
No. ______ into shares of Common Stock of EARTH SCIENCES, INC. (the "Company")
according to the conditions hereof, as of the date written below.

                                            ---------------------------------
                                            Date of Conversion

                                            ---------------------------------
                                            Applicable Conversion Price

                                            [SUBSCRIBER]

                                            ----------------------------------
                                            Signature

                                            Address:

                                            ----------------------------------

                                            ----------------------------------

* The original Debenture and Notice of Conversion must be received by the
Company by the third business day following the Date of Conversion.Exhibit 10.16

Exhibit 10.16

                      AMENDED AND RESTATED PROMISSORY NOTE

US $250,000                                       Date:  September 8, 2000

     FOR VALUE RECEIVED, the undersigned, Earth Sciences, Inc., a Colorado
corporation (the "Maker") promises to pay to the order of Tectonic Construction
Co. (the "Holder"), the principal sum of Two Hundred and Fifty Thousand Dollars
(US $250,000) together with interest on the principal sum outstanding from time
to time at the annual rate equal to the greater of (i) the prime rate as
reported by Bank One, Denver Colorado ("Prime Rate") plus two percent (2%), or
(ii) ten percent (10%), adjusted quarterly and computed on the basis of the
actual number of days elapsed in a 365-day year. Interest on the outstanding
principal balance of this Promissory Note shall accrue from September 8, 2000
and shall be payable quarterly beginning on September 30, 2000. If not sooner
paid, the entire unpaid principal balance and all accrued but unpaid interest
shall be due and payable in full on September 8, 2003 (the "Maturity Date").
This Promissory Note is issued as a replacement of and contains modifications to
the Maker's previous promissory note dated May 20, 1998 (as amended) in the
principal amount of $250,000 issued to the Holder (the "Prior Note"). The
Holder's acceptance of this Promissory Note and concurrent relinquishment and
cancellation of the Prior Note is expressly conditioned upon the Maker's payment
of all outstanding attorneys' fees, accrued and unpaid interest, and other
charges owing on the Prior Note as of the date of this Promissory Note.

     The principal of, and interest on, this Promissory Note are payable in such
coin or currency of the United States of America as at the time of payment is
legal tender for payment of public and private debts, at the address as
designated in writing by the Holder from time to time. The Maker may prepay a
portion or all of this Promissory Note at any time without penalty. The Maker
shall provide the Holder with no less than thirty (30) days' written notice of
any prepayment. The forwarding of the Maker's check shall, subject to
collection, constitute a payment of interest and principal hereunder and shall
satisfy and discharge the liability for principal and interest on this
Promissory Note to the extent of the sum represented by such check. Any payments
received by the Holder (including those payable as a result of the Holder's
demand for quarterly principal, as described below) will be applied in the
following order: (i) any collection and other costs, including, without
limitation, attorneys' fees, which the Holder may have incurred in procuring the
Maker's performance hereunder; (ii) any valid charges assessed by the Holder;
(iii) payment of the interest then accrued and due on the unpaid interest and
unpaid principal balance of this Promissory Note; and (iv) principal.

     The Holder may, in its sole discretion, with at least ninety (90) days'
advance written notice to the Maker, demand payment of principal, which payment
shall be applied in the same order described above. The combined total amount of
quarterly principal which the Holder may demand pursuant to this Promissory Note
and pursuant to the 10% Convertible Debenture of even date herewith issued by
the Maker to the Holder (the "Debenture") shall not exceed $100,000 in any
quarter. The first quarterly payment of principal shall not be due earlier than
January 1, 2001, provided that the Holder demands same in writing by no later
than October 1, 2000.

     The Holder shall be entitled, at any time during the period commencing on
and after September 8, 2000 and expiring on the Maturity Date, to convert up to
the entire outstanding principal amount on this Promissory Note into shares of
common stock, par value $.0l per share of the Maker (the "Common Stock") at a
conversion price for each share of the Common Stock of the lesser of $.21 or the
average trading price per share of Common Stock on the Conversion Date (as
defined below). Nevertheless, the aggregate combined number of shares of Common
Stock into which this Promissory Note and the Debenture may be converted shall

<PAGE>

not exceed 1,000,000. Such conversion shall be effectuated by surrendering the
Promissory Note to the Maker with the form of conversion notice attached hereto
as Exhibit A, executed by the Holder evidencing the intent to convert the
Promissory Note. The amount of accrued but unpaid interest as of the Conversion
Date shall not be subject to conversion but shall be paid in cash as of the
Conversion Date. No fraction of shares of the Common Stock or scrip representing
fractions of shares will be issued on conversion, but the number of shares of
the Common Stock issuable shall be rounded to the nearest whole share. The date
on which notice of conversion is given shall be deemed to be the date on which
the Holder has delivered this Promissory Note, with the conversion notice duly
executed, to the Maker, or if earlier, the date set forth in such notice of
conversion if the Promissory Note is received by the Maker within three business
days thereafter. Such date is referred to herein as the "Conversion Date."
Facsimile delivery of the conversion notice shall be accepted by the Maker.
Certificates representing Common Stock upon conversion will be delivered to the
Holder within ten (10) business days from the date the notice of conversion is
delivered to the Maker. The Common Stock issuable upon conversion will not have
been registered under the Securities Act of 1933, and will be issued in reliance
upon exemptions from the registration requirements of the Securities Acts of
1933, and the transfer of such Common Stock will be subject to restrictions
imposed by applicable securities laws. A legend restricting the transfer of the
Commons Stock may be placed on any Certificate representing the Common Stock. If
the Holder converts less than then entire outstanding principal amount of this
Promissory Note, the Maker shall execute and issue to the Holder a substitute
promissory note for the remaining unpaid and unconverted principal amount, and
shall deliver same to the Holder together with the stock certificate(s).

     This Promissory Note is subject to the following additional provisions:

     1.   Any of the following shall constitute an "Event of Default":

          a.        If the Maker fails to pay any principal or interest on this
                    Promissory Note or the Debenture as and when the same is due
                    and payable, and such nonpayment continues for five (5)
                    business days after the receipt of written notice that the
                    Maker is in default; or

          b.        If any of the representations or warranties made by the
                    Maker or its affiliates herein, in the Debenture, in the
                    Security Agreement dated September 8, 2000 between the Maker
                    and the Holder (the "Security Agreement"), or in any
                    certificate or financial or other written statements
                    heretofore or hereafter furnished by or on behalf of the
                    Maker in connection with the execution and delivery of this
                    Promissory Note or the Debenture, or in the security
                    agreement or the guaranty agreement, both of even date
                    herewith, by and between the Holder and ADA Environmental
                    Solutions, LLC, a Colorado limited liability company and
                    affiliate of the Maker ("ADA ES") is false or misleading in
                    any material respect (the Debenture and the ADA ES
                    agreements are sometimes collectively referred to
                    hereinafter as the "Collateral Agreements"); or

          c.        If the Maker and/or ADA ES fail to perform or observe, in
                    any material respect, any other covenant, term, provision,
                    condition, agreement or obligation of the Maker under this
                    Promissory Note, under the Debenture, or under the Security
                    Agreement, or under any of the Collateral Agreements, or
                    under any document or instrument granting security for
                    amounts owing under this Promissory Note including, without
                    limitation, either of the Security Agreements (defined
                    below), and such failure remains uncured for a period of
                    five (5) business days (or such other cure period stated in
                    the agreement under which a default has occurred) after the
                    receipt of written notice of such default (it being
                    understood that in the case of defaults which cannot

<PAGE>

                    reasonably be cured within a 5-day period, no grace period
                    shall be necessary as a precondition to the failure to
                    perform such covenant constituting an Event of Default); or

          d.        If the Maker (i) makes an assignment for the benefit of
                    creditors or commences proceedings for its dissolution; or
                    (ii) applies for or consents to the appointment of a
                    trustee, liquidator or receiver for its, or for a
                    substantial part of its, property or business; or

          e.        If a trustee, liquidator or receiver is appointed for the
                    Maker or for a substantial part of its property or business
                    without its consent, and is not discharged within sixty (60)
                    days after such appointment; or

          f.        If bankruptcy, reorganization, insolvency or liquidation
                    proceedings or other proceedings for relief under any
                    bankruptcy law or any law for the relief of debtors is
                    instituted by or against the Maker and, if instituted
                    against the Maker, is not dismissed within sixty (60) days
                    after such institution or the Maker by any action or answer
                    approves of, consents to, or acquiesces in any such
                    proceedings or admits the material allegations of, or
                    default in answering a petition filed in any such
                    proceedings; or

          g.        If the Maker fails to make any required material payments,
                    fees, taxes, costs, or insurance premiums when due beyond
                    any applicable grace period; or

          h.        If the Maker defaults on the payment of any other material
                    indebtedness, except for Maker's current indebtedness to the
                    Bank of Hong Kong, for borrowed money beyond any applicable
                    grace period; or

          i.        If any judgment, levy or attachment is rendered against the
                    Maker or any of its assets or properties in an amount in
                    excess of $50,000 and such judgment, levy or attachment is
                    not dismissed, stayed, bonded or discharge within thirty
                    (30) days of the date of entry thereof; or

          j.        If the control of the Maker, ADA-ES, Inc., ADA ES, or Earth
                    Sciences Extraction Company, an Alberta, Canada limited
                    partnership ("ES Extraction"), is changed by reason of
                    merger or acquisition of shares of either of such companies,
                    or if substantially all assets of either of such companies
                    is sold, destroyed, or otherwise transferred; or

          k.        If the Maker allows any of the following to occur without
                    the prior written waiver of the Holder:

                    i.    the declaration of a dividend to any  shareholder of
                          the Maker;

                    iii.  the declaration of a distribution to  Maker by ADA ES
                          or ADA-ES, Inc.;

                    iv.   capital expenditures in any calendar quarter exceeding
                          $100,000; or

                    v.    diminution by more than $100,000 of consolidated
                          working capital at any calendar quarter end date,
                          irrespective of this or any other promissory note or
                          debenture, to less than the current consolidated
                          working capital of Maker as of June 30, 2000, which
                          was a deficit of $766,000.

<PAGE>

Upon the occurrence of any Event of Default or at any time thereafter, and in
each and every such case, unless such Event of Default is waived in writing by
the Holder (which waiver shall not be deemed to be a waiver of any subsequent
Event of Default) at the option of the Holder and in the Holder's sole
discretion, then or at any time thereafter, the whole of said principal sum then
remaining unpaid hereunder, together with all interest accrued thereon, and all
other sums owing hereunder or under the Security Agreements, shall immediately
become due and payable by the Holder's written notice to the Maker
("Acceleration") and the liens given to secure the payment of this Promissory
Note may be foreclosed and the Holder may pursue all rights and remedies
available under this Promissory Note, or under the Security Agreements, or
otherwise available at law or in equity. If an Event of Default due to
non-payment of this Promissory Note or of the Debenture occurs and the Holder
does not deliver to the Maker a written notice of default and Acceleration, then
the Maturity Date shall automatically and without notice to the Holder be
changed to the next September 8 following the date of the Maker's first missed
payment hereunder.

     2.   Following the occurrence of an Event of Default due to non-payment of
          this Promissory Note or of the Debenture, and for so long as any such
          Event of Default shall remain outstanding and uncured, if the Holder
          does not declare this Promissory Note in default and provide the Maker
          with a written notice of Acceleration, without notice to the Maker all
          unpaid principal and all other interest and charges payable hereunder
          shall accrue interest at the annual rate equal to the greater of (i)
          Prime Rate plus five percent (5%) or (ii) fifteen percent (15%).
          Following the occurrence of an Event of Default, and for so long as
          any such Event of Default shall remain outstanding and uncured, and
          upon the Holder's written notice of such Event of Default and
          Acceleration to the Maker, the Maker promises to pay interest on the
          outstanding principal balance of this Promissory Note, and on any and
          all other amounts then outstanding, at an annual rate of interest
          equal to the greater of (i) Prime Rate plus five percent (5%) or (ii)
          eighteen percent (18%) . In either case above, any interest which has
          accrued at the applicable default rate shall be paid at the time of
          and as a condition precedent to the curing of any default under any
          statutory right to cure. The fluctuating default rates at which
          interest accrues shall be adjusted simultaneously, at each announced
          change of the Prime Rate. Failure to exercise such option or charge
          such increased interest shall not be a waiver of the right to do so at
          any future time or with respect to any other default.

     3.   No provision of this Promissory Note shall alter or impair the
          obligation of the Maker, which is absolute and unconditional, to pay
          the principal of, and interest on, this Promissory Note at the time,
          place, and rate, and in the coin or currency herein prescribed. This
          Promissory Note and all other promissory notes now or hereafter issued
          of similar terms are direct obligations of the Maker. The Maker shall
          pay all costs and expenses, including reasonable attorneys' fees,
          which the Holder may incur in connection with any effort or action to
          collect amounts due under this Promissory Note.

     4.   No recourse shall be had for the payment of the principal of, or the
          interest on, this Promissory Note, or for any claim based hereon, or
          otherwise in respect hereof, against any incorporator, shareholder,
          officer or director, as such, past, present or future, of the Maker or
          any successor corporation, whether by virtue of any constitution,
          statute or rule of law, or by the enforcement of any assessment or
          penalty or otherwise, all such liability being, by the acceptance
          hereof and as part of the consideration for the issue hereof,
          expressly waived and released.

     5.   The rights or remedies of the Holder as provided in this Promissory
          Note, the Security Agreements, and the Collateral Agreements shall be
          cumulative and concurrent and may be pursued singly, successively, or
          together against the Maker, the property described in the Security

<PAGE>

          Agreements and the Collateral Agreements, and any other funds,
          property or security held by the Holder for the payment hereof or
          otherwise at the sole discretion of the Holder. The failure to
          exercise any such right or remedy shall in no event be construed as a
          waiver or release of such rights or remedies or the right to exercise
          them at any later time.

     6.   In the event the interest provisions hereof or any exaction provided
          for herein, in the Security Agreements, in the Collateral Agreements,
          or in any other instrument securing this Promissory Note shall result,
          because of any reduction of principal, or for any other reason at any
          time during the life of this loan, in any effective rate of interest
          which, for any month, transcends the limit of the usury or any other
          law applicable to the obligation evidenced hereby, all sums in excess
          of those lawfully collectible as interest for the period in question
          shall, without further agreement or notice between or by any party
          hereto, be applied to principal immediately upon receipt of such
          moneys by the Holder, with the same force and effect as though the
          payor had specifically designated such extra sums to be so applied to
          principal and the Holder had agreed to accept such extra payment as a
          premium-free prepayment. In no event shall any agreed to or actual
          exaction as consideration for this obligation transcend the limits
          imposed or provided by the laws applicable to this transaction or the
          Maker hereof in the jurisdiction in which any of the security herefor
          is located for the use or detention of money or for forbearance in
          seeking its collection.

     7.   The Maker and all endorsers, guarantors and all persons liable or to
          become liable on this Promissory Note waive presentment, protest and
          demand, notice of protest, demand and dishonor and nonpayment of this
          Promissory Note, and consent to any and all renewals and extensions in
          the time of payment hereof, and agree, further, that at any time and
          from time to time without notice, the terms of payment herein may be
          modified or the security described in the Security Agreements released
          in whole or in part or increased, changed or exchanged by agreement
          between the Holder hereof and any owner of the property affected by
          said Security Agreements without in any way affecting the liability of
          any party to this instrument or any person liable or to become liable
          with respect to any indebtedness evidenced hereby. The right to plead
          any and all statutes of limitation as a defense to any demand on this
          Promissory Note, or any guaranty hereof, or any agreement to pay the
          same, or any demand secured by the Security Agreements, or any and all
          obligations or liabilities arising out of or in connection with this
          Promissory Note or in the Security Agreements, is expressly waived by
          each and every of the Maker, endorsers, or guarantors to the fullest
          extent permitted by law.

     8.   Any forbearance of the Holder in exercising any right or remedy
          hereunder or under the Security Agreements, or otherwise afforded by
          applicable law, shall not be a waiver of or preclude the exercise of
          any right or remedy. The acceptance by the Holder of payment of any
          sum payable hereunder after the due date of such payment shall not be
          a waiver of the Holder's right to either require prompt payment when
          due of all other sums payable hereunder or to declare a default for
          failure to make prompt payment. The Holder shall at all times have the
          right to proceed against any portion of the security held herefor in
          such order and in such manner as the Holder may deem fit, without
          waiving any rights with respect to any other security. No delay or
          omission on the part of the Holder in exercising any right hereunder
          shall operate as a waiver of such right or of any other right under
          this Promissory Note.

     9.   This Promissory Note shall be governed by and construed in accordance
          with the laws of the State of Colorado without regard to the choice of
          law provisions thereof, and in the event this Promissory Note is

<PAGE>

          placed in the hands of any attorney for collection or is collected
          through any legal proceedings, the undersigned promises to pay (in
          addition to costs and disbursements otherwise allowed), to the extent
          permitted by law, reasonable attorneys' fees and legal costs (whether
          or not suit is commenced and whether or not incurred in connection
          with appeal of a lower court judgment or order or in collecting any
          judgment entered therein), and if foreclosure is made by the Public
          Trustee or any other public official, reasonable attorneys' fees and
          legal costs shall be added by the Public Trustee or such public
          official to the cost of foreclosure. The undersigned hereby represents
          that the proceeds of the loan evidenced by this Promissory Note will
          be used for a commercial or business purpose.

     10.  Time is of the essence with regard to the performance of the
          obligations of the Maker in this Promissory Note and each and every
          term, covenant and condition herein by or applicable to the Maker.

     11.  This Promissory Note is secured by (i) that certain security agreement
          dated May 20, 1998 between ES Extraction and the Holder, which pledges
          the accounts receivable of ES Extraction (ii) the Security Agreement,
          and (iii) the security agreement by and between the Holder and ADA ES
          (collectively referred to herein as the "Security Agreements").

     12.  The Maker hereby irrevocably waives, to the fullest extent permitted
          by law, any and all right to trial by jury in any legal proceeding
          arising out of or relating to this Promissory Note and the other
          Security Agreements or the transactions contemplated thereby. In any
          action which may be brought under this Promissory Note, the Holder
          hereby irrevocably consents to the personal jurisdiction of any State
          District Court or Federal Court located in the State of Colorado, and
          further stipulates and agrees that venue shall be proper in the State
          of Colorado for any such actions (save and except for the Calgary
          Security Agreement for which venue shall be proper in the province of
          Alberta in the City of Calgary), and further agrees not to seek a
          change of venue to any court outside the State of Colorado without the
          consent of the Holder.

     13.  All notices required or permitted to be given pursuant to the terms
          hereof shall be in writing and shall be delivered either by (a)
          certified mail, return receipt requested, in which case notice shall
          be deemed received three (3) business days after deposit, postage
          prepaid in the U.S. mail, (b) a reputable messenger service or a
          nationally-recognized overnight courier, in which case notice shall be
          deemed received one (1) business day after deposit with such messenger
          or courier, (c) facsimile or other telecopy transmission (followed
          with "hard copy" sent by a nationally-recognized overnight courier or
          mail as aforesaid), in which case notice shall be deemed received when
          the facsimile or other telecopy transmission is received, provided
          such receipt occurs before 5:00 p.m. recipient's local time on a
          business day, otherwise at 8:30 a.m. recipient's local time on the
          next business day or (d) personal delivery with receipt acknowledged
          in writing, in which case notice shall be deemed received upon
          delivery. Notices shall be deemed given or sent upon deposit in the
          U.S. mail in the case of clause (a) above, or upon deposit with a
          reputable messenger or courier in the case of clause (b) above.
          Notices shall be deemed given or sent upon receipt of electronic
          confirmation in the case of clause (c) above or upon receipt in the
          case of clause (d). All such notices shall be addressed as follows:

<PAGE>

                           To Maker:

                           Earth Sciences, Inc.
                           Attn:  Mark McKinnies
                           8100 Southpark Way #B-2
                           Littleton, CO  80120
                           Fax:  303-734-0330

                           To Holder:

                           Tectonic Construction Co.
                           100 Cherry
                           Denver, CO  80220
                           Fax:  303-394-9822

                           With a Copy To:

                           Gorsuch Kirgis LLP
                           Attn:  Stephen A. Weinstein, Esq.
                           Tower I, Suite 1000
                           1515 Arapahoe Street
                           Denver, CO  80202
                           Fax:  303-376-5001

     IN WITNESS WHEREOF, the Maker has caused this instrument to be duly
executed by an officer thereunto duly authorized.

                                            "MAKER"

                                            EARTH SCIENCES, INC.

                                            By: /s/ Mark H. McKinnies
                                            --------------------------------
                                            Name: Mark H. McKinnies
                                            Title: President
                                            Date: September 8, 2000
                                            --------------------------------

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