GUARANTY

      THIS GUARANTY is given as of the 17th day of March, 1997, by
GUARANTORS, as hereafter defined, in favor of THOMAS W. MARMON, as Trustee of
the THOMAS W. MARMON TRUST, with a mailing address of Thomas W. Marmon,
Trustee of the Thomas W. Marmon Trust, c/o Ceres Corporation, 4390 Airwest
Drive SE, Grand Rapids, Michigan 49512 ("Marmon"), pursuant to a loan made by
Marmon to ETS INTERNATIONAL, INC., a Virginia corporation ("Borrower"). 
Guarantors are wholly-owned direct or indirect a subsidiaries of Borrower.

      1.    Guarantors.  As used in this Guaranty, "Guarantors" means,
collectively, the undersigned corporations, and every reference to
"Guarantors" in this Guaranty shall mean each such corporation individually. 
Each of the undersigned corporations is jointly and severally liable for the
payment of the Indebtedness (as defined below) under this Guaranty.

      2.    Guaranty.  In consideration of any credit heretofore or hereafter
extended by Marmon to Borrower, Guarantors hereby absolutely,
unconditionally, and irrevocably guarantee prompt payment when due, and at
all times thereafter, of (i) any and all existing and future indebtedness,
obligations, and liabilities of Borrower to Marmon under a certain note of
even date herewith executed by Borrower in favor of Marmon, and (ii) any and
all renewals, extensions, replacements and modifications of that note and all
interest, late charges and reasonable expenses accrued thereon (collectively
the "Indebtedness").  The Indebtedness also includes any and all indebtedness
and obligations now or hereafter owing to Marmon by Borrower, regardless of
whether any such indebtedness or obligation is (i) not presently intended or
contemplated by Borrower, Marmon or Guarantors; (ii) indirect, contingent or
secondary; or (iii) unrelated to, or of a different kind of class from, any
indebtedness or obligations of Borrower to Marmon that are now owing or are
committed or contemplated.

      3.    Unlimited Liability.  Except as provided by Paragraph 12, each
Guarantor's liability for the payment of the Indebtedness under this Guaranty
is unlimited.

      4.    Expenses.  Guarantors shall reimburse Marmon for all costs,
reasonable attorney fees, and other expenses at any time expended or incurred
by Marmon in the collection or attempted collection of the Indebtedness or in
the enforcement of this Guaranty or the realization upon any security now or
hereafter granted for this Guaranty.

      5.    Unconditional.  The effectiveness of this Guaranty is not subject
to the satisfaction of any conditions, including, without limitation, the
signing of this or another guaranty, or the granting of any other security,
by any person, firm or corporation.  Marmon may grant or continue credit from
time to time to Borrower without notice to or authorization from Guarantors,
regardless of Borrower's financial or other condition at the time of any such
grant or continuation.  Marmon shall have no obligation to disclose or
discuss with Guarantors his assessment of Borrower's financial condition. 
The execution of this Guaranty by Guarantors, however, shall create no
obligation or duty of Marmon to grant or continue credit to Borrower.
<PAGE>
      6.    Application of Payments.  Marmon in its sole discretion may,
without affecting, impairing, or reducing Guarantors' obligations under this
Guaranty, (i) apply payments or collections received from any source to the
payment of indebtedness other than the Indebtedness, even though Marmon could
have applied those payments to the Indebtedness; and (ii) apply payments or
collections received from Guarantors or from any present or future security
for this Guaranty to any liability of Guarantors under this Guaranty or to
any liability of Guarantors for payment to Marmon of any other indebtedness. 
Any payments or collections that Marmon applies to the liability of
Guarantors under this Guaranty shall be applied to costs or expenses
described in Paragraph 4 above and to the components of the Indebtedness, all
in such manner as Marmon in its sole discretion shall determine.

      7.    Rights Against Debtor.  Guarantors will not exercise or enforce,
and hereby waive, any right of contribution, reimbursement, recourse, or
subrogation available to Guarantors against Borrower or any other person
liable for payment of all or part of the Indebtedness, or as to any security
therefor, unless and until all of the Indebtedness is paid in full and
discharged.

      8.    Warranties and Representations.  Each Guarantor warrants and
represents to Marmon that (i) all financial statements and other information
concerning such Guarantor furnished to Marmon are true and correct in all
material respects; (ii) the execution, delivery, and performance of this
Guaranty by such Guarantor has been validly authorized by all necessary
corporate action of its board of directors and/or shareholders and will not
violate its articles of incorporation or bylaws or any law, rule, judgment,
order, agreement, or instrument binding it, nor require the approval of any
public authority or other third party; and (iii) this Guaranty constitutes
the valid and binding obligation of such Guarantor and is enforceable in
accordance with its terms.

      9.    Waivers.  Guarantors waive (i) notice of the acceptance of this
Guaranty and of the extension or continuation of all or any part of the
Indebtedness; (ii) presentment, protest, notice, demand, or action with
respect to any default in payment of all or any part of the Indebtedness and
with respect to any default by any Guarantor in its obligations under this
Guaranty; and (iii) any right to require Marmon to sue Borrower, any other
Guarantor or any other person obligated with respect to all or any part of
the Indebtedness or to foreclose or realize upon any security for all or any
part of the Indebtedness.  Guarantors waive any and all defenses, claims, and
discharges of Borrower or any other obligor with respect to the Indebtedness,
except the defense of discharge by payment.  Without limiting the generality
of the foregoing, Guarantors will not assert, plead, or enforce against
Marmon any defense of waiver, release, discharge in bankruptcy, statute of
limitations, res judicata, statute of frauds, anti-deficiency statute, fraud, 
incapacity minority, usury, ultra vires, lack of authorization, illegality,
or unenforceability that may be available to Borrower or any other person
liable in respect of any Indebtedness or any setoff available against Marmon
to Borrower or any such other person, whether or not on account of a related
transaction.  Guarantors shall be liable for any deficiency remaining after
foreclosure of or realization upon any security for all or part of the
Indebtedness, whether or not the liability of Borrower or any other obligor
for the deficiency is discharged pursuant to statute or judicial decision.
<PAGE>
      10.   Termination or Revocation.  This Guaranty shall continue in
effect until receipt by Marmon of written notice of its termination or
revocation and, notwithstanding that receipt, thereafter as to Indebtedness
incurred, arising, or committed for prior to receipt by Marmon of notice of
termination or revocation.  A notice of revocation or termination must be in
writing, shall not be effective until received by Marmon and shall be
effective only as to the Guarantor giving the notice, and this Guaranty shall
remain in effect as to the other Guarantors not giving the notice.

      11.   No Impairment of Guaranty.  The validity and enforceability of
this Guaranty shall not be impaired or affected by any of the following
(whether occurring before or after receipt by Marmon of notice of termination
of this Guaranty) with respect to all or part of the Indebtedness or any
agreement relating thereto or with respect to any present or future guaranty
or other security for all or part of the Indebtedness: (i) any extension,
modification, renewal, indulgence or substitution; (ii) any failure or
omission to enforce any right, power, or remedy; (iii) any waiver of any
right, power, or remedy or of any default; (iv) any release, surrender,
compromise, settlement, subordination, or modification, with or without
consideration; (v) the unenforceability or invalidity of the Indebtedness or
of any present or future guaranty for all or part of the Indebtedness; (vi)
any failure by Marmon to perfect or secure any priority of its rights with
respect to any security; or (vii) any consent by Marmon to any sale or
transfer of any security; all whether or not the undersigned shall have had
notice or knowledge of any act, omission, or circumstance referred to in this
Paragraph.

      12.   Enforceability.  If any one or more provisions of this Guaranty
should be invalid, illegal or unenforceable in any respect, the validity,
legality and enforceability of the remaining provisions contained herein
shall not in any way be affected, impaired, prejudiced or disturbed thereby. 
If at any time any portion of the obligations of any Guarantor under this
Guaranty shall be determined by a court of competent jurisdiction to be
invalid, unenforceable or avoidable, the remaining portion of the obligations
of that Guarantor under this Guaranty shall not in any way be affected,
impaired, prejudiced or disturbed thereby and shall remain valid and
enforceable to the fullest extent permitted by applicable law.  If at any
time all or any portion of the obligations of any Guarantor under this
Guaranty would otherwise be determined by a court of competent jurisdiction
to be invalid, unenforceable or avoidable under Section 548 of the U.S.
Bankruptcy Code or under a similar applicable law of any jurisdiction
(including without limitation laws relating to fraudulent conveyances or
fraudulent transfers), then notwithstanding any other provisions of this
Guaranty to the contrary that obligation or portion thereof of that Guarantor
under this Guaranty shall not exceed (a) the maximum amount which could be
incurred hereunder by that Guarantor without rendering this Guaranty void or
unenforceable under applicable law relating to fraudulent conveyance,
fraudulent transfer or the like after taking into account the probability of
that Guarantor making any payment pursuant to this Guaranty, the amount of
such probable payment, and all consideration and value directly or indirectly
received by that Guarantor from Marmon or the Borrower as a result of Marmon
making loans and other financial accommodations to the Borrower now or
hereafter, less (b) one dollar.  If any Guarantor claims that its liability
hereunder is subject to the foregoing limitation, then that Guarantor agrees
that it has the burden of proof as to all matters pertaining to that
limitation in light of the fact that it has possession of all the financial
information needed to determine the amount of such limitation.
<PAGE>
      13.   Independence of Obligations.  The liability of Guarantors
hereunder is independent of any other guaranties or obligations at any time
in effect with respect to all or any part of the Indebtedness and may be
enforced regardless of the existence, validity, enforcement, or
nonenforcement of any such other guaranties or other obligations.  Marmon is
authorized to release or modify the obligations of or surrender any security
given by or waive any rights against Borrower or any Guarantor, without in
any manner affecting or impairing the liability of the other Guarantors.

      14.   Return of Payments.  If any payment applied by Marmon to the
Indebtedness is set aside, recovered, rescinded, or required to be returned
for any reason (including, without limitation, the bankruptcy, insolvency, or
reorganization of Borrower, any Guarantor, or any other person liable in
respect of any Indebtedness), the Indebtedness to which the payment was
applied shall for the purposes of this Guaranty be deemed to have continued
in existence, notwithstanding the application, and this Guaranty shall be
enforceable as to such Indebtedness as fully as if Marmon had not made the
application.

      15.   Applicable Law, Venue, Jurisdiction.  This Guaranty and the
rights and obligations of the parties shall be governed by and interpreted in
accordance with the laws of the Commonwealth of Virginia, without giving
effect to principles of conflicts of laws.  Guarantors irrevocably agree and
consent that any action against Guarantors for collection or enforcement of
this Guaranty may be brought in any state or federal court that is located in
or whose jurisdiction includes Kent County, Michigan, and that any such court
shall have jurisdiction over Guarantors for that action.

      16.   Complete Agreement.  This Guaranty contains the entire agreement
between Guarantors and Marmon with respect to the subject matter hereof. 
There are no promises, terms, conditions, or obligations other than those
contained herein.  This Guaranty may not be modified except by writing signed
by the party to be charged. 

       17.  Notices.  Any notices or communications required or permitted
under this Guaranty shall be in writing and shall be deemed given when served
either personally or by certified United States mail (postage prepaid), or by
overnight express courier, addressed to Guarantors at their respective
addresses set forth below, and to Marmon at its address set forth on the
first page of this Guaranty, or to such other place as a party shall
designate by notice served upon the other parties in accordance with this
Paragraph.

      18.   Binding Effect.  This Guaranty shall be binding upon and shall
inure to the benefit of Marmon and Guarantors and their respective successors
and assigns.  Marmon may assign this Guaranty in connection with an
assignment of all or any portion of the Indebtedness.

      19.   Security.  Guarantors acknowledge that their obligations under
this Guaranty are secured by those security agreements of even date herewith
between each Guarantor and Marmon.

      20.   Corporate Benefit.  Each Guarantor is a wholly-owned direct or
indirect subsidiary of Borrower and will therefore derive substantial direct
and indirect benefits from the extensions of credit by Marmon to Borrower. 
Accordingly, this Guaranty is necessary and convenient to the conduct,
promotion and attainment of the business of Borrower and is in furtherance of
the corporate purposes of each Guarantor.
<PAGE>
      IN WITNESS WHEREOF, Guarantors have executed and delivered this
Guaranty as of the date first above written.

WITNESSES:                                GUARANTORS:

                                          ETS WATER AND WASTE MANAGEMENT,
                                          INC. (d/b/a Stamie E. Lyttle
s/R. Neal Keesee, Jr.                     Company)
----------------------- 

s/Jennifer A. Perdue                      By s/John D. McKenna
-----------------------                      ----------------------------
                                             Its  CEO
                                                  -----------------------

                                          Address:
                                          2210 Belt Blvd. at Hopkins Road
                                          Richmond, Virginia  23224

                                          ETS ANALYTICAL SERVICES, INC.
s/R. Neal Keesee, Jr.               
----------------------- 

s/Jennifer A. Perdue                      By s/John D. McKenna
-----------------------                      ----------------------------
                                             Its  CEO
                                                  -----------------------

                                          Address:
                                          1401 Municipal Road, NW
                                          Roanoke, Virginia 24012
<PAGE>

WITNESSES:                                ETS, INC.

s/R. Neal Keesee, Jr.               
----------------------- 

s/Jennifer A. Perdue                      By s/John D. McKenna
-----------------------                      ----------------------------
                                             Its  CEO
                                                  -----------------------

                                          Address:
                                          1401 Municipal Road, NW
                                          Roanoke, Virginia  24012


WITNESSES:                                ETS LINER, INC.
                                          (d/b/a/ Pipeliner Installers)

s/R. Neal Keesee, Jr.               
----------------------- 

s/Jennifer A. Perdue                      By s/John D. McKenna
-----------------------                      ----------------------------
                                             Its  CEO
                                                  -----------------------

                                          Address:
                                          2551 N.W. 15th Court
                                          Pompano Beach, Florida  33069
<PAGE>