<PAGE>

                                                                      EXHIBIT 31

                                  CERTIFICATION


I, Dennis C. Zensen, Chairman of the Board, President and Chief Executive
Officer, certify that:

    1.  I have reviewed this annual report on Form 10-K of Sylvan Inc.;

    2.  Based on my knowledge, this report does not contain any untrue statement
        of a material fact or omit to state a material fact necessary to make
        the statements made, in light of the circumstances under which such
        statements were made, not misleading with respect to the period covered
        by this report;

    3.  Based on my knowledge, the financial statements, and other financial
        information included in this annual report, fairly present in all
        material respects the financial condition, results of operations and
        cash flows of the registrant as of, and for, the periods presented in
        this report;

    4.  The registrant's other certifying officer and I are responsible for
        establishing and maintaining disclosure controls and procedures (as
        defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal
        control over financial reporting (as defined in Exchange Act Rules
        13a-15(f) and 15d-15(f)) for the registrant and have:

        a)  Designed such disclosure controls and procedures, or caused such
            disclosure controls and procedures to be designed under our
            supervision, to ensure that material information relating to the
            registrant, including its consolidated subsidiaries, is made known
            to us by others within those entities, particularly during the
            period in which this annual report is being prepared;

        b)  Evaluated the effectiveness of the registrant's disclosure controls
            and procedures and presented in this annual report our conclusions
            about the effectiveness of the disclosure controls and procedures as
            of the end of the period covered by this annual report, based on
            such evaluations; and

        c)  Disclosed in this annual report any change in the registrant's
            internal control over financial reporting that occurred during the
            registrant's most recent fiscal quarter (the registrant's fourth
            fiscal quarter in the case of an annual report) that has materially
            affected, or is reasonably likely to materially affect, the
            registrant's internal control over financial reporting; and

    5.  The registrant's other certifying officer and I have disclosed, based on
        our most recent evaluation of internal control over financial reporting,
        to the registrant's auditors and the audit committee of the registrant's
        board of directors:

        a)  All significant deficiencies and material weaknesses in the design
            or operation of internal control over financial reporting which are
            reasonably likely to adversely affect the registrant's ability to
            record, process, summarize and report financial information; and

        b)  Any fraud, whether or not material, that involves management or
            other employees who have a significant role in the registrant's
            internal control over financial reporting.



March 26, 2004                              /s/ DENNIS C. ZENSEN
                                            -------------------------------
                                                Chairman of the Board, President
                                                and Chief Executive Officer
                                                (Principal Executive Officer)




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<PAGE>

                                                                      EXHIBIT 31

                                  CERTIFICATION

I, Donald A. Smith, Chief Financial Officer, certify that:

    1.  I have reviewed this annual report on Form 10-K of Sylvan Inc.;

    2.  Based on my knowledge, this annual report does not contain any untrue
        statement of a material fact or omit to state a material fact necessary
        to make the statements made, in light of the circumstances under which
        such statements were made, not misleading with respect to the period
        covered by this report;

    3.  Based on my knowledge, the financial statements, and other financial
        information included in this annual report, fairly present in all
        material respects the financial condition, results of operations and
        cash flows of the registrant as of, and for, the periods presented in
        this report;

    4.  The registrant's other certifying officer and I are responsible for
        establishing and maintaining disclosure controls and procedures (as
        defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal
        control over financial reporting (as defined in Exchange Act Rules
        13a-15(f) and 15d-15(f)) for the registrant and have:

        a)  Designed such disclosure controls and procedures, or caused such
            disclosure controls and procedures to be designed under our
            supervision, to ensure that material information relating to the
            registrant, including its consolidated subsidiaries, is made known
            to us by others within those entities, particularly during the
            period in which this annual report is being prepared;

        b)  Evaluated the effectiveness of the registrant's disclosure controls
            and procedures and presented in this annual report our conclusions
            about the effectiveness of the disclosure controls and procedures as
            of the end of the period covered by this annual report, based on
            such evaluations; and

        c)  Disclosed in this annual report any change in the registrant's
            internal control over financial reporting that occurred during the
            registrant's most recent fiscal quarter (the registrant's fourth
            fiscal quarter in the case of an annual report) that has materially
            affected, or is reasonably likely to materially affect, the
            registrant's internal control over financial reporting; and

    5.  The registrant's other certifying officer and I have disclosed, based on
        our most recent evaluation of internal control over financial reporting,
        to the registrant's auditors and the audit committee of the registrant's
        board of directors:

        a)  All significant deficiencies and material weaknesses in the design
            or operation of internal control over financial reporting which are
            reasonably likely to adversely affect the registrant's ability to
            record, process, summarize and report financial information; and

        b)  Any fraud, whether or not material, that involves management or
            other employees who have a significant role in the registrant's
            internal control over financial reporting.


March 26, 2004                              /s/ DONALD A. SMITH
                                            -------------------------------
                                                Chief Financial Officer
                                                (Principal Financial Officer)



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