<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/A 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.

June 7, 2004                                /s/  DENNIS C. ZENSEN
                                            ------------------------------
                                               Chairman of the Board, President
                                               and Chief Executive Officer
                                               (Principal Executive Officer)

                                       42
<PAGE>

                                                                      EXHIBIT 31

                                  CERTIFICATION

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

      1.    I have reviewed this annual report on Form 10-K/A 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.

June 7, 2004                                    /s/  DONALD A. SMITH
                                                ----------------------------
                                                   Chief Financial Officer
                                                   (Principal Financial Officer)

                                       43