Proof of Concept Studies for the Practical Application of Joule Heating as a Phytosanitary Treatment for Export Pinus radiata (D. Don) Logs

Abstract

Following initial feasibility work in 2007 [1] and a MAFBNZ funded project in 2009 [2], the Joule heating concept for log sterilization was incorporated into the STIMBR PGP project as section 1.5.2. This report details the construction, commissioning and testing of the log sterilizing apparatus which had largely been conceived and designed by the EPECentre before the start of this project. The procedure for sterilizing test logs is described and the results obtained with two such logs are presented and discussed against the objectives of section 1.5.2. Finally suggestions for further work, refinements to the system and tests to fill gaps in current knowledge are proposed, including the author’s current impression as to how a wharf-side machine might operate. Tests on the first log show that after treatment all measured locations in the timber exceed 56C for over 5 hours. Tests on the second log show that after treatment all measured locations in the timber exceed 56C for over 8 hours and 70C for about 3.5 hours. In both cases this includes the geometric centre of the log. These tests, therefore, show that Joule heat sterilization undoubtedly can work.