The Physical Properties of Surface Layer Thermally Modified Wood and Energy Consumption in the Preparation Process

Surface layer thermal modification (SLTM) not only improves the dimensional stability of wood but also effectively shortens production time. However, limited research has been conducted on how treatment conditions influence the properties of SLTM wood and energy consumption during the production process. This study compared the physical properties of SLTM wood with conventional thermally modified (CoTM) wood treated at 185 °C, 200 °C, and 215 °C, as well as the energy consumption during processing. Samples were subjected to SLTM at three temperatures (185 °C, 200 °C, and 215 °C) two times (2 h and 3 h) and two target surface layer thicknesses (6 mm and 12 mm). The results showed SLTM improved dimensional stability, with the anti-swelling efficiency (ASE) after water absorption increasing by a maximum of 2.4 times compared to CoTM185-2h. Increases in treatment temperature, time, and target surface layer thickness all contributed to enhanced ASE. At 96% relative humidity, SLTM wood samples exhibited lower equilibrium moisture content (16.6% to 19.2%) than CoTM185-2h (19.5%). SLTM also reduced the total treatment time by 1.9 h to 10.8 h compared to CoTM treatments. SLTM demonstrated energy savings ranging from 215 kW∙h to 1567 kW∙h, resulting in a reduction in CO2 emissions by 73 kg to 729 kg per 1 m3 of processed wood. These findings suggest that SLTM provides a promising strategy for the energy-efficient utilization of plantation wood.