Towards better integration of wood protection in the forestry wood industry chain - a case study on hybrid poplar
J Van Acker
Wood and wood products are limited in service life as in the forest ecosystem trees at end of their life are degraded to re-enter the bio-geochemical cycle. Humans can select wood species with a level of natural durability fit for an envisaged end use. Mainly those applications that require a long service life under conditions that are similar to those at soil level in a forest ecosystem have been the early focus for wood preservation. Testing wood preservatives intended for enhanced performance of wood in soil or water contact was originally based primarily on performance benchmarked with wood species having higher natural durability.
Over the last decades, wood protection has altered focus towards end uses out of ground contact even sometimes specifically for interior applications. Parallel to this evolution wood modification treatments were assessed also to improve general performance of wood species. Besides an increased potential for using low durability wood species, mainly dimensional stability related properties were envisaged.
The forestry-wood chain has evolved in the second half of last century from mainly production based strategies to policies based on ecosystem services in a sustainability framework. Today forests are intended to provide services for the bio-economy, human health, biodiversity and climate control. An increased need for more renewable resources both for material and energy use has initiated extra focus on the potential to produce more lignocellulosic biomass, in short to increase wood production. Forest types identified as primary forest as well as (semi)-natural forests require conservation measures limiting the option to increase volume that can be harvested. One option is to provide in complementary production in planted forests. Both forestry and agriculture can take part in this. The cultivation of poplar hybrids in the temperate regions is a key option for the current and future bio-economy. These fast-growing trees are producing lightweight hardwood material with a low natural durability.
All wood protection methods are of interest to be evaluated for this wood resource, making it suitable even for high quality applications. Poplar, for many reasons, has been nominated as hardwood with the best potential to perform similarly as softwoods for applications in wood construction. Benchmarking with wood species like spruce is relevant for several engineered wood products like plywood, LVL and even CLT. Wood treatments to increase durability have also evolved from traditional wood preservation towards modification techniques such as thermally modified timber depending on the performance required or fit for purpose in relation to a specific combination of use class and service life.