This study compared the life cycle environmental impacts of different wood waste processing methods in three impact categories: climate impact, acidification impacts and eutrophication impacts. The wood waste recovery methods examined were the use of wood waste in terrace boards made out of wood composite which replace impregnated terrace boards, incineration of wood waste in a multi-fuel boiler instead of peat and the use of wood waste in the production of particleboard in either Finland or Central Europe. The results of the life cycle analysis are based on source materials derived from literature, previous Finnish life cycle assessments and database inventory materials. As such, the results do not directly illustrate the impacts of any individual processing facility.

The net life cycle emissions of wood composite were positive in all impact categories, meaning that the emissions were higher than the emissions avoided in the production of the replaced impregnated wood. The uncertainty assessments of the environmental impacts show that results are strongly dependent on whether the plastic used in production is virgin or recycled plastic. In other words, the environmental load of wood composite production is inversely proportional to the share of recycled plastic used to produce the composite. No inventory data was available on the acidification impacts and eutrophication impacts of the production of impregnated wood. The climate impact of wood composite production is lower than that of particleboard production but higher than that of energy recovery, as long as the plastic used in production consists primarily of recycled plastic.

High-quality wood waste is suitable for the production of particleboard. In fact, in the current market situation all particleboards are produced from industrial wood side streams and waste. Since using wood waste in the production of particleboard does not therefore replace virgin raw materials, no processes are avoided and the results consist only of direct emissions.

The energy recovery of wood waste was found to be the best option in Finland in regard to net environmental impacts in all environmental impact categories. Using wood waste to replace fossil fuels in energy production can also reduce the carbon-dioxide emissions resulting from energy production and facilitate the realisation of set climate objectives. According to the EU’s Waste Framework Directive, re-use and material recycling should be preferred to energy recovery from waste. However, according to the Directive reaching the best overall environmental outcome may require specific waste streams departing from the hierarchy where this is justified by life cycle thinking on the overall impacts of the generation and management of such waste. Based on this study, the energy recovery of wood waste is a justified option in Finland and results in an overall better environmental outcome in regard to life cycle impacts compared to the other recycling methods examined. This should be taken into consideration in the setting of recycling targets based on the EU’s waste directives and in the definition of calculation methods for the recycling rate of wood.