Forest pests and wood pellets: A literature review of the opportunities and risks in the United States’ northeastern forests

Abstract

As interest in alternatives to fossil fuels increases, low quality timber may become more attractive as feedstock material for biomass energy. This low-quality timber, referred to here as salvage wood, can be used to manu- facture wood pellets, a densified biomass energy product which can be used for electricity and heating. The process of converting wood to pellets also results in total pest mortality in the final product, an important consideration given wood pellet’s international market and global concerns about phytosanitation, or the risk of pest spread. However, there is still potential to spread pests in the wood pellet supply chain. To better under- stand the potential benefits for forest health and the phytosanitary risks of the use of salvaged wood in the wood pellet supply chain, our study systematically reviews the literature published between 2000 and 2018, gleaning applicable considerations for the northeastern United States (US), a region already affected by the highest density of damaging forest pests in the country and an up-tick in wood pellet use. Our review focuses on three pest species likely to incur considerable change in northeastern US forests: emerald ash borer (Agrilus planipennis or EAB; an exotic, invasive species), hemlock woolly adelgid (Adelges tsugae Annand, or HWA; an exotic, invasive species), and southern pine beetle (Dendroctonus frontalis Zimmermann, or SPB, a native species). Our review finds that wood pellets are being recognized as phytosanitary in their final form and that the forest health opportunities for the use of salvaged wood exist are beginning to be acknowledged in the region. However, our results also indicate that the spread of pests is still possible in the feedstock pre-treatment supply chain, which have yet to be directly addressed in US-related scientific literature. Our review concludes that further research and action on the phytosanitary risks in the supply chain focus on individual pest species behavior during harvesting, on-site comminution of feedstock material, and local processing at facilities within USDA APHIS (United States Department of Agriculture Animal and Plant Health Inspection Service) quarantine zones for maximum mitigation. The results of these considerations can accrue benefits for forest health, mitigate the spread of forest pests, and support the use of an alternative energy to fossil fuels in a changing climate.