Chapter 12 - Production of Wood Pellets from Waste Wood

Abstract

This chapter describes a case study where Grade A waste wood is converted to wood pellets. Based on current supply chains in the United Kingdom, it is assumed that these are used to displace coal in coal-fired power stations, where the pellets can easily be crushed and directly injected into the boilers. An attributional life cycle assessment (LCA) is performed on the pellet production system, with the system boundaries starting at biomass collection and ending at the pellet plant ‘gate.’ The results show that pellet production from waste wood incurs a GHG burden of 111kg CO2 eq./t. On an energy-content basis, waste wood pellets can deliver GHG savings of 93% compared to coal. Two consequential ‘counterfactual’ systems are considered: one where the wood pellets displace the feedstock supply available to chipboard manufacturers and one where the waste wood is diverted from landfill. In order to satisfy chipboard demand, virgin timber must be sourced, and this is attributed as a ‘penalty’ to the pellets. This has a small effect on GHG emission saving potential (they are reduced to 90%). Diverting waste wood away from landfill will lead to GHG emission savings, though the foregone potential from carbon sequestration in landfill means that the savings could be reduced to 84% if at one extreme none of the wood decays in landfill, although the overall impact of this counterfactual scenario depends on this factor.