Environmental and economic assessment of torrefied wood pellets from British Columbia

Abstract

With increasing international trade in wood pellets for use as fuel, the carbon footprint over the supply chain is of growing concern. The Canadian province of British Columbia (BC) is endowed with clean electricity and rich biomass resources, which are essential for developing a low-carbon wood pellet industry. This work aims to quantify the life cycle Greenhouse Gas (GHG) emissions of torrefied wood pellets in comparison with conventional pellets, derived from forest residues in BC and transported to replace coal at power plants in Europe, the Asia Pacific region and elsewhere in Canada. The GHG reduction costs in different markets are also quantified. Five possible production configurations are analysed with uncertainties taken into consideration. Torrefied wood pellets are found to have better environmental performance than conventional pellets. The best production process, which follows the sequence drying-torrefaction-grinding-pelletization, can reduce primary energy consumption and carbon footprint by about 30% compared to conventional pellets. Over the life cycle, transportation contributes most GHG emissions (>50%), while electricity use, including sawmilling and pellet production, represents the greatest energy consumption (~50%). Life cycle analysis reveals that GHG emissions from the supply chain offset at most 15% of the savings from using BC torrefied wood pellets to replace coal. GHG reductions are greatest when the pellets are used in overseas markets, especially the Asia Pacific region and the EU, rather than domestic Canadian markets. The current carbon taxation level cannot cover the abatement cost of BC pellets; other mechanisms are still needed to support the sustainable development of the industry.