Using life-cycle assessment to evaluate environmental impacts of torrefied briquette production from forest residues.
This report presents life-cycle impact assessment analysis of near-woods processing of post-harvest forest residues (a biomass raw material) into torrefied wood for bioenergy production. The study was part of the Waste to Wisdom project with a broader goal of evaluating the use semimobile biomass conversion technologies to optimize biomass logistics, thereby overcoming the barriers of valorizing woody biomass residues for renewable energy and material production. Cradle-to-grave analysis of the torrefied briquettes (TOB) supply chain included feedstock procurement, hauling, feedstock preparation and bioconversion (torrefaction and densification) stages, product transportation (distribution), and combustion of TOB in domestic wood stoves for heat generation. The results showed that a large portion of the global warming (GW) impact of the TOB supply chain resulted from the torrefaction process (59%) followed by the drying process with about 24% of the contribution. The large contribution of these processes resulted from propane use. Comparative analysis showed that 50% substitution of propane used in domestic heating with TOB resulted in a 41% decrease in GW impact. The near-woods operation resulted in a 55% lower GW impact compared with transporting the feedstock to an in-town facility with access to grid electricity.