Life cycle assessment of microwave torrefaction and pellet production from agri-forest residues

The study performed a life-cycle assessment of biofuel pellet production from microwave (MW) torrefied camelina straw and switchgrass through various pathways. A cradle-to-gate analysis and identifies the environmental impact, such as global warming associated with feedstock production, preparation, pretreatment by torrefaction, and densification of MW camelina straw (CS) and switchgrass (SG) pellets, using recycled plastic (high-density polyethylene (HDPE)) as a binder, was compared based on the functional unit of 1 kg CS and SG pellets. The regional method Impact 2002+, which uses midpoint and endpoint approaches, was applied to translate inventory data into potential environmental impacts. The results showed that MW-torrefied/biocarbon/HDPE pellet production generated lower global warming potential (0.00327 kg CO₂ eq. for torrefied CS with biocarbon/HDPE pellet and 0.00224 kg CO₂ eq. for torrefied SG with biocarbon/HDPE), and other categories varied in environmental impacts. This suggests that blending torrefied biomass-MW absorber (biocarbon) with HDPE to produce CS and SG pellets resulted in reduced GHG emissions, yielding a promising outcome that would help alleviate the environmental burden of waste plastic disposal.