Life cycle assessment of bioenergy production from wood sawdust

Bioenergy derived from wood waste plays a crucial role in mitigating climate change and contributing to the circular economy. This study performs a life cycle assessment of pellet production from wood sawdust and subsequent electricity generation through different pathways. Firstly, the environmental impact of producing pellets from untreated mixed sawdust, steam exploded (SE) shavings (at 180 °C for 9 min), and torrefied (TF) sawdust (at 230 °C for 45 min) was compared using the Functional unit (FU) of 1 Kg. Secondly, the environmental impact of generating 1 MJ electricity from untreated sawdust, SE pellets, and TF pellets was compared in terms of impact categories and damage assessment. The scope of the study was defined from the gate (received feedstock) to the gate (produced output ex-factory). The results revealed that TF pellets were more environmentally friendly relative to other forms except for two impact categories: ozone layer depletion and aquatic eutrophication. SE treatment was the most damaging alternative for producing pellets, especially with respect to global warming; it produced 0.56 kg CO2 equivalent (eq.) per FU around 4 times higher than untreated pellets (0.16 kg CO2 eq./FU). After environmental impact analysis, it was found that electricity generation from SE pellets caused more damage to the environment compared to the other feedstock paths for electricity production. Utilizing TF pellets for electricity generation is more beneficial in terms of ecosystem quality, climate change, and resource depletion.