Life-cycle assessment of microwave-assisted pyrolysis of pine sawdust as an emerging technology for biodiesel production

Abstract

Although biofuels are often presented as a renewable and eco-friendly substitute to fossil fuels, it is crucial to have a comprehensive understanding of the complete environmental consequences of biofuel production to make well-informed choices about their usage. This study evaluated the environmental impacts of producing biodiesel from microwave-assisted pyrolysis (MAP) of pine sawdust using life-cycle assessment. A cradle-to-gate system boundary approach encompassing pine cultivation, biomass pre-processing, pyrolysis, and biofuel synthesis via transesterification was used. The ecoinvent v3.7 in openLCA v2.0 software was used to assess the environmental sustainability of the system. The ReCiPe 2016 (H) midpoint impact assessment methodology was used to analyze 18 environmental impact categories. The results showed that producing 1 kg of biofuel from MAP of pine sawdust had environmentally favorable impacts for most categories except global warming potential (1.18 kg CO2 eq.), photochemical oxidant formation (0.71 kg NMVOC eq.), and human toxicity (2.46 kg 1,4-DCB eq.). Biomass production contributed significantly to global warming, freshwater ecotoxicity, human toxicity, and marine ecotoxicity. Pyrolysis contributed 33 % of global warming potential due to non-condensable gas emissions. Biofuel synthesis impacted human toxicity, photochemical oxidant formation, and terrestrial ecotoxicity, mainly due to methanol use. Implementing sustainable practices such as using organic fertilizers, optimization of transportation routes, implementing gas cleaning technologies and effective waste management practices can enhance the environmental performance of this biofuel production system.