Biogas and bioethanol production from pinewood pre-treated with steam explosion and N-methylmorpholine-N-oxide (NMMO): A comparative life cycle assessment approach

In this study, the lignocellulosic biofuel production from pinewood, pretreated with steam explosion and N-methylmorpholine-N-oxide (NMMO), was investigated from a life cycle perspective in Sweden. To perform this study four scenarios, i.e. ethanol and biogas production by NMMO (Sc-1) and steam explosion (Sc-3) pretreatments, and biogas production by NMMO (Sc-2) and steam explosion (Sc-4) pretreatments, were developed. The consequential life cycle assessment (CLCA) methodology with a cradle to gate approach was employed and two functional units, i.e. 105,263 tonnes pinewood input to the biofuel plant and 1 MJ energy produced, were selected in order to assess the environmental impacts of pinewood-based biofuel production. The results revealed that bioenergy production with NMMO-based pretreatment method was more environmentally friendly than steam explosion process in terms of human health, ecosystem quality, resources and climate change. Moreover, it was shown that the Sc-2 in which methane was the single outcome of the plant (the main product) outperformed the other scenarios in terms of environmental performance and energy balance.