Environmental sustainability of wood-derived ethanol: a life cycle evaluation of resource intensity and emissions in Maine, USA

The existing methods of process-based life cycle assessment (LCA) fail to account for the role of ecosystem goods and services derived from natural capital. This study presents an in-depth analysis of resource consumption and atmospheric emissions across a wood-derived bioethanol supply chain. The analysis is based on energy consumption, Industrial Cumulative Exergy Consumption (ICEC), and Ecological Cumulative Exergy Consumption (ECEC) of resources used in the production of one ton of ethanol from woodchips using the near-neutral hemicellulose extraction technology. We found that when compared with fossil-based fuels and corn ethanol, wood-based cellulosic ethanol derived under the near-neutral hemicellulose extraction process demonstrated superior environmental performance. Renewable resources − mostly sunlight and detrital matters – are the dominant contributors to ICEC analysis, whereas non-renewable resources such as crushed stone, crude oil, ores and minerals contribute more to total ECEC. Lime manufacturing, inorganic chemicals production for green liquor preparation, and anthraquinone production have the highest resource consumption. The woodchip washing process and transportation stages consume relatively fewer resources. A performance metric analysis suggests that even though cellulosic ethanol uses a renewable feedstock, its environmental sustainability performance is reduced due to the large consumption of non-renewable resources during the ethanol production stage.