Life cycle assessment of renewable diesel produced from biomass and animal waste

Fuel production from lignocellulosic feedstocks has attracted great interest in recent years due to opportunities to diversify and decarbonize energy supply, address climate change, and produce energy from domestic sources. The low energy density, miscibility with water, blending wall limit, and other aspects of ethanol produced from lignocellulose  have supported an interest in synthesizing drop-in or infrastructure compatible fuels from biomass. The fermentation of cellulosic sugars to fatty acid derivatives offers a promising means of manufacturing fuels [e.g., fatty acid ester ether (FAEE), biodiesel] that can be blended with petroleum-based fuels (Paap et al 2013). Moreover, fatty acid derivatives can be upgraded to fully oxygen-free alkanes (renewable diesel) in the range of diesel fuels. Another lower cost source of free fatty acid feedstock is animal fats, such as poultry waste from rendering facilities. Currently the dominant commercial biofuel from animal fats is biodiesel; however, poultry fats can also be converted to renewable diesel (Kaewmeesri, Srifa et al 2015). We examine the life cycle environmental performance of renewable diesel produced from the bioconversion of lignocellulose, specifically examining greenhouse gas (GHG) emissions and fossil energy demand and compare its performance to renewable diesel and biodiesel produced from rendered poultry waste, the latter of which has an approximate life cycle GHG intensity and fossil energy demand of 20 g CO₂e/MJ and 0.25 MJ/MJ. We discuss scenarios and opportunities for improving the performance of biomass-to-renewable diesel pathways, including the effects of feedstock choice and biorefinery co-products.