Influence of avoided biomass decay on a life cycle assessment of oil palm residues-based ethanol

Lignocellulosic (bio)ethanol from oil palm agricultural residue was investigated regarding feedstock availability and environmental impacts while accounting for avoided biomass decay. A life cycle assessment (LCA) was carried out at both pilot- and large-scale plants, from oil palm empty fruit bunch (EFB) collection until ethanol production and use. The primary data were gathered from a pilot plant at Research Center for Chemistry BRIN, Indonesia. Producing bioethanol at a large scale required 59.8% of available feedstock within a 200 km radius, with the need for chemical fertilizer to substitute EFB-based fertilizer to replenish soil nutrients. Global warming potential impacts, evaluated using CML IA Baseline 2016, indicating 8.06 and - 0.14 kg CO2eq/kg would be generated at pilot- and large-scale plants, respectively. Considering the use of ethanol from large scale plant by car, the GWP impact for bioethanol, gasoline, and E5 (blending of 5% ethanol and 95% gasoline) is - 3.07, 84.07 and 81.23 g CO2eq/MJ, respectively. The negative value of such an impact at the large scale indicated that bioethanol would lead to 1.42% and 3.38% reduction of GWP at production phase and E5 use phase, respectively. Some options were investigated to improve the GWP impact and energy profit ratio at the plant level, covering main impact contributors such as energy sources, enzymes, and chemical materials. The consideration of avoided decay may lead to further potential implication for E5 policy, which can contribute to achieving 7.46% of the national GHGs reduction target in the transportation sector. Further research would be recommended, at larger scales, to identify various biomass decay emission profiles as well as spatialized biomass availability while ensuring to maintain soil quality.