Energy and Greenhouse Gas Evaluation of Biodiesel and Bio-hydrogenated Diesel from Palm Oil in a Life Cycle Perspective

Biodiesel, produced from seed oils via the transesterification process, is one of the promising alternative fuels for transportation in Thailand because of its potential environmental benefits. Recently, bio-hydrogenated diesel (BHD), produced from new process technologies based on hydro-treating process converting seed oils to diesel fuel, has been emerged. BHD has become more interesting as alternative fuel because of its similarity to conventional diesel. In Thailand, palm oil is found to be a suitable raw material for bio-based fuels due to its large available quantity of feed stock. The objective of this study is to evaluate the energy consumption and greenhouse gas (GHG) emissions of biodiesel and BHD from palm oil as transportation fuels in Thailand using life cycle technique. The system boundary covers the entire life cycle from well-to-wheel (WTW) including oil palm plantation, crude palm oil extraction, biofuel production, logistics and distributions, and lastly the consumption of fuels. Functional unit of this study is 1 kg of fuel. The results indicate that the energy consumption of biofuel pathways is higher than conventional diesel. The biofuel production stage (transesterification and hydro-treating process) and palm oil extraction stage are the major contributors of energy use for both biodiesel and BHD. Net energy ratio (NER) of 5% biodiesel blend (B5), 5% BHD blend (BHD5) and diesel are 4.79, 5.34 and 5.38 respectively. GHG emissions are mainly from oil palm plantation stage and biofuel production stage. Compared to the conventional diesel, biodiesel and BHD are significant lower in GHG emissions. Between biodiesel and BHD, the energy ratio and GHG emissions of BHD are better than those of biodiesel. It is recommended that introducing a good management in cultivation as well as developing new technology for industrial processing will give an opportunity to improve the energy efficiency of biodiesel and BHD comparable to conventional diesel.