Energy and GHG balances of ethanol production from cane molasses in Indonesia

This study analyses the sustainability of fuel ethanol production from cane molasses in Indonesia. Life cycle assessment (LCA) is performed to evaluate the net emissions (climate change impact) and energy inputs (resource consumption) in the production chain. The lifecycle greenhouse gas (GHG) emissions in the production and use of ethanol are estimated at 29 gCO2eq per MJ of ethanol produced which is a 67% reduction in comparison to gasoline emissions. Net Energy Value (NEV) and Net Renewable Energy Value (NREV) are −7 MJ/l and 17.7 MJ/l, while the energy yield ratio (ER) is 6.1. Economic allocation is chosen for dividing environmental burdens and resource consumption between sugar (i.e. main product) and molasses (i.e. co-product used for fuel production). Sensitivity analysis of various parameters is performed. The emissions and energy values are highly sensitive to sugarcane yield, ethanol yield, and the price of molasses. The use of sugarcane biomass residues (bagasse/trash) for efficient cogeneration, and different waste management options for the treatment of spent wash (effluent of distilleries) are also explored. Surplus bioelectricity generation in the efficient cogeneration plant, biogas recovery from wastewater treatment plant, and their use for fossil fuel substitution can help improve energy and environmental gains. The study also compares important results with other relevant international studies and discusses issues related to land use change (LUC) impact.