Biofuels and Bioenergy

In this study, alternative lignocellulose biorefineries annexed to a typical sugarcane mill were investigated, which produce ethanol (EtOH), lactic acid (LA) or Methanol (MeOH), or co-produce EtOH and LA, all with surplus electricity for sale, by the conversion of bagasse and harvesting residues (brown leaves). The energy demands of the combined complex (sugar mill and biorefinery) were not met by burning the residues of biorefinery therefore, a portion of feedstock or a fossil source (coal) were burnt along with residues in the centralized CHP unit. A thorough simulation was developed using Aspen Plus for each biorefinery scenario for which energy assessment, economic evaluation based on Monte Carlo simulation, and environmental life cycle analysis (LCA) were carried out, in a multi-criteria assessment of the desirability of each scenario.The lactic acid production process was found to be the most energy intensive process with highest chemical consumption and the highest conversion of biomass carbon input to products. Consumption of coal as an alternative source of energy enhanced the available biomass for valorization. Biorefineries with coal combustion producing ethanol or ethanol&lactic acid had better environmental performance than methanol producing biorefineries, based on 1 ton of product. The co-production of EtOH and LA showed the largest likelihood of economic success, while some of the EtOH producing scenarios could achieve a positive NPV. MeOH producing scenarios had a zero likelihood of a positive NPV without substantial financial incentives or improved market prices.