(567f) Co-Production of Bioethanol and Bio-Lactic Acid in a Biorefinery Concept: A Comprehensive Study
Biorefineries are seen as a key component for the transition toward a sustainable and low carbon bio-economy. In this research, alternative biorefineries annexed to a typical South African sugar mill are investigated to co-produce ethanol (EtOH), lactic acid (LA) and/or electricity, utilizing bagasse and a component of harvesting residues (brown leaves) as feedstock. Studied scenarios are EtOH production (scenario 1), EtOH form glucose and LA from xylose (scenario 2), EtOH form xylose and LA form glucose (scenario 3) and LA production (scenario 4), all of which are associated with some level of export electricity production. Aspen simulation of the scenarios were developed considering all supplementary units such as evaporation, water treatment, boiler and steam/power generation in addition to the process units. Economic evaluation, energy assessment and Life Cycle Analysis (LCA) of the developed simulations were carried out to determine the viability of each scenario. In order to supply the combined energy demands of both sugar mill and biorefinery, a 35 to 40% bypass of lignocellulose directly to the boiler section was required, to achieve integrated scenarios that were bio-energy self-sufficient, with no supplementation with fossil fuels. Based on the economic analysis, scenario 4 achieved the highest Internal Rate of Return (IRR) of 20.9%, while scenario 1 had the lowest IRR of 10.7%. Since EtOH, LA and enzyme prices strongly affect the profitability of biorefinery scenarios, sensitivity analysis was carried out, which identified scenario 2 as the most economically robust, having the least sensitivity to these price variations.