Is anaerobic co-digestion the missing link to integrate sugarcane biorefinery?

Abstract

This study evaluated the potential of energy generation from anaerobic co-digestion (AcD) of vinasse and hemicelluloses hydrolysate within the context of an integrated 1G-2G sugarcane biorefinery as a mean to ensure its technical, economic and environmental feasibility. Environmental impact indexes for 2G ethanol and biogas production process, such as carbon footprint, which varied from 12.3 to 50.02 g CO2/MJ and reduction of greenhouse gas (GHG) emissions (from 42.7 to 85.9%), were obtained in all scenarios. Economic indicators showed the unviability of 1G-2G sugarcane mill integration adopting AcD of wastes, considering technologies for 2G ethanol production in view of their high capital and operational costs (pretreatment). However, by fixing the experimental methane yield at 0.245 Nm3 kg COD−1r which has been obtained for two-stage anaerobic systems and by considering the use of 50% of bagasse surplus for biogas production, it was possible to achieve internal rate of return (IRR), return on investment (ROI) and payback period of 21.8%, 59.50% and 10.55 years respectively. Moreover, when experimental methane yield is increased in 10% in such scenario, it was possible to achieve internal rate of return (IRR), return on investment (ROI) and payback period of 26%,89.05% and 5.36 years, respectively.