Technical, Economic and Environmental Assessment of Ethanol Production using a Biochemical-Thermochemical Hybrid Route

Abstract

The present work proposes, in the context of a Biorefinery, to assess the biochemical-thermochemical hybrid route through the recovery of the residual cellulignin from pre-treatment and hydrolysis of sugarcane bagasse and straw in an integrated first- and second-generation ethanol plant (1G2G plant), by means of residual cellulignin gasification in a thermochemical ethanol plant. In this assessment, a decentralized plant concept is considered, in which four first- and second-generation ethanol biochemical plants (1G2G biochemical plants) processing 4 million tonnes of sugarcane per year (4 MTC/y) each and producing first- and second-generation ethanol supply residual cellulignin for a central standalone feedstock flexible thermochemical plant, configuring an 1G2G biochemical-thermochemical ethanol hybrid scenario. As base scenario, four 1G2G autonomous plants with residual cellulignin burned in the boilers is selected. For the routes comparison, main technical, economic and environmental aspects of each scenario are assessed. Results showed an increase in total anhydrous ethanol production for 1G2G biochemical-thermochemical ethanol hybrid scenario, besides higher alcohols that are also produced in this scenario. An increase of capital investment is observed for the 1G2G biochemical-thermochemical ethanol hybrid scenario justifying the Internal Rate of Return (IRR) lower than the base scenario, yet with a positive net present value (NPV). Environmental results showed similar impacts for both scenarios.