Thermo-economic and environmental comparison of supercritical water and enzymatic hydrolysis of sugarcane bagasse in a biorefinery concept

Abstract

In this study, we discuss the difference regarding thermo-economic and environmental (water intake) aspects between two methods of biomass hydrolysis. A thermo-economic model was developed using Aspen Plus® and MATLAB software in order to analyze the energy efficiency, as well as, the economic impact of the hydrolysis process integrated into a traditional ethanol production process from sugarcane. The study aimed at comparing the enzymatic route for sugarcane bagasse ethanol production with the supercritical water-based one. The use of supercritical water hydrolysis (SCWH) process showed promising results, being the process energetically self-sufficient when considering pumping of liquid streams with biomass content of 20% and the decompression of the steam separated after SCWH with a turbine, in order to produce electricity. In terms of economics, the biorefinery concept using enzymatic route presented the highest production costs due to the higher total investment cost and the cost for the raw materials, which is 14% higher than the biorefinery with SCWH, giving a payback time for the investments of 7.5 years, meanwhile 6.2 for the SCWH route. Also better results were obtained for water intake for the SCWH option, being lower than the maximum permitted for a new investment on the Brazilian sugarcane sector.