Evaluating integration and pretreatment options, for first- and second-generation bioethanol production by adjacent sugarcane mills

Integrated first- and second-generation (1G2G) bioethanol production from sugarcane molasses and lignocelluloses offers an economic and environmentally viable pathway to support decarbonisation of the transport and chemical sectors. The techno-economic performance of on-season versus year-round operation of a sugarcane biorefinery, leveraging the economies of scale benefits of using feedstock supplied by adjacent mills were assessed. Five different 1G2G configurations, varying in terms of sugar utilisation strategies, pretreatment technologies and inter-mill feedstock logistics were considered. Adopting year-round operation reduced the minimum ethanol selling price (MESP) by 11 %, compared to on-season only operation due to improved capital utilisation. Despite having the lowest MESP (1.16 US$/L), lignocelluloses storage for off-season use was deemed impractical due to biomass storage space requirements. Adding feedstock from one adjacent mill reduced MESPs by 11–22 %, and by 32 % for integration with 2 mills when only processing C5 sugars at host-mill. Liquid hot water (LHW) pretreatment coupled with hot water recycling and co-fermentation of C5 and C6 sugars was the most cost-effective and practical scenario (MESP = 1.25 US$/L). Hot water recycling was effective in reducing the energy (1.2 GJ/tonne biomass) and water demand (less 50 %). Doubling solids loading in LHW pretreatment reduced the MESP by over 11 %, demonstrating its potential for process intensification. Unlike previous studies, the benefits of regional mill integration were quantified.