Sugarcane bagasse valorization to xylitol: techno-economic and life cycle assessment

A detailed techno-economic analysis and life cycle assessment (LCA) of a novel bio-refinery that produces xylitol from sugarcane bagasse are provided. The proposed process includes dilute acid pretreatment in pressurized conditions followed by fermentation (upstream section). The fermentation broth is then sent for separation and purification to the downstream section. Calculations are performed for a plant with 4 t/h of dry bagasse throughput. With a fermentation yield of 0.54 g xylitol per g of xylose, the plant produced 437.4 kg/h of xylitol. Upstream data are adapted from experimental studies, while ASPEN PLUS® flowsheet simulation is used to obtain data for the downstream section. The xylitol production facility is assumed to be annexed to an existing sugar mill in India. The total utility requirement in the process is reduced using heat integration strategies. Cradle-to-gate scope is considered for the LCA and 1 kg of xylitol is taken as the functional unit. The product cost of xylitol is calculated to be 230 INR/kg (US$3.17/kg). For a 4 year payback period, the selling price of xylitol must be 450 INR/kg (US$6.2/kg). The fermentation and pretreatment sections are the major components of the product cost. The LCA results show that the life cycle greenhouse gas emissions are 2.759 kg CO2 eq. per kg xylitol. The electricity requirement within the plant is identified as the major source of greenhouse gas emissions, and reduction of fermentation duration is identified as a key factor. The results identify opportunities to improve the process from an economic as well as an environmental standpoint