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

A detailed techno-economic analysis (TEA) and life cycle assessment (LCA) of a novel bio-refinery that produces xylitol from sugarcane bagasse. The proposed process includes dilute acid pretreatment in pressurized condition 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 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 get 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 LCA and 1 kg of xylitol is taken as the functional unit. The product cost of xylitol is calculated to be 230 INR/kg ($ 3.17/kg). For a four year payback period, the selling price of xylitol must be 450 INR/kg ($ 6.2/kg). Fermentation and pretreatment sections are the major components of the product cost. LCA results show that life cycle greenhouse gas emissions are 2.759 kg CO2 eq. per kg xylitol. Electricity requirement within the plant is identified as the major sources of greenhouse gas emissions, and reduction in fermentation duration is identified as a key factor. The results identify opportunities to improve the process from economic as well as environmental standpoint.