Continuous pilot scale process demonstrating waste fibre as a feasible feedstock to ethanol and biogas production

Production processes for lignocellulosic bioethanol face challenges with increasing feedstock costs, high investment costs due to e.g. expensive pretreatment technologies and finding ideal ways to integrate the process to existing facilities. The FibreEtOH process was developed to tackle these challenges and run in pilot scale to demonstrate a profitable ethanol production process from waste fibre. The FibreEtOH process integrated to a pulp and paper mill consists of fractionation of solid recovered fuel, sanitation of the material by heat treatment, continuous liquefaction (prehydrolysis) of the waste fibre, simultaneous saccharification and fermentation of C6 sugars and biogas production from the fermented residue. Waste fibre fractionated from solid recovered fuel is a stable all-year-round feedstock with high hexose content (44-56%) and acceptable ash content (13-14%). Thermal or chemical pretreatment is not required for this material as experimental work showed reduction rather than improvement in hydrolysis yield and rate after pretreatment. Hydrolysis of glucan was found to be fast but recalcitrant mannose- and glucose-containing soluble oligo- and polysaccharides were produced that would require additional helper enzymes for hydrolysis to C6 sugars. The whole process from fractionation to biogas production was demonstrated in pilot-scale with promising results. Continuous runs in pilot-scale were operated for up to 12 days with efficient ethanol production and without major problems from bacterial contamination. The results presented here demonstrate the feasibility of the FibreEtOH concept as a potential production process for lignocellulosic bioethanol.