Design of an integrated biorefinery for bioethylene production from industrial forest byproducts

The global forest industry is focused on developing waste valorization technologies. Regional resources use in biorefineries could be a strategy to improve profitability and mitigate the environmental impact of the involved industrial sectors, adding a new value chain to the forest industry. This study develops the mass and energy balance for bioethylene and lignin production from industrial pine sawdust (IS), a primary wood processing in Argentina. The proposed production process is composed of: (i) soda-ethanol pretreatment to remove the lignin; (ii) simultaneous saccharification and fermentation (SSF) to convert the cellulose to glucose and then to ethanol; (iii) ethanol recovery (95%); (iv) ethanol dehydration to bioethylene and; (v) bioethylene recovery through an ethylene tower and stripper. In the proposed process, 107 kg of bioethylene per ton of dry sawdust could be obtained, recovering 208 kg of lignin. Energy consumption is about 1885 MW h t-1 of dry sawdust. The highest consumption is in pretreatment and ethanol recovery processes, which can be reduced by 42%. Regarding economic assessment, the internal rate of return (IRR) and net present value (NPV) were 10.08% and 5.21 MM USD, respectively. Sensitivity analysis shows that the most influential parameters are lignin and bioethylene market prices and energy and enzyme costs. We identified the significant technical-economic factors, uncertainty, and risks in the pine sawdust biorefinery design for bioethylene and lignin production.