Bioethanol: optimising wood pre-treatment for profitable production

Pre-treatment by steam explosion has already proved its effectiveness in various industrial sectors, but remains very costly for the production of second-generation (2G) bioethanol: it represents 30 to 50% of equipment costs for the entire bioethanol production process and 20 to 25% of operational costs.

Based on this problem, scientists from UMR FARE, in collaboration with the company Européenne de Biomasse, as part of Edwige Audibert's CIFRE PhD thesis, aimed to maximise ethanol production while limiting the cost of pre-treatment.

The results obtained were used to determine the optimum pre-treatment conditions for 3 species of wood (oak, poplar and spruce) and show that ethanol production increases with the severity of pre-treatment up to medium severity conditions and then becomes stable, demonstrating that the most drastic conditions are not the most appropriate to apply. Based on these data, and taking into account the specific yield ranges of the steam explosion process operated by Européenne de Biomasse, the scientists have succeeded in establishing scenarios for oak and poplar only, in order to optimise the pre-treatment stage and thus maximise bioethanol production, while remaining economically viable.

The best compromise for oak corresponds to around 15 minutes of pre-treatment at 198°C, with a bioethanol yield of 129 mg/g of dry matter and a 22% increase in economic investment. For poplar, it corresponds to approximately 10 minutes of pre-treatment at 205°C, with a yield of 111 mg/g of dry matter and a 16% increase in investment. Compared with optimum yields calculated without any economic criteria, this represents a very moderate reduction of 9% and 4% respectively for oak and poplar, while pre-treatment costs are reduced by 25 to 50%.

This study shows that it is possible to optimise the pre-treatment and conversion of plant biomass to suit a company's industrial conditions in terms of material and operational investment criteria, using bioethanol as an example. This method could therefore be easily transferred to the production of other products of interest derived from glucose, such as bioplastics or biosolvents.

Press release from INRAE : https://www.inrae.fr/actualites/bioethanol-optimiser-pretraitement-du-bois-production-rentable

Article: Audibert E, Floret J, Quintero A, Martel F, Rémond C, Paës G (2025) Determination of trade-offs between 2G bioethanol production yields and pretreatment costs for industrially steam exploded woody biomass. Applied Energy 380, 125028. https://doi.org/10.1016/j.apenergy.2024.125028

Contacts: Pr Caroline Rémond, caroline.remond@univ-reims.fr & Dr Gabriel Paës, gabriel.paes@inrae.fr