Eco-friendly strategy for the joint valorization of invasive macroalgae and fast-growing wood to produce advanced biofuels

A novel sustainable scheme to jointly valorize Sargassum muticum (Sm) and Paulownia wood (PW) was proposed in this work, employing the advanced environmentally friendly microwave-assisted autohydrolysis (MA) as pretreatment. Sm is an invasive macroalga that has been drastically spread in the Atlantic coast of Europe, causing environmental damage. Conversely, Paulownia elongata x fortunei is a fast-growing biomass with a high biomass production and potential for biofuels production. Thus, the concomitant valorization of both biomasses may lead to benefits related to environmental protection and bioeconomy. A sequential approach was proposed: first stage of glucose production from Sm (treated by MA and enzymatic hydrolysis to obtain a glucose-rich liquor), and second stage with MA-pretreated PW followed by saccharification and fermentation, employing in this process the glucose rich solution obtained from algae, to obtain simultaneously second and third generation bioethanol. These approaches enabled to add the ethanol production from both biomasses, leading to up to 45.2 g ethanol/L (70% ethanol yield), boosting ethanol titers compared to using only one biomass (up to 27.8 g/L) and confirming the benefits of combining MA-processed biomass. Furthermore, up to 87% of the energy may be recovered, reflecting a suitable approach within an integrated strategy.