| Abstrakt: |
Purpose: Given that the depletion of fossil fuels is an important issue that should be tackled urgently, alternative routes are being sought for biofuels production. This paper, under this context, studied the potential synergies of co-treatment of two kinds of agro-waste (brewers' spent grains, BSG and spent coffee grounds, SCG) towards the direction of biodiesel and bioethanol production, alleviating at the same time their treatment and management issues. Methods: The technical feasibility of oil extraction and ethanol production was studied and optimized in both laboratory and bench scale. A treatment train including alkaline pretreatment of SCG and dilute acid pretreatment of BSG, neutralization of the solutions by mixing them, enzymatic saccharification and ethanolic fermentation led to the production of bioethanol. Results: The co-treatment of BSG and SCG proved beneficial and optimum experimental conditions were defined by setting the bioethanol production cost as optimization parameter. The lowest ethanol production cost (3.9€/kg) was observed for scenario 4 (SCG/BSG mixture, chemical pretreatment (0.5 N, 5 h), enzymatic hydrolysis (400 µL/g cellulose, 16 h)) and scenario 5 (SCG/BSG mixture, chemical pretreatment (0.5 N, 5 h), enzymatic hydrolysis (800 µL/g cellulose, 5 h)). Further upscaling of the process verified the technical feasibility of process units leading to a further increase of ethanol yield and thus a decrease in the production cost. Conclusions: Conclusively, it was demonstrated that the recovery and extraction of the oil content of BSG and SCG and the achievement of high ethanol yields is technically feasible. Within this context, an integrated biorefinery was presented, making evident that these substrates could reverse the eminent energy crisis via biofuels production. [ABSTRACT FROM AUTHOR] |
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