Integrated production of second-generation ethanol and biogas from sugarcane bagasse pretreated with ozone.

Abstract

Considering the lignocellulosic biorefinery, the present work evaluated the energy potential related to biogas production from the anaerobic digestion (both at one- and two-stage) of the main residues derived from sugarcane bagasse (SB) pretreatment with ozone aiming its further use for 2G ethanol. The results showed that 2G ethanol production was maximized under mild ozonation conditions (7.5 mgO3 gSB−1

), generating 30 L ethanol tonSB−1

, which corresponds to a revenue of 17 USD tonSB−1 with sale.

Despite not leading to profits, the use of electric energy generated through CHP system (by burning the biogas produced at two- stage anaerobic digestion) covered the energy costs involved in SB ozonation. A combined pretreatment consisting of SB

ozonation followed by alkaline extraction (AE) provided the highest 2G ethanol production (66 L tonSB−1

) under the most

severe conditions (97.5 mgO3 gSB−1

), and resulted in 37 USD tonSB−1 with ethanol sale. Despite this, process sustainability was only achieved when the anaerobic digestion of main residues was taken into account and the combined O3+AE was used under the mildest SB ozonation. At these conditions, the surplus energy (~ 30 MW per harvest) had the potential to supply about 320,000 inhabitants during the crop harvest.