초록
<P><B>Abstract</B></P> <P>This study investigates the feasibility of producing bioethanol from solid digestate after a mechanical fractionation (i.e. centrifugal milling), in order to improve the energy recovery from agricultural wastes and the sustainability of anaerobic digestion plants. A bioethanol yield of 37gkg<SUP>−1</SUP> TS was evaluated for the solid digestate fraction. Mass and energetic balances were performed and compared between two scenarios: (A) one-stage bioethanol fermentation and (B) two-stage anaerobic digestion–bioethanol fermentation, in order to evaluate the feasibility and the advantages of the two-stage process. Results revealed that, compared to the one-stage process, the dual anaerobic digestion–bioethanol process permitted: (i) to diversify biofuels production; (ii) to provide the thermal energy sufficient for drying digestate (13,351kWh<SUB>th</SUB> day<SUP>−1</SUP>), for the subsequent milling step; (iii) to reduce the electric energy requirement for the milling step (from 23,880 to 3580kWh<SUB>el</SUB> day<SUP>−1</SUP>); (iv) to produce extra electrical energy of 8483kWh<SUB>el</SUB> day<SUP>−1</SUP>; (v) to improve the reduction of waste streams generated (from 13% to 54% of organic matter removal).</P> <P><B>Highlights</B></P> <P> <UL> <LI> The heat surplus from AD process can fully cover solid digestate drying. </LI> <LI> The grindability of digestate appeared two times higher than that of feedstock. </LI> <LI> The two-stage process generated an extra electrical energy of 8483kWh<SUB>el</SUB> day<SUP>−1</SUP>. </LI> <LI> Coupling AD with bioethanol fermentation permitted a COD removal of 54%. </LI> </UL> </P>