3-Routes platform for recovery of high value products, energy and bio-fertilizer from urban biowaste: the Revenue Project

This innovative Biorefinery platform is based on the integration of a mild thermal pre-treatment and a solid/liquid separation unit to parallel-integrated bioprocesses specifically selected on food waste distinctive chemical composition: a liquid fraction, rich in readily fermentable sugars, to be transformed into valuable biobased products, and a solid organic residue to enhance biomethane production generating a fully hygienized digestate to be recycled. The preliminary results in terms of VFAs yields and composition from the acidogenic stage, and the methane conversion rate from the anaerobic digestion of the solid residue, are here presented. The integration of a mild thermal pretreatment promoted the transformation and the conversion rates into volatile fatty acids through the optimization of operational pH and HRT of the primary fermentation step. Secondary fermentation reaction as chain elongation to MCFAs (as caproic acid) occurred in the same reactor without external donor addiction probably because of the in situ formation of lactate. The solid residue fed into semi-pilot anaerobic digesters assured process stability (no acidification phenomena occurred) despite the short HRT of 20d. The weakening of the lignocellulosic matrix by the thermal pre-treatment had a positive impact on the anaerobic conversion increasing methane production (+20%), in particular during weekend, when feeding was stopped.