Municipal Food Waste to Biomethane and Biofertilizer: A Circular Economy Concept

This research is a dual resources recovery approach of biomethane and biofertilizer from as received municipal food waste (MFW) using the concept of circular economy. In this research MFW is first pretreated in hydromechanical process to produce broth suitable for anaerobic digestion (AD). The MFW broth then underwent mesophilic wet AD process to produce biomethane and biofertilizer. Three selected feedstock and inoculum ratios (F/I) of 1:2, 1:1 and 2:1 by volume for 30 days retention time were considered. Among three F/I ratios, the F/I ratio of 1:1 digester was found to be the best batch condition for 30 days retention time for maximum biomethane production. MFW broth had ash content of 31.51% of total solid (TS), higher heating value (HHV) of 18.32 MJ kg(-1) of TS and C/N ratio of 15.29. The batch F/I of 1:1 AD produced the maximum biomethane of 347.69 L kg(-1) TS, 511.92 L kg(-1) volatile solid (VS), 232.74 L kg(-1) COD and 701.56 L kg(-1) TOC, respectively. The biomethane was accounted for about 60% of the produced biogas in this mesophilic batch digester. Digestate was available as a liquid biofertilizer with 4.61% N, 3.33% P, 0.39% K, 1.17% S, 0.29% Ca, 0.14% Mg and 6.82% Na contents of TS of MFW broth, which will be a substitute of chemical fertilizer. This biomethane and biofertilizer can reduce GHG emission of Ontario, Canada which can contribute to the enrichment of the circular economy.