Diversifying the products from the organic fraction of municipal solid waste (OFMSW) by producing polyhydroxyalkanoates from the liquid fraction and biomethane from the residual solid fraction

Abstract

This study describes the diversification of products obtainable from the organic fraction of municipal solid waste (OFMSW) by producing polyhydroxyalkanoates (PHA) from the liquid fraction and biomethane from the residual solid fraction. OFMSW samples were taken during the 2021 season from two full field scale plants treating wastes. After solid/liquid (S/L) separation, 80% of initial organic acids (OAs) were released in the liquid stream. OAs were then used as feed for PHA production and residual solid cakes were tested for biomethane production. Complete mass balance and energy balance were calculated. PHAs production was of 115 ± 23 (n = 6) g kg^{- 1} OFMSW (TS) and residual biomethane of 219 ± 3 g kg^{- 1} OFMSW TS, (n = 6). Energy balance indicated that nearly 40% of OFMSW energy was recovered as products. This value was lower than that obtained previously when AD was performed before OAs separation (i.e. 64%).

Keywords: Anaerobic Digestion (AD); Liquid and Solid Fractions; Organic Fraction of Municipal Solid Waste (OFMSW); Polyhydroxyalkanoates (PHAs); Volatile Fatty Acids (VFAs).