Implementing polyhydroxyalkanoates production to anaerobic digestion of organic fraction of municipal solid waste to diversify products and increase total energy recovery

A simple biorefinery aimed at producing both biomethane (CH4) and polyhydroxyalkanoates (PHAs), was proposed to valorize the organic fraction of municipal solid waste (OFMSW). Anaerobic digestion (AD) was tested at different organic loading rates (OLR-I-II-III) (i.e. 3, 4 and 6 g L−1 d−1, respectively), producing biomethane and volatile fatty acids (VFAs)-rich digestate, the VFAs were then used to produce PHAs. Specific biogas and CH4 production remained similar when adopting different OLRs (biogas of 522–600 NL kg−1 VS and CH4 of 64–67% v/v). VFAs concentrated with OLR increases and their patterns were modified. PHA production was in the range of 117–199 g kg−1 OFMSWTS with the lowest production being associated to different polymer composition. The net energy recovery of this simple biorefinery accounted for 64% of OFMSW energy content, and the PHAs produced represented over 30% of the total energy.