Waste carbon streams are increasingly viable options for the reduction in production costs for PHA synthesis. Oxalate is a major byproduct in the alumina industry and using that carbon provides an opportunity to reduce Bayer liquor processing costs while producing a marketable product. Standard waste water treatment inoculum was adapted to oxalate in a mixed microbial culture (MMC) and co-fed oxalate and propionate (50:50 carbon ratio) under accumulating conditions (C/N ~120). The MMC accumulated the co-polymer polyhydroxybutyrate-co-hydroxyvalerate (PHBV) ~18.6% by weight (~55% HV) after cycling between accumulation and growth conditions. This represents a 4-fold increase in PHA yields from MMC using oxalate as a carbon source reported in the literature. These findings present evidence via GCMS, NMR and thermal analysis preformed on an isolated polymer that more useful co-polymers can be synthesised from oxalate providing further evidence that the valorization of highly oxidised waste carbon streams is possible
