Abstract: The various embodiments herein provide a system and a method of synthesis of thermoplastic biopolymer such as poly-?-hydroxy butyric acid wherein the activated sludge and synthetic waste water are acclimatized in a sequential batch reactor. The diazotrophs are reacted with CO2 in a secondary carbon source reactor. The acclimated activated sludge and the prepared diazotrophs are enriched for production of poly-?-hydroxy butyric acid in a polymer production reactor. The produced polymer is purified and collected. Herein, CO2 is used as a secondary carbon source and is produced from a CO2 generator. The diazotrophs used is azotobacter spp. Chorochome. The system comprises of a sequential batch reactor, a secondary carbon source reactor and a polymer production reactor.