Environmental life cycle comparison of polyhydroxyalkanoates produced from renewable carbon resources by bacterial fermentation

Large-scale fermentative production of poly(3-hydroxybutyrate-co-5mol% 3-hydroxyhexanoate) [P(3HB-co-5mol% 3HHx)] from soybean oil as sole carbon source is simulated using a recombinant strain of Ralstonia eutropha harboring a polyhydroxyalkanoate (PHA) synthase gene from Aeromonas caviae. Its production costs, life cycle inventories (LCI) of energy consumption and carbon dioxide emissions from the cradle-to-factory gate are calculated and compared with the counterparts for microbial production of poly(3-hydroxybutyrate) [P(3HB)] from glucose as sole carbon source. In addition, the values of bio-based polymers are compared with those of petrochemical polymers. Annual production of 5000 tonnes of P(3HB-co-5mol% 3HHx) is estimated to cost from 3.5 to 4.5 US$/kg, depending on presumed production performances. Similar scale production of P(3HB) from glucose is estimated to cost 3.8-4.2 US$/kg. In contrast to the comparable production costs between P(3HB-co-5mol% 3HHx) and P(3HB), life cycle inventories of energy consumption and carbon dioxide emissions favor the former product over the latter, reflecting smaller inventories and higher production yields of soybean oil compared to glucose. The life cycle inventories of energy consumption and carbon dioxide emissions of bio-based polymers are markedly lower than those of typical petrochemical polymers. (C) 2003 Elsevier Science Ltd. All rights reserved.