Recycling PET To A Higher Value Plastic

Polyethylene terephthalate (PET), the common plastic used to make drink bottles, can now be recycled into a higher value biodegradable polyhydroxyalkanoate (PHA) plastic, according to an international team led by Kevin E. O'Connor of University College Dublin (Environ. Sci. Technol., DOI: 10.1021/es801010e). PET is one of the world's highest volume polymers, produced on a scale of billions of pounds per year. But only about 23% of PET bottles in the U.S. are recycled each year, in part because of the relatively high handling costs and the low value of the downstream products. O'Connor and colleagues are trying a different approach: Pyrolize PET by heating it to 450 °C under low-oxygen conditions to produce solid, liquid, and gaseous fractions. The liquid and gaseous fractions can be burned to produce electricity, whereas the solid fraction (72% by weight) is terep hthalic acid that can be used as a feedstock for the bacterial production of PHAs. Certain bacteria are known to naturally synthesize PHAs as a means of energy storage, and they have been genetically engineered to produce PHAs commercially (see page 21). The researchers screened bacteria in the soil surrounding a PET production facility and demonstrated that three Pseudomonas strains they found can produce PHAs from the terephthalic acid pyrolysis fraction.