"Naturally produced polyesters" may sound like a phrase lifted from a marketing campaign, but feed sugar to certain types of bacteria and you've got yourself a plastic production line.
That's the case with polyhydroxyalkanoate (PHA) polyesters, the two main members of which are polyhydroxybutrate (PHB) and polyhydroxyvalerate (PHV). These biodegradable plastics closely resemble man-made polypropylene. While they're still less flexible than petroleum-based plastics, you'll find them in packaging, plastic films and injection-molded bottles.
Production costs have mostly put PHA in the shadow of cheaper, petroleum-based plastics, but a little creativeness in sourcing inexpensive raw materials may make it a top choice soon. Corn-steeped liquor, molasses and even activated sludge could all supply the sugar the bacteria need to produce the plastic.
PHAs biodegrade via composting; a PHB/PHV composite (92 parts PHB/8 parts PHV, by weight) will almost completely break down within 20 days of cultivation by anaerobic digested sludge, the workhorse of biological treatment plants [source: Nolan-ITU Pty Ltd].