Biodegradable Plastic From Waste Methane

PHA Producing Bacteria
Scanning electron micrograph of methane-eating bacteria used to create biodegradable PHA plastics. Credit: NSF/Mango Materials

Researchers from Stanford University are making biodegradable plastic from waste methane. PHA or PolyHydroxyAlkanoate is a group of biodegradable polymers produced by bacteria. These bacteria convert carbon from sugar via fermentation into PHA. The bacteria are harvested, dried and the pellets of PHA removed to be molded into plastic.

One problem with this process is the use of agricultural land and foodstuffs is required to feed the bacteria. The Stanford researchers are bypassing this by feeding the bacteria methane to use as a carbon source. Methane is much less expensive than sugar and can be easily collected from waste at landfills, water treatment plants and livestock farms. This has the added bonus of lowering the environmental impact of a greenhouse gas.

The researchers have started a company called Mango Materials to pursue this research. They have produced high yields of PHA with waste methane from biogas and wild bacteria on the laboratory scale. Mango Materials believe their process can be ramped up to the commercial scale. Their current plan is to use the biogas waste methane produced at an average waste water treatment plant. They estimate they can produce more than two million pounds of PHA per year based on their current yields.