Plastic from Grass: A Biodegradable Polymer

Researchers at Metabolix in Cambridge, Massachusetts, are genetically engineering switchgrass to produce a biodegradable polymer that can be extracted directly from the grass.

At present, Most of the plastics which are sold worldwide come from petroleum and they are not suitable for our healthy life. In many countries Plastic Shopping bags are banned for it's harmful effect to the environment. So, a biodegradable polymer can be more helpful and more useful in every sphere of our life and researchers are trying to get a good solution. Researchers at Metabolix in Cambridge, Massachusetts, are genetically engineering switchgrass to produce a biodegradable polymer that can be extracted directly from the grass.

Metabolix already sells such a polymer, but it’s produced by bacteria that feed on plant sugars in expensive fermenters.

A plant-based process, which could use crops grown on marginal lands, would require less equipment.

Metabolix estimates that it could ultimately sell its plant-based polymers at less than half today’s prices. Whereas today’s end products are niche items like biodegradable plastic shopping bags, more widely used types of products and packaging could then become economical.

Two decades ago, MIT scientists discovered metabolic genes that allow bacteria to naturally produce a polymer called PHA — but that requires bacteria feeding on plant sugars in expensive fermenters. A plant-based process would require less equipment and only marginal land.

To realize their plants-to-plastics vision, Metabolix scientists are now working on inserting those genes, along with others that regulate growth, into plants:

1. First, they coax the plant to produce and store a type of PHA called PHB, used to make injection-molded products that house electronics.
2. Months later, industrial processes extract PHB from cut and dried grass.
3. There are also chemical production methods: extract PHB using solvents or use heat to convert PHB into crotonic acid which could be used as feedstock for polymers.
4. They think leftover grass could be burned as a biomass energy source.

The switchgrass must produce 10 percent of its weight in PHB to be economically competitive:
The company has already nearly doubled the PHB content in switchgrass, from 1.2 percent in 2008 to 2.3 percent last year, including 7 percent in the leaves.

Sources: smartplanet.com, technologyreview.com
Image:    smartplanet.com