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Making Biodegradable Plastic From Grass

Plastics are used widely in our day to day lives. They are organic polymers of high molecular mass and also contain other substances. Plastics are derived from petrochemicals and are not biodegradable. Usually, biodegradable plastics are plastics that can be decomposed by bacteria or any other organisms.

All the plastics sold today in the market are not biodegradable causing many environmental problems. With the increasing negative effects of plastic, the need for biodegradable plastic usage has increased. To make it available, researchers at Metabolix in Cambridge, Massachusetts genetically engineered switchgrass to produce plastic that can be extracted from the grass.

indexThis discovery could lead to a new path transforming the economics of biodegradable polymers. Though, Metabolix sells such a polymer produced by bacteria that grow on plant sugars in costly fermenters, a plant-based process would require less equipment using crops grown on marginal lands.

Due to its low cost of making, Metabolix estimate that it can sell its plant-based polymers at a low price in-turn making biodegradable plastic shopping bags and other products more economical.

The scientists found out that the metabolic genes that allow bacteria in soil to naturally produce a polymer known as PHA. It took them decades to optimize metabolic systems in the bacteria to produce good amounts of PHA. And working out the same thing on plants is even more difficult as it is more complex and time-consuming process.

But Metabolix plant scientists did not give up, they are working again to insert genes and other substances that influence plant growth. These genes are inserted into various types of plants including sugarcane, switchgrass and camelina.

Focusing on switchgrass, they are persuading the plant to produce and store a specific type of PHA, known as PHB. Plant can store PHB in its tissues and it can be used to make injection-molded products such as electronics housings etc. The company is also trying hard on chemical production steps. These steps include extraction of the PHB using solvents and also a thermal method of converting the PHB into a chemical called crotonic acid.

After the PHB is extracted or the crotonic acid which is used as a feedstock for polymers is produced, the grass remains can be burnt as a biomass energy source. This energy source is capable of producing lower net carbon emissions more than fossil fuels.

The company estimates that the grass must produce 10 percent of its weight as PHB to be in competition with other sources of biodegradable plastics. If that happens, we can get biodegradable plastic and its products at a low cost. It has successfully doubled the amounts of PHB in switchgrass, from about 1.2 percent to 2.3 percent in just 4 years.

This process too, would produce some carbon emissions as growing and harvesting plants requires fossil-fuel-based fertilizers and fossil-fuel-powered machines. Though, it requires much deeper study, researchers as of now, predict that it would be cleaner than producing plastic from fossil fuels.

This plants-to-plastic vision is by Metabolix’s chief scientific officer, Oliver Peoples, a former MIT research scientist and his colleague Anthony Sinskey, an MIT biology professor. If this process is practiced widely in future, the demand for grass harvesting may increase leading to the raise in biodegradable plastic which in-turn saves environment from many bad effects of regular plastic.

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