Cinderella's carriage

Biodegradable plastic car parts can be made from miscanthus grass

Published: Thursday 31 January 2002

-- (Credit: Illustrations: Kumar)car. A few decades back this word was synonymous with opulence and luxury -- a status symbol, which very few could afford. But with economic upsurge came changes that brought with them a plethora of environmental problems. Nowadays, many discard their cars within a span of few years, giving rise to a quandary because of their non-biodegradable nature. In the us, for example, 10-11 million cars are disposed of annually, out of which 75 per cent end up in landfills. Environmental Defense, a non-profit organisation , describes the situation as a "massive waste management problem".

The solution to this problem is fairly undemanding: own a car that's partially made of grass. Sounds fanciful, but is very much realistic, thanks to a discovery made by scientists at the University of Warwick, Coventry, the uk. According to them, a grass called miscanthus can be used to make biodegradable plastic car parts such as hubcaps and dashboards. Miscanthus , commonly known as 'elephant grass', grows quickly in arid climates to heights of nearly three metres without using pesticides or fertilisers ( Environmental Heath Perspective , vol 109, no 9, September 2001).

The plastic produced from miscanthus looks like the commonly used one. The material base is created by bacteria, which under induced stress produce starch-based plastic-like polymers that can be harvested from a bioreactor. To reduce costs, manufacturers had until recently added inert, non-biodegradable fillers such as talc or chalk to these bacterial polymers. "But these fillers do not fit well with the goal of biodegradation," says Nick Tucker, a research fellow at the university's Warwick Manufacturing Group. Substituting non-biodegradable fillers with miscanthus dust, he suggests, allows commercially viable quantities of bioplastic to be produced at a competitive price.

Miscanthus requires less drying than other plant species. It also has physical properties that enhance binding to the polymer matrix used in the filler material. "Car parts made with miscanthus would be available in the market within two to three years," claims Tucker. According to him, they would look and feel similar to the parts of ordinary cars, till they are composted in a landfill. Over time, microbes would nibble and then decompose them to carbon dioxide and water.

However, some are amused by the idea, and contend that such car parts might decompose in the garage. "Not to worry," assures Tucker. "Our goal is a biodegradable plastic that will hold up for at least 14 years -- the average life-span of a vehicle in the European Union. Moreover, these plastics will only break down in the presence of concentrated levels of bacteria, like those you find in a compost pile."

Miscanthus has got many other uses. It is already being used in Europe as a source of bioenergy. Its c4 photosynthetic pathway allows it to fix high levels of combustible carbon from the air.

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