Drive your car into the ground. (Materials Science).

If you really want to impress your green friends, what better way than by driving a car that's made partially of grass? The car looks and feels like any other until it's composted in a landfill. Then, over time, microbes snack on remnants of the aging hulk and decompose them to carbon dioxide and water.

If that sounds farfetched, consider the activities of a group of scientists at the University of Warwick in the United Kingdom. Research fellow Nick Tucker and his colleagues in the university's Warwick Manufacturing Group have discovered that a grass called Miscanthus can be used to make biodegradable plastic parts such as hubcaps and dashboards. Miscanthus, also called "elephant grass," is truly a crop for the future: Europeans burn it in power plants as a source of bioenergy, and the stems can be fermented and distilled to produce an ethanol fuel. It grows quickly in arid climates to heights of nearly 12 feet without pesticides or fertilizers, and it produces up to 8 tons of biomass per acre.

Part of the grass's appeal lies in its C4 photosynthetic pathway, which allows it to fix high levels of combustible carbon from the air. "That's one of the reasons it's attractive as a fuel crop," Tucker explains.

Biodegradable materials are another use for this hardy perennial. Don't expect your Miscanthus car to look like a thatched hut, though. The plastics produced by Tucker's group look perfectly ordinary. 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, nonbiodegradable fillers such as talc or chalk to these bacterial polymers. "We felt these fillers didn't fit well with the goal of biodegradation," says Tucker. Substituting nonbiodegradable fillers with Miscanthus dust, he suggests, will allow commercially viable quantities of bioplastic to be produced at a competitive price.

Miscanthus requires less drying than other species. Also it has physical properties that enhance binding to the polymer matrix used in the filler material. Another example of a C4 plant that could possibly be used in the making of biodegradable materials is wheat straw.

Tucker and his university colleagues are working with a group of 20 British farmers who grow Miscanthus and who have created a company called Biomass Industrial Crops Limited to exploit the plant's multiple uses. Commercially available car parts made with Miscanthus should be available within 2-5 years, he says.

The current emphasis on car parts stems in part from a European Union directive, issued in 2000, that holds European manufacturers financially responsible for end-of-life disposal of their products beginning in 2003. Natural biodegradation could go a long way toward helping manufacturers meet these targets, says Charles Griffith, automobile project director at the Ecology Center, a nonprofit organization based in Ann Arbor, Michigan.

American automobile manufacturers don't face a similar mandate, but the problem of landfill space for expired cars in the United States is still acute: 75% (by volume) of the country's 10-11 million vehicles disposed of annually wind up in landfills. The nonprofit group Environmental Defense describes the situation as a "massive resource-consumption and waste-management problem."

That may be true, but would anyone buy a car that might decompose in the garage? "Not to worry," says Tucker. "Our goal is a biodegradable plastic that will hold up for at least fourteen years, which is the average life-span of a vehicle in the European Union. These plastics only break down in the presence of concentrated levels of bacteria, like those you find in a compost pile."