Your imagination is the only limit when it comes to dreaming up applications for environmentally friendly plastics made from renewable materials. Plastic tractor parts, a soya bean oil-based replacement for timber, and even rubberised plastic armour plating for military tanks have all been developed.

It is a science that combines the latest aerospace industry manufacturing techniques with dirt-cheap raw materials that come straight from the field.

The results are plastic materials that are low-cost, renewable and biodegradable, and a new "sink" that can take carbon dioxide out of the atmosphere.

"We can grow the molecules we want in the field and combine the molecules we want in the laboratory," states Prof Richard Wool of the University of Delaware.

He is the director of the ACRES lab, Affordable Composites from Renewable Resources, based in the university's Department of Chemical Engineering. Although he has worked in the US for many years he is originally from Cork and did his undergraduate degree at UCC.

He has built a research team at the University of Delaware that aims to develop products from renewable resources and is filing patents on new processes and products.

"We should be interested in renewables because we will run out of petroleum in 70 years and gas in 80 years. If we can come up with environmentally friendly technologies that are as good as what is available now it would make for a better world. A pound of beans is a pound of fossil fuel equivalent saved."

Prof Wool literally takes to the field when he needs raw materials for his work.

He uses wheat straw, soya bean oil, flax fibres, linseed oil, all of which can be chemically changed and processed into plastic composites. "We design all of the molecules using oils and molecules that are made from plants. We control all the chemistry and physics," he says.

"It is a new, blossoming field in the US. It was really being pushed along by President Clinton," he adds, following an executive order in August 1999 giving $300 million (€353 million) to help fund research into materials made from renewable resources.

While genetic engineering will help to improve the level of control applied by the chemists, it is not an essential part of the process, Prof Wool says. The vegetable oil molecule is very stable and can be heated to high temperatures as in cooking, but won't "polymerise" or become a plastic.

It can however be chemically altered by adding epoxy or acrylic, which causes the polymer chains found in plastics to form. The great advantage is that the chemists can dictate the polymer architecture and control the reactions, leading to a predictable plastic. The renewable raw material also means that there is an alternative to petroleum-based plastics.

The key, however, is the molding and manufacturing technologies applied to these new materials, skills that have come from the aerospace industry. Aircraft and space vehicles use composites made from layers of different substances combined and then molded into a particular shape.

These techniques can be applied to the renewable materials, opening up a startling range of options, for example, the rubber military tank. "The tank of the future is going to be a lightweight composite armoured vehicle," Prof Wool states.

One project involved developing an unusual polymer architecture that included grains of rubber. "We made fantastic ballistic impact-resistant tank parts", he says, prepared as a 15-layer, 2.5cm-thick composite armour that did not include metal.

The tractor and harvester parts included sheets made using aerospace-industry moulding technology and advanced chemistry. Wheat straw was formed into a mat and then coated with the soya bean oil-based resin, leaving a flexible sheet with the consistency of leather. When heated and formed in the mold, it hardens into a rigid, tough and inexpensive plastic that can substitute for metal sheeting.

Other materials can be made by pouring liquid resins over the reinforcing fibre-matting in a static mold, with curing being accomplished chemically. This is the approach applied in Prof Wool's single-part, plastic house roofs.

A roof is like a jigsaw of parts that just pop apart in heavy wind. His answer is a monolithic roof built something like a boat hull. No matter how the wind blows it can't break up.

In this case a mold of board or styrene is put in place and the fibre mat held in position. The soya or vegetable oil-based resin is then poured in and cured. The great advantage is the materials are effective and are very cheap, he says.

He adds that it would be possible to build an entire home using low-cost oils and waste fibres taken from the fields. "There is good polymer science in taking materials we only knew how to cook with several years ago and turning them into composites," he says.