Innovation: Tests sow the seeds of plastic revolution

OILSEED rape plants under test at Durham University could represent an important stage in the quest to grow plastic.

The plants were bred by Zeneca Seeds, which has already shown that oilseed rape can be genetically engineered to produce a bioplastic called polyhydroxybutyrate (PHB).

Now Zeneca is working with Durham to develop plants that will produce the plastic only in their seeds, rather than the whole plant, and to increase the yield from 0.1 per cent of the plant weight to an economically viable 1 to 10 per cent.

Zeneca estimates that plastic produced this way will cost pounds 1 per kilogram, about twice the cost of conventional plastics. The great attraction is that the engineered plastic comes from a renewable resource and is biodegradable.

Tony Fenton, manager of the project at Zeneca Seeds, says estimates of the market at pounds 1 per kg indicate that the whole of the UK's existing oilseed rape acreage would be needed to meet demand.

Zeneca has proved that consumers are prepared to pay a premium for these materials - with Biopol, claimed to be the first fully biodegradeable commercial plastic. Production of Biopol is now up to 1,000 tons a year, from 300 tons when the plant at Billingham on Teeside opened in 1990. At its launch, Biopol sold for pounds 10 per kg and was used mainly for packaging expensive cosmetics. Biopol now sells at pounds 7 to pounds 12 per kg, depending on grade, and economies of scale will eventually bring the price down to pounds 3.

Biopol is made in fermenters by bacteria, which convert sugar into PHB. The bacteria produce PHB naturally as an energy store, like humans accumulate fat. Genes from the plastic-producing bacteria are inserted into oilseed rape to induce it to make PHB.

Mr Fenton says Zeneca decided to work on oilseed rape because it has a high content of a substance called acetyl coenzyme A, a building-block both for the oil which the plant produces naturally and for PHB. The work being carried out with Durham University aims to switch off one of the genes which controls the production of oil from acetyl coenzyme A, allowing the inserted bacterial genes to convert it to PHB.

The plant still produces some oil in its seeds, otherwise they will not germinate. Given this, Zeneca has developed a modification to the oilseed rape extraction process, allowing first oil and then plastic to be extracted. This modification is being patented.

Zeneca also plans to breed plants which produce plastics with a variety of other properties. It is working with the University of Indiana in the US to modify oilseed rape metabolism to produce more flexible plastics and with the University of Gottingen in Germany to introduce different bacterial genes to produce a rubbery plastic.

The handling properties of bioplastics are different from those of conventional plastics, but David Barstow, manager of Zeneca Bioproducts, says the experience Zeneca is building up in using Biopol in existing moulding machines will be relevant to plastics derived from oilseed rape.

Mr Fenton says field trials should take place within four years, but on present plans it will be 2006 before the seeds are available to farmers.