When enthusiasts talk of sustainable development, the eyes of most people glaze over. Ther

e is a whiff of sack-cloth and ashes about their arguments, which usually depend on people giving up the comforts of a modern economy to achieve some debatable greater good. Yet there is a serious point at issue. Modern industry pollutes, and it also seems to cause significant changes to the climate. What is needed is an industry that delivers the benefits without the costs. And the glimmerings of just such an industry can now be discerned.

That industry is based on biotechnology. At the moment, biotech's main uses are in medicine and agriculture. But its biggest long-term impact may be industrial. Here, it will diminish demand for oil by taking the cheapest raw materials imaginable, carbon dioxide and water, and using them to make fuel and plastics.

Plastics and fuels made in this way would have several advantages. They could accurately be called "renewables", since nothing is depleted to make them. They would be part of the natural carbon cycle, borrowing that element from the atmosphere for a few months, and returning it when they were burned or dumped. That means they could not possibly contribute to global warming. And they would be environmentally friendly in other ways. Bioplastics are biodegradable, since bacteria understand their chemistry and can therefore digest them. Biofuels, while not quite "zero emission" from the exhaust pipe (though a lot cleaner than petrol and diesel), would be cleaner overall even than the fuel-cell technology now being touted as an alternative to the internal-combustion engine. That is because making the hydrogen that fuel cells use is not an environmentally friendly process, and never will be—unless it, too, uses biotechnology.

All this will, in the end, depend on costs. But these do not look unfavourable. Already, the price of bioplastics overlaps the top end of the petroleum-based plastics market. Bulk production should bring prices 'down, particularly when the raw materials are free. Meanwhile, ethanol would be a lot easier to introduce than fuel cells. Existing engines will run on it with minor tweaking, so there is no need to change the way ears are made. And since, unlike hydrogen, it is a liquid, the fuel-distribution infrastructure would not need radical change.

The future could be green in ways that traditional environmentalists had not expected. Whether they will embrace that possibility, or stick to sack-cloth, remains to be seen.

According to the author, applying biotechnology to industry

A．has brought about sustainable development.

B．proves to be nothing but an imagination.

C．will deprive most people of modern comforts.

D．contributes to the environmentally sound development.