Martin Ince outlines the increasingly influential views of Ernst von Weizsacker, who says we can produce more while using less resources

Ernst von Weizsacker has a thing about yoghurt. Not just any old yoghurt: strawberry yoghurt. If he is right, the three billion strawberry yoghurts eaten each year by him and his fellow Germans could point the way to a world in which we could be richer than we are - but enjoy our affluence with far less damaging environmental impact.

Von Weizsacker's institution, the Wuppertal Institute for Climate, Environment and Energy, became famous throughout Germany in 1993 when one of its researchers, Stefanie Borg, showed that the yoghurt, its ingredients and packaging, travelled 8,000km in the course of being manufactured and delivered. This, despite the yoghurt being a German product with only small inputs from Poland and the Netherlands. Something like the distance from Wuppertal to the midwest of the United States was eaten up in truck journeys for milk, strawberries, packaging and other materials.

According to von Weizsacker, better ways of doing things are obvious. Strawberries, milk and other ingredients can be produced locally, while packaging can be recycled. Only one part of the yoghurt, the aluminium lid, is best made in bulk and shipped, because of the energy intensiveness of aluminium production. And there is an even better way of making yoghurt: cut out distribution altogether by reviving home production, an especially attractive option for "downsizers" who prefer leisure time to cash.

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The lesson, says von Weizsacker, is that there are few technical problems about reducing the resources that go into producing the things people want. The barriers are psychological, or have to do with the need to use existing investments rather than scrap them.

Along with Amory and Hunter Lovins, who run the Rocky Mountain Institute in Colorado, one of the world's premier energy think-tanks, von Weizsacker has just produced a new book, Factor Four, in which yoghurt is one of many examples illustrating ways of getting twice as much wealth from half the resources we use today.

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Von Weizsacker cites work done by Amory Lovins on cars, which shows that it is feasible to go far beyond the few per cent improvement in fuel economy which car-makers plan for the next few years. At present, about 1 per cent of the fuel burnt in a car engine goes to push the driver along the road, a total which ultralight cars using hybrid electric and liquid fuel engines can beat easily. Doing hundreds of miles to the gallon, an ultralight car could cross the US on a tank of petrol. But the depressing part of the story, as von Weizsacker sees it, is that even the modest improvements in fuel economy seen in US vehicles in the last decade have had no effect. Instead, they have been cancelled out by Americans choosing to drive massive off-road vehicles instead of standard cars.

While von Weizsacker favours some green taxes, he prefers to advocate ways of making companies behave more rationally by giving them a stake in change. An example is the chemical company Dow, which makes solvents for dissolving grease. These chemicals are carcinogenic and the German government has tightened conditions for their use almost to the point of making them illegal. Dow Germany responded by improving the technology for transporting and storing the chemicals to avoid evaporation losses, and, more creatively, switched from selling solvents to leasing them.

According to Von Weizsacker, this sort of move helps retrain engineers to emphasise resource productivity rather than labour productivity, the achievement they are now taught to maximise. But he does not hide the fact that he also wants resources to cost more. Again, the best idea is not to double prices overnight but to allow them to rise at perhaps 5 per cent a year in real terms, and to make it known that this trend will continue.

At the same time, cash could be saved, he says, by eating into the vast sum (he mentions $700 billion a year) spent on subsidising damaging activities like unsustainable farming, water use and transport. Von Weizsacker expects a victory for green economics in December in Kyoto, Japan, when the international meeting to set the next century's emissions of climate-altering greenhouse gases takes place. He thinks that this meeting will be one of the first at which the "win-win" approach triumphs - the view that cutting the emission of greenhouse gases can enhance rather than damage economies.

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According to von Weizsacker, the technologies that can make the current rich world's way of life less damaging can also allow economic growth in the poor world to be less threatening. He was founding president of the technical university of Kassel, Germany, and recalls attending the World Rectors' Conference. He says: "I asked the rectors from the developing world what they were proudest of: they all talked about things like their new robotics centres. Since robots replace cheap labour with expensive capital, this struck me as an odd priority. I suggested they get a chair of energy efficiency instead, but this just made them look at me suspiciously."

As von Weizsacker sees it, the changes we now need are less sweeping than those that have already transformed many industries in recent decades, especially the arrival of microelectronics. This time, change will cross established orthodoxy, for example by making the chemical industry, not the steel-makers, the main supplier of car bodies.

But he warns that Europeans and Americans may have to find out the hard way. "Samsung (the Korean multinational) is already using Factor Four in its thinking," he says, and seems to have got the message faster than its rivals in Europe and the US.

Factor Four by Ernst von Weizsacker, Amory B Lovins and Hunter L Lovins is published by Earthscan at Pounds 15.99.

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