When Ren Gnther's car is running low on fuel, he doesn't drive to the nearest filling station. The taxi driver goes to a local snack bar.

He collects used frying fat in a large container, takes it home, filters the brown concoction and then pours it straight into the tank of his Mercedes C220 Diesel.

Collecting the old oil takes some effort, but it means he can drive his car rather cheaply - for practically nothing.

Is used cooking oil a fuel alternative? Even on the basis of the most generous calculations, the republic's entire supply of old cooking oil would not suffice to replace 1 per cent of the diesel fuel used in Germany. Nevertheless, the recyclers are tapping the pulse of the age. After all, car drivers aren't the only ones beginning to wonder what will actually happen when the crude oil - and therefore diesel and petrol - finally runs out.

Although the oil price has again fallen slightly since its all-time high of 70 dollars a barrel at the end of August 2005, oil remains more than twice as expensive as it was only two years ago.

And a price recovery is nowhere in sight. Experts are warning, the years of permanently cheap oil are over. At the same time, a growing number of geologists believe that worldwide oil extraction will soon "inexorably fall."

To make matters worse, the burning of fossil fuels is also one of the main causes of global warming - and is therefore responsible not only for hurricanes, but also for rising sea levels and for droughts in Southeast Europe and elsewhere.

Experts are already celebrating "green gold," fuel from the fields that can be grown over and over again.

Meanwhile, they are also putting their faith in hydrogen, an energy source that is theoretically available in ample quantities and is also non-polluting.

However, more efficient energy use is the first step, especially for car drivers, say the analysts at Deutsche Bank and the experts of the Umwelt-Sachverst ndigenrat, a specialist environmental commission.

This scenario will indeed hit no other group as hard as the millions of vehicle users. Almost half of the 114 million tons of petroleum products that were processed in German refineries last year flowed into vehicle fuel tanks.

The next largest item - heating oil - provides heat in roughly one third of all German homes.

However, whereas it has long been possible to build houses that can be kept comfortably warm without any heating, road traffic - 55 million cars, trucks, buses and motorcycles - would come to a standstill without petrol and diesel.

So far, only 35,000 motor vehicles are powered by natural gas - and bio-fuel does not meet more than 2 per cent of the demand for conventional petrol and diesel.

Nevertheless, the nearer the end of the oil era draws, the more avidly car drivers are clutching at alternatives.

Workshops that adapt vehicles to run on vegetable oil are doing a magnificent trade; Kai Lorenz of Aachen-based conversion firm Unicar is registering some 50 enquiries a day alone. The cost of the engine modifications is more than 2,000 euros (US$2,540).

Although Germany already leads the world when it comes to biodiesel, there are limits to its development. According to the Federal Finance Ministry, no more than 3.7 per cent of Germany's fuel needs could be met by domestic rapeseed production.

However, the costs of producing ethanol are still so high that production would be uneconomical. Even the importation of cheap ethanol made from Brazilian sugar cane would not enable this alternative to oil to achieve a breakthrough.

Accordingly, great hopes are currently being placed on the second generation of renewable fuel, BTL (biomass to liquid).

It is not made merely from the seeds, but from entire plants. Initially, they are gasified - everything from roots to leaves - and then synthesized into a liquid fuel, a complicated process. Yet the energy yield is great and the fuel produced meets the highest standards.

New alternatives

Saxon company Choren Industries is already conducting production trials of a fuel with the brand name SunDiesel. Mercedes and Volkswagen have successfully tested it.

Because the chemical composition of this synthetic fuel can be precisely adapted to the requirements of the propulsion system of the future, a cross between the diesel and petrol engine, engineers are already enthusing about the "designer fuel".

What is more, it produces almost no more carbon dioxide than the plants originally absorbed from the earth's atmosphere before they were processed into fuel.

As a result of forecasts of this kind, others also hope to be able to supply the motoring community in the future - Werner Mller, for example. In the face of dwindling oil and gas reserves, the former economics minister and current chairman of RAG, the Essen-based energy group that also owns coal producer Deutsche Steinkohle AG, attaches "growing importance" to coal liquefaction.

Although German coal is still too expensive for the process, in China, for example, the first modern coal liquefaction plant is already planned to begin operating in 2007.

Environmental and energy experts are putting a damper on the hopes for coal-based fuel, primarily because of the significant environmental burdens.

However, they also admit that no other oil substitute has a real chance in the short term - except, perhaps, for natural gas.

Although natural gas-powered automobiles are a little more expensive than diesel or petrol vehicles, consumers benefit from lower running costs because natural gas has been exempted from fuel taxation until 2020 in Germany.

The natural gas reserves stored in the earth's crust will last a little longer than global oil reserves. Furthermore, natural gas does less harm to the environment than conventional fuels when burned. Its molecules contain fewer carbon and more hydrogen atoms.

So far, however, the dawn of an era of clean and plentiful hydrogen has remained just a splendid idea. A hydrogen car has never been presented at a car show and there are very few public hydrogen filling stations.

"Energy needs time, decades rather than years," says Carl-Jochen Winter, professor emeritus of energy and engineering. Because the alternatives will either be technologically underdeveloped, too expensive or too scarce, vehicles will have to continue using familiar substances, fuels refined from oil, for some time.

Perhaps, however, they will consume much less of it. After all, conventional engines still have enormous potential for efficiency improvements, for example, by reducing engine size - a process referred to in modern German as "downsizing" - or enhancements in gear design.

Source: Deutschland magazine

(China Daily 09/13/2006 page22)