oomsday prophets estimate that at the present rate of consumption
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the world's supply of fossil fuel from known fields could be exhausted within 40 years. If that happens no amount of demonstrating about fuel duty rebates or privileges for essential users will get a single truck moving to its destination—Britain's 400,000 HGVs will rust in hauliers' yards up and down the country.
Fortunately there are alternatives to oil—some available now, others just around the corner and a few which are 20-30 years down the pipeline. This latest crop should arrive just as the last oil wells are drying up.
LPG (liquefied petroleum gas) and natural gas are perhaps the most readily available of these with manufacturers like lveco, MAN and Volvo producing gas-powered engines. Behind them come electric motors; diesel/electric hybrids; alcohol-based fuels like methanol and ethylene; hydrogen and fuel cell technologies; and "bio-fuels" made from crops.
LPG
This clean, efficient fuel enjoys several advantages over diesel or petrol. There is believed to be enough gas under the North Sea to last long after its oil reservoirs have been drained dry. LPG is virtually emission free so it attracts a far lower rate of duty at the pumps and typically retails at around 42p/lit. Fuel tank sizes remain the same as with diesel.
LPG's principle disadvantage is, for the time being, a lack of available outlets—and a lack of CVs ready to run on gas, particularly over 3.5 tonnes.
Natural gas
Together with LPG, natural gas should be seen as the main alternative fuel for HGVs, according to Jonathan Murray, head of Transport Programmes at the Energy Saving Trust. Like LPG, it produces almost no particulate emissions with much less NOx than diesel. The other advantages of natural gas include its price, long-term availability and ease of distribution to the pumps. "There is no reason why the gas supply should not be hooked up to the normal gas supply network," says Murray. "Once the capital costs involved in linking up the filling stations have been done, the cost of delivery of the gas would be almost nothing."
The main disadvantages concern the energy content or density of the Fuel. To provide the sort of range needed from an HGV, natural gas has to be compressed (CNG) or chilled into a liquid form (LNG). The increased pressure in the tank (up to zoo bar) demands either steel or carbon fibre construction. But the weight of a steel tank would eat into payloads, while a carbon fibre tank would cost about £5,000. Whichever material is chosen, the tank must be able to withstand a direct impact and deal with the risk of fire.
"Fire would heat the gas to a point where it would burst even a fully strengthened tank," says Murray. "To get round the problem, the tanks are fitted with safety valves which allows the controlled escape of gas in fire situations."
Then there is the cost of converting an engine to run on gas. At current prices this works out at around £15,000 for a tractor. The government offers grants of up to 75% through its Powershift programme, but the cost to the operator would still be substantial. A further disadvantage is that a product of natural gas is methane, the most destructive of the six global warming gases identified at the Kyoto Summit in 1997. And while the latest gas engines are now fitted with a methane catalyst to stop methane emission, there are still natural gas engines on the road without catalysts.
Despite the disadvantages, Merton Council runs its refuse fleet on CNG, and Sutton Council, fiercely proud of its green credentials, boasts 68 gas vehicles.
Diesel-electric hybrids
The concept of the hybrid engine is a simple one. A small diesel engine powers the vehide and charges its batteries. When more power is required than can be delivered by the diesel, the electric motor assists. In the urban environment, where pollution concerns are at their greatest, the vehide is powered only by electricity. MAN and Mercedes are looking at this technology but it is still at the prototype stage. Sutton Council uses 19 electric cars and vans for urban services like meals on wheels.
Alcohol
The most Lorin-non alcohol fuels are methanol and ethanol. "There is a serious disadvantage to alcohol," says Geoffrey Day of the ETA. "[fit comes into contact with water it is almost impossible to extract it. This problem is likely to occur when there are spillages, either on the forecourt or at the scene of an accident and the alcohol gets into the water supply. It is a question of what risks you are prepared to take."
Hydrogen/fuel Cells
The use of hydrogen as a fuel source is not expected to be commercially viable for perhaps 30 years. At the root of the problem is the production of sufficient hydrogen. There is also a problem with the storage of the gas.
However, fuel-cell technology, in which hydrogen and oxygen come together to produce an electric current, is comparatively well advanced and will probably be ready in about five years' time.
The likely option for hauliers will be to carry bottled hydrogen that will react with oxygen drawn from the air to provide the electrical power source. The water (from the hydrogen and oxygen) will be used as an engine coolant.
Igo-fuels
Although a number of engines have been produced to run on fuel obtained from various crops, concerns have been expressed at the practical and political levels, not the least of which is the vast areas of arable land that would have to be given up to produce sufficient crops for fuel production.
For details of experimental synthetic diesel, see CM 5-ir October, page 40.