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Thursday, 13 February, 2003, 00:26 GMT
Winding road to cleaner streets
![]() Congested Britain suffers bad air pollution
![]() We can engineer our way out of pollution, if not away from the congestion which makes it so bad. People of the next generation will use fuels so much cleaner than ours they will wonder how we survived. But - at least to begin with - we shall find it expensive to make the change. There are a number of substitutes for petrol and diesel fuel: biodiesel, electricity, ethanol, hydrogen, methanol, natural gas, propane, and solar energy. Biodiesel is a renewable fuel made from vegetable oils or recycled restaurant fats. It reduces serious air pollutants such as particulates, carbon monoxide, and hydrocarbons. Alternative land-use Blends of 20% biodiesel with 80% petroleum diesel can be used in unmodified diesel engines, or biodiesel can be used in its pure form, though that may require engine modifications.
Fuel cell vehicles use electricity produced from a reaction when hydrogen and oxygen are combined in the fuel cell "stack". The cells produce no pollution and leave only two by-products: heat and water. Ethanol is an alcohol-based fuel made from grain crops, such as wheat, that have been converted into sugars. Ethanol produced from biomass - trees and grasses - is called bioethanol. This is an option that might appeal to farmers looking to use their land to grow a saleable crop, despite the European farm surpluses. Methanol is another alcohol fuel, most of it produced from natural gas, though coal or biomass are suitable as well. Here already Supplies of hydrogen are virtually unlimited as it can be produced from cheap and renewable sources - water, for one. Either alone, or mixed with natural gas, it can power a car. But its optimum use is as fuel for fuel cell vehicles.
Propane or liquefied petroleum gas (LPG), a by-product of natural gas processing and crude oil refining, is already widely available, and produces fewer emissions than conventional fuels. Finally, there is solar energy, captured by photovoltaic cells. It does work, but no major manufacturer is developing it at the moment. Hedging the bets All these fuels hold promise for the future, though all cost much more than conventionally engined vehicles at the moment. For most, there is a further cost barrier for engine makers, as well as for the people buying the cars: the need to invest in new fuel production, storage and distribution methods. One stepping stone to the future is available right now, in the form of hybrid vehicles, using both petrol and electric propulsion. They can achieve worthwhile emission reductions, and most are able to use their electric motors during coasting and braking to generate electricity to top up their batteries.
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