Jim Sprott: Oxygenated fuel a reliable, cheap way to clean up exhaust gases

The Government has done the correct thing in discarding the proposed testing of vehicle exhaust emissions as part of warrants of fitness.

New Zealand should learn from the experience of British Columbia's AirCare programme.

In the Canadian province, all petrol-fuelled vehicles must be tested at an AirCare station annually, at $28 a test.

For a vehicle travelling 10,000km a year, with a fuel consumption of 9 litres per 100km, this compliance cost equates to about 3c a litre of petrol. If a vehicle travels 5000km a year, the cost a litre doubles to 6c.

For vehicles with exhaust gas catalytic converters, the ongoing replacement cost of these items adds an impost of some 10c to 12c a litre on the fuel cost.

Thus exhaust gas quality regulation would cost about 12c to 15c a litre of petrol for an average car with an exhaust gas catalyst. The results of this programme are far from impressive.

These are high prices to pay for a questionable result, especially when improved exhaust gas emissions can be achieved far more reliably at a fraction of these costs by adopting the oxygenate (ethanol) option.

Fuel of this type is used widely throughout North America, where it is often known as gasohol. New Zealand, especially in Auckland and other population centres, should follow the lead of many American states, where oxygenated petrol is mandatory. (Petrohol would seem to be a good name for this product here.)

The British Columbia AirCare programme provided graphic proof of the efficacy of gasohol in improving exhaust-gas quality. The provincial Government had installed first-class exhaust-gas testing equipment with a computerised data base providing the expected exhaust-gas quality for every make and model of vehicle.

When AirCare was introduced, a considerable number of vehicles failed the test, and the owners were required to make costly ($400 to $1000) repairs.

But then it was found that if vehicles hitherto using petrol which had failed the test were then operated on gasohol (the Mohawk brand containing 10 per cent ethanol), many easily passed, and the sales of Mohawk gasohol jumped by 35 per cent.

But many vehicle owners (whose vehicles had passed the AirCare test using gasohol) then reverted to the cheaper petrol and consequently enhanced harmful exhaust emissions. This naturally detracted considerably from the benefits expected from the AirCare programme.

The point is that improved exhaust-gas quality is far more reliably achieved, and at considerably lower cost, by mandating the use of oxygenated fuel, rather than by attempting to regulate exhaust quality.

The use of ethanol as an oxygenate in petrol is now permitted under the New Zealand petroleum products specifications regulations, up to a maximum proportion of 10 per cent by volume.

Ethanol is the chemical name for the compound generally known as ethyl alcohol.

An oxygenate in the context of fuel technology is an organic substance which contains oxygen in the molecule, is miscible with hydrocarbon fuels and is a fuel in its own right.

The function of an oxygenate is to promote the controlled and complete oxidation (burning) of a hydrocarbon fuel, such as petrol, and higher boiling hydrocarbon fuels, such as diesel.

This is achieved when all carbon in the fuel has been oxidised to carbon dioxide and all hydrogen oxidised to water.

Oxygenates greatly help this by providing oxygen to the hydrocarbon while in the most intimate contact, namely in solution.

This initiates the combustion, which then proceeds more smoothly and completely than in the absence of an oxygenate.

Furthermore, petrol in New Zealand may contain up to 45 per cent of aromatics, an appallingly high proportion by international standards.

Aromatics do not burn well in high-speed engines and thus contribute greatly to unburned hydrocarbons, a main cause of atmospheric pollution.

Aromatics are added to petrol to improve octane rating. But ethanol is superior to aromatic hydrocarbons as an octane-enhancer, and thus high-octane petrohol can be produced with a much lower proportion of harmful aromatics.

Ethanol is not a suitable oxygenate for diesel fuels. But the new generation of bio-diesel or higher alcohols provide excellent results when incorporated into diesel fuel.

Bio-diesel is a mixture of the methyl esters of long-chain "fatty" acids, now produced by highly sophisticated synthesis from vegetable oils.

New Zealand chemical engineer Dr Richard Gapes is an international expert in this important technology, having perfected a means of "trans-esterification" of vegetable oils while doing research in Vienna.

This technology would be ideal for commercial use in Australia and New Zealand.

* Dr Jim Sprott is an Auckland consulting chemist.