The introduction of unleaded petrol in Australia in July 1985 was a necessary element of an overall long term national strategy to control motor vehicle pollution and to prevent serious adverse consequences for public health and the environment. The reasons behind this controversial decision are examined along with its impact on those parties involved, but with particular emphasis on the petroleum refining industry.
The need for unleaded petrol was not only to reduce lead emissions to the atmosphere but also 'to reduce other noxious vehicle exhaust emissions that are considered a potential health and environmental problem. The latter emissions are controlled by means of a catalytic converter installed in the exhaust system with unleaded petrol required because of the poisoning effect of lead on the catalyst, rendering it ineffective.
The subject of lead in the environment and especially lead in petrol continues to raise issues of uncertainty and risk, with certain aspects of these explored in this paper. Lead is added to petrol by refiners because it is the lowest cost method of boosting octane levels in order to reduce knock in spark ignition engines. The alternatives to lead addition are more expensive octane enhancing compounds or more severe refinery processing which involves the use of significant additional energy as well as decreasing the yield of gasoline from crude oil consumed.
This paper draws attention to the variety and complexity of the effects that the unleaded petrol legislation has on the refining industry. There will be increased pressure on octane upgrading processes which will require additional refinery capital investment. The processing options available for octane enhancement are discussed with the choice depending on economics and process unit availability, i.e. the selection of options is refinery specific. To illustrate the magnitude of costs involved in this choice, an economic analysis of processing options available for an existing refinery is presented as a case study.
It can be concluded that the introduction of unleaded petrol was a much needed move towards the elimination of a potential health hazard which should benefit society as a whole now as well as for future generations. Since there is limited evidence that these emission controls have caused an improvement in city air quality, it is recommended that a post audit be carried out in the years to come. This will determine the actual benefit in economic terms of the investment of community financial resources in unleaded petrol and catalytic converters.