The growth in international markets for autocatalysts has been driven by efforts to legislate for cleaner air. Johnson Matthey has played a vital role in the improvement of air quality through the manufacture of autocatalysts for cleaning vehicle exhaust emissions from petrol and diesel fuelled cars and continuously regenerating traps (CRTs) for treating emissions from heavy duty diesel vehicles.

Johnson Matthey has been active in assessing the impact that our autocatalyst products can have on air quality, with particular regard to emissions of carbon monoxide (CO), oxides of nitrogen (NOx), volatile organic compounds (VOCs) and particulates (PM10). The following study demonstrates the reductions in these emissions that should be achieved in the UK through the use of autocatalysts, CRTs and improved engine technology.

Using Government publications and data obtained direct from the National Atmospheric Emissions Inventory (AEA Technology) and the Department of Transport, estimates have been made of the vehicle emissions that would have been expected in the future without the benefit of autocatalyst technology. The reductions in these emissions due to autocatalysts have been estimated by deducting predicted values of emissions from these figures. The predicted values were obtained using complex mathematical models to take into account the continued introduction and upgrading of catalysts.

Emission reductions to 2025 are shown graphically for the four main pollutants and as a total saving in figure 5. Each graph shows the estimated actual emission and the "engine-out" emission i.e. the emissions without autocatalysts and traps. The blue area represents the emission savings.

It should be borne in mind that pollution reductions may be brought about by means other than catalysts e.g. by changes in engine design or fuel or by Government initiatives to promote the use of public transport. Such changes could have an effect on the actual contribution made by autocatalysts.