Pollution ‘quick fix’ creates a motoring myth
Legislation on catalytic converters may be delaying 'lean burn' engines which reduce exhaust fumes by cutting fuel consumption. Enthusiasm for the expensive rhodium and platinum equipment being built into the exhaust pipes of new cars has delayed something better - reducing pollution by more efficient engines.
The expensive stainless steel canisters which turn exhaust gases into water, carbon dioxide and nitrogen are a relatively crude stop-gap. They increase fuel consumption, and foster the notion that pollution is being dealt with, while research into engines with far lower toxic emissions remains in abeyance.
Researchers have not lost sight of the 'lean-burn' goal, but having been preoccupied with meeting US and European statutes demanding catalytic converters, there has been little progress. Car manufacturers have had to meet hastily drawn-up legal requirements which may turn out second-best to a global policy of burning smaller quantities of hydrocarbon fuel.
"Catalytic converters were no more than a 'quick fix'," according to one senior motor industry engineer. "They were adopted by environmentalists when there was little else available and laws were pushed through before anybody had a chance to develop an alternative. Now they are mandatory and better solutions are not coming forward. Everybody was in such a hurry to be seen to be doing something that we have ended up with a second-best by law."
Joseph Lowrey BSc (Eng) a notable technical writer on the motor industry, describes the sort of engineering that conceals symptoms rather than curing fundamental faults as, "Inventing rubber gloves as a cure for leaky fountain pens. The truly green way to minimise pollution is to burn less fuel."
Catalytic converters do not filter impurities from car exhausts. They change the nature of the gases by chemical reaction as they pass through a honeycomb coated with the precious platinum and rhodium. This removes oxygen from the offensive oxides of nitrogen, and uses it to turn hydrogen and carbon into carbon dioxide and water. The water is fine, but too much carbon dioxide gives the world's plant life a lot of photo-synthesising to do.
The converters need to be hot to work properly, together with an engine running on a strictly chemically correct air/fuel mixture. Gas going through it must contain exactly the right proportions of oxygen molecules to burn all the hydrogen and carbon atoms.
If the mixture is rich in petrol the device will lack the necessary oxygen; if it is weak excess oxygen will remain bonded to the nitrogen as oxides of nitrogen.
Unfortunately the chemically correct mixture is not always what the engine works best on. For the highest power output it needs more fuel at full throttle, and for best economy it needs more air at part-throttle, so catalyst-equipped engines lose two ways - less power and heavier fuel consumption. They also demand expensive back-up systems to ensure they meet the regulations reliably for large mileages.
The motor industry's response has been to increase engine capacity to make up for power losses and ignore the fuel consumption penalty. Small economical engines of 1.0 litre and under have virtually disappeared. The British government's initiative to encourage small cars by imposing less stringent exhaust purity was overruled, with the result that more fuel will continue to be burned in larger engines producing more unwanted carbon dioxide.
The introduction of lead-free fuel was a necessary prerequisite for catalytic converters, whose action can be destroyed by a tankful of leaded. But removing the lead and fitting converters has done nothing to make the world less profligate with fuel. "The environmentalists had a fixation with them," remains the engineer's view. "They were encouraged by the rhodium and platinum mining lobby. Together they have delayed small efficient engines by ten years."
Make that 25.