From Richard T. Corbett
Something seems not quite right with your piece on a microwave emissions
converter
(7 October, p 11).
It might eliminate pollutants such as unburnt hydrocarbons and soot particles—and
so much the better if it turned them to diamond—but I fail to see how a practicable
system could reduce carbon dioxide emissions.
To do this, the car as a whole—engine plus converter—would have
to oxidise the hydrocarbon fuel to carbon and water vapour, and the carbon
produced would weigh around three-quarters as much as the fuel used. This
corresponds to a lump of diamond around the size of a breeze block for every
tankful of petrol.
How big a reaction vessel would be needed to hold such quantities without
clogging? Having to carry around the weight of the vessel and the accumulating
diamond would surely compromise the car’s fuel efficiency. And wouldn’t the
car’s fuel efficiency be lower to start with, since the reaction to carbon gives
less energy than the reaction to carbon dioxide?
Rachel Nowak writes: The industrial diamonds would not be made in the car.
The carbon powder would be removed by a filter and then taken to a factory to
make the diamonds. However, Corbett is correct to point out that the weight of
carbon—albeit powder, not diamond—could be a problem. The designers
get around this by connecting the microwave emissions converter to the engine so
that it only operates when the car is idling. This would cut down the worst sort
of emissions in cities, and also ensure the car doesn’t end up accumulating too
much carbon. In fact, the filter would only have to be changed roughly every
10,000 kilometres.
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The car’s fuel efficiency wouldn’t be affected in the manner that Corbett
suggests because the device works on the exhaust, not the combustion part of the
engine (for more information see:
www.swin.edu. au/iris/smog/Microwave-Smog%20Buster_files/v3_ document.htm).
Broxburn, West Lothian
