From Newscientist:
A chemical originally obtained from urine might be able to reduce emissions of nitrogen oxides from diesel engines by up to 80 per cent. A diesel truck has set off from a lab in the Netherlands to test the idea as it trundles around Europe's roads.
The catalytic converters used with petrol engines don't work for diesels because of the high concentrations of oxygen in the exhaust gas, say researchers at the Dutch national laboratory TNO. But new European emissions regulations coming into effect in 2005 demand heavy NOx reductions from diesels.
So TNO, Dutch truck maker DAF, and American catalytic converter manufacturer Engelhard have been trying to tackle the problem.
Going organic
The system they've come up with injects a urea solution into the catalytic converter. Urea is a nitrogen-rich organic compound that was originally isolated from animals' urine but which is now made industrially - for fertiliser - by reacting ammonia with carbon dioxide.
Inside the converter, heat from the exhaust gases convert the urea into ammonia, which reacts with the harmful nitrogen oxides in the catalytic converter, transforming them into harmless nitrogen and water vapour. Trucks equipped with 900-litre diesel tanks will need an extra 50-litre tank for the urea solution, says TNO.
One oil company, Elf, is studying potential ways of distributing urea via gas stations. Ray Holloway, director of Britain's Petrol Retailers Association, says it could cost £1000 to install a single urea pump on a forecourt.
"With profit margins as low as 1.5p per litre of diesel that represents a substantial investment," he said. Sadly, although the toilets at service stations receive a steady supply of urea, TNO says there's not enough to make it worth collecting motorists' donations.
Cheers,
Ian
