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鈥檚 roads.
The catalytic converters used with petrol engines don鈥檛 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.
The system they鈥檝e come up with injects a urea solution into the catalytic
converter. Urea is a nitrogen-rich organic compound that was originally isolated
from animals鈥� urine but which is now made industrially鈥攆or
fertiliser鈥攂y 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.
Advertisement
One oil company, Elf, is studying potential ways of distributing urea via gas
stations. Ray Holloway, director of Britain鈥檚 Petrol Retailers Association, says
it could cost 拢1000 to install a single urea pump on a forecourt. 鈥淲ith
profit margins as low as 1.5p per litre of diesel that represents a substantial
investment,鈥� he said. Sadly, although the toilets at service stations receive a
steady supply of urea, TNO says there鈥檚 not enough to make it worth collecting
motorists鈥� donations.