A British bus company is testing a new secret weapon that it hopes will help forward its push to cut its polluting emissions -- sheep urine.
The company, Stagecoach, has fitted a bus in the southern English city of Winchester with a tank containing the animal waste, which is sprayed into exhaust fumes to reduce emissions of harmful nitrous oxides.
Andrew Dyer, managing director of Stagecoach South, said: "It is a novel way of reducing pollution but we believe it will work."
"There is nothing to worry about -- we won't be asking passengers to leave a sample and we won't be carrying a resident sheep at the back of the bus," he said.
The scheme is backed by the local Hampshire county council as part of an effort to reduce pollution.
The bus carried its first passengers last month.
The urine is collected by the fertilizer industry from farmyard waste and refined into pure urea, which is then sold on to be used in the green engine technology. Ammonia from the urea reacts with nitrous oxides in the exhaust fumes and converts them to nitrogen gas and water, which is released as steam.
Dyer said the idea was no laughing matter.
"I got some laughs when I told a transport conference in Birmingham that sheep urine could be the key to cleaner vehicles but it is becoming a reality," he said.
"This is the latest in green technology and we believe it will help make our cities better places to be for the public," he said.
New EU regulations to be introduced in October next year will bring tighter restrictions on emissions, he said.
The urea-injection system was developed by UK engine manufacturer Cummins.
Andy Wren of Hampshire county council said: "We are running many anti-pollution initiatives, but the sheep urine idea gets the attention."