Sheep urine is the latest weapon in the fight against inner-city pollution.
A purified version of the creatures' wee is being sprayed into exhaust fumes in a bid to reduce harmful emissions from a bus in Hampshire.
The technology is being trialled in Winchester and it's expected to be fitted to other buses.
The purified wee is odourless and colourless. It reacts with toxic gases and turns them into nitrogen and water, which are released as steam.
"This is a serious project," said the bus operator. "Air quality is an issue in so many towns and cities, particularly historic ones like Winchester."