ENGINEERS at a North-East engine manufacturer have discovered a new way of helping the environment - and there is an inexhaustible supply of the vital ingredient.

The company is experimenting with sheep urine in an effort to cut the harmful emissions being pumped into the atmosphere by buses.

The plan is to fit buses with tanks containing urea, which is injected into exhaust fumes.

The ammonia in the urine converts harmful nitrous oxides into nitrogen and water.

The urine is collected by the fertiliser industry from farmyard waste and refined into pure urea, which is then sold for use in buses.

The system was developed by Cummins, of Darlington, and has been adopted by transport firm Stagecoach. The system is being tested on a bus in Winchester, Hampshire, and if it is successful it will be used on a whole fleet of buses.

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 as they leave the vehicle, and we certainly won't be carrying a resident sheep at the back of the bus.

"This is the latest in green technology and we believe it will help make our cities better places to be for the public."

Cummins marketing manager Steve Nendick said: "It is a quite simple idea, but it is very effective.

"The engine also burns less fuel, which is very good news for the world's resources."