Spare the lawn and save the planet

HERE'S THE perfect excuse if you want to avoid mowing the lawn this afternoon. Cutting the grass is bad for the planet.

Your spouse won't believe you, but it is true - the US government says so. The aroma of newly cut grass, it claims, is not so much a scent, more the stink of a nasty chemical cocktail.

Scientists from the US National Oceanographic and Atmospheric Administration and the University of Colorado have discovered that cut grass gives off an immediate "burst of volatile organic compound emissions ... followed by a second, more intense emission lasting for several hours when the cuttings start to dry".

So chemicals released by mowing help cause smog. And putting the cuttings on the compost heap makes things even worse.

The scientists believe that when the grass is "wounded" by the mower blades it resorts to chemical warfare - releasing large amounts of a dozen pollutants, including meth-anol, acetaldehyde, acetone and butanone.

Those volatile organic compounds form an important constituent of the summer smog which increasingly shrouds cities, and Professor Ray Fall, Colorado University's professor of chemistry and biochemistry, says mowing the lawn "certainly contributes to it". Grazing animals don't help either. "Every time even a cow chomps the grass you get these little surges," he adds.

The scientists say harvesting crops adds 1.6 million tons of acetone to the atmosphere a year, compared with eight million tons released naturally.

Some volatile organic compounds can cause cancer, but Professor Fall is quick to scotch any hint of a health scare. "It just doesn't seem likely that the smell of freshly mown grass is toxic," he says, rapidly disposing of an even better excuse for reluctant mowers to remain in their armchairs.