If you thought cars and planes were the enemy when it comes to the environment, it could be time to think again.

There's a new baddie in town and he's got four furry legs.

Flatulent cows have been targeted in a new move by the Government to cut atmospheric methane levels.

Because of their four-chambered stomachs, cows fart up to 600 litres of methane every day, which is enough to fill 40 party balloons.

Methane is a much more powerful greenhouse gas than its more common counterpart carbon dioxide, with one kilo of methane warming the Earth 23 times as much as the same mass of CO2.

Environment secretary David Miliband warned of penalties for farmers of livestock which fart too much at the annual Oxford Farmers' Conference in Oxford last week.

This proposed tax on cattle and their, ahem, emissions could affect around 700 farmers in East Sussex.

Chris Todd from Brighton and Hove Friends of the Earth said: "Surely we need to focus on the real issues, don't we? Cows fart in China as much as they fart over here, I suspect, but really we have to tackle what humans are doing to the planet and start tackling that as soon as possible.

"Methane is highly powerful as a greenhouse gas but, quite honestly, how do you come up with a sensible suggestion to stop that? We should be worrying more about transport emissions than about cows farting."

One local farmer who could be affected is Richard Connell, owner of Lower Roundhurst Farm. He says "It has to be slightly tongue in cheek!

We have an organic farm which we think contributes in a good way to the environment but the side-effect is methane. It's like almost every other issue in the world - there's a good and a bad side.

"If we didn't have the animals, we wouldn't have the methane but if people didn't fly aeroplanes we wouldn't have a lot of pollution. As with many things you have to get a sensible balance."

The National Farmers' Union says agriculture is responsible for 35 per cent of all UK methane emissions and 86 per cent of that is released by livestock farming.

However, it's not only breaking wind that's a problem.

According to New Scientist magazine, gas released from flatulence is far less of a problem than that of belching and about 20 per cent of all global methane emissions is thought to be from sheep, cow and farm animal burps.

A spokesperson from the union said "The NFU is committed to ensuring farming is part of the solution to climate change, rather than being part of the problem.

"We strongly support research aimed at reducing methane emissions from livestock farming.

However, the greenhouse gases emitted by farming need to be balanced against the vital role the industry plays both in carbon sequestration and in providing climatefriendly alternatives, such as bio-energy in its various forms, to fossil fuel energy sources."

There are many natural sources of methane, including wetlands and volcanoes, but a United Nations report showed just over half of all methane emissions were man-made.

The worst culprits are energy use, landfill and domestic livestock.

Cattle farming is widespread throughout Sussex and there are about half a million cattle in the South East of England. Another 560 farmers in West Sussex could also be hit by the "fart tax".

There are a lot of factors which influence methane emissions from cattle and scientists have even produced a burping "vaccine".

The quality of feed and type of carbohydrate in the animals' diet all have an effect. The vaccine, developed by Australian company CSIRO, tricks the animals' immune systems into producing antibodies to methanecausing bacteria in their stomachs.

Trials showed that not only were the bacteria surplus to the animals' digestion but also that cutting the methane somehow boosted animal growth.

In January last year, a study on sheep at the Rowett Research Institute in Scotland showed a 70 per cent decrease in methane formation.

Richard Connell comments, "We look after our land well. We've never done it but if we totted up our environmental balance sheet, I'd like to think cow farts are the least of our worries. We look to other sources before we start attacking cows."