英语听力：自然百科 绿色养牛法

　　The Underhill Farm in Somerset, England, is the picture of rural tranquility. But the lush green pastures disguise the fact that farms like this are contributing to global warming. That's because just one cow can produce up to 500 liters of methane gas a day. In fact the methane produced by the manure of a typical cow translates to a little over one and half tones of carbon dioxide emissions per year, that's about the same amount generated annually by a commuter driving to and from work alone each day.

　　In a bid to turn that around, the cows here are being fed a new diet that can reduce gas and cut methane emissions by 20%. All farms have to do is feed the cows a more natural diet by mixing straw and hay with their food. But getting the cows to eat it is easier said than done. A special machine is used to cut the straw into strips which can be mixed with silage, weed, maize, soil or sugar beet.

　　What we’ve realized and seen and now scientifically proved and that’s part of our technology is that cows still actually need fiber, but in that fiber we've got to make sure that they eat it. So we process it and that’s where we have a unique mixer-wagon that will process the forage and give us the forage that we believe are the right length for the cows.

　　The diet has the added environmental benefit that for each liter of milk only around 23 liters of methane is produced instead of previous levels of about 28 liters.

　　This is a win-win situation. It’s a good way of using straw which is a low value by-product essentially of the bleaching of cereal grain for a beneficial purpose in terms of increasing food productivity, might increase milk. (At) the same time it's reducing green house gas emissions which is a serious environmental problem associated with the rearing of cattle.

　　Methane accounts for 16% of global green house gas emissions, that is far less than the most prevalent green house gas, carbon dioxide which accounts for about 75% of the global total.