Forquitesometime,scientistshavebeenfindingwaystopowerca...

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For quite some time, scientists have been finding ways to power cars and other machines with natural fuel made from cooking oil and even water. Now researchers in Argentina say they have come up with a way to create fuel from another unlikely source—cow burps(嗝)

Cows have bacteria in their stomachs to help them digest their food. As they break down the food, those bacteria create methane, which the cows burp out when they belch (打嗝). Methane is a powerful greenhouse gas. It traps heat in the atmosphere and in turn can cause Earth’s temperature to gradually increase. Methane is at least 20 times more effective at trapping heat than carbon dioxide, another gas released into the air as pollution.

Researchers have tried to find ways to get cows to produce less of the gas. One method they’ve come up with is reducing the amount of corn and soy (大豆) in cows’ feed.

But scientists from Argentina’s National Institute for Agricultural Technology have taken a different approach. Instead of trying to reduce the amount of methane cows produce, they thought, why not turn it into fuel? After all, each cow releases 250

to 300 liters of pure methane a day. That’s enough to keep a refrigerator running for 24 hours.

To collect a cow’s burps, the scientists fix a plastic tank onto the animal’s back and connect it through a tube to the cow’s stomach. They then put the burps through a process that separates the methane from the other gases. “It’s the same as having natural gas,” says Guillermo Berra, head of the institute’s animal physiology group.

“As an energy source, it’s not very practical at the moment, but if you look ahead to 2050, when fossil fuel reserves are going to be in trouble, it is an alternative,” says Guillermo Berra.

Turning the methane into fuel can also help reduce the amount of greenhouse gases produced in Argentina, which has around 51 million cows. In 2006, the United Nations called livestock(牲畜) one of the most serious near-term threats to the global climate—more dangerous to Earth’s atmosphere than all the world’s cars and trucks combined.

28. According to the text, methane is produced_____.

A. by the bacteria in cows’ stomachs

B. by the bacteria in cows’ food

C. when cows are eating food

D. when cows suffer from stomachache

29. By reducing the amount of corn and soy in cows’ feed, researchers want to _____.

A. turn methane into fuel

B. get more methane from cows

C. keep cows strong and healthy

D. reduce the methane cows produce

30. What is Paragraph 5 mainly about?

A. How to turn a cow’s burps into fuel.