After the gases get into the air, they may become clouds. Then they will on the ground with rain. It is one of the reasons for water pollution. And the wastefrom factories is put into rivers and lakes. Then we cannot have clean water for our life, even for drinking.

    Many plastic bags areeverywhere in our life. They cause the white pollution. Because of it, animals eat these bags for food. Then they will become, and some will even die.

    So try to stop pollution as soon as possible in our life.

    When the Audet family turns on the lights at Blue Farm, they are using electricity that comes from cows- cow manure(粪肥).

    Cows produce a lot of waste. One cow can create 30 gallons of waste each day. Now imagine the output of over 1,000 cows at Blue Farm. That's really a big amount.

    When farmers clean their barns, they put the waste together，and spread some of it on their fields for fertilizer(肥料). But now places like Blue Farm have a new way of using cow waste. They use it to produce electricity.

    Here's how it works: A big machine moves back and forth cleaning the barn floor. "The cows are animals of habit; they get used to it,and just lift one foot and then another to let it go by. "says Marie Audet.

    The machine pushes the manure into a big 600-gallon tank like a small swimming pool. The tank is called a digester(化粪池) because what happens there is just like what happens inside a cow: Bacteria(细菌) get to work and continue to digest the manure.

    Methane gas(甲烷;沼气) in the atmosphere is known as a "greenhouse" gas because it keeps heat just like a greenhouse does, causing our planet to warm up. That's an environmental concern. But the digester has a good result. Its gas is kept and used to power electric generators(发电机).

    At Blue Farm, the generators make enough electricity to power 400 homes. The Audet family sells the extra electricity they can't use themselves.

    Pollution is one important topic in China now. Many different kinds of pollution have increased while China is developing itself. Pollution is bad for animals and plants, and it even makes people's health. In our daily life, we can see different kinds of pollution in many places.

    Land pollution isby solid( 固体) waste, such as cans, bottles and some other things which aren't broken down. It makes the environment look very bad.

    However, air pollution is more serious than land pollution. It is much worse in cities and towns because of the fumes(废气) fromand people's activities. When people drive their cars, fumes, which are mostly made up of CO2, NO2 and SO2, are given off.