On the face of it, biofuels look like a great solution. Since plants absorb carbon dioxide as they grow, crops grown for biofuels should suck up about as much carbon dioxide as coming out of the tailpipes of cars that burn these fuels. And unlike underground oil reserves, biofuels are a renewable resource since we can always grow more crops to turn into fuel.

　　Unfortunately, it’s not so simple. The process of growing the crops, making fertilizers and pesticides, and processing the plants into fuel consumes a lot of energy. Also, because much of the energy used in production comes from coal and natural gas, biofuels don’t replace as much oil as they use.

　　Topic Green energy: biofuels

　　The history of biofuels ●Ethanol could be used as fuel a (1) _______ago.

　　●People (2)______ biofuels for a long time because of enough and cheap gasoline and diesel.

　　●Biofuels are becoming popular because of (3)_____ oil prices and environmental concern.

　　(4)_________ between biofuels and fossil fuels ●Biofuels are made from plants that are grown today.

　　●Fossil fuels are made from plants and animals buried (5)________ millions of years ago.

　　Today’s popular use of biofuels ●A variety of biofuels are being (6) ________around the world.

　　●In the USA, car fuels are generally a (7)_______ of gasoline and ethanol.

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