human
I've been hearing about the new "green" cars that run on alternative fuels. Is it true that they're better for the environment?
assistant
Yes, some of them are. Alternative fuel vehicles use a variety of sources like biofuel, electricity, and hydrogen to power their engines. Biofuel is made from plant matter such as vegetable oils or animal fats, which can be produced in a sustainable way without depleting natural resources. Electric vehicles are powered by energy stored in batteries, which produce fewer emissions than internal combustion engines. Hydrogen fuel cells use hydrogen gas to generate electricity and water vapor, making them one of the most efficient forms of transportation.