solar power

wind power

global warming

flex fuel

Good things also have a down side

Ethanol is a possible alternative to fossil fuel because it has a cleaner emission. It means ethanol will give off less pollution in the atmosphere. Another advantage to ethanol is that it has a higher octane rating. This means that ethanol can handle more heat in the engine before knocking occurs. Knock is when fuel is ignited before the spark plug gets to detonate the fuel. The bad side to ethanol is the amount of energy available compared the the same amount of fossil fuel. This means that fuel economy decreases. Cost of producing ethanol is more expensive than fossil fuel as a result, federal tax incentives reduce the price to be able to compete with regular gasoline.

http://auto.howstuffworks.com/how-e85-ethanol-flex-fuel-works.htm/printable
http://www.eere.energy.gov/cleancities/blends/ethanol.html

Fuel cell

Fuel cell is a type of alternative fuel which uses hydrogen. The Hydrogen is used by a energy conversion device called a fuel cell to produce energy. The way fuel cell can produce energy is by converting chemical energy in hydrogen into energy. The only by product is heat and water. Fuel cell has a membrane that only allows protons of the hydrogen atom to pass, but not the electron. The electron has to go around the membrane by going through a circuit. As it goes through a circuit, electricity is produced. At this point, it can power electrical devices. After it has gone through the circuit, the electron bonds with the oxygen atom at the other side along with the proton. This seems to be a perfect solution to fossil fuel, but its cost and durability are problems when developing this technology.
http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/doe_h2_fuelcell_factsheet.pdf