These days, the watchword is bio-fuels derived from organic material. The two most common biofuels are bioethanol and biodiesel. Bioethanol produced from starch or sugar crops in the same process that gives homemade liquor. Yeast ferments sugar to ethanol which is distilled to remove water. Biodiesel is made from vegetable oils or animal fats.
The United States has been to increase the production of ethanol from corn, but can not replace the imported oil. World corn prices have already increased the grain is diverted from the food chain in the fuel tank. Corn is difficult to grow a crop, requiring high inputs of fertilizers and pesticides. According to some estimates pessimistic, it requires about as much energy to grow corn and convert it to ethanol is ethanol produced by the end.
On the other hand, there are a lot of excitement about the technologies for producing ethanol from cellulose. Cellulose, the main structural components of plants, consisting of long chains of sugars. An effective process to convert cellulose into sugars would enable its production of ethanol from straw, crop waste, wood chips, and perhaps even scrap cardboard and paper.
is another alternative source of energy for locomotion. Hydrogen can be burned or converted into electricity by fuel cells. Prototype hydrogen cars exist, but paradoxically, the hydrogen is used to feed normally derived from natural gas. Hydrogen can be made by splitting water, but this requires a significant input of energy. Storage and transportation of hydrogen are also problems to solve, if hydrogen cars are not to be practical.
Battery-electric cars continue to improve. The biggest challenge in making them commercially viable to develop a battery to power the vehicle over long distances, can be recharged, and is not expensive. A popular hybrid car around the restrictions on drums, combining gasoline and electric power. Furthermore, during braking, the electric motor acts as a generator of hybrid cars to recharge the batteries.
Hydrogen and fuel cells are basically a means of storing energy from other sources, so that it can be transferred to the vehicle. Other methods of energy storage are possible. For example, energy can be pumped into the air in a pressurized tank without a car. After the expansion of the air moves piston engine. Emissions from cars are clean, but, of course, actual emissions will depend on how the energy used to compress the air was produced. Air Car Prototype exists, but research continues in order to market the idea. The biggest challenge is to create a car that can achieve a variety of useful run on a single tank of compressed air.