One of the most important principles of the strategy to reduce the use of petroleum fuels is to implement ‘drop-in’ substitutes. These are typically liquid fuels that can be used in place of gasoline or diesel fuel with little or no vehicle modification.
While some are controversial, and non are perfect, they are still important as part of a three-pronged strategy: 1) Increases Efficiency, 2) Increase Conservation, and 3) Implement drop-in substitutes.
Here are the top alternative fuel sources, listed in order of importance.
1. Biodiesel. This alternative fuel source is made from animal fats and vegetable oils. The most common sources of biodiesel are restaurant grease and soybean oil. Waste fats are less expensive than using crops to produce biodiesel, but they also require more initial refining. Biodiesel can be used in most diesel engines without much (or any) modification, up to about 20% biodiesel / 80% diesel mix. Some modifications may be required when using concentrations greater than 50% biodiesel or in cold climates. The big problem with biodiesel is the use of food crops and/or farmland to produce it.
2. Ethanol/Cellulosic Ethanol. Ethanol is produced by the fermentation of sugars, either from starch crops such as corn, wheat, and barley, but also cellulosic sources like trees, switch grass, corn stalks, grass clippings and other ‘waste’ materials. Ethanol can be used in most gas vehicles up to nearly 20% without any problem, but higher concentrations required conversion. Ethanol has created the largest controversy when it comes to biofuels and for good reason–noone really thinks that using a food crop (corn) to produce fuel is a good idea. However, cellulosic sources could be a huge win in the future.
3. Natural Gas. This alternative fuel source is made from crude oil or gas wells. It is considered to be a good alternative due to its domestic availability and clean burning qualities. The use of natural gas provides lower emissions and better performance than gasoline or diesel. One of its greatest advantages is the reduction of carbon monoxide which is abundant in diesel and gas fueled vehicles. The only problem with natural gas is the required conversion, the availability of refueling stations, and the necessity of carrying a cylinder of explosive fuel in your trunk.
4. Electricity. Electric cars are gaining popularity all of the world. When compared to diesel or gasoline, powering an electric car from the grid (even when ‘dirty power’ is used) is still cleaner. Additionally, it centralized air pollution to one point source which is easier to regulate and manage. The great thing about having an electric car is that it can be charged from home with a solar electric system, which means no emissions at all. Electricity still has limitations as an alternative fuel source, namely range and availability of plug-in stations.
6. Hydrogen Fuel Cells. This alternative fuel source produces electricity from the reaction of oxygen to water and air, and oxidation. Fuel cells are still out there since hydrogen must be produce from electricity anyway — might as well drive a standard electric car.