Unless you have been living under a rock for the past decade, chances are you have heard about biofuels and how they are going to change our energy supply forever. The truth with biofuels is often a far stretch from the hype published on TV and magazines across the nation. Everyone seems to be searching for the “silver bullet” energy solution, especially when it comes to transportation, but unfortunately, that solution has not yet been discovered, and may never be.

Biofuels are a group of fuels that can be produced by the byproducts of living organisms. The major biofuels are ethanol, butanol, biodiesel and vegetable oil, biogas or methane, producer or wood gas, and biomass or wood. Some can be grown as crops, but most require processing before they get into your fuel tank. On the other hand, if used effectively, biofuels can not only be good for the environment but may also make the services of car hire ireland and other world-class companies more effective and perhaps less costly. Each major biofuel has its pros and cons, and for the DIYer, some are definitely more attractive than others. So let's take a look at these new world-savers and examine just how they can fit into our integrated sustainable lifestyles.

Comparison Chart >>

Ethanol
Ethanol is a relatively old biofuel, having its origins in alcohol production. Basically, ethanol is produced by fermenting a feedstock, like sugar or starch to create a “mash” of water, ethyl alcohol, and various byproducts. The mash is then distilled or filtered to extract the ethanol from the water mix. Because the mash is usually only 7-15% ethanol, large amounts of energy are needed for distillation. The remaining ethanol is then filtered again to remove the last bits of water before being mixed with gasoline, like in E85, or used directly in your vehicle. Modifications must be made to the vehicle to be able to run ethanol, as the compression ratio, timing, injection, and burn rates are different. This makes ethanol complicated to use.

Butanol
Butanol is similar to ethanol, but is produced in a slightly different way. Instead of using yeasts, like with ethanol, butanol production involves using bacteria to ferment the feedstock into butyric acid. The acid is then processed by a second bacteria into butanol. Butonal production is difficult, mainly because the concentration levels are hard to achieve beyond 2.5% in the water/butanol solution. This makes distillation a tough process, require lots of external energy to harvest the remaining butanol. Some new technologies are being developing to extract the butanol using filters and sieves to avoid the additional energy input for distillation. Butanol can be used directly in any gasoline engine without modification, making it an attractive biofuel alternative to ethanol.

Biodiesel
Biodiesel and vegetable oils have been used as alternative fuels since the 1930's. In fact, the original diesel engine ran on peanut oil. Diesel engines are different than gasoline engines, in that they use compression to ignite the fuel instead of a spark, although modern version may use spark and/or glow plugs to aid the ignition process. Diesels enjoy a higher efficiency because of this and are attractive as work vehicles because of their available low-speed torque. Vegetable oils are derived from oil plants like canola (rape), sunflowers, peanuts, and soybeans. The seeds are pressed to extract the oil, and then the oil is processed through filters and chemicals to remove free fatty acids and odors. The oil can then be used directly in an engine with some modifications and issues, or can be processed further to remove the glycerin and add an alcohol (methanol) to increase energy content and storage lifetimes. Oils coagulate at low temperatures, created starting problems in cold weather, and this is one of the reasons they are usually processed into a biodiesel for use. Oddly enough, hydrogenated oil was invented for this reason, to prevent the solidification of the oils in cold weather,m but after WWII, the market for the new oil was lost, so the production of hydrogenated oils went towards food products. Oil crops need a lot more land to grow than alcohol crops, with oil production in the 100-200 gallons per acre versus 500-1000 gallons per acre for ethanol or butanol, although oil contain more energy per gallon with 120 kBtu vs 80-110 kBtu for the alcohols. The advantage lies in the fact that oils don't require additional energy for distillation.

Biogas
Biogas and/or methane is a very attractive fuel for off-grid homesteads because of its ease of production. It can be made from ANYTHING that was alive at one time, including dead animals, waste agricultural products, manure, and other organic wastes. It has a lot energy content compared to liquid fuels because it is a gas. Compressing methane is not advantageous for the small farm because of the energy and cost involved. Because of this, methane is best used for stationary applications, like generators, stoves, water heaters, and anywhere that you could use natural gas or propane. Biogas has an average energy content of about 750 Btu per cubic foot of gas at atmospheric pressure (not compressed). It has been produced for years in China and India as a source of energy for small farms, and techniques for the production of the fuel are well tested. Methane can be mixed with diesel or other fuels as well to provide a hybrid fuel source.

Wood gas
Wood gas or Producer gas, is probably one of the oldest gaseous fuels in use. It is basically hydrogen and carbon monoxide and can be produced from anything that has carbon, hydrogen and oxygen. Production involves incomplete combustion to slightly oxidize the carbon and produce a smoke or exhaust that can be used in an Internal Combustion Engine. It is most used in mobile applications for tractors or trucks. Wood is the preferred feedstock, but any organic substance can be used, and even tires and plastics can be used as well. Slight modifications to the engine are necessary, but usually, the engine maintains it ability to burn other fuels. Production requires a gasifier unit that turns the feedstock into the producer gas and a charcoal. The gas is then cooled and filtered before entering the engine. Producer gas is actually a very efficient use of wood, and is said to me more than 3 times more efficient that burning wood. Engines do notice a reduction of power by about 30-40%.

Wood and biomass can be used as a fuel source simply by burning them, but the preferred method is aerobically composting. This differs from biogas production in that very little methane is produced, and rather, large amounts of heat are produced instead. These systems are most commonly used to heat homes and water and are little more than pipes running through a compost pile. Some advanced systems place the compost in a insulated container to greatly increase efficiency and reduce heat loss. Biomass has an energy content of about 5 – 8 kBtu per pound, depending on feedstock.

Biofuel Comparison Chart

Fuel	Energy	Feedstock	Production	Processing	Usage	PROs	CONs
Ethanol	71k1	Jerusalem Artichokes 900 gal/acre	Yeast Fermentation	Distilation and filtering	Engine Modifications	Large Productionper acre, relatively easy to handle	Additional energy required for processing and engine modifications
Butanol	105k 1	Milk Whey, Jerusalem Artichokes 900 gal/acre	Bateria Fermentation, 2 stage	Distilation and filtering	No mods required	No mods, easy to handle, fits current infrastructure	Requires additional input for processing, 2 stage production
Biodiesel	119k 1	Sunflowers, castor beans, oil crops, waste oil	Press	Deacidification and removing odors and/or glygerin	Slight mods for straigh veggie oil	High energy content, easy to produce, slight engine mods	Low yield per acre, some processing using chemicals
Biogas	750 2	Anything Organic and wastes from other biofuels	Anaerobic Composting (Digesting)	Basic Filtering	Gas Carborator	Easy to produce, many feedstocks, can be joined with other processes	Low Energy Content per unit, hard to transport
Wood Gas	200 2	Biomass, wood, plastics, tires	Gasification and Destructive Distillation	Filtering and Cooling	Gas Carborator, timing	Eay to produce, many feedstocks, slight engine mods	Low energy content, hard to transport as gas, requires production unit onboard
Wood Biomass	8k 3	Anything organic	Combustion	none	na	Many feedstocks, low capital investment, very easy to maintain, easy to grow	Low energy output per unit, heat is only output, bulky

^{1 - Btu per gallon}

^{2 - Btu per cubic foot}