Biodiesel is a fuel derived from a process called esterification of renewable feedstocks such as animal waste fat, soybeans and vegetable oil. To make biodiesel, the base oil is put through a process called "esterificiation". This refining method uses an industrial alcohol (ethanol or methanol) and a catalyst (substance that enables a chemical reaction) to convert the oil into a fatty-acid methyl-ester fuel (biodiesel). Biodiesel can be used in diesel with little or no modifications and burns with less sulfur and aromatic emissions. In 2006, 250 million gallons of B100 were sold. By 2008, that number had nearly tripled to 700 million gallons.
Biogas is gas produced from the breakdown of organic matter, such as sewage, biomass, and municipal solid waste. It employs a technique called anaerobic digestion in which certain kinds of microbes work to break down organic matter in airtight containers (digesters) and convert it to hydrocarbons. The biogas produced in a digester is actually a mixture of gases, with methane and carbon dioxide making up more than 90 percent of the total. Biogas typically contains smaller amounts of hydrogen sulfide, nitrogen, hydrogen, methylmercaptans and oxygen.
Additional hydrocarbons, such as propane, can be produced using digesters that heat water to supercritical temperatures by applying intense heat and pressure to catalyze the fermentation of sugars found in corn and sugarcane. Biogasses and biopropane have a wide variety of applications, from residential heating to industrial processes, and when compressed for use as a transportation fuel.
Butanol is an energy dense pure alcohol formed by fermentation from corn, grass, leaves, and other biomass. Having double the amount of carbon as ethanol, which equates to a 25 percent increase in harvestable energy (BTU's), the molecule has an energy content similar to that of gasoline. Butanol can be burned without modifications in an existing gasoline engine and is said to be less corrosive than ethanol. Also, when the fuel is burned it emits no NOX, SOX, or carbon monoxide and its CO2 output is considered to be "green".
Under U.S. Environmental Protection Agency (EPA) regulations, biobutanol can be blended as an oxygenate with gasoline in concentrations up to 11.5 percent by volume (i.e., the EPA considers blends of 11.5% or less biobutanol with gasoline to be "substantially similar" to pure gasoline). Blends of 85 percent or more biobutanol with gasoline are required to qualify as an EPA alternative fuel.
Ethanol is an alcohol made by fermenting the sugar and starch components of crops including wheat, corn, sugar cane and other feedstocks. Ethanol can be produced using enzyme digestions, fermentation, and distillation and is the most commonly utilized biofuel in the world, especially in Brazil and the United States. Nearly all of U.S. gasoline contains ethanol in a low-level blend to meet the renewable standard requirements under the Clean Air Act. Ethanol is also increasingly available in E85, an alternative fuel that can be used in flexible fuel vehicles.
Ethyl teritary butyl ether (ETBE) is an oxygenated gasoline fuel component and ether that is derived from ethanol and isobutylene. ETBE's properties of high octane, low boiling point and low vapour pressure make the fuel a good gasoline blending component for refiners addressing octan and bio-component needs. ETBE presents a practical, efficient development for biofuels as a cleaner burning crude-alternative.
Methyl tert-butyl ether (MTBE) is a chemical compound that is manufactured by the chemical reaction of methanol and isobutulene. MTBE is most exclusively used as a fuel additive in motor gasoline to replace lead as an octane enhancer, and was being produced at over 200,000 barrels per day in 1999. Oxygenated fuel was mandated in the Clean Air Act Amendments of 1990 (CAA) due to the fact that oxygen helps gasoline burn more completely, reducing harmful tailpipe emissions.
Advanced Technologies such as Algae or pyrolysis plan to make a range of green crudes from either woody biomass or algae. These crudes would then be processed in standard refining technology which is readily available to convert these renewable crudes into renewable gasoline, jet or diesel.
Today many Advanced biofuels technologies plan to make renewable diesel which is the same as petroleum derived diesel fuel. These companies will use a range of difference feedstocks similar to biodiesel and some will have technologies which utilize refining technologies now in place. Petro-diesel is commonly defined as any liquid fuel utilized in diesel engines with the most common being fractional distillate or separation of petro-fuel oil for the production of diesel. Diesel fuel is produced from petroleum and from various other sources. The resulting products are interchangeable in most applications. Diesel-powered cars generally have a better fuel economy than equivalent gasoline engines and produce less greenhouse gas emission. Their greater economy is due to the higher energy per-litre content of diesel fuel and the intrinsic efficiency of the diesel engine.
Similar to renewable diesel, many advanced biofuels companies plan to make a renewable jet fuel from a variety of feedstocks and technology applications. Almost all of those who plan to do so will make jet fuels which will meet the current ASTM specifications for commercial or military use. Jet Fuel is a kerosene-based fuel that may be tailored from many different types of hydrocarbons to run aviation-turbine power units.
Renewable gasoline or synthetic gasoline is on the agenda of several advanced biofuels companies. Some will convert sugars to gasoline while others will use cellulosic materials and gasification. Current gasoline, also referred to as petrol, is a petroleum-derived liquid mixture which is most widely used as the fuel of choice in internal combustion engines. It consists mostly of aliphatic hydrocarbons from the fractional distillation of petroleum, enhanced with iso-octane or the aromatic hydrocarbons toluene and benzene to increase its octane rating. Small quantities of various additives are common, for purposes such as tuning engine performance or reducing harmful exhaust emissions. Some gasoline mixtures available in the market today also contain low blends of ethanol as a partial alternative fuel.