Biofuels 101: Biofuels Journal Springer
Biomass can be turned directly into liquid fuels, known as “biofuels,” to help meet transportation fuel needs, unlike other renewable energy sources. Ethanol and biodiesel are the two most popular forms of biofuels in use today, both of which are from the first generation of biofuel technology.
BETO is working with industry to produce next-generation biofuels made from non-food (cellulosic and algae-based) resources. BETO has spent the last decade focusing on cellulosic ethanol and investing in technological advancements around the supply chain. These activities were active in validating important technologies for the development of cellulosic ethanol. Advances in hydrocarbon biofuels, also known as “drop-in” fuels, will act as petroleum replacements in existing refineries, tanks, pipelines, pumps, trucks, and smaller engines, thanks to the Office’s previous work on cellulosic ethanol.
Learn more about biofuels by watching the Energy 101 Video: Biofuels. [VideoSiteExplosion id=17]
ETHANOL
Ethanol (CH3CH2OH) is a sustainable fuel made from a variety of plant materials referred to as “biomass.” Ethanol is an alcohol that is blended into gasoline to increase octane and reduce smog-causing pollution like carbon monoxide.
E10 is the most popular ethanol blend (10 percent ethanol, 90 percent gasoline). Some cars, known as flexible fuel vehicles, are designed to run on E85 (a gasoline-ethanol blend containing 51–83 percent ethanol, depending on geography and season), an alternative fuel with significantly higher ethanol content than standard gasoline. In the United States, ethanol is used in about 97 percent of gasoline.
The majority of ethanol is made from plant starches and sugars, but scientists are working on ways to use cellulose and hemicellulose, the non-edible fibrous content that makes up the majority of plant matter. In reality, in the United States, many commercial-scale cellulosic ethanol biorefineries are currently operational.
Fermentation is a typical process for converting biomass to ethanol. Microorganisms (such as bacteria and yeast) metabolize plant sugars and generate ethanol throughout fermentation.
BIODIESEL is a renewable energy source
Biodiesel is a cleaner-burning alternative to petroleum-based diesel fuel made from renewable sources such as fresh and used vegetable oils and animal fats. Biodiesel is made by mixing alcohol with vegetable oil, animal fat, or recycled cooking grease. It is nontoxic and biodegradable.
Biodiesel, like petroleum-based gasoline, is used to power compression-ignition (diesel) engines. Biodiesel can be blended in any percentage with petroleum diesel, including B100 (pure biodiesel) and B20 (the most popular blend) (a blend containing 20 percent biodiesel and 80 percent petroleum diesel).
HYDROCARBON “DROP-IN” FUELS THAT REGENERATE
Petroleum fuels, such as gasoline, diesel, and jet fuel, are made up of a complex combination of hydrocarbons (hydrogen and carbon molecules) that are burned to generate electricity. A variety of biological and thermochemical processes may be used to extract hydrocarbons from biomass. Biomass-based renewable hydrocarbon fuels are almost identical to the petroleum-based fuels they’re meant to replace, which means they’ll work with today’s generators, pumps, and other facilities.
World Energy in Paramount, California, is currently generating renewable diesel from waste fats, oils, and greases on a commercial scale. Several companies are involved in retrofitting existing brown-field sites or developing new green-field facilities in the United States for renewable diesel and jet fuel. More information on Renewable Hydrocarbon Fuels can be found here.
DECONSTRUCTION OF BIOFUEL CONVERSION PROCESSES
Advanced biofuels (cellulosic ethanol and renewable hydrocarbon fuels, for example) are usually made in a multistep phase. First, the plant cell wall’s sturdy rigid structure must be broken down, which involves the biological molecules cellulose, hemicellulose, and lignin bound tightly together. There are two ways to do this: high temperature deconstruction or low temperature deconstruction.
Deconstruction at High Temperature
Extreme heat and pressure are used in high-temperature deconstruction to break down solid biomass into liquid or gaseous intermediates. In this pathway, there are three main routes:
- Pyrolysis is a term that refers to the process of
- Gasification is the process of converting carbon dioxide into
- Liquefaction caused by hydrothermal heat.
Biomass is heated rapidly at high temperatures (500°C–700°C) in an oxygen-free atmosphere during pyrolysis. Heat causes biomass to decompose into pyrolysis vapor, steam, and char. The vapors are cooled and condensed into a liquid “bio-crude” oil after the char is extracted.
Gasification is a somewhat different method in which biomass is subjected to a higher temperature range (>700°C) with some oxygen present to create synthesis gas (or syngas), which is a mixture primarily made up of carbon monoxide and hydrogen.
Hydrothermal liquefaction is the favored thermal process when dealing with wet feedstocks including algae. To transform biomass into liquid bio-crude oil, this method uses water at moderate temperatures (200°C–350°C) and high pressures.
Deconstruction at Low Temperature
To break down feedstocks into intermediates, low-temperature deconstruction usually employs biological catalysts such as enzymes or chemicals. First, biomass is pretreated to break down the physical structure of plant and algae cell walls, allowing sugar polymers like cellulose and hemicellulose to be more easily accessed. During the hydrolysis process, these polymers are broken down enzymatically or chemically into simple sugar building blocks.
