Biomass
There are many types of biomass—organic matter such as plants, residue from agriculture and forestry, and the organic component of municipal and industrial wastes—that can now be used to produce fuels, chemicals, and power. Wood has been used to provide heat for thousands of years. This flexibility has resulted in increased use of biomass technologies. According to the Energy Information Administration, 53% of all renewable energy consumed in the United States was biomass-based .in 2007.
Biomass technologies break down organic matter to release stored energy from the sun. The process used depends on the type of biomass and its intended end-use
Biomass technologies break down organic matter to release stored energy from the sun. The process used depends on the type of biomass and its intended end-use
Biofuels
Biofuels are liquid or gaseous fuels produced from biomass. Most biofuels are used for transportation, but some are used as fuels to produce electricity. The expanded use of biofuels offers an array of benefits for our energy security, economic growth, and environment. Current biofuels research focuses on new forms of biofuels such as ethanol and biodiesel, and on biofuels conversion processes.
Ethanol
Ethanol—an alcohol—is made primarily from the starch in corn grain. It is most commonly used as an additive to petroleum-based fuels to reduce toxic air emissions and increase octane. Today, roughly half of the gasoline sold in the United States includes 5%-10% ethanol.
Biodiesel
Biodiesel use is relatively small, but its benefits to air quality are dramatic.
Biodiesel is produced through a process that combines organically-derived oils with alcohol (ethanol or methanol) in the presence of a catalyst to form ethyl or methyl ester. The biomass-derived ethyl or methyl esters can be blended with conventional diesel fuel or used as a neat fuel (100% biodiesel).
Biofuel Conversion Processes
Biomass solids can be converted to liquid or gaseous biofuels in a variety of processes.
Ethanol
Ethanol—an alcohol—is made primarily from the starch in corn grain. It is most commonly used as an additive to petroleum-based fuels to reduce toxic air emissions and increase octane. Today, roughly half of the gasoline sold in the United States includes 5%-10% ethanol.
Biodiesel
Biodiesel use is relatively small, but its benefits to air quality are dramatic.
Biodiesel is produced through a process that combines organically-derived oils with alcohol (ethanol or methanol) in the presence of a catalyst to form ethyl or methyl ester. The biomass-derived ethyl or methyl esters can be blended with conventional diesel fuel or used as a neat fuel (100% biodiesel).
Biofuel Conversion Processes
Biomass solids can be converted to liquid or gaseous biofuels in a variety of processes.
Ethanol
Ethanol Ethanol is a renewable fuel made from various plant materials, which collectively are called "biomass." Ethanol contains the same chemical compound (C2H5OH) found in alcoholic beverages. Studies have estimated that ethanol and other biofuels could replace 30% or more of U.S. gasoline demand by 2030.
Nearly half of U.S. gasoline contains ethanol in a low-level blend to oxygenate the fuel and reduce air pollution. Ethanol is also increasingly available in E85, an alternative fuel that can be used in flexible fuel vehicles.
Several steps are required to make ethanol available as a vehicle fuel. Biomass feedstocks are grown and transported to ethanol production facilities. After ethanol is produced at the facilities, a distribution network supplies ethanol-gasoline blends to fueling stations for use by drivers.
What is Ethanol Ethanol (also known as ethyl alcohol, grain alcohol, and EtOH) is a clear, colorless liquid. Its molecules contain a hydroxyl group (-OH) bonded to a carbon atom.
Ethanol is made of the same chemical compound—and it is the same renewable biofuel—whether it is produced from starch- and sugar-based feedstocks such as corn grain (as it primarily is in the United States) and sugar cane (as it primarily is in Brazil) or from cellulosic feedstocks.
Making ethanol from cellulosic feedstocks—such as grass, wood, crop residues, or old newspapers—is more challenging than using starch or sugars. These materials must first be broken down into their component sugars for subsequent fermentation to ethanol in a process called biochemical conversion. Cellulosic feedstocks also can be converted into ethanol using heat and chemicals in a process called thermochemical conversion.
Ethanol works well in internal combustion engines. In fact, Henry Ford and other early automakers thought ethanol would be the world's primary fuel before gasoline became so readily available. A gallon of pure ethanol (E100) contains 34% less energy than a gallon of gasoline.
Ethanol is a high-octane fuel. Octane helps prevent engine knocking and is extremely important in engines designed to operate at a higher compression ratio, so they generate more power. These engines tend to be found in high-performance vehicles. Low-level blends of ethanol, such as E10 (10% ethanol, 90% gasoline), generally have a higher octane rating than unleaded gasoline. Low-octane gasoline can be blended with 10% ethanol to attain the standard 87 octane requirement.
Ethanol Blends Ethanol is blended with gasoline in various amounts for use in vehicles. Low-level blends, up to E10 (10% ethanol, 90% gasoline), are classified as "substantially similar" to gasoline by the U.S. Environmental Protection Agency, meaning they can be used legally in any gasoline-powered vehicle.
E85 (85% ethanol, 15% gasoline) can be used in flexible fuel vehicles, which are designed to tolerate the fuel's high ethanol content. E85 cannot be used legally in standard gasoline-powered vehicles.
The 15% gasoline content in E85 enables flexible fuel vehicles to operate normally under cold conditions; fueling a vehicle with pure ethanol (E100) creates problems during cold-weather operation.
Other than lower gas mileage, motorists will see little difference when using E85 versus gasoline. E85 has about 27% less energy per gallon than gasoline. However, E85 is typically priced lower than gasoline, so that cost per mile is comparable.
Nearly half of U.S. gasoline contains ethanol in a low-level blend to oxygenate the fuel and reduce air pollution. Ethanol is also increasingly available in E85, an alternative fuel that can be used in flexible fuel vehicles.
Several steps are required to make ethanol available as a vehicle fuel. Biomass feedstocks are grown and transported to ethanol production facilities. After ethanol is produced at the facilities, a distribution network supplies ethanol-gasoline blends to fueling stations for use by drivers.
What is Ethanol Ethanol (also known as ethyl alcohol, grain alcohol, and EtOH) is a clear, colorless liquid. Its molecules contain a hydroxyl group (-OH) bonded to a carbon atom.
Ethanol is made of the same chemical compound—and it is the same renewable biofuel—whether it is produced from starch- and sugar-based feedstocks such as corn grain (as it primarily is in the United States) and sugar cane (as it primarily is in Brazil) or from cellulosic feedstocks.
Making ethanol from cellulosic feedstocks—such as grass, wood, crop residues, or old newspapers—is more challenging than using starch or sugars. These materials must first be broken down into their component sugars for subsequent fermentation to ethanol in a process called biochemical conversion. Cellulosic feedstocks also can be converted into ethanol using heat and chemicals in a process called thermochemical conversion.
Ethanol works well in internal combustion engines. In fact, Henry Ford and other early automakers thought ethanol would be the world's primary fuel before gasoline became so readily available. A gallon of pure ethanol (E100) contains 34% less energy than a gallon of gasoline.
Ethanol is a high-octane fuel. Octane helps prevent engine knocking and is extremely important in engines designed to operate at a higher compression ratio, so they generate more power. These engines tend to be found in high-performance vehicles. Low-level blends of ethanol, such as E10 (10% ethanol, 90% gasoline), generally have a higher octane rating than unleaded gasoline. Low-octane gasoline can be blended with 10% ethanol to attain the standard 87 octane requirement.
Ethanol Blends Ethanol is blended with gasoline in various amounts for use in vehicles. Low-level blends, up to E10 (10% ethanol, 90% gasoline), are classified as "substantially similar" to gasoline by the U.S. Environmental Protection Agency, meaning they can be used legally in any gasoline-powered vehicle.
E85 (85% ethanol, 15% gasoline) can be used in flexible fuel vehicles, which are designed to tolerate the fuel's high ethanol content. E85 cannot be used legally in standard gasoline-powered vehicles.
The 15% gasoline content in E85 enables flexible fuel vehicles to operate normally under cold conditions; fueling a vehicle with pure ethanol (E100) creates problems during cold-weather operation.
Other than lower gas mileage, motorists will see little difference when using E85 versus gasoline. E85 has about 27% less energy per gallon than gasoline. However, E85 is typically priced lower than gasoline, so that cost per mile is comparable.
Biodiesel
Biodiesel is a domestically produced, renewable fuel that can be manufactured from vegetable oils, animal fats, or recycled restaurant greases.
What is Biodiesel? Biodiesel is a liquid fuel made up of fatty acid alkyl esters, fatty acid methyl esters, or long-chain mono alkyl esters. It is produced from renewable sources such as new and used vegetable oils and animal fats and is a cleaner-burning replacement for petroleum-based diesel fuel. It is nontoxic and biodegradable.
Like petroleum diesel, biodiesel is used to fuel compression-ignition (diesel) engines. B20, which is 20% biodiesel and 80% petroleum diesel, is the most common biodiesel blend in the United States.
Biodiesel Blends Biodiesel can be legally blended with petroleum diesel in any percentage. The percentages are designated as B20 for a blend containing 20% biodiesel and 80% petroleum diesel, B100 for 100% biodiesel, and so forth.
B20 B20—the most common biodiesel blend in the United States—is 20% biodiesel and 80% petroleum diesel. Using B20 avoids many of the cold-weather performance and material compatibility concerns associated with B100.
B20 can be used in nearly all diesel equipment and is compatible with most storage and distribution equipment. B20 and lower-level blends generally do not require engine modifications. Not all diesel engine manufacturers cover biodiesel use in their warranties, however. Users should consult their vehicle and engine warranty statements before using biodiesel. It is similarly important to use biodiesel that meets prescribed quality standards (ASTM D6751-07b).
Biodiesel contains about 8% less energy per gallon than petroleum diesel. For B20, this could mean a 1 to 2% difference, but most B20 users report no noticeable difference in performance or fuel economy. Greenhouse gas and air quality benefits of biodiesel are roughly commensurate with the blend; B20 use provides about 20% of the benefit of B100 use and so forth.
B100 B100 or other high-level biodiesel blends can be used in some engines built since 1994 with biodiesel-compatible material for parts such as hoses and gaskets. As biodiesel blend levels increase significantly beyond B20, however, a number of concerns come into play. Users must be aware of lower energy content per gallon and potential issues with impact on engine warranties, low-temperature gelling, solvency/cleaning effect if regular diesel was previously used, and microbial contamination.
B100 use could also increase nitrogen oxides emissions, although it greatly reduces other toxic emissions. All these issues can be handled, but currently B100 use might be best for professional fleets with maintenance departments prepared to deal with this fuel.
What is Biodiesel? Biodiesel is a liquid fuel made up of fatty acid alkyl esters, fatty acid methyl esters, or long-chain mono alkyl esters. It is produced from renewable sources such as new and used vegetable oils and animal fats and is a cleaner-burning replacement for petroleum-based diesel fuel. It is nontoxic and biodegradable.
Like petroleum diesel, biodiesel is used to fuel compression-ignition (diesel) engines. B20, which is 20% biodiesel and 80% petroleum diesel, is the most common biodiesel blend in the United States.
Biodiesel Blends Biodiesel can be legally blended with petroleum diesel in any percentage. The percentages are designated as B20 for a blend containing 20% biodiesel and 80% petroleum diesel, B100 for 100% biodiesel, and so forth.
B20 B20—the most common biodiesel blend in the United States—is 20% biodiesel and 80% petroleum diesel. Using B20 avoids many of the cold-weather performance and material compatibility concerns associated with B100.
B20 can be used in nearly all diesel equipment and is compatible with most storage and distribution equipment. B20 and lower-level blends generally do not require engine modifications. Not all diesel engine manufacturers cover biodiesel use in their warranties, however. Users should consult their vehicle and engine warranty statements before using biodiesel. It is similarly important to use biodiesel that meets prescribed quality standards (ASTM D6751-07b).
Biodiesel contains about 8% less energy per gallon than petroleum diesel. For B20, this could mean a 1 to 2% difference, but most B20 users report no noticeable difference in performance or fuel economy. Greenhouse gas and air quality benefits of biodiesel are roughly commensurate with the blend; B20 use provides about 20% of the benefit of B100 use and so forth.
B100 B100 or other high-level biodiesel blends can be used in some engines built since 1994 with biodiesel-compatible material for parts such as hoses and gaskets. As biodiesel blend levels increase significantly beyond B20, however, a number of concerns come into play. Users must be aware of lower energy content per gallon and potential issues with impact on engine warranties, low-temperature gelling, solvency/cleaning effect if regular diesel was previously used, and microbial contamination.
B100 use could also increase nitrogen oxides emissions, although it greatly reduces other toxic emissions. All these issues can be handled, but currently B100 use might be best for professional fleets with maintenance departments prepared to deal with this fuel.
Biofuel Conversion Processes
The conversion of biomass solids into liquid or gaseous biofuels is a complex process. Today, the most common conversion processes are biochemical- and thermochemical-based. However, researchers are also exploring photobiological conversion processes.
Biochemical Conversion Processes In biochemical conversion processes, enzymes and microorganisms are used as biocatalysts to convert biomass or biomass-derived compounds into desirable products. Cellulase and hemicellulase enzymes break down the carbohydrate fractions of biomass to five- and six-carbon sugars in a process known as hydrolysis.
Yeast and bacteria then ferment the sugars into products such as ethanol. Biotechnology advances are expected to lead to dramatic biochemical conversion improvements. Thermochemical Conversion Processes Heat energy and chemical catalysts can be used to break down biomass into intermediate compounds or products. In gasification, biomass is heated in an oxygen-starved environment to produce a gas composed primarily of hydrogen and carbon monoxide.
In pyrolysis, biomass is exposed to high temperatures in the absence of air, causing it to decompose. Solvents, acids, and bases can be used to fractionate biomass into an array of products including sugars, cellulosic fibers, and lignin.
Photobiological Conversion Processes Photobiological conversion processes use the natural photosynthetic activity of organisms to produce biofuels directly from sunlight. For example, the photosynthetic activities of bacteria and green algae have been used to produce hydrogen from water and sunlight.
Biochemical Conversion Processes In biochemical conversion processes, enzymes and microorganisms are used as biocatalysts to convert biomass or biomass-derived compounds into desirable products. Cellulase and hemicellulase enzymes break down the carbohydrate fractions of biomass to five- and six-carbon sugars in a process known as hydrolysis.
Yeast and bacteria then ferment the sugars into products such as ethanol. Biotechnology advances are expected to lead to dramatic biochemical conversion improvements. Thermochemical Conversion Processes Heat energy and chemical catalysts can be used to break down biomass into intermediate compounds or products. In gasification, biomass is heated in an oxygen-starved environment to produce a gas composed primarily of hydrogen and carbon monoxide.
In pyrolysis, biomass is exposed to high temperatures in the absence of air, causing it to decompose. Solvents, acids, and bases can be used to fractionate biomass into an array of products including sugars, cellulosic fibers, and lignin.
Photobiological Conversion Processes Photobiological conversion processes use the natural photosynthetic activity of organisms to produce biofuels directly from sunlight. For example, the photosynthetic activities of bacteria and green algae have been used to produce hydrogen from water and sunlight.
BioPower
Biopower is the production of electricity or heat from biomass resources. With 10 gigawatts of installed capacity, biopower technologies are proven options in the United States today. Biopower technologies include direct combustion, co-firing, and anaerobic digestion.
Direct Combustion
Most electricity generated from biomass is produced by direct combustion using conventional boilers. These boilers primarily burn waste wood products from the agriculture and wood-processing industries. When burned, the wood produces steam, which spins a turbine. The spinning turbine then activates a generator that produces electricity.
Co-Firing
Co-firing involves replacing a portion of the petroleum-based fuel in high-efficiency coal-fired boilers with biomass. Co-firing has been successfully demonstrated in most boiler technologies, including pulverized coal, cyclone, fluidized bed, and spreader stoker units. Co-firing biomass can significantly reduce the sulfur dioxide emissions of coal-fired power plants and is a least-cost renewable energy option for many power producers.
Anaerobic Digestion
Anaerobic digestion, or methane recovery, is a common technology used to convert organic waste to electricity or heat. In anaerobic digestion, organic matter is decomposed by bacteria in the absence of oxygen to produce methane and other byproducts that form a renewable natural gas.
Content Credit: U.S. Department of Energy - Office of Energy Efficiency & Renewable Energy
Direct Combustion
Most electricity generated from biomass is produced by direct combustion using conventional boilers. These boilers primarily burn waste wood products from the agriculture and wood-processing industries. When burned, the wood produces steam, which spins a turbine. The spinning turbine then activates a generator that produces electricity.
Co-Firing
Co-firing involves replacing a portion of the petroleum-based fuel in high-efficiency coal-fired boilers with biomass. Co-firing has been successfully demonstrated in most boiler technologies, including pulverized coal, cyclone, fluidized bed, and spreader stoker units. Co-firing biomass can significantly reduce the sulfur dioxide emissions of coal-fired power plants and is a least-cost renewable energy option for many power producers.
Anaerobic Digestion
Anaerobic digestion, or methane recovery, is a common technology used to convert organic waste to electricity or heat. In anaerobic digestion, organic matter is decomposed by bacteria in the absence of oxygen to produce methane and other byproducts that form a renewable natural gas.
Content Credit: U.S. Department of Energy - Office of Energy Efficiency & Renewable Energy