Bioenergy technologies use renewable biomass resources to produce an array of energy products including electricity, transportation fuels, heat, chemicals, and other materials.
Bioenergy is stored energy from the sun contained in biomass materials such as plant matter and animal waste. The term "biomass" refers to any plant-derived organic matter available on a renewable basis, including dedicated energy crops and trees, agricultural food and feed crops, agricultural crop wastes and byproducts, wood wastes and byproducts, aquatic plants, weeds, animal wastes, municipal wastes, and other waste materials. In essence, biomass is the fuel and bioenergy is the energy contained in the fuel.
The use of food crops such as soybeans and corn for biofuel production has increasingly fallen out of favor due to their impact on food prices and availability, their water and fertilizer demands, and their use of farmland that could otherwise produce food. In the United States, corn-based ethanol is currently the largest source of biofuel as a gasoline substitute or additive, but recent scientific studies indicate that corn-based ethanol could actually cause more harm to the environment and contribute to climate change and rising food costs, potentially hurting more than it helps.
Advanced biofuels (also called second and third generation biofuels) rely on non-food crops and other sources for feedstock, such as algae and switchgrass. Planting non-food crops for fuel will not spark food shortages or drive up food prices, and many of these crops, such as jatropha, can be grown on arid land where food cannot grow. Another advantage of many biofuels over traditional fuel types is that they are biodegradable, and therefore relatively harmless to the environment if spilled.
Fourth generation biofuels, still in the research phase, will use microorganisms to turn carbon dioxide directly into fuels.
Cellulosic ethanol is a biofuel produced from wood, grasses, or the non-edible parts of food crops. Cellulose is contained in nearly every plant, tree and bush found in meadows, forests, and fields all over the world and requires little to no agricultural effort or cost to grow.
This third generation biofuel, also called oilgae, is made from algae. Algae production requires very few inputs (such as the fertilizer necessary for many first generation biofuels) and algaculture enjoys high yields in return, deriving as much as 30 times more energy per acre than land feedstocks.
Biodiesel is derived from a wide range of new and used vegetable oils and animal fats which are nontoxic, biodegradable, and renewable. Biodiesel is a cleaner-burning replacement for petroleum-based diesel fuel that can often be used without any vehicle alterations.
Bioenergy is most commonly used in the form of liquid fuels for transportation, home heating and cooking. Current bioenergy fuel sources include agricultural byproducts, pulp/paper mill byproducts, urban wood waste, forest byproducts, energy crops, landfill methane, and animal waste.
Biodegradable outputs from industry, agriculture, forestry and households can be used for biofuel production. Examples of biodegradable wastes include straw, timber, manure, rice husks, sewage, and food waste. There are multiple production methods, including using anaerobic digestion to produce biogas, gasification to produce syngas or by direct combustion.
Power plants can burn bioenergy feedstocks directly to produce steam to drive a turbine, which turns a generator that converts the power into electricity. In some industries, the spent steam from the power plant is also used for manufacturing processes or to heat buildings. Such systems, known as ‘combined heat and power’ (CHP) systems or cogeneration, greatly increase overall energy efficiency. Another method, called co-firing, involves mixing biomass with fossil fuels for use in conventional power plants.
Development, Deployment and Economics
Biofuels derived from plant materials are among the most rapidly growing renewable energy technologies. The global leaders in biofuel development and use are Brazil, the United States, France, Sweden and Germany, although biofuel industries are expanding throughout Europe, Asia and the Americas.
In January 2009, Continental Airlines successfully flew a Boeing 737 twin-engine jet powered partly by algae and jatropha to demonstrate the potential for future biofuel applications in aviation. Other airlines are also experimenting with biofuels to diversify their fuel sources and as a potential substitute for fossil fuels, although commercial usage is still years away.
In some countries, agricultural products are being grown for biofuel production. These include corn, switchgrass, and soybeans, primarily in the United States; rapeseed, wheat and sugar beet primarily in Europe; sugar cane in Brazil; palm oil and miscanthus in Southeast Asia; sorghum and cassava in China; and jatropha in India. Hemp has also been proven to work as a biofuel.
Bioenergy ranks second (to hydropower) in renewable U.S. primary energy production, and accounts for three percent of the primary energy production in the United States.
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