Bioenergy or "biomass energy" is any type of fuel or power that is made from living matter or biomass. Biomass is a scientific term for organic or living matter that is available on a renewable basis, such as plants. Today, fuel produced from biomass like agricultural products, forest products, and waste provides more than 3 percent of this nation's energy demands. Bioenergy is clean, renewable energy.
Bioenergy has been described as solar energy stored up in plant matter, and in many ways all of the energy used by living things is ultimately derived from the Sun. The Sun is constantly bombarding Earth with its energy, and about one-tenth of 1 percent of the energy that reaches our surface is "fixed" or captured by green plants using the process of photosynthesis (by which a plant converts light energy into chemical energy or food). This "fixing" of solar energy is the basis of and supports all the life found in Earth's major ecosystems. It provides, by way of the food chain, all of mankind's food either directly or indirectly. So when we eat fruit and vegetables, we are consuming the energy from the Sun that had been captured and converted by a plant. When we eat meat like the beef of a cow, we are at least one step removed from the green plant and are getting the energy from the cow (who got the energy from the plant).
Ever since humans learned how to control fire, they have been burning wood to cook and to keep warm—that is, they have been using a form of biomass energy or bioenergy. In our recent history, mankind has been burning "fossil fuels," like coal, oil, and natural gas, instead of wood. These are called fossil fuels because they were formed over a span of millions of years out of the remains of dead animals and plants. Coal, oil, and natural gas can therefore be described as biomass energy in concentrated form. However, since these fossil fuels take millions of years to form, they cannot be considered a renewable resource. In other words, we may run out of then at some point in the future.
Besides someday running out, fossil fuels also pose another problem. Burning coal, natural gas, and oil creates serious pollution. When these fuels are burned (in order to get them to release their energy), they release carbon dioxide and other gases into the atmosphere, some of which are known as "greenhouse gases." These gases keep some of the Sun's heat from radiating back off Earth's surface and trap it in much the same way that the glass in a greenhouse does. This natural phenomenon is known as the greenhouse effect. Therefore, the more fossil fuels we burn, the more greenhouse gases we produce, and the more heat we trap—making Earth warmer than it should be. Many believe that this global warming will do more harm than good by causing too much or too little rain, or even by melting the polar ice. Another major effect of burning fossil fuels is the release of methane gas. When dissolved in rain, it makes what is called "acid rain," which is quite harmful to trees as well as to the fish in our lakes, rivers, and streams.
Biogas: Methane produced by the decomposition of organic material by bacteria.
Biomass: Any biological material used to produce energy.
Digestor: Sealed, enclosed facility in which bacteria digest or decompose organic material.
Ethanol: An alcohol made by fermenting a biomass that is high in carbohydrates, such as corn or sugarcane.
Fossil fuel: A fuel such as coal, oil, or natural gas that is formed over millions of years from the remains of plants and animals.
Greenhouse effect: The warming of Earth's atmosphere due to water vapor, carbon dioxide, and other gases in the atmosphere that trap heat radiated form Earth's surface.
Since fossil fuels present us with major pollution problems (and may eventually run out anyway), and nuclear energy confronts us with the dilemma of what to do with nuclear waste, bioenergy has become an increasingly attractive alternative. Probably the most attractive aspect of bioenergy is that it is truly a renewable energy source. The production of vegetative matter throughout the world continues on its own at an astounding rate and can be supplemented whenever needed by additional planting. Compare the millions of years necessary for the development of fossil fuels to that of a single growing season for grass. Besides being an easily renewable resource, bioenergy is also non-polluting. Where fossil fuels spew large amounts of carbon dioxide into the air, using renewable biomass adds no carbon dioxide. Even better, biomass energy recycles carbon dioxide since plants take it in during photosynthesis and use it to make their own food. Biomass energy does have some disadvantages, such as collecting biomass takes a lot of time, large storage areas are needed, and simply burning it wastes a lot of its heat energy.
Despite these limitations, bioenergy is becoming increasingly attractive mainly because it can be converted into either liquid or gas forms. Starting with almost any types of fast-growing trees and grasses—as well as leftovers from agriculture or forestry, and the organic parts of city and industrial wastes—biomass can be converted directly into liquid fuels for our transportation needs. The two most common liquid "biofuels" are ethanol and biodiesel. Ethanol is an alcohol made by fermenting a biomass that is high in carbohydrates, such as corn or sugarcane. Fermentation happens when yeast digests sugar and produces alcohol as a by-product (this is how beer and wine are made). The alcohol produced is added to gasoline and is often called gasohol. Biodiesel is made adding vegetable oils or even animals fats like recycled cooking grease to diesel fuel.
Gas can also be produced from biomass and is used to generate electricity. Biogas can be made from materials like sewage and waste that are allowed to be decomposed by bacteria. Under the proper conditions in a sealed facility called a digester, the bacteria go to work and decompose this organic material, thereby producing a flammable gas called methane. This sometimes happens naturally in a landfill, and methane is produced by decaying biomass. The digester, however, captures the methane, then pipes it to a storage tank to be used to run turbines that make electricity. Finally, crops that have a high oil content, like coconuts, sunflowers, and soybeans, can be converted chemically into a fuel oil that can be burned like petroleum to make electricity.
Since the United States imports about half of its oil from parts of the world that are sometimes politically unstable, its Department of Energy (DOE) began a program to step up the investigation of alternative fuels like bioenergy. The DOE sponsors a program of biomass research that involves universities, private companies, and government laboratories across the nation, and as a consequence, U.S. production of ethanol approached 1.5 billion gallons (5.7 billion liters) per year by the end of 2000. The DOE also estimates that if two-thirds of the nation's unused cropland were used to grow what are called energy crops, those 35 million acres (14 million hectares) could produce between 15 and 35 billion gallons (57 and 132 billion liters) of ethanol each year to fuel cars, trucks, and buses. As a natural source of alternative energy, bioenergy is a reliable, safe, and clean fuel, and chances are that in the near future the liquid coming from the gasoline nozzle into your car will have its roots in both a farm field as well as an oil field.
[ See also Alternative energy sources ]