Biomass

Introduction

Biomass is the total mass of biological material, both living and recently dead, in a defined area. In an ecological context, biomass often refers to the amount of biological material in different parts of an ecological pyramid or in different ecological communities. In terms of energy supply, biomass refers to plant material that is grown as a source of energy.

Historical Background and Scientific Foundations

Nearly all of the biomass on Earth is produced by photo-synthesis performed by plants and algae. Photosynthesis converts solar energy into the energy in the chemical bonds of molecules. Inherent in the idea of biomass is the notion that energy is stored in organic materials. Transformations to organic materials release energy that can then be converted to other forms of energy and matter.

In ecology, the concept of biomass is often used to describe ecological pyramids. These pyramids summarize the various types of organisms in a particular environment. The bottom of the pyramid usually consists of organisms that convert sunlight into stored chemical energy through photosynthesis. These organisms are producers. The next level of the pyramid consists of organisms that consume the producers. These organisms are the primary consumers. The next level consists of secondary consumers, those

that eat the primary consumers. Because the transfer of energy from one level of an ecological pyramid to another is inefficient, the biomass at each level also decreases. In general, the biomass of a given level is only 10% of the preceding level.

Industrial engineers use the concept of biomass to describe the quantity of a plant crop that can be used as an energy source. Related terms are biofuels and bioenergy. Some of the plants most often used for biomass are corn, sugarcane, grasses, and hemp. Garbage, wood, landfill gases, and alcohol fuels may also be considered biomass.

Impacts and Issues

As fossil fuels become more expensive and concern about the increase in carbon dioxide and other pollutants produced by fossil fuels in the atmosphere intensifies, industrial researchers have become more invested in developing alternative energy sources. Biomass is one of these alternatives.

Many industrial scientists argue that burning of bio-mass is a carbon-neutral contributor to greenhouse gases in the environment. In its simplest form, this argument states that because the photosynthesis that produces the crops draws carbon dioxide out of the environment, burning the plants for energy releases the same carbon dioxide back into the atmosphere. Critics argue that the fertilizer and farm equipment required to produce the biomass add significant carbon dioxide to the atmosphere.

WORDS TO KNOW

: A fuel made from a combination of plant and animal fat. It can be safely mixed with petro diesel.

: Energy for technological use derived from materials produced by living things. Wood, methane from anaerobic bacteria, and liquid fuels manufactured from crops are all forms of bioenergy.

: Ethanol produced by fermentation using yeast or bacteria. Most ethanol is bioethanol, but methods to produce it using purely chemical processes also exist.

: A fuel derived directly by human effort from living things, such as plants or bacteria. A biofuel can be burned or oxidized in a fuel cell to release useful energy.

: System of species that live together in a given ecosystem and interact with each other. For example, all plants, animals, insects, and microorganisms living in or interacting with a lake form a single ecological community.

: Representation of the ascending levels of biomass productivity in an ecosystem, where each level eats the level below it. Green plants are the basis of a typical ecological pyramid, with top predators—predators on whom no other species preys—at the top.

: Fuels formed by biological processes and transformed into solid or fluid minerals over geological time. Fossil fuels include coal, petroleum, and natural gas. Fossil fuels are non-renewable on the timescale of human civilization, because their natural replenishment would take many millions of years.

: The process by which green plants use light to synthesize organic compounds from carbon dioxide and water. In the process, oxygen and water are released. Increased levels of carbon dioxide can increase net photosynthesis in some plants. Plants create a very important reservoir for carbondioxide.

IN CONTEXT: BIOENERGY FEEDSTOCKS

“Biomass from agricultural residues and dedicated energy crops can be an important bioenergy feedstock, but its contribution to mitigation depends on demand for bioenergy from transport and energy supply, on water availability, and on requirements of land for food and fibre production. Widespread use of agricultural land for biomass production for energy may compete with other land uses and can have positive and negative environmental impacts and implications for food security.”

SOURCE:Metz, B., et al, eds. Climate Change 2007: Mitigation of Climate Change: Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.

Research continues into developing biomass that both creates less pollution than fossil fuels and provides a more economical source of energy. Some ideas for accomplishing these goals include collecting methane gas produced by biomass decomposition in landfills, burning municipal waste in order to slow its accumulation in landfills, and developing technologies to burn wood in a cleaner fashion. In addition, using bioethanol and biodiesel may result in fewer pollutants than the combustion of fossil fuels.

See Also Biofuel Impacts; Biosphere; Carbon Dioxide (CO₂); Carbon Sequestration Issues; Carbon Sinks; Energy Efficiency; Energy Industry Activism; Ethanol; Industry (Private Action and Initiatives); Methane; Natural Gas; Petroleum; Petroleum: Economic Uses and Dependency; Renewable Energy; Social Cost of Carbon (SCC).

BIBLIOGRAPHY

Books

Raven, Peter H., and Linda R. Berg. Environment. Hoboken, NJ: John Wiley and Sons, 2006.

Web Sites

“BIOMASS—Renewable Energy from Plants and Animals.” Energy Information Administration, October 2006. < http://www.eia.doe.gov/kids/energyfacts/sources/renewable/biomass.html> (accessed October 16, 2007).

“Introduction to Biogeochemical Cycles.” University of Colorado. < http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html> (accessed October 16, 2007).

Juli Berwald

Biomass

Suppose you take a walk in the forest one day and you look around you at all the trees and think, "That's a lot of wood, I wonder how much all these trees weigh?" Biologists ask the same question. Biomass is the total mass of all the trees (after the water has been taken out).

The term "biomass" is actually applied to three related but slightly different concepts. The total dry weight of all living organisms that can be supported at each trophic level in a food chain is known as the biomass. The term is also applied to the dry weight of all living organic matter in an entire ecosystem. Finally, people interested in alternative sources of energy use the term to apply to the total mass of all plant materials and animal wastes that can be used as fuel.

Plants use a complex chemical process known as photosynthesis to combine carbon dioxide, water, and sunlight to produce carbohydrates (sugar and cellulose), fats, and proteins. The solar energy that drives photosynthesis is stored in the chemical bonds of these molecules. These carbohydrates, fats, and proteins make up biomass. Biomass, then, can be considered to be stored solar energy.

The energy stored in carbohydrates and other compounds by photosynthesis can be released by burning or by metabolism. When animals eat plants, their bodies slowly release the energy stored in the chemical bonds and this energy becomes available to the animals for muscular activity or maintaining body temperature. When biomass is burned, the water and carbon dioxide are released back into the atmosphere. Therefore, biomass is a renewable energy resource.

The total amount of biomass produced each year is about eight times the world's energy consumption. However, the energy density of each unit of biomass is much smaller than the energy content of fossil fuels ("old" biomass), so much more mass must be burned to produce the same amount of energy. Also, the world's biomass is widely distributed, so concentrating and transporting the biomass remains a problem. There are experimental projects that convert biomass into alcohol or natural gas. But worldwide, only about 7 percent of the biomass produced each year is used as fuel, so this energy resource remains underutilized.

The amount of biomass generally decreases at each higher trophic level. In a temperate grassland, for example, the amount of biomass at each trophic level is only about 10 percent of the biomass of the level below it. If there are 10,000 kilograms (22,000 pounds) of producers (grasses and other plants), there will be only 1,000 kilograms of primary consumers (grasshoppers, voles, bison), 100 kilograms of secondary consumers (shrews, hawks, small cats), and only 10 kilograms of tertiary consumers (large cats, wolves, humans).

The remaining 90 percent of the available energy from biomass at each level is converted to waste heat. This energy loss at each trophic level generally limits food chains to no more than four or five levels.

Marine environments usually reverse the amounts of biomass in the first two trophic levels. The mass of primary consumers (small fish and shrimp) is generally much larger than the mass of producers. This happens because the primary producers are tiny phytoplankton that grow and reproduce rapidly instead of large plants that grow and reproduce slowly.

see also Biomes; Food Web.

Elliot Richmond

Bibliography

Curtis, Helena, and N. Sue Barnes. Biology, 5th ed. New York: Worth Publishing, 1989.

Miller, G. Tyler, Jr. Living in the Environment, 6th ed. Belmont, CA: Wadsworth Publishing Company, 1990.

Purves, William K., and Gordon H. Orians. Life: The Science of Biology. Sunderland, MA: Sinauer Associates, 1987.

American Bioenergy Association

This interest group located in Washington D.C., works to promote the use of bioenergy resources as alternative energy sources. The ABA strives to gain support through the federal government by proposing policies such as tax incentives, increased budget allocations, and research funding. The ABA argues that using biomass would cut U.S. dependence on oil from the Persian Gulf, and fuel the nation's economy.

Biomass

Biomass is a measure of the amount of biological substance minus its water content found at a given time and place on the earth's surface. Although sometimes defined strictly as living material, in actual practice the term often refers to living organisms, or parts of living organisms, as well as waste products or non-decomposed remains. It is a distinguishing feature of ecological systems and is usually presented as biomass density in units of dry weight per unit area. The term is somewhat imprecise in that it includes autotrophic plants, referred to as phytomass, heterotrophic microbes , and animal material, or zoomass. In most settings, phytomass is by far the most important component. A square meter of the planet's land area has, on average, about 22.05 – 26.46 lb (10 – 12 kg) of phytomass, although values may vary widely depending on the type of biome . Tropical rain forests average about 45 kg/m² while a desert biome may have a value near zero. The global average for heterotrophic biomass is approximately 0.1 kg/m², and the average for human biomass has been estimated at 0.5 g/m² if permanently glaciated areas are excluded.

The nature of biomass varies widely. Density of fresh material ranges from a low of 0.14 g/cm³ for floats of aquatic plants to values greater that 1 g/cm³ for very dense hardwood. The water content of fresh material may be as low as 5% in mature seeds or as high as 95% in fruits and young shoots. Water levels for living plants and animals run from 50 to 80%, depending on the species , season, and growing conditions. To insure a uniform basis for comparison, biomass samples are dried at 221°F (105°C) until they reach a constant weight.

Organic compounds typically constitute about 95% by weight of the total biomass, and nonvolatile residue, or ash, about 5%. Carbon is the principle element in biomass and usually represents about 45% of the total. An exception occurs in species that incorporate large amounts of inorganic elements such as silicon or calcium, in which case the carbon content may be much lower and nonvolatile residue several times higher. Another exception is found in tissues rich in lipids (oil or fat), where the carbon content may reach values as high as 70%.

Photosynthesis is the principle agent for biomass production. Light energy is used by chlorophyll-containing green plants to remove (or fix) carbon dioxide from the atmosphere and convert it to energy rich organic compounds or biomass. It has been estimated that on the face of the earth approximately 200 billion tons of carbon dioxide are converted to biomass each year. Carbohydrates are usually the primary constituent of biomass, and cellulose is the single most important component. Starches are also important and predominate in storage organs such as tubers and rhizomes. Sugars reach high levels in fruits and in plants such as sugar cane and sugar beet. Lignin is a very significant non-carbohydrate constituent of woody plant biomass.

[Douglas C. Pratt ]

RESOURCES

BOOKS

Lieth, H. F. H. Patterns of Primary Production in the Biosphere. Stroudsburg, PA: Dowden, Hutchinson, and Ross, distributed by Academic Press, 1978.

Smil, V. Biomass Energies: Resources, Links, Constraints. New York: Plenum Press, 1983.

Biomass

Biomass consists of all of the biological material in a community, including living organisms, or parts of living organisms, as well as waste products and incompletely decomposed remains of living organisms. The term broadly includes plants (referred to as phytomass), bacteria, fungi, and animal material, or zoomass. Biomass density is a distinguishing feature of ecological systems and is usually presented as the amount of dry biomass per unit area. To insure a uniform basis for comparison, biomass samples are dried at 221°F (105°C) until they reach a constant weight.

In most settings, phytomass is by far the most important component of biomass. A square yard (0.84 m²) of the planet’s land area has, on average, about 18-22 lb (8.4-10 kg) of phytomass, although values may vary widely depending on the type of Biome. Tropical rain forests contain four or five times the average while desert biomes may have a value near zero. The global average for non-plant biomass is approximately 1% of the total. Organic compounds typically constitute about 95% by weight of biomass, and inorganic compounds account for the remaining 5%. An exception occurs in species that incorporate large amounts of inorganic elements such as silicon or calcium, in which case the inorganic portion may be several times higher.

Photosynthesis is the principle agent for biomass production. Lightenergy is used by chlorophyll-containing green plants to remove (or fix) carbon dioxide from the atmosphere and convert it to energy rich organic compounds or biomass. It has been estimated that on the face of Earth approximately 200 billion tons of carbon dioxide are converted to biomass each year. Carbohydrates are usually the primary constituent of biomass, and cellulose is the single most important component. Starches are also important and predominate in storage organs such as tubers and rhizomes. Sugars reach high levels in fruits and in plants such as sugarcane and sugar beet. Lignin is a very significant non-carbohydrate constituent of woody plant biomass.

In the energy industry, the term biomass is used to indicate the amount of recently living organic material that can be used as fuel. It is very often used in conjunction with the study of biofuels such as corn and soybeans, but it may also refer to manure and other animal products. In this context, biomass does not refer to organic materials that have undergone geologic processes.

Biomass

Biomass consists of living organisms, or parts of living organisms, as well as waste products and incompletely decomposed remains of living organisms. The term is quite encompassing and includes plants (referred to as phytomass), microbes, and animal material, or zoomass. Biomass density is a distinguishing feature of ecological systems and is usually presented as the amount of dry biomass per unit area. To insure a uniform basis for comparison, biomass samples are dried at 221°F (105°C) until they reach a constant weight.

In most settings, phytomass is by far the most important component. A square yard (0.84 m2) of the planet's land area has, on average, about 18–22 lb (8.4–10 kg) of phytomass, although values may vary widely depending on the type of biome . Tropical rain forests contain four or five times the average while desert biomes may have a value near zero . The global average for non-plant biomass is approximately 1% of the total. Organic compounds typically constitute about 95% by weight of biomass, and inorganic compounds account for the remaining 5%. An exception occurs in species that incorporate large amounts of inorganic elements such as silicon or calcium , in which case the inorganic portion may be several times higher.

Photosynthesis is the principle agent for biomass production. Light energy is used by chlorophyll containing green plants to remove (or fix) carbon dioxide from the atmosphere and convert it to energy rich or ganic compounds or biomass. It has been estimated that on the face of the earth approximately 200 billion tons of carbon dioxide are converted to biomass each year. Carbohydrates are usually the primary constituent of biomass, and cellulose is the single most importan t component. Starches are also important and predominate in storage organs such as tubers and rhizomes. Sugars reach high levels in fruits and in plants such as sugarcane and sugar beet . Lignin is a very significant non-carbohydrate constituent of woody plant biomass.