Biomass
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 photosynthesis 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 biomass 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. 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.
Words to Know
Biodiesel: A fuel made from a combination of plant and animal fat. It can be safely mixed with petro diesel.
Bionergy: 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.
Bioethanol: Ethanol produced by fermentation using yeast or bacteria. Most ethanol is bioethanol, but methods to produce it using purely chemical processes also exist.
Biofuel: 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.
Ecological Community: 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.
Ecological Pyramid: 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.
Fossil Fuels: 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.
Photosynthesis: 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 carbon dioxide.
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.
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 May 5, 2015).
‘‘Introduction to Biogeochemical Cycles.’’ University of Colorado. <http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html> (accessed May 5, 2015).
