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bioweb.sungrant.org » Technical » Biomass Resources » Land Base

Land Base	Printer Friendly

The biomass resources of the United States are distributed across a land area of approximately 2.3 billion acres. Beginning in northern Alaska and extending to the Mexican border, the U.S. land base includes a great variety of climates, soils, vegetation types and topographic features. It is the local interaction of these factors that makes any given land area more suitable for some uses than for others.   The most recent land use census (USDA-ERS, 2006) found that in 2002 the predominant uses of land in the U.S. consisted of forest use (651 million acres), grassland pasture and range (587 million acres), and cropland (442 million acres). Urban land (60 million acres) constituted just 3% of the total U.S. land area. National and state forests, wilderness and wildlife areas, national defense installations, and other special use lands together made up 197 million acres. Miscellaneous lands such as deserts and bodies of water made up 60 million acres of the total land base. Of all these types of land use, the largest contributors to the U.S.’s  biomass resources were the agriculture and forestry sectors (figure 1).

Agriculture
It is the agricultural sector that currently produces the largest share of biomass crops, such as corn for ethanol and soybeans for biodiesel, as well as new crops in use or evaluation as sources of biomass energy and bioproducts. The last agricultural census (USDA-ERS, 2002) showed the total U.S. cropland at 442 million acres. Cropland use is typically dynamic, due to annual crop and land rotations to conserve soil fertility, and the need to shift land use in response to market trends. The 2002 census reported 340 million acres as cropland used for crops (as opposed to cropland pasture being grazed in rotation [62 million acres]), and idle cropland (40 million acres). Of the idle cropland acres, 35 million acres were enrolled under the expanding Federal Conservation Reserve Program or CRP (figure 2). Harvesting of biomass is permitted by the CRP under certain conditions.                      The major crops produced on U.S. cropland in 2002 were corn (69 million acres), soybeans (72.5 million acres), wheat (50 million acres), alfalfa (22 million acres), other hay (38 million acres), and cotton (13 million acres). The remaining crop acres were in miscellaneous grain and oil seed crops, and fruits and vegetables.    At present, corn, soybeans, alfalfa and other hay are produced primarily for livestock feed. A significant and increasing portion of corn production is currently used to produce bioenergy and bioproducts. In 2005, about 2.15 billion bushels of corn were used to produce 3.9 billion gallons of fuel ethanol. Corn is also used to produce bioproducts, such as polylactic acid (biodegradable plastic) and 1,3-propanediol, used to produce Sorona®, a synthetic fabric. Soybean oil goes mainly to food uses; however, industrial uses include soybean oil used to produce biodiesel - 30 million gallons in 2004, using about 20 million of the U.S. total 1.65 billion soybean bushel production. About 4% of the soybean oil produced in 2004 was used to produce bioproducts such as inks, adhesives and binders, plastics and detergents, among others.

Forestry
The most recent forestry census of the U.S. (USDA-USFS, 2003) showed nearly a third of the land area of the United States covered by forests; 57% percent of all U.S. forest land is privately owned. Public forest land is dominant in the western U.S., where large tracts of federal land went unclaimed by early homesteaders, while private forest land predominates in the East (figure 3).                       Approximately 57% of growing stock in U.S. forests consists of softwood, with the remaining 43% in hardwoods. Nearly 90% of total hardwood timber lies in the Eastern United States. Hardwoods are used mostly for lumber and other construction products, while pine and other softwoods are used primarily for paper and pulp. Wood and forest product residues are increasingly used to produce both bioproducts and bioenergy.

Trends in U.S. Land Use
Among the most consistent trends in major uses of land has been an upward trend in special-use and urban areas, and a downward trend in cropland and total grazing land. Between 1997 and 2002, total U.S. cropland area declined by almost 14 million acres (3%). Much of this decline took place in Eastern states where the expansion of urban areas has encroached on farmland, resulting in the permanent loss of cropland to housing, commercial development and other urban uses. Forest-use land increased about 1% between 1997 and 2002, reversing an earlier decline. Most of this increase took place in the Western states as a result of citizen conservation movements.

References
USDA Economic Research Service. (2006). Major Uses of Land in the United States 2002. Retrieved from http://www.ers.usda.gov/publications/EIB14/eib14.pdf USDA National Agricultural Statistics Service. (2004). 2002 Census of Agriculture. Retrieved from http://www.nass.usda.gov/Census_of_Agriculture/index.asp US Forest Service-USDA. (2003). Forest Resources of the United States