A. Land Areas

The availability of land suitable for production of terrestrial biomass can be estimated by several techniques. For the United States, one method relies on a land capabilities classification scheme in which land is divided into eight classes (Table 4.6) (U. S. Dept, of Agriculture, 1966). Classes I to III are suit­able for cultivation of many kinds of crops; Class IV is suitable only for lim­ited production; and Classes V to VIII are useful only for permanent vegetation such as grasses and trees. The U. S. Department of Agriculture surveyed nonfederal land usage for 1987 in terms of these classifications and arrived at the breakdown shown in Table 4.7 (U. S. Dept, of Agriculture, 1989). Out of about 568 million ha, which corresponds to about 60% of the 50-state area, about 43% of the land (246.4 million ha) was in Classes I to III, 13% (75.6 million ha) was in Class IV, and 43% (246.3 million ha) was in Classes V to VIII. The actual usage of this land at the time of the survey is shown in Table 4.8 (U. S. Dept, of Agriculture, 1989). This table shows that of all the land judged suitable for cultivation in Classes I to III, only about 58% of it was

TABLE 4.6 Land Capability Classification by United States Department of Agriculture*

Class Description

I Few limitations that restrict use.

II Moderate limitations that reduce the choice of plants or require moderate conservation practice.

III Severe limitations that reduce the choice of plants or require special conservation

practices, or both.

IV Very severe limitations that reduce the choice of plants or require very careful

management, or both.

V Not likely to erode, but other limitations, impractical to remove, that limit use largely to pasture, range, woodland, or wildlife habitat.

VI Severe limitations that make soils generally unsuited to cultivation and limit their use largely to pasture or range, woodland, or wildlife habitat.

VII Severe limitations that make soils unsuited to cultivation and that restrict use largely to pasture or range, woodland, or wildlife habitat.

VIII Limitations that preclude use for communical plants and restrict use largely to recreation, wildlife habitat, water supply, or to esthetic purposes.

“U. S. Dept, of Agriculture (1966).

“Adapted from U. S. Dept, of Agriculture (1989). Data are for the 48 contiguous states, Hawaii, and the Caribbean area. bThis area is 72.35% of the land surveyed, or 60.55% of the total 50-state area excluding the outlying areas (938.50 million ha). The federal land, water, and developed land areas are 17.43, 2.14, and 3.34% of the total 50-state area, respectively.

"Adapted from U. S. Dept, of Agriculture (1989). Totals may not be precise summations because of rounding. Cropland is land used for production of crops for harvest alone or in rotation with grasses and legumes. Pastureland is land used for production of adapted, introduced, or native species in a pure stand, grass mixture, or a grass-legume mixture. Rangeland is land on which the vegetation is predominantly grasses, grass-like plants, forbs, or shrubs suitable for grazing or browsing. Forest is land that is at least 10% stocked by trees of any size or formerly having had such tree cover and not currently developed for nonforest use. Other land is land such as farmsteads, strip mines, quarries, and lands that do not fit into the other land use category.

actually used as cropland, the locations of which are shown in Table 4.9 (U. S. Dept, of Agriculture, 1989). Also, the combined areas of pasture, range, and forestlands made up about 66% of the total nonfederal lands. This survey suggests that there is ample opportunity to produce biomass for energy appli­cations on nonfederal land that is not used for foodstuffs production. Large areas of land in Classes V to VIII not suitable for cultivation would appear to be available also for biomass energy applications, and sizable areas in Classes I to IV that are not being used for crop production seem to be available. Land now used for crop production could also be considered for simultaneous or sequential growth of biomass for foodstuffs and energy. Portions of the federally owned lands, which are not included in this survey, might also be dedicated to biomass energy applications. Careful design and management of land-based biomass production areas could very well result in improvement or upgrading of lands to higher land capability classifications.