Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 217

If biomass is to play a major role in the energy supply of the world, energy farming is required. However, it is uncertain whether fallow land will be available to produce biomass for energy instead of food. The main stimulus in the European Union and the United States for introducing non-food crops in agriculture is the surplus production of food. Worldwide food demand is expected to increase considerably, but the amount and type of food that will be required depend on many factors. Population growth, as well as increasing incomes, may result in shifts to more protein-rich diets; both lead to increased demand for food crops. Loss of agricultural land caused by erosion, limited water resources and the increased demand for land for urbanization, infrastructure, and also preservation of nature all limit the possibilities for energy crops.

The availability of land for energy farming, however, does not depend only on the availability of agricultural land. Degraded land, for instance, which is not really suitable for food crops can represent a large potential for energy farming. At the same time, energy crops may help restore these damaged soils. Yields, however, will generally be lower than from good quality land.

Land that is needed to grow energy crops competes with land used for food and wood production unless surplus land is available. Furthermore, the demand for biomass (especially woody biomass) as a renewable energy source has increased continuously in recent years, especially for the direct provision of heat and power generation. However, the biomass potential is limited due to technical constraints and ecological restrictions, as well as the sustainability principles of land management, leading to a predicted supply shortfall.

To avoid competition with food and feed production land, there is the need to establish marginal sites with low soil quality, but sufficient water availability. Tree species capable of stump sprouting, such as poplar, willow, and black locust, can attain high biomass increments on cropland with low soil quality, but sufficient water supply due to their low nutrient requirements and deep-reaching roots. For example, sites for biomass production can be established on cropland with a low depth-to-groundwater table that poplars or willows with deep-reaching roots can utilize, but is inaccessible to annual cultures. The annual crop yield is typically low on croplands with low soil quality. Therefore, these lands can be seen as agricultural marginal sites, where the combination of yields and prices barely covers the cost of production.

There is the need to conduct an assessment of the potential for land use based on (i) hydrological and climatic conditions, (ii) restrictions by various boundaries, from the technical, ethical, and ecological standpoints, and (iii) energy potential, considering the effect of global climate change.

See also: Biomass.