According to the scientists, biofuels can be a sustainable part of the world's energy future, especially if bioenergy agriculture is developed on currently abandoned or degraded agricultural lands.

Using these lands for energy crops, instead of converting existing croplands or clearing new land, avoids competition with food production and preserves carbon-storing forests needed to mitigate climate change.

Sustainable bioenergy is likely to satisfy no more than 10% of the demand in the energy-intensive economies of North America, Europe, and Asia.

But for some developing countries, notably in Sub-Saharan Africa, the potential exists to supply many times their current energy needs without compromising food supply or destroying forests.

For their research, the scientists estimated the global extent of abandoned crop and pastureland and calculated their potential for sustainable bioenergy production from historical land-use data, satellite imaging, and ecosystem models.

Agricultural areas that have been converted to urban areas or have reverted to forests were not included in the assessment.

The researchers estimated that globally up to 4.7 million square kilometers (approximately 1.8 million square miles) of abandoned lands could be available for growing energy crops.

The potential yield of this land area, equivalent to nearly half the land area of the United States, depends on local soils and climate, as well as on the specific energy crops and cultivation methods in each region.

But the researchers estimate that the worldwide harvestable dry biomass could amount to as much as 2.1 billion tons, with a total energy content of about 41 exajoules. hile this is a significant amount of energy (one exajoule is a billion billion joules, equivalent to about 170 million barrels of oil), at best it would satisfy only about 8% of worldwide energy demand.

The study revealed larger opportunities in other parts of the world.

In some African countries, where grassland ecosystems are very productive and current fossil fuel demand is low, biomass could provide up to 37 times the energy currently used.

According to Christopher Field of the Carnegie Institution's Department of Global Ecology, "Our study shows that there is clearly a potential for developing sustainable bioenergy, and we've been able to identify areas where biomass can be grown for energy, without endangering food security or making climate change worse." (ANI)