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levels of sulfur and ash that are lower than those that coal

produces.

Some problems associated with obtaining energy

from biomass include the use of land and water that

might otherwise be dedicated to agriculture. This shift

toward energy production might decrease food produc-

tion, contributing to higher food prices and reducing

food supplies even as the population is growing.

Also, as mentioned earlier, at least half of the world’s

population relies on biomass as its main source of en-

ergy. Unfortunately, in many areas people burn wood

faster than they replant trees. Intensive use of wood for

energy has resulted in severe damage to the environ-

ment, including soil erosion, deforestation and desertifi-

cation, air pollution, and degradation of water supplies.

Excessive use of crop biomass can also harm soil

quality. Crop residues, such as cornstalks, are increas-

ingly being used for energy. Crop residues left in and on

the ground prevent erosion by holding the soil in place;

their removal would eventually deplete the soil of miner-

als and reduce its productivity.

Some U.S. energy companies convert corn, sugar-

cane, or wood crops to alcohol; others are interested in

the commercial conversion of agricultural and municipal

wastes into ethanol. Currently, the profitability of ethanol

is possible only because of government subsidies that re-

duce ethanol’s cost.

In 2010, just over 1.4 million barrels of ethanol were

consumed each day worldwide. Of this, almost 60 per-

cent was used in the United States, 27 percent was used

in Brazil, and just 7 percent in all of Europe. By com-

parison, the United State consumed 22 percent of the

world’s gasoline, while Europe consumed 17 percent

and Brazil just 2.5 percent.

Biomass is attractive as a source of energy—and popu-

lar with U.S. politicians—because it reduces dependence

on fossil fuels. It is popular with consumers because they

can easily shift from gasoline and diesel without disrup-

tive lifestyle changes. Also, biomass often makes use of

waste products, thereby reducing our waste disposal prob-

lem. Although it is not completely free of the pollution

problems of fossil fuels, biomass combustion produces

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This small-scale biogas digester is being evaluated at a research center. Animal manure placed in the digester decomposes,

releasing methane gas that can be used as cooking fuel.