Biofuels - The Oxford Topic of Food, Politics, and Society - page 184

the land (Lal et al. 1999). Worldwide, the amount of biomass produced is significantly
greater: our estimate totals 1,764 x 109 tons of biomass produced per year (Pimentel et al.
2010), almost a thousand times greater than the US biomass production.
In developing countries, about 2 kcal (kilocalories) of wood are utilized in cooking 1
kcal of food (Fujino et al. 1999). Thus, more biomass, land, and water are needed to pro-
duce the biofuel for cooking than are needed to produce the food to be cooked (Pimentel
and Pimentel 2008). Worldwide, most biomass is burned for cooking and heating, but
biomass can also be converted into electricity. Assuming an optimal yield globally of
three dry metric tons per hectare per year of woody biomass, harvested sustainably
(Ferguson 2001, 2003), a gross energy yield of 13.5 million kcal/ha results. Harvesting
this wood biomass requires an energy expenditure of approximately thirty liters of die-
sel fuel per hectare, plus the embodied energy for cutting and collecting wood for trans-
port to an electric power plant. Thus, the energy input per output ratio for such a system
is calculated to be 1:25 (Hendrickson and Galland 1993).
Per capita consumption of woody biomass for heat in the United States amounts to
625 kilograms (kg) per year (Kitani 1999). The diverse biomass resources (wood, crop
residues, and dung) used in developing nations averages about 630 kg per capita per
year (Kitani 1999). Woody biomass has the capacity to supply the United States with
about 5 quads (1.5 x 1012 kWh thermal) of its total gross energy supply by the year
2050, provided that the amount of forestland stays constant (Pimentel 2008). A city of
100,000 people using the biomass from a sustainable forest (3 t/ha per year) for elec-
tricity requires approximately 200,000 ha of forest area, based on an average electri-
cal demand of slightly more than 1 billion kilowatt hours (kWh) (860 kcal = 1 kWh)
(Pimentel 2008).
Air quality impacts from burning biomass are less harmful than those associated with
coal, but more harmful than those associated with natural gas (Pimentel 2001). Biomass
combustion releases more than two hundred different chemical pollutants, including
fourteen carcinogens and four cocarcinogens, into the atmosphere (Burning Issues
2006). As a result, approximately 4 billion people globally suffer from continuous expo-
sure to smoke (Smith 2006). In the United States, wood smoke kills 30,000 people each
year (Burning Issues 2011), although many of the pollutants from electrical power plants
that use wood and other biomass can be mitigated. These controls include the same
scrubbers that are frequently installed on coal-fired plants.
The estimated 1.8 billion tons of biomass produced per year on US land area trans-
lates into about thirty-two quads of energy, which means that the solar energy captured
by all plants in the United States per year equates to only 32% of the energy currently
consumed as fossil energy (Pimentel et al. 2008). The United States lacks the volume of
biomass to produce the ethanol and biodiesel fuel to make the United States oil indepen-
dent (Pimentel et al. 2012).
Of the total world land area in cropland, pasture, and forest, about 38% is cropland
and pasture and about 30% is forests ( FAO 2013). Devoting a portion of this cropland
and forestland to biofuels will stress both managed and unmanaged ecosystems and
would not, in any event, be sufficient to solve the world fuel problem.