Environmental Engineering Reference
In-Depth Information
Table 3.4
Ammonia emissions in the United States from animal husbandry
operations estimated by the Environmental Protection Agency for the year 2002.
Animal Group
Ammonia emissions (Tonne/year)
Dairy (cows and heifer)
507,358
Beef (beef cattle, bulls, and calves)
596,953
Poultry (chickens and turkeys)
604,225
Swine (breeding and market pigs)
390,425
Sheep
22,577
Goats (milking and Angora goats)
12,753
Horses
64,805
Total
2,198,723
Adapted from Environmental Protection Agency, 2004.
In addition, ammonium ions can combine with sulfate and nitrate ions resulting from the
conversion of nitrogen dioxde and sulfur dioxide from fossil fuels burning present in the
atmosphere to form ammonium nitrate and ammonium sulfate, respectively. Both ammonium
nitrate and sulfate can be carried by the wind to remote locations and deposited on the ground
in unwanted places, thus altering the balance of ecosystems that are naturally deficient in
nitrogen.
It is estimated that the world amount of ammonia gas released to the atmosphere due to
animal husbandry is around 22 million tons per year, of which 13 million tons are from cattle
production (Monteny, 2002). Table 3.4 summarizes the estimated ammonia emissions for
different animal groups in the United States for the year 2002 as reported by the U.S.
Environmental Protection Agency (2004).
In terms of energy spent to produce animal protein, livestock takes vast amounts of energy
per unit of energy obtained back from the food product. Figure 3.5 illustrates the input of
energy for animal protein from different sources expressed as a ratio between energy input and
energy output in the U.S. It is clear that chicken is the most efficient animal at converting feed
into protein while lamb is the most inefficient.
Emission of greenhouse gases from animal production
Globally, livestock is responsible for 9 percent of the anthropogenic emission of carbon
dioxide, 65 percent of nitrous oxide, and 37 percent of methane (CH
4
). When transformed into
dioxide equivalent, emissions from livestock production accounts for 18 percent of the total
of human-related activities and are more than the emissions of the transportation sector. The
carbon dioxide emissions come from the respiratory process, on-farm fossil fuel use,
deforestation, release from soils, and production of feed including fertilizers. Emissions of
nitrous oxide and methane are mostly the result of manure decomposition and enteric
fermentation (FAO, 2006). Readers with more interest in this topic may consult
Livestock's
Long Shadow—Environmental Issues and Options
.
Fisheries
A direct impact of fishing is the depletion of the resource in the near future unless steps are
taken to limit the catch to allow species time to recover. As indicated by estimates, the
remaining mass of predatory fish, such us bluefin tuna, Atlantic cod, and swordfish, is just
