Energy use is primarily associated with prechain
sources, particularly the production of purchased feed.
Therefore, the total fossil energy use for producing cattle
in this region is very sensitive to assumptions making
up prechain emissions (Fig. 1b). One of the most
important factors is the energy required to produce corn.
The value determined and used for this region (3.75 MJ/
kg DM) was similar to that used previously for corn
produced in the Midwest (Rotz et al., 2013). This value
can vary depending on the production practices used
and the amount of irrigation required. Energy use was
found to be slightly sensitive to the fuel used to produce
feed within our defined production system. Total fossil
energy use was not sensitive to that used in animal feeding,
manure handling, and animal housing.
More than 95% of the water used in beef cattle
production in this region is used to produce feed
through crop irrigation. Therefore, the nonprecipitation
water footprint is highly sensitive to crop use and
insensitive to drinking water use by cattle.
The major source of reactive N loss is NH3 emission
from grazing land and feedyards. The reactive N
footprint was most sensitive to NH3 emission, moderately
sensitive to nitrate leaching from grazing land
and N2O emission, and relatively insensitive to fuel
combustion and prechain sources (Fig. 1c). To reduce
the reactive N footprint, major steps must be taken to
reduce NH3 emissions and the N saved must be efficiently
used for feed production to avoid greater losses
from other sources. This will be particularly challenging
because over half of the NH3 emission comes from
open pastures and rangeland (Table 5).
Overall Conclusions and Implications
Environmental footprints of beef cattle production
in the Kansas, Oklahoma, and Texas region were found
to be 18.3 ± 1.7 kg CO2e/kg CW, 51 ± 4.8 MJ/kg CW,
2,470 ± 455 L/kg CW, and 138 ± 12 g N/kg CW for