beef production are faced with an industry char- acterized by distortions such as the availability of
land subsidies that reduce producer costs and labour not valued in the market economy. Efforts
are under way to seek to limit some of the distor- tions that have led to the underpricing of an
environmentally costly form of protein. Ideas for reducing livestock production have centred in the
United States on proposals for limiting grazing rights on public lands Repetto, 1992. Controls
on related organic pollution are better established than land-use restrictions. In the UK, farmers are
provided financial incentives to curb nitrogen runoff MAFF, 1996. Farm effluent in the
United States is controlled as a ‘non-point’ source under national Clean Water legislation US EPA,
1972. In the Netherlands, farmers are fined if they do not use approved practices for disposing
of livestock wastes Wilkins, 1997
Concern over the threats posed by long-term climate change has led to an interest in controlling
emissions of the greenhouse gas methane, gener- ated as a by-product of the digestive processes of
livestock. Livestock are believed to be the most important source of anthropogenic methane inter-
nationally Watson et al., 1992. Strategies to reduce greenhouse gas emissions from livestock
production have centred largely upon increasing animal productivity, in part through higher-qual-
ity feeding US EPA, 1994. These policies do not usually include consideration of indirect emissions
related to energy used to produce stockfeed and changes in carbon fixation on land.
In this paper, several measures of the global environmental impacts of beef production are as-
sessed for two contrasting production modes. Greenhouse gas emissions from beef production
are assessed
stepwise considering
several boundaries of analysis for each of two systems —
American feedlot and Sahelian pastoral beef pro- duction. A comprehensive approach to under-
standing greenhouse gas emissions from beef production is presented. This approach considers
indirect emissions from livestock production and related land use. The approach includes the as-
sessment of indirect sources — carbon dioxide flux related to embodied energy in on-farm use and
stockfeed production, and the carbon storage po- tential foregone on land appropriated for raising
livestock — in addition
to direct
sources — methane emissions from enteric fermentation and
animal wastes. The greenhouse gas emissions related to both
pastoral and feedlot production modes are com- pared with other environmental impact indicators
for these modes — both quantitatively and qualita- tively with reference to their potential usefulness
in assessing livestock systems generally. Green- house gas emissions are compared with a com-
posite
indicator of
sustainability in
agro- ecosystems, called biophysical capital alteration.
Greenhouse gas emissions from each system are summarized for three boundaries of analysis: 1
direct methane emissions, 2 direct emissions plus embodied fuel combustion, and 3 direct methane
and embodied fuel plus the carbon offset opportu- nity foregone in addition to the other emissions.
The difference in estimated biophysical capital alteration and greenhouse gas emissions for the
two systems are compared to reveal whether the environmental impacts as determined by each ap-
proach are similar.
These greenhouse gas emissions indices, when compared with market values per unit of beef, can
be used to estimate a shadow price of an expected global warming impact as a proportion of the
market value of the good. The comprehensive greenhouse gas approach can be expressed in
climate change costs, taking the form kg CO
2
equivalent. Measured as a proportion of the mar- ket value of beef, this measure can be used to
determine the value of a tax on beef that would, in theory, be comparable with projected environ-
mental impacts. The approaches compared are summarized in Table 1.
2. Methodology and results
Greenhouse gas emissions from two livestock production systems at opposite ends of the spec-
trum as regards energy inputs, are assessed ac- cording to a range of indicators — biophysical
capital loss, topsoil loss, and greenhouse gas emis- sions. These systems have already been evaluated
for topsoil loss and biophysical capital loss
parameters by Giampietro et al. 1992. In this analysis, a comprehensive greenhouse gas emis-
sions analysis of these systems is summarized based on the same specific livestock management
practices assumed by Giampietro and colleagues. Details of the assumptions involved in assessing
greenhouse gases from these particular feedlot and pastoral beef production modes can be found
in Subak 1999. Other assessments of greenhouse gas intensity of livestock production involving
embodied fossil fuel inputs have also been com- pleted by Loethe et al. 1997, Ward et al. 1993
and Jarvis and Pain 1994.
Beef production systems vary greatly in their use of resources and labour and, spatially, the
resource boundaries of intensive systems tend to be much greater than the immediate farm. Most
feedlot systems rely on crops grown outside the cattle farm. Cattle diet and management differs in
most respects between the feedlot and pastoral modes. The key assumptions for both beef pro-
duction modes are presented in Table 2. In the pastoral example used here, stocking rates are
assumed to be 18 ha per animal unit and forage grass is the only feed source in the African
nomadic system. Details of daily gains are derived from Bremen and de Wit 1983 and de Leeuw
and de Haan 1983. The US feedlot system in- cludes a foraging phase for the young animals
followed by a feedlot phase where animals con- sume a variety of crops grown on arable land. In
the US feedlot system, all feed is produced on or in an area near a farm operating in New York
State, displacing New York State’s natural ecosys- tems. Diet composition and weight gain are based
on data from Ensminger 1987 and the National Research Council 1989. Greenhouse gases are
emitted in the US system through fossil fuel con- sumption embodied in the beef production pro-
cess through on-farm energy use, and through energy use outside the farm for fertilizer manufac-
ture and irrigation. In both the Sahelian and US systems, methane is released directly from the
animals through enteric fermentation in the cattle rumen. Loss of carbon storage on land is also
assessed for both systems. For the feedlot system, the opportunity cost of carbon uptake potential
on cultivable land through foregone afforestation is considered. In the Sahel, periodic burning re-
duces the average standing biomass stock on pas- tureland and this is also calculated.
Greenhouse gas emissions are calculated on a common unit of measure — emissions per kg of
beef on a carbon dioxide equivalent basis see
Table 1 Costing production for 1 kg of beef
Approach Practitioner
Indicator Expenditures of labour, capital
Production costs: inputs of Agricultural economics
Farmer Jones labour, capital, resources
and resources are assessed Conventional pollution
National and state Nitrogen pollution from wastes
Nitrogen, sulphur, potassium, environmental and agricultural
etc. environmental analysis
and fertilizers, conventional agencies
and toxic airborne pollutants from fuel combustion and
pesticide applications; topsoil loss
All factors of production are Biophysical capital alteration
Wm
2
kgm
2
Giampietro from Odum assessed as energy inputs with
reference to biomass stock and displacement
Ecological economics The total costs of production
Wm
2
or Wkg e.g. Costanza, 1980
expressed in energy terms e.g. Cline, 1992
Climate change costs tonne CO
2
equivalent Discounted expected impacts
from global warming Greenhouse gas emissions
Greenhouse gas emissions Ward et al., 1993; Jarvis and
CH
4
, CO
2
, N
2
O emissionskg Pain, 1994; Subak, 1997, 1999
from production processes analysis
animal product
Table 2 Diet and management assumptions for Sahelian pastoral and US feedlot beef production
Pastoralsubsis- Feedlotforage
tence Lifetime days
394 1000
Time in forage days 1000
144 250
Time in feedlot days 270
Final weight kg 550
165 Beef yield kg
297 Diet kgheadday
Corn 7.1
11.5 Corn silage
Soya 0.45
Pasture 4.3
Crop yield kghayr Corn
6500 Corn silage
26 000 2500
Soya 1000
Pasture Area required haheadlife
0.41 Fodder crops
Pasture 21
1000 Opportunity cost of fodder in net carbon uptake kg Chayr
Burning frequency of pasture land year 10
430 409
Carbon storage opportunity lost kgheadlife Fertilizers for fodder kgNha
206 195 forage
N
2
O emission factor kg N
2
Okg N fertilizer 2
Greenhouse gas embodied in fossil fuel for on-farm use, irrigation, fertilizer manufacture, 24 167
fuel extraction MJhead 463
CO
2
kghead CH
4
kghead 2.9
N
2
Okghead 0.1
4.5 7.5
Methane conversion 40
Digestability of feed 75
65 forage Enteric fermentation emissions factors kg CH
4
headyear 50
29 1
CH
4
from manure kg CH
4
headyear 2
Table 3. The results indicate that methane emis- sions from the pastoralist system are nearly twice
that of the feedlot system. This is because the African cattle have a higher methane conversion
rate from lower quality feed, live longer than feedlot animals, expend more energy eating over a
larger range, and produce less meat. These factors compensate for the fact that the animals are eat-
ing less than the feedlot animals. However, when carbon dioxide embodied in fuel is considered as
well, higher emissions are found in the feedlot system. In fact, the estimated level for the feedlot
system is more than double that of the pastoralist system when carbon sinkstock losses are also
considered. It has been proposed that sustainability in agri-
culture can be evaluated according to changes in ‘biophysical capital’ in a system. Biophysical capi-
tal alteration describes an ecosystem’s ability to use solar energy to maintain the biosphere’s struc-
ture and function Giampietro and Pimentel, 1991; Giampietro et al., 1992. Sustainability of
human activities as proposed by Giampietro and colleagues is indicated by the stability of the
Table 3 Greenhouse gas emissions kg CO
2
equivalentkg beef
a
1+embodied fuels 2 2+sinkstock loss
Enteric fermentation and wastes 1 Feedlot
9.1 3.6
14.8 6.9
8.4 6.8
Pastoralist
a
Global warming potentials for methane of 24.5 and 320 for nitrous oxide, integrated over a 100-year time horizon, are used to derive CO
2
equivalence IPCC, 1995.
dynamic equilibrium between biophysical and hu- man – technological capitals. High levels of bio-
physical capital represent relatively high stocks of biomass, but significant alteration involves a di-
minishment in biomass stock, and loss of a flow of solar energy at a given density. Unsustainable
alteration of biophysical capital may be seen as human exploitation of natural processes such that
the flow of energy in the ecosystem is insufficient to maintain the original structuresfunctions. It
has also been suggested that this indicator can be used to evaluate depletion of resources and spe-
cies richness.
Biophysical capital alteration, according to this definition, can be quantified. Specifically, biophys-
ical capital is determined by the quantity of solar energy, i.e. watts of solar energy W, that is used
in the work of self-organization Wm
2
within a given biomass structure kgm
2
, thereby indicat- ing the level of energy dissipated to maintain 1 kg
of biomass structure Wkg. Emissions analysis can be compared with biophysical capital loss
Wkg, which has already been evaluated for the African and American beef production systems
Giampietro et al., 1992. Giampietro et al. 1992 concluded that the biophysical capital alteration
Wkg for the US feedlot system is about twice that of the Sahelian pastoral system. The results
of the most comprehensive greenhouse gas emis- sions analysis provide relative values that are
similar to the sustainability value Wkg, where the impact of the feedlot system is about double
that of the pastoral mode see Table 4.
A comparison of the relative environmental impact of the two beef production modes in top-
soil loss, methane, biophysical capital alteration and total greenhouse gas emissions, appears in
Table 5. Results of the comprehensive greenhouse gas emissions analysis and the biophysical capital
alteration approach are similar, with environmen- tal impacts of the feedlot system greater than that
of the pastoral system in both approaches. Under the biophysical capital alteration measure, envi-
ronmental impacts are 1.7 times greater for the feedlot mode, and considering comprehensive
greenhouse gas emissions, the impact of the feed- lot system is about 1.8 times greater than the
pastoral mode. Further research would be needed to demonstrate whether these results would hold
more generally.
3. Evaluating the environmental impacts
