Agriculture Reference
In-Depth Information
stock industries cope with these pressures, an objective set of algorithms
that can compare how various livestock types impact the environment and
meet growing food demands will be needed.
Sequestering atmospheric carbon dioxide (CO
2
) as soil carbon is a po-
tential strategy for reducing GHG emissions [9]. About one third of the
soil carbon stock was lost when virgin soils were fi rst broken with the
plow in Canada and this stock declined further under continued mecha-
nized cultivation [10]. Better farming practices over the last twenty years,
however, have reversed this trend. Canada's agricultural soils, which were
estimated to have been a small CO
2
source in 1991, were a small sink by
2001 [11]. But there are tradeoff effects with regard to the extent to which
all of these practices are applied and which crops are grown. For example,
increases in nitrous oxide (N
2
O) and methane (CH
4
) emissions from live-
stock and crop productions have been offset by carbon sequestration in
soils [11]. Forage crops enhance soil organic matter, but feeding those
crops to livestock increase CH
4
emissions [12].
The main objective of this paper was to present a dynamic, quantitative
model for estimating GHG emissions and determining the carbon foot-
print of Canadian livestock industries. To determine the long term impact
of changes in livestock populations on the carbon footprint of Canadian
farms, this model integrates the changes in soil carbon associated with
shifts among livestock populations with their annual GHG emission bud-
gets. The second objective was to demonstrate the linkages among GHG
emission calculations that are livestock type specifi c and their relationship
with soil carbon. To achieve the second objective four scenarios for live-
stock industry interactions (described below) were assumed.
6.2 EXPERIMENTAL SECTION
6.2.1 DEVELOPMENT OF A LIVESTOCK GHG MODEL
6.2.1.1 BACKGROUND
Commodity assessments have been previously completed for the Canadian
dairy, beef pork and poultry industries [13-16]. However, these assessments
