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Since the early 2000s, there has been a rapid expansion of the use of LCA in the agricultural sector to calculate the environmental impact of a wide range of livestock commodities. A major notable deficiency of LCA applied to agricultural systems is that they do not generally consider positive contributions (i.e., fixation of atmospheric carbon dioxide [CO2]) to GHG fluxes. Agriculture and forestry are distinct from all other large-scale human activities in that both remove large quantities of CO2 from the atmosphere each year, converted primarily to plant biomass and soil organic carbon (C). The economics and sustainability of specialized poultry (and swine) sectors are heavily dependent on the availability of local feed-grade grains and processing co-products. In consideration of these realities, it is reasonable to posit that GHG emissions from poultry production should be viewed in the context of regionalized, integrated crop–poultry production systems. The purpose of this article therefore is to present an argument for a paradigm shift in how GHG emissions from poultry production should be considered. Specifically, poultry production in this article will be contextualized as a value-adding activity integrated within modern crop production systems, rather than as an activity conducted in isolation. In support of this argument, the authors present a crude but empirically-based estimate of the net C balance of integrated grain crop–poultry production systems in 2 representative Canadian jurisdictions. These calculations differ from conventional LCA processes as they take into account both estimated LCA-based GHG emissions as well as estimates of atmospheric CO2 fixation.
All data sources utilized in this study are in the public domain and are fully available for verification purposes. Data pertaining to production tonnage of corn grain in the province of Ontario and of wheat in Alberta, both for the 2018 crop year, were drawn from the agricultural statistics. Data regarding chicken and egg production in both Alberta and Ontario for the 2018 calendar year were obtained from Agriculture and Agri-Food Canada (2019) and Statistics Canada (2019). Carbon footprints (kg of CO2 eq/T grain production) for corn and wheat grain crops were taken from a recent report by the Canadian Roundtable for Sustainable Crops (2019). Estimates of the GHG footprint of direct energy, fertilizer manufacturing, seed and pesticide, and nitrous oxide (N2O) contributions were averaged for sites in Alberta and Ontario. The calculated C content of broiler chicken biomass is based on average market liveweights of 2.25 kg/bird and 2.44 kg/bird in Alberta and Ontario respectively. The C content of egg (0.423 kg CO2 eq/kg egg mass) was calculated likewise, from the standard protein (105 g/kg egg mass) and fat (89 g/kg egg mass) content reported for a single large egg, corrected for C content of the constituent amino acids and fatty acids according to reported profiles. All C content parameters were converted to a CO2 equivalency by correcting total C content for the relative contribution of C to the molecular weight of CO2 (27.3%).
In 2018, Alberta ranked second among the Canadian provinces in the production of wheat, whereas ranking fourth and fifth (out of 10) for production of chicken meat and eggs, respectively. In comparison, Ontario was the largest producer of corn, chicken meat, and eggs in Canada in 2018. The slightly greater average weight (and therefore estimated protein and fat content) of chickens at marketing resulted in the average chicken produced in Ontario containing a slightly greater amount of fixed C compared to chickens from Alberta. The distribution of egg weights across Grade A weight classes were nearly identical in each province, resulting in identical C fixed per unit of egg mass. When the net GHG footprint of poultry production is included to form the integrated crop–poultry system in each province, the footprint of total poultry production is offset by the net CO2 fixation of the respective crops by factors of 82.2 and 18.2 in Alberta and Ontario, respectively. Put differently, the calculated total GHG footprint of poultry production in Alberta and Ontario corresponds to only 1.2 and 5.5% of the calculated total net CO2 fixation of their respective cropping systems. Where most LCA studies agree is that more than 90% of the GHG footprint of feed is directly attributable to the GHG footprint of the principal feed ingredients, with only minor contributions from processing and transport. For a proper accounting of C flux in the crop–poultry system, the contribution of crop-derived feedstuffs to the overall GHG footprint of chicken liveweight and eggs should therefore be removed, as the GHG footprint of the feed crops is already counted in the net balance calculation for the cropping component of the integrated system.
In conclusion, the current public concern around GHG emissions mitigation has placed increased scrutiny on all large-scale human activities and their impact on the environment. The boundaries that have been used by LCA models of agricultural commodities appear to be at odds with the symbiotic co-existence and complementarity characteristic of modern livestock and crop production. Further, by failing to acknowledge real world estimates of C fixation by crop biomass, GHG foot-printing exercises run the risk of misrepresenting reality. Because GHG foot-printing is increasingly finding its way into public discourse around climate change policy, exclusion of C fixation perpetuates a faulty assumption that agriculture (and more specifically, animal agriculture) is a net contributor to the problem of GHG emissions, rather than part of a combined solution. The authors encourage further discussion and research into this specific question and a more vigorous, balanced, and holistic assessment of the net environmental impact of poultry and livestock production as they pertain to ongoing climate change policy discussions.