Accounting for uncertainty in the quantification of the environmental impacts of Canadian pig farming systems1

Abstract

The objective of the study was to develop a life cycle assessment (LCA) for pig farming systems that would account for uncertainty and variability in input data and allow systematic environmental impact comparisons between production systems. The environmental impacts of commercial pig production for 2 regions in Canada (Eastern and Western) were compared using a cradle-to-farm gate LCA. These systems had important contrasting characteristics such as typical feed ingredients used, herd performance, and expected emission factors from manure management. The study used detailed production data supplied by the industry and incorporated uncertainty/variation in all major aspects of the system including life cycle inventory data for feed ingredients, animal performance, energy inputs, and emission factors. The impacts were defined using 5 metrics-global warming potential, acidification potential, eutrophication potential (EP), abiotic resource use, and nonrenewable energy use-and were expressed per kilogram carcass weight at farm gate. Eutrophication potential was further separated into marine EP (MEP) and freshwater EP (FEP). Uncertainties in the model inputs were separated into 2 types: uncertainty in the data used to describe the system (α uncertainties) and uncertainty in impact calculations or background data that affects all systems equally (β uncertainties). The impacts of pig production in the 2 regions were systematically compared based on the differences in the systems (α uncertainties). The method of ascribing uncertainty influenced the outcomes. In eastern systems, EP, MEP, and FEP were lower (P < 0.05) when assuming that all uncertainty in the emission factors for leaching from manure application was β. This was mainly due to increased EP resulting from field emissions for typical ingredients in western diets. When uncertainty in these emission factors was assumed to be α, only FEP was lower in eastern systems (P < 0.05). The environmental impacts for the other impact categories were not significantly different between the 2 systems, despite their aforementioned differences. In conclusion, a probabilistic approach was used to develop an LCA that systematically dealt with uncertainty in the data when comparing multiple environmental impacts measures in pig farming systems for the first time. The method was used to identify differences between Canadian pig production systems but can also be applied for comparisons between other agricultural systems that include inherent variation.

Environmental impact of the typical heavy pig production in Italy

“…Our EP is similar or slightly higher than the findings of other researchers on pigs of lighter slaughter weight (Basset Mens and van der Werf, 2005;Dalgaard, 2007;Reckmann et al, 2013;Dourmad et al, 2014;Mackenzie et al, 2015). Nitrate and phosphate released in water and ammonia emitted in the air contributed respectively for 64%, 21% and 5% to EP.…”

“…The results are comparable but slightly higher than those reported on lighter pigs (Basset-Mens & van der Werf, 2005;Dourmad et al, 2014;Mackenzie et al, 2015). The main use of energy was related to the production of purchased feed (63.0±14.7%).…”

“…Vergé et al, 2009;Pelletier et al, 2010;Wiedemann et al, 2010;Dourmad et al, 2014;Mackenzie et al, 2015;González -Garcia et al, 2015). Aramyan et al (2011) assessed GWP per kg LW in a number of European countries: values varied from a minimum of 2.55 to a maximum of 2.97 kg CO2 eq but pig weights at slaughter were always lower than 120 kg.…”

“…In our study it was on average 0.004 ± 0.00008 g SB eq per kg LW, much lower than the result reported by Mackenzie et al (2014). As obtained by Mackenzie et al (2015), the major contribution is generated by the production of purchased feed (83.3%).…”

“…A number of papers analyzed through a LCA approach the environmental impact of the production of pigs slaughtered at a standard LW of 90-120 kg (Basset-Mens and van der Werf, 2005;Dalgaard, 2007;Vergé et al, 2009;Pelletier et al, 2010;Wiedemann et al, 2010;Aramyan et al, 2011;Dourmad et al, 2014;Mackenzie et al, 2015) but studies focusing on the impact evaluation of heavy pig production are presently lacking.…”