The Carbon Footprint of Lamb in Canada – More Research Needed
Lamb doesn’t often make global headlines, but a few years ago the greenhouse gas emissions from lamb production were reported to be higher than any other meat. Headlines like “Eating lamb is worst for the environment1” didn’t match with the image most people have of healthy lambs frolicking in healthy pastures. Recent suggestions to tax red meat through a carbon food tax doesn’t help either2. Higher reported emissions for lamb translate into a higher carbon footprint, the shorthand term for global warming impact, usually expressed per unit product. The global warming impact for agriculture relies on three main greenhouse gases (GHG); methane, nitrous oxide and carbon dioxide. Rising carbon dioxide (CO2) levels have been associated with the burning of fossil fuels. Methane, from enteric fermentation in the rumen and from manure, is 25 times more potent than CO2, the main greenhouse gas. Nitrous oxide from soil management and manure is 298 times more potent than CO2. The carbon footprint adjusts these impacts and expresses them in CO2 equivalents, or CO2e per functional unit. A functional unit may be kg live weight (LW), for example.
This may seem straightforward, but all carbon footprints are not created equal. Methods and calculations differ, lack of reliable data results in generalizations and assumptions with lots of resultant variability and uncertainty. Many calculations are within a specific “cradle to farm gate” boundary for a farm level assessment using a method called “life cycle assessment”, or LCA. Then there are direct emissions, such as rumen emissions, versus the indirect emissions, which may arise from processes traced back to the production of the feed that the lamb eats (fertilizers, land clearing). In general, it is not advised to compare carbon footprints using different methods, but that doesn’t stop researchers from doing that. One paper, aware of this reality, compared the carbon footprint of New Zealand to Welsh lamb and clearly demonstrated that the variability between sheep farms undermined any attempts to generalize about the claims made for the carbon footprints of lamb for a region or country3. The authors advised that more on-farm research was needed to collect sufficient data from similar farms within regions to aid in the understanding of the variation in carbon footprints. Another Welsh study five years later compared 64 sheep farms, and found that carbon footprints can vary with local conditions and management choices4. In particular, regardless of type of farm, the number of lambs reared per ewe, lamb growth rate, percentage of ewe and replacement ewe lambs not mated, and concentrate use had the greatest impact on the carbon footprint of lamb. Although Welsh lamb carbon footprints varied by farm type with lowland 10.85, upland 12.85 and hill 17.86 kg CO2e/kg LW, the authors concluded that nationally, the carbon footprint of lamb could be reduced by improving the productivity of the poor producing farms and reducing the productivity gap between farms.
Canada covers several ecoregions with varying climates and sheep production systems and breeds. Cattle are the main ruminant species in Canada, producing over 95% of enteric fermentation emissions. Cattle production systems are well-characterized and have been thoroughly studied regarding environmental impacts. Sheep are a minor species in Canada, although consumer demand for lamb is growing and over half of the lamb consumed is an imported product. There is little Canadian research regarding sheep production environmental impacts through tools such as LCA or carbon footprinting. Estimation of greenhouse gas emission intensities from sheep are generally based on values from the UN’s Intergovernmental Panel on Climate Change (IPCC). For sheep in Canada, IPCC Tier 1 emission factors are used for enteric fermentation, and IPCC Tier1/ 2 values are used for manure emissions.
The IPCC methodology to determine GHG emissions is rated by its level of detail and accuracy. Tier 1 is the lowest level, and emissions are obtained by multiplying by the population of animals in a livestock category by an emission factor (EF). For Tier 2, climate and type of manure storage is taken into account, but a lot more data is needed for Tier 2, especially in a country like Canada with such a wide range of climates and farming types.
The Canadian carbon footprint for sheep was recently reported to be significantly higher than the beef carbon footprint using national livestock population data and modelling using Tier 1/Tier 2 methodologies5. However, the uncertainty of the IPCC Tier 2 Canadian livestock model has been determined to be especially high for lamb methane emissions, primarily when values are assigned at the national scale6. Developing parameters that are country-specific with regional refinements, and using appropriate production stages for livestock, would reduce the uncertainties and produce more accurate greenhouse gas emission values and carbon footprints. The Canadian enteric methane values for sheep are based on Tier 1, at 8 kg methane/head/year regardless of age. In contrast, the UK enteric methane emission factors for sheep are age specific, at 8 kg methane/head/year for adult sheep, but 40% of that value for lambs less than one-year-old (3.2 kg methane/head/year), allowing for a further adjustment to the average age lamb is shipped. As to why lamb would have higher emissions, there are suggestions that wool is not counted as a product in these calculations (GHG), and would contribute to lower dressing percentages. The study also made broad management and feed assumptions which should be verified, and assumed a shorter reproductive lifespan for ewes than has been reported. More on-farm research, industry collaboration with scientists, better regional data and better models for sheep are definitely needed.
Based on the need for more production and regional-specific research, a carbon footprint project was conducted in the Gulf Islands of BC using my farm as an example. My farm is typical for the region, with a mild temperate Mediterranean-type climate, home-grown feed, and an extended grazing season. We supplement our pasture and grass hay with Sheep-Lyx nutrient block supplement according to the nutrient value of the forage and balanced with the nutrient needs of the sheep. The carbon footprint calculated using the cradle to gate LCA method included most emissions related to the production of lamb.
Three modelling systems were used to estimate the carbon footprint of lamb. Farm data was put into the models. The results were as follows:
UK- All-Tech Sheep E-CO2 “What If?” Tool (2015): 9.4 kg CO2e/ kg LW lamb
UK/US- Cool Farm Tool (Excel version 2.0): 5.13 kg CO2e/ kg LW lamb
Canada-Holos (version 2.2): 7.53 kg CO2e/ kg LW lamb
The variability in carbon footprint can be partly attributed to the different default values used for each model which can reduce the complexity and simplify the results. In general, a UK model may be used as a proxy for the Gulf Islands because of similarities in sheep breeds and climate. However, there are differences in feed sources, energy sources, management and resources such as soil. Based on other studies, 90% or more of the carbon footprint was expected to be on-farm. The other 10% was expected to come from upstream emissions (fertilizer, off-farm feed) and can inform the producer regarding sourcing of inputs to the farm and their impact. The majority of the emissions from this project were from methane, regardless of the tool or model used. The primary source of methane was from enteric fermentation.
The simplest system to use was the Alltech E-CO2 tool. The tool models UK scenarios based on industry data. The Tool has three basic farm systems; rearing lambs to finishing, rearing to store sale, and stores purchased to finish. Basic information from farm records are used, and “what-if” scenarios can help advise management decisions to improve the carbon footprint. This tool is useful for exploring different scenarios for sheep management, but is not sensitive enough to provide an accurate carbon footprint.
The Cool Farm Tool (CFT) has an online version as well as an Excel spreadsheet version. The CFT is useful for farm level calculations to estimate GHG emissions. The calculator is based on peer-reviewed data and goes beyond simple Tier 1 by including geographic locations. However, Canada was a single region for this model, reducing the model’s reliability.
Holos is a farm level GHG calculator developed by Agriculture and Agri-Food Canada, and it includes a research version7. Holos is specific for Canada using ecodistricts to account for climatic, soil type, topography and precipitation differences. Soil carbon factors are incorporated into the model. Estimates of uncertainty are identified. Holos allows for the estimation of carbon accumulation and losses, by calculating the impact of land use change such as land-clearing or planting of trees. Looking at the entire farm, our farm is a carbon sink because of the amount of forest we have. Holos is also being developed as a carbon footprinting tool and beyond carbon footprinting to include more environmental impacts8.
All three tools are easily accessed and free on the Internet for producers to use.
The carbon footprint results for my farm are being used to help determine hotspots for improvements in management, and to adjust future data collection so that a follow-up carbon footprint project can fine-tune the emission estimates. The results are a first step in understanding the impact of our local sheep production systems on greenhouse gas emissions, and to identify the gaps in data and modelling methods for regional, provincial and national carbon footprint projects.
1Brown, L. (2011). Eating lamb is worst for the environment, 19 July 2011. Earth Times. www.earthtimes.org.
2Ong, S. (2016). Taxing red meat to fight climate change, 24 May 2016. Science Line. www.scienceline.org.
3Edwards-Jones, G., Plassmann, K., Harris, I. (2008). The carbon footprint of sheep farming in Wales. Bangor University, Wales. Available to download at http://hccmpw.org.uk/medialibrary/publications/carbonfootprintsheepreportapril1508FINAL%20REPORT-1.pdf
4Jones, A., Jones, D., Cross, P. (2013). The carbon footprint of lamb: Sources of variation and opportunities for mitigation. Agricultural Systems 123, 97-107. Doi: 10.1016/j.agsy.2013.09.006.
5Dyer, J., Verge, X., Desjardins, R., Worth, D. (2014). A comparison of greenhouse gas emissions from the sheep industry with beef production in Canada. Sustainable Agriculture Research 3,65-75.
6 Karimi-Zindashty, Y., MacDonald, J., Desjardins, R. Worth, D., Hutchinson, J., Verge, X. (2011). Climate Change and Agriculture Paper: Sources of uncertainty in the IPCC Tier 2 Canadian Livestock Model. Journal of Agricultural Science. 1-14. doi: 10.1017/S002185961100092X.
7Little, S.M., J. Lindeman, K. Maclean and H.H. Janzen (2008). Holos - A tool to estimate and reduce GHGs from farms. Methodology and algorithms for Version 1.1.x. Agriculture & Agri-Food Canada, Ottawa, Ontario.
8 Krobel, R., Janzen, H., Beauchemin, K., Bonesmo, H., Little, S., McAllister, T. (2013). A proposed approach to estimate and reduce the environmental impact from whole farms. Acta Agriculturae Scand Section A dx.doi.org/10.1080/09064702.2013.770912