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.
References
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
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