Emissions from Livestock are Biogenic

1. Emissions from livestock arise from enteric and manure-related emissions, as well as the emissions caused from the crop residue remaining after harvesting the crops eaten by livestock.

   This cycle is biogenic because it sequesters more CO2 via the growth of crops used to feed livestock than is emitted from livestock after eating them.

2. Enteric emissions are of concern because they are comprised mostly of methane (CH4) which has a higher short-term warming impact than longer-lived CO2.

   However, manure-related emissions in Canada have been flat for over 25 years and enteric emissions have declined from 20 years ago and have been flat for the past 15 years.

   Since methane breaks down by 50% every 8 - 10 years, Canadian agricultural methane is not causing increased warming, and any reduction in it will contribute to cooling. In other words, this is more of an opportunity, than a problem, in Canada.

3. We examined the carbon cycle related to a single lactating dairy cow weighing 600 kg using IPCC Tier 2 emission factors, in the context of the biogenic cycle of crops grown to feed it.

   The net annual carbon sequestration is 5.5 Mg CO2e per dairy cow, even if we burden livestock emissions of N2O and CH4 using GWP100 weights (i.e. treating them on the same basis as non-biogenic fossil fuel emissions).

   If we factor in the biogenic aspect of livestock emissions, net sequestration per dairy cow per year is 10 Mg CO2e.

4. We also examined a typical Ontario dairy farm with 190 head of cattle growing enough food on its 1300 acres to feed its cattle. The total volume of crops grown is over 1500 Tonnes annually and dairy herd generates 750,000 L of milk and 4 Tonnes of manure per year.

   We analyzed all 3 scopes of farm emissions, including upstream agrichemical production and shipping to farm, and calculated the sequestration of existing trees and the amount attributable in the residue after harvesting the crops. Even excluding sequestration within the harvested yield, the farm operates on a better than net-zero basis.

   Because the farm grows all its own food, we were easily able to trace the fate of carbon via the crops grown and fed to cattle. We accounted for enteric and manure-related emissions of CH4 and N2O using GWP100 weights as well as the amount of CO2 via bovine respiration. We also traced the amount of carbon that went into milk and cow biomass, as well as input to and respiration from soil.

   Net sequestration within each annual biogenic cycle was calculated to be an average of 10.8 Tonnes of CO2e per head. This result is consistent with our modelling of a single adult dairy cow due to the mix of cows of various ages in the herd.

5. Using a conservative estimate of 7.5 T CO2e per head per year and multiplying by the number of dairy cows registered by Agriculture Canada for 2022, we determine that the diary sector in Canada is sequestering, on an unpaid basis, at least 10.4 MT of CO2e per year.

   If we use the social cost of carbon established via the federal carbon tax as a fair price for carbon, the diary sector is producing a social value of at least $678 M per year. This valuation is low because it is based on treating enteric emissions as anthropogenic, a biogenic valuation works out to over $930 M per year, or $250 K per dairy farm.

6. Our research shows that dairy emissions are biogenic and there is no compelling reason that similar results would not be obtained via a similar analsysi for other livestock such as sheep, poultry, pigs, etc. In fact, non-ruminant livestock would likely sequester more carbon within their biogenic carbon cycles because they do not produce enteric emissions.

   In summary, livestock related emissions are no different than the emissions from any other bioenergy source becasue they are non-additive to global warming in Canada. Any reduction in livestock emissions presents an opportunity to further increase excess sequestration as a means to mitigate climate change.

   Even without further emission reduction, the production of agricultural products from livestock is more accurately viewed as a means of carbon capture and storage than as an emissions problem.

7. Even though both the FAO and the US EPA identifies enteric emissions as biogenic, Environment Canada's National Inventory of GHG fails to even footnote this important distinction and presents agricultural methane as if they are the same as methane emissions from the fossil fuel extraction and combustion.

   The important difference is that while agricultural methane has been shown to not contribute to global warming because it is biogenic, methane from fossil fuels does. This makes the presentation of emissions in the National Inventory more uncertain than necessary as it would be more accurate to show enteric emissions in a manner equivalent to other emissions from bioenergy sources.

   Further, the omission of the net sequestration of the carbon within the harvested yield of crops grown to feed livestock is a significant omission by Environment Canada in calculating carbon removal in Managed Lands. This also adds uncessary uncertainty that obscures the sustainability of Canadian agriculture.

You can download further details in the full report or return to the overview of the 4-part series.