Ten per cent of Canada's greenhouse gas emissions are from crop and livestock production, excluding emissions from the use of fossil fuels or from fertilizer production.
The main gases emitted by agricultural activities are:
- Carbon dioxide (CO2), which is released during soil cultivation;
- Methane (CH4), which is associated with cattle and livestock manure; and
- Nitrous oxide (N2O), which comes from using fertilizer and manure
Conversely, agriculture helps slow climate change by storing carbon on agricultural lands. Storing, or sequestering, carbon in soil as organic matter, perennial vegetation, and in trees reduces carbon dioxide amounts in the atmosphere.
For more information on how to estimate farming greenhouse gas emissions and test ways to reduce these emissions, please visit: Holos software program.
Agricultural activities inevitably result in multiple Greenhouse Gas emissions. Nitrous oxide emissions can originate directly from field-applied organic and inorganic fertilizers, crop residue decomposition, cultivation of organic soils, and from the storage of manure. Indirect nitrous oxide emissions can originate from nitrogen moved offsite such as from the volatilization and re-deposition of ammonia and from nitrogen leaching and run-off.
Methane emissions from agricultural sources in Canada are mainly a result of enteric fermentation in ruminant animals and from the anaerobic decomposition of stored manure. When organic matter in feed or manure decomposes under anaerobic conditions, a portion is released as methane.
Agricultural soils can either emit or absorb carbon dioxide. The difference is determined by the net effect of carbon dioxide absorption from the atmosphere by growing crops, and subsequent storage in the soil in the form of crop residues and soil organic matter, and emissions to the atmosphere via decomposition of crop residue and soil organic matter.
Agriculture emits all three greenhouse gases: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N20). These gases differ, though, in their ability to trap heat; tonne for tonne, CH4 is more than 20 times as effective at trapping heat as CO2, and N20 is about 300 times as effective as CO2.
To compare the emissions of these gases on equal terms, we usually speak of CO2 equivalents (for example, N20 has 298 CO2 equivalents).
Agriculture also removes CO2 from the atmosphere - croplands and grazing lands can be managed to remove and store large amounts of CO2 as soil organic carbon.
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