Potential for mitigating atmospheric ammonia in Canada

Most ammonia (NH3) emissions (85%) in Canada come from agricultural sources (400 kt/yr). There are international conventions that require countries to mitigate NH3 emissions but there are no federal or provincial guidelines in Canada stipulating emission targets or best practices for agriculture. This study examines the potential for mitigating atmospheric NH3 using a range of approaches. Taking current farm practices into account, employing proven low-cost measures (low-emission slurry application and slurry storage covers) would reduce annual emissions from livestock operations by 16 kt NH3-N, while using all available low-cost measures would reduce emissions by 79 kt NH3-N or 26% of livestock emissions. Another 36 kt/yr could be avoided by improving fertilizer practices, so that the total potential reduction would be about 29% of all agricultural emissions. Emissions from beef cattle and pig production could be reduced by 18% if consumption was cut by 50%, with greater mitigation if production for export was reduced, although the economic and social consequences need to be considered. Mitigation practices must be viewed in the context of possible pollution swapping especially in surplus nitrogen situations. Emissions must also be considered in terms of atmospheric NH3 transport to and from the USA, therefore bi-national agreements to jointly reduce emissions might be needed. It may be more cost-effective in Canada to strategically reduce emissions to minimize risks to health (from particulate matter) and the environment rather than to reduce annual national emission targets.