Nutrient Cycling in Agroecosystems 60: 317���326, 2001. �� 2001 Kluwer Academic Publishers. Printed in the Netherlands. 317 Canadian greenhouse gas mitigation options in agriculture R.L. Desjardins1,���, S.N. Kulshreshtha2, B. Junkins3, W. Smith1, B. Grant1 & M. Boehm4 1Research Branch, Agriculture and Agri-Food Canada, Ottawa, Canada K1A 0C6 2Department of Agricultural Economics, University of Saskatchewan, Saskatoon, Canada S7N 5A8 3Policy Branch, Agriculture and Agri-Food Canada, Ottawa, Canada K1A 0C5 4Centre for studies in Agriculture, Law and the Environment, University of Saskatchewan, Saskatoon, Canada S7N 5A8 (���Corresponding author e-mail: desjardins@em.agr.ca) Key words: agroecosystems, CO2 equivalent, economic model, enteric fermentation, greenhouse gas, methane, mitigation options, nitrous oxide, nutrient management Abstract In 1991, on farm management practices contributed 57.6 Tg CO2 equivalent in greenhouse gas emissions, that is, about 10% of the anthropogenic GHG emissions in Canada. Approximately 11% of these emissions were in the form of CO2, 36% in the form of CH4 and 53% in the form of N2O. The CO2 emissions were from soils CH4 emissions were from enteric fermentation and manure, and N2O emissions were primarily a function of cropping practices and manure management. With the emissions from all other agricultural practices included, such as the emissions from fossil fuels used for transportation, manufacturing, food processing etc., the agricultural sector���s contributions were about 15% of Canada���s emissions. In this publication, several options are examined as to their potential for reducing greenhouse gas emissions. These involve soil and crop management, soil nutrient management, improved feeding strategies, and carbon storage in industrial by-products. The Canadian Economic Emissions Model for Agriculture (CEEMA) was used to predict the greenhouse gas emissions for the year 2010, as well as the impact of mitigation options on greenhouse gas emissions from the agricultural sector. This model incorporates the Canadian Regional Agricultural sub-Model (CRAM), which predicts the activities related to agriculture in Canada up to 2010, as well as a Greenhouse Gas Emissions sub-Model (GGEM), which estimates the greenhouse gas emissions associated with the various agricultural activities. The greenhouse gas emissions from all agricultural sources were 90.5 Tg CO2 equivalent in 1991. Estimates based on CEEMA for the year 2010 indicate emissions are expected to be 98.0 Tg CO2 equivalent under a business as usual scenario, which assumes that the present trends in management practices will continue. The agricultural sector will then need to reduce its emissions by about 12.9 Tg CO2 equivalent below 2010 forecasted emissions, if it is to attain its part of the Canadian government commitment made in Kyoto. Technologies focusing on increasing the soil carbon sink, reducing greenhouse gas emissions and improving the overall farming efficiency, need to be refined and developed as best management practices. The soils carbon sink can be increased through reduced tillage, reduced summer fallowing, increased use of grasslands and forage crops, etc. Key areas for the possible reduction of greenhouse gas emissions are improved soil nutrient management, improved manure storage and handling, better livestock grazing and feeding strategies, etc. The overall impact of these options is dependent on the adoption rate. Agriculture���s greenhouse gas reduction commitment could probably be met if soils are recognized as a carbon sink under the Kyoto Accord and if a wide range of management practices are adopted on a large scale. None of these options can currently be recommended as measures because their socio-economic aspects have not been fully evaluated and there are still too many uncertainties in the emission estimates. Introduction The gaseous composition of the Earth���s atmosphere is changing at an accelerated rate because of the in- fluence of human activities. Of particular concern to society are the concentrations of N2O, CO2 and CH4, which are currently increasing at rates ranging from 0.3 to 0.9% per year, largely because of anthropogenic

318 Figure 1. Greenhouse gas emissions in Canada and the projected gap by 2010 to meet the Kyoto commitment. effects on the carbon and nitrogen cycles. In order to slow the increase in the atmospheric concentration of these gases, large reductions in their emissions will be required. Agriculture has been identified as an import- ant source of CO2, CH4 and N2O (Cole et al., 1993 Janzen et al., 1999). Knowledge of the role of agroecosystems in the greenhouse gas budget is essential if we are to estimate the importance of agriculture in mitigating the increase of greenhouse gases through changes in management practices (Rosenberg et al., 1998). This paper provides an estimate of the greenhouse gas emissions from agricultural sources. It discusses the uncertainties as- sociated with the emission estimates and it presents elements that can contribute to a strategy to allow the Agriculture and Agri-Food sector in Canada to meet its part of the commitment made by the Canadian government in Kyoto. The challenge for Canada Canada was among 174 nations that negotiated the Kyoto protocol in 1997. This treaty commits 38 de- veloped nations to reduce their greenhouse gas emis- sions for an overall reduction of 5.2% below 1990 levels. Canada has agreed to lower its emissions to 6% below the 1990 levels. In order to compare emis- sions of greenhouse gases, global warming potentials of the various gases are used. Carbon dioxide is used as the reference. Over 100 years, 1 kg of CH4 has the same warming potential as 21 kg of CO2, while 1 kg of N2O has the same warming potential as 310 kg of CO2 (IPCC, 1996). Once the emissions of methane and nitrous oxide are multiplied by the global warm- ing potentials of these gases, the emissions are in CO2 equivalent. Canada���s greenhouse gas emissions from anthro- pogenic sources were approximately 599 Tg CO2 equivalents in 1990 (Jaques et al., 1997 McIlveen and Desjardins, 1998). If Canada���s commitment in Kyoto is to be met we must lower our greenhouse gas emissions to approximately 563 Tg CO2 equivalent by 2008���2012 (Figure 1). To reach that target, Canada is expected to have to cut emissions by about 140���185 Tg CO2 equivalent from what they would be by 2010, under a business as usual scenario. The National Climate Change process In 1998, the Canadian government set up a process to permit the main sectors of the economy to develop a national implementation strategy to reduce its heat- trapping emissions to 6% below 1990 levels between 2008 and 2012, in accordance with the Kyoto Accord. This involved the creation of the National Climate Change Secretariat. Four groups were formed by the secretariat: (i) a Public Education and Outreach group, with responsibility to inform the public with respect to climate change issues, (ii) a Technology group, with responsibility to support the development of tech-