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Considering Greenhouse Gas Emissions Important for Sustainable Agriculture

July 16, 2014

Understanding greenhouse gas emissions from agriculture is important in developing an agricultural waste strategy for four primary reasons:

1. The most promising mitigation strategy for reducing greenhouse gas emissions from agriculture is by developing mandatory nutrient management plans, as reducing nitrous oxide emission from soils is the single largest contributor to agricultural greenhouse gas emissions. Nutrient management plans also reduce negative impacts on ground and surface water.

2. Implementing anaerobic digestion to reduce greenhouse gas emissions can easily be overstated as methane emission from manure storage comprises 10% or less of the greenhouse gas emissions from livestock farms.

3. Significant private and public funding is being used to mitigate greenhouse gas emissions from agriculture, therefore it is important to use internationally accepted protocols and to have good science to support it.

4. Ammonia emission from agriculture also increases greenhouse gas emissions via increased nitrous oxide emissions.

The next number of posts will consider the science on greenhouse gas emissions from agriculture in a global perspective, a Canadian perspective, and an Abbotsford perspective. We will include some of the science of the processes involved in order to understand relevance and mitigation strategies.

Global Greenhouse Emissions from Agriculture

Agriculture accounts for 10-12% of the total global emissions of greenhouse gases (Smith et al. 2007).  Agriculture accounts for about 60% of the world nitrous oxide emissions, and 50% of the methane emissions. Worldwide, nitrous oxide and methane emissions from agriculture increased 17% from 1990 to 2005. In North America, the main contributor to increasing emissions is management of manure from cattle, poultry and swine production, and manure application to soils.

Worldwide agricultural N2O emissions were projected to increase by 35-60% to 2030 due to increased nitrogen fertilizer use, and increased animal manure production (FAO 2003). Methane emissions are expected to increase by 60% due due to increases in livestock numbers.

The best options to reduce GHG emissions from agriculture include improve crop management, including nutrient use (Smith et al. 2007). They also noted that:

“Agricultural mitigation measures often have synergy with sustainable development policies, and many explicity influence social, economic, and enviornmental aspects of sustainability.”

“Improving N use efficiency can reduce nitrous oxide emisions and indirectly reduce GHG emissions from N fertilizer manufacture. By reducing leaching and volatile losses, improved efficiency of N use can also reduce off-site nitrous oxide emissions.”

Nitrous oxide emission from soil and methane emission from enteric fermentation (emissions from ruminant’s stomachs) represent 70% (38% for nitrous oxide and and 32% for methane) of the non CO2 emissions from agriculture (US EPA 2006). Manure management accounts for 7% of the total nitrous oxide and methane emissions from agriculture.

Gattinger et al. (2011) reported that that nutrient management (optimizing fertilizer and manure application to crop needs, including timing and method of application) would reduce nitrous oxide emissions from soils by 30 to 75%, which is the strategy that provides the greatest opportunity to reduce agricultural GHG emissions.

World Livestock Production is a Significant Contributor to GHG Emissions

Using a Life Cycle Assessment (LCA) approach, FAO (2103) estimated that GHG emissions from the livestock sector worldwide represents 14.5% of human-induced GHG emissions, of which beef production, milk production, pork production, and poultry production contribute 41%, 20%, 9% and 8%, respectively (FAO 2013). These calculations included CO2 emissions from transportation and storage (approximately 20% of total emissions), which was not included in the Smith et al. (2007) calculations. Food production and processing represented 45%, and enteric fermentation from ruminants represented 39%, whereas manure storage and processing represent 10% (4.3% from methane and 5.2% from nitrous oxide).

Canada’s Agricultural GHG Emissions

In 2002, agriculture related GHG emissions contributed 8% of the total national emissions in Canada, and accounted for 65% of Canada’s emissions of nitrous oxide and 26% of the methane emissions (Kebreab et al. 2006).  They further noted that domestic animals contribute 32% of Canadian agricultural emissions (primarily CH4 from the stomachs of ruminant animals), 17% from manure management, and 50% from soils (which is mostly nitrous oxide), and concluded that animal agriculture contributes more than 50% of the agricultural greenhouse gas emissions in Canada. Because more than 50% of agriculture’s contribution to greenhouse gas emissions is nitrous oxide from soils, Agriculture and Agri-Food Climate Change Table (2000) identified farm nutrient management plans as a mechanism for optimizing nitrogen applications and a strategy to reduce N2O emissions. Using a LCA approach for the dairy industry in eastern Canada, McGeough et al. (2012) estimated that methane from the rumen accounted for 48% of the GHG emissions, methane from manure was 8%, and nitrous oxide from soils was 40%.  Using a farm management model, Biocap (2006) estimated that a 10% reduction in manure application rate resulted in a 28% greater GHG emission reduction.

GHG Emissions from Agriculture in the Fraser Valley

Greenhouse gas emissions from agriculture in the Fraser Valley were calculated for the year 2000 (Levelton 2004). They estimated that 31% of agricultural GHG came from cattle (all methane emissions), 27% from manure (approximately 80% methane, 14% from fertilizer application (all nitrous oxide), and 25% from engines used in agricultural production (as carbon dioxide).  Of the total methane emissions, 61% were from livestock and 38% were from animal manure. Of the total nitrous oxide emissions, 29% was from manure, 59% from fertilizers applied to soil, and 12% from non-road engines. They reported that 60% of manure related GHG emission came from poultry manure management(2/3 of that being methane, 1/3 nitrous oxide, and 31% from cattle manure management (98% of this being methane).  They also reported 10,000 tonnes of ammonia emission, of which 68% originated from the poultry industry. Ammonia emission is a concern as it also contributes to nitrous oxide emissions when the ammonia is redeposited on the soil or water.

Recommendations for Agriculture in the Fraser Valley

Methane from ruminant animals and nitrous oxide emission from manure and fertilized soils are the greatest contributors to agricultural greenhouse gas emissions.  Manipulating animal diets is one approach to reducing methane emissions from the ruminant animal, however so far, the potential mitigation options are limited. One of the most promising strategies for mitigating agricultural GHG is to optimize nitrogen use, which can be managed by implementing nutrient management planning. Worldwide and in Canada, methane emissions from manure are estimated at 10% of the agricultural greenhouse gas emissions, whereas the estimate in the Lower Fraser Valley was approximately 25%. If 25% of our agricultural GHG emissions resulted from manure management, perhaps anaerobic digestion may be a good strategy for GHG mitigation as well.

In future posts we will address some of the strategies to reduce greenhouse gas emissions from agriculture.  This involves considering more recent science to create the best estimates of greenhouse gas emissions from agriculture. We will use agricultural census data from 2011 for Abbotsford to estimate GHG emissions.

References

Agriculture and Agri-Food Climate Change Table. 2000. Reducing Greenhouse Gas Emissions from Canadian Agriculture – Options Report. Publication # 2028E

Biocap. 2006. The potential for agricultural greenhouse gas emission reductions in the temperate region of Canada through nutrient management planning. Soil Resource Group. OMAFRA, Ontario. A Biocap Research Integration Program Synthesis Paper.

FAO, 2003. World Agriculture: Towards 2015/2030. An FAO Perspective. FAO, Rome, 97 pp.

Gattinger, A., J. Jawtusch, A. Muller and J. Olesen. 2011. Mitigating Greenhouse Gases in Agriculture: A challenge and opportunity for agricultural policies.  Dlakonisches Werk der EKD, Stuttgart, Germany.

Gerber, P.J., H. Steinfeld, B. Henderson, A. Mottet, C. Opio, J. Dijkman, A. Falcucci, and G. Tempio. 2013. Tackling climate change through livestock – A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO), Rome.

Kebreab, E., K. Clark, C. Wagner-Riddle and J. France. 2006. Methane and nitrous oxide emissions from Canadian animal agriculture: A review. Can. J. Animal Science 86:135-158

Levelton Consultants. 2004. Analysis of Best Management Practices and Emission Inventory of Agricultural Sources in the Lower Fraser Valley (www.abbotsfordtoday.ca/wp-content/uploads/2010/05/draftreport_dec6_final.pdf

Mc Geogh, E.J., S.M. Little, H.H. Janzen, T.A. McAllister, S.M. McGinn and K.A. Beauchemin. 2012. J. Dairy Science 95: 5164-5175

Smith, P., D. Martino, Z. Cai, D. Gwary, H. Janzen, P. Kumar, B. McCarl, S. Ogle, F. O’Mara, C. Rice, B. Scholes, O. Sirotenko. 2007. Agriculture. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

US EPA 2006. Global Anthropogenic Non-CO2 Greenhouse Gas Emissions. 1990-2020. United States Environmental Protection Agency, EPA 430-R-06-003. Washington, DC.

 

 

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