Canada’s Air Pollutant Emissions Inventory Report 2022: annex 2.5

A2.5 Estimation methodologies for Agriculture by sector/subsector

Agricultural Fuel Combustion

Description

Agricultural Fuel Combustion covers emissions resulting primarily from combustion sources used for space/water heating and crop drying.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5, SO_x, NO_x, VOCs, CO, NH₃, Pb, Cd, Hg, dioxins/furans, B[a]p, B[b]f, B[k]f, I(cd)p

Emissions are calculated for 10 types of fuel: natural gas, natural gas liquids, kerosene and stove oils, light fuel oil, heavy fuel oil, Canadian bituminous coal, sub-bituminous coal, lignite coal, anthracite coal, and imported coal.

Total usage by fuel type and province and territory is multiplied by pollutant-specific emission factors.

Activity data

Statistics Canada (n.d.[i])

Emission factors (EF)

TPM, PM₁₀, PM_2.5, SO_x, NO_x, VOCs, CO: U.S. EPA (1998)
(Emission factors are chosen to represent the typical type of combustion equipment for each fuel type)

TPM, PM₁₀, PM_2.5, SO_x, NO_x, VOCs, CO for natural gas fuel: U.S. EPA (2004)
Sulphur contents of liquid fuels: EC (2010)
Sulphur contents of coal: CEA (2002)

NH₃: Battye et al. (1994) and Coe et al. (1996)

Pb, Cd, Hg, dioxins/furans, B[a]p, B[b]f, B[k]f: CARB (2005) and U.S. EPA (1998, 2003, 2004)
(Emission factors are selected to represent the typical type of combustion equipment for each fuel type)

Animal Production

Description

Animal Production covers emissions from the volatilization of NH₃ from nitrogen (N) in manure, particulate matter (PM) that is released from feeding and housing, and volatile organic compounds (VOCs) that are released during livestock feeding, housing and manure management.

Ammonia volatilization is a chemical process that occurs when manure is excreted or stored without a cover. Once excreted, manure moves through a number of stages until it is eventually cycled back to farm fields. Ammonia volatilization occurs at each stage of this cycle, including animal housing, transport to long-term storage, storage, and application of manure to the field.

Livestock production results in primary PM emissions from the aerial transport of feed particles, feather fragments, fecal material, skin debris or dander, animal wastes, mould spores, bacteria, fungi, litter fragments, etc. Ventilation systems are required in livestock buildings for air exchange and, as a result, a portion of the PM in confined livestock buildings is emitted into the atmosphere via the ventilation system.

VOC emissions from livestock production are the result of biological processes that partially breakdown feed, especially silage, during storage and digestion. Emissions from excreted manure also occur during all stages of the manure management cycle. Sites of emission therefore include silage stores, livestock housing, manure stores and agricultural fields on which manure is applied or that are used for grazing.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5, NH₃, VOCs

Ammonia

The methodologies for NH₃ emissions were developed by Environment and Climate Change Canada (ECCC) in collaboration with Agriculture and Agri-Food Canada (AAFC) through a national research project: the National Agri-Environmental Standards Initiative (NAESI).

Methods describing the estimates of NH₃ emissions from Canadian livestock are published for most major livestock categories (dairy, non-dairy, swine and poultry). Details on parameters used and animal category-specific methodologies are available from a few publications (Sheppard and Bittman, 2010; Sheppard and Bittman, 2012; Sheppard et al., 2007a, 2007b, 2009a, 2009b, 2010, 2011a, 2011b; Chai and al., 2016).

For dairy and swine, the methodology used to estimate NH₃ emissions has been updated to make it compatible with the current methodology used for the estimation of greenhouse gases (GHG) (see Annex 3.4 of the National Inventory Report [NIR]). Although the specific emission factors used in estimating NH₃ emissions have not been modified, the total emissions per head have changed as a result of changes in rates of N excretion per animal and the proportions of manure stored in different manure systems over time.

Methodologies for minor animals, such as horses, goats, fur-bearing animals (mink, fox), wild boars, deer, elk, rabbit and poultry, were taken from Battye et al. (1994).

Particulate Matter (TPM, PM₁₀, PM_2.5)

The methodologies for PM emissions from livestock production are developed by AAFC for publication in the National Agri-Environmental Health Analysis and Reporting Program (NAHARP) report, published every five years with the Agricultural Census. The method is consistent with the EMEP/CORINAIR Emission Inventory Guidebook (EEA, 2002), but uses country-specific emission factors. Methodologies are published in Pattey and Qiu (2012) and Pattey et al. (2015).

Volatile Organic Compounds (VOCs)

For all livestock except dairy cattle, the methodology for estimating VOC emissions was based on the Tier 1 methodology outlined in the 2013 EMEP/EEA Air Pollutant Emission Inventory Guidebook (EEA, 2013).

Emissions from dairy cattle were calculated using the Tier 2 approach provided in the 2013 EMEP/EEA Air Pollutant Emission Inventory Guidebook. Country-specific parameters, including feed gross energy intake, silage content, and time spent in housing, are consistent with those used to calculate GHG emissions in the NIR, as described in Annex 3.4 of Part II.

Activity data

Annual cattle, sheep and swine populations are calculated as the simple mean of semi-annual or quarterly surveys , n.d.[b], n.d.[c], n.d.[d]). These smaller surveys are corrected to the Census of Agriculture (COA) population estimates that are collected every five years to ensure the accuracy of the estimates.

The populations of other livestock, such as horses, goats, bison, llamas and alpacas, deer and elk, wild boars, rabbits, and poultry, are taken from the COA exclusively, and annual populations are developed by linear interpolation in order to avoid large changes during census years. Where populations for certain alternative livestock animal categories were not available in the COA, values were held constant or extrapolated back to zero.

The breeding mink and fox population estimates were taken from an annual Statistics Canada survey titled Supply and Disposition of Mink and Fox on Fur Farms (Statistics Canada, n.d.[e]). Rabbit populations were taken from responses to the COA as provided on the AAFC Red Meat Market website (AAFC, 2016).

Emission factors (EF)

Ammonia

Non-dairy cattle and poultry ammonia emission factors are a weighted average of a variety of different emission fractions associated with the stages of the manure and animal production cycle.

The input to the emission factor equation originates from a combination of the Livestock Farm Practices Survey (LFPS), which defines feed distribution to and consumption by animals throughout the year, and generic parameters derived from scientific literature or expert opinion. This information is distributed spatially across Canada by ecoregion.

Animal populations are reassigned to a matrix of animal housing and manure management systems based on their relative proportion in the overall farm population.

The fractions of NH₃ emitted at each step in the manure cycle are taken in part from the EMEP/CORINAIR Emission Inventory Guidebook (EEA, 2002) and in part from Canadian studies. The resulting weighted emission factors are applied to populations of animal subcategories taken from census data at the ecoregion spatial scale.

The models employed to calculate NH₃ emissions from beef and swine production are described in Sheppard and Bittman (2010, 2012) and Sheppard et al. (2010).

Dairy cattle:

Ammonia emissions are calculated according to Sheppard et al. (2010), with modifications according to Chai et al. (2016), based on the activity data and methodology outlined for Agriculture in the NIR (ECCC, 2021). Total N excretion for dairy cattle is calculated according to the Tier 2 methodology as described in the IPCC 2006 Guidelines (IPCC, 2006).

Ammonia emission factors from Sheppard et al. (2011a) are expressed as fractions of total N using calculated total ammoniacal nitrogen (TAN) fractions (Chai et al., 2016) to produce ammonia N loss factors by ecoregion for housing and manure storage, manure application, and manure deposited on pasture, range, and paddock.

Manure management storage information was derived from Sheppard et al. (2011b) to identify proportions of manure excreted on pasture and in exercise yards and information on the quantity of manure stored as liquid and solid manure was drawn from Statistics Canada (1996), the Farm Environmental Management Surveys (2001, 2006, 2011) (Statistics Canada, n.d.[f]) and the 2005 Livestock Farm Practices Survey (Statistics Canada, 2007). A time series of manure storage was developed on the basis of relationships between liquid storage and time on pasture with farm size to account for changes in manure storage between 1990 and the present.

Emissions from manure applied to agricultural soils were consistent with Sheppard et al. (2010) as modified according to Chai et al., 2016.

Swine:

Ammonia emissions are calculated according to Sheppard et al. (2010) with modifications used to convert TAN fractions to Total N that are consistent with the method used for dairy (Chai et al., 2016) and based on the activity data and methodology outlined for Agriculture in the NIR (ECCC, 2021). Total N excretion for swine is calculated according to the Tier 1 methodology described in the 2006 IPCC Guidelines (IPCC, 2006), and modified to use a country-specific animal mass time series for market swine as described in Annex 3.4 of the NIR.

Ammonia emission factors from Sheppard et al. (2010) are expressed as fractions of total N using calculated TAN fractions (Chai et al., 2016) to produce ammonia N loss factors by ecoregion for housing and manure storage, and manure application to agricultural soils.

Manure management storage information on the quantity of manure stored as liquid and solid manure was drawn from a series of Farm Management Surveys for years 1995, 2005, 2006 and 2011. A time series of manure storage was developed on the basis of relationships between liquid storage and farm size to account for changes in manure storage between 1990 and the present.

Particulate Matter

Total particulate matter (TPM) emission factors for poultry are taken from Van Heyst (2005) and Van Heyst and Roumeliotis (2007). Emission factors for cattle and swine are average values from Takai et al. (1998) and Seedorf (2004). In the case of PM₁₀ and PM_2.5, emissions are estimated from TPM emission factors multiplied by 0.45 and 0.1 to produce PM₁₀ and PM_2.5 emission factors, respectively.

Average animal weights are used to convert emission factors in the form of g d^-1 AU^-1 to units of kg head^-1 year^-1.

The emission factors for cattle are also assigned to the other animal types by assuming that the emission factors per animal unit for sheep, goats, bison, llamas, alpacas and horses are the same as those for cattle. Average body weight of cattle are consistent with information provided by Boadi et al. (2004) and with weight corrections for cattle according to the methodology outlined in the NIR (ECCC, 2021). All other animal weights were consistent with values used to estimate N excretion in ECCC (2021).

Currently no emissions are estimated for mink, fox, wild boars, deer, elk or rabbit.

Volatile Organic Compounds (VOCs)

The emission factors for all animals except dairy cattle were taken from Table 3-3 of the EMEP/EEA Air Pollutant Emission Inventory Guidebook 2013 (EEA, 2013). For livestock categories where a choice of emission factors was provided, the non-silage emission factor was used, except for beef cattle in feedlots where the silage emission factor was used. A weighted emission factor for beef cattle was calculated using the fraction of time spent during each stage of production according to Boadi et al. (2004).

For dairy cattle, emission factors were calculated for six separate sources of emissions as described in the EMEP/EEA tier 2 methodology. Gross energy intake, silage content of feed, and fraction of time spent in barns, were all calculated based on country-specific data compiled in order to estimate GHG emissions (see Annex 3.4 of the NIR). In the EMEP/EEA tier 2 methodology, NH₃ emissions are used as a proxy to estimate the proportion of VOC emissions that occur in housing and manure storage and during manure application. The proportions were derived from NH₃ emissions from the Canadian Ammonia Model, which was modified to account for the shift in manure management practices in the dairy sector (see ammonia methodology).

Inorganic Fertilizer Application (under Crop Production)

Description

Fertilizer Application includes emissions resulting from the application of synthetic N fertilizers for annual and perennial crop production.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5, NH₃

Ammonia

The method is a simplified version of the approach adopted by Sheppard et al. (2010) for application on an annual time step.

The methodology uses a regression model developed by Bouwman et al. (2002) with derived NH₃ emission factors, and takes into account the most important parameters influencing emissions from synthetic N fertilizer application, based on a meta-analysis of scientific literature.

Particulates

Methodology is under review.

Activity data

Data on the types of N fertilizer used on farms are published by Statistics Canada (n.d.[g])

Areas of seeded annual and perennial crops: Statistics Canada (n.d.[h])

Soil properties, including pH and cation exchange capacity, are included in calculations using soil polygon information from a national-scale spatial database describing the types of soils associated with landforms.

Emission factors (EF)

Ammonia emission factors are calculated using the multiple linear regression equation from Bouwman et al. (2002). The approach uses different regression parameters for synthetic N fertilizer types, method of N application, crop type, and soil pH and cation exchange capacity.

A matrix of emission factors is derived for each combination of these conditions occurring across Canada. The average provincial and national emission factors are weighted averages of the relative proportion of each combination of fertilizer type and fertilizer application practice on different soil types in different ecodistricts across the country.

TPM, PM₁₀ and PM_2.5 methodology is under review.

Sewage Sludge Application (under Crop Production)

Description

Sewage sludge application (i.e. biosolids) includes NH₃ emitted when sewage sludge is land-applied on agricultural soils for annual and perennial crop production.

General inventory method

Pollutant(s) estimated:
NH₃

Ammonia

The methodology is aligned with reporting of NH₃ losses from land application of sewage sludge in the NIR. In contrast to the 2016 EMEP/EEA simplified Tier 1 methodology for estimating per capita emissions from sewage sludge, the use of the NIR methodology allows consistency among pollutant estimates. The methodology takes into account population change, but also captures trends in provincial land-application rates and regulations as well as characteristics of the material, such as N content.

Activity data

Data on the production and management of biosolids were derived from an Environment and Climate Change Canada commissioned report (Cheminfo Services Inc., 2017). The dataset was generated through a combination of telephone surveys and reports by the municipal wastewater treatment services from 33 Census Metropolitan Areas and from municipal and provincial environmental departments/ministries across Canada. This survey was representative of 63% of the Canadian population on wastewater treatment plants (WWTP) located in Canadian Metropolitan Areas (CMAs). It did not include Prince Edward Island (PEI) and Canadian territories. The data were compiled at five-year intervals (1990–2015). Although there were some gaps and inconsistencies owing to a lack of complete management information and changes in provincial regulations on biosolids, this is the only known source of data for a quantitative estimate of biosolids available at the national scale

The time series of biosolid production data was produced through a series of analytical steps. First, a provincial-level per capita model was constructed to establish “baseline biosolid production.” Production was assumed to be directly proportional to the population of a geographical area. Different spatially scaled roll-ups of Statistics Canada population estimates were evaluated for best-fit of the data including CMA populations, aggregated CMA populations, and provincial populations. Regression analysis indicated that the provincial population-based model was the most accurate based on the strength of the correlation coefficients. The data generated using this approach were not significantly different from the years for which data were reported by Cheminfo Services Inc. (2017). Therefore, the smoothed annual provincial biosolid production was derived using the linear model. For PEI, annual estimates for biosolid production were developed based on expert opinion and using a national average per capita figure (22.5 kg /person/year). This analysis created a complete series of biosolid production at a provincial scale.

Secondly, the regional rates of land application of biosolids (dry tonnes) were derived using the proportions reported in Cheminfo Services Inc. (2017) adjusted for federal, provincial and municipal regulations and restrictions. At the federal level, the regulations imposed by the Canadian Council of Ministers of the Environment (CCME) were applied. Later the provincial restrictions based on the nutrient content of the biosolids and any restrictions on the frequency of biosolid application to lands were incorporated.

Biosolids are typically subjected to various digestion and decomposition methods in wastewater treatment plants (WWTP) prior to land application. These methods have significant implications for the nutrient content of the biosolids and therefore influence the potential for emission when land applied. Accordingly, as the final step, a combination of survey results and literature analyses were used to identify the major digestion processes, and estimates from Dad et al. (2018) was used to establish the nutrient content of the biosolids.

Emission factors (EF)

The default loss factor (Frac_GASm) for organic N from the 2019 refinement to the 2006 IPCC guidelines was used to quantify NH₃ emissions (IPCC, 2019).

Harvesting (under Crop Production)

Description

Agricultural harvest activities entrain PM into the air. PM generated from agricultural harvesting, also known as grain dust, includes grain and dry plant particles, moulds, pollen and spores, silica, bacteria, fungi, insects, and possibly pesticide residues. These emissions are generated by vehicles travelling over the soil or by the processing of plant materials by agricultural equipment.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5

PM emissions from agricultural harvest operations are computed by multiplying an emission factor and an activity factor relating emissions to the area harvested.

Activity data

Activity data for PM emission estimates from crop harvesting rely on a combination of data from the Census of Agriculture and area estimates based on Earth Observation data. Activity data on areas of major field crops at an ecodistrict level from 1990 to 2020 are consistent with the data reported in the Agriculture and the Cropland Remaining Cropland category of the Land Use, Land-use Change and Forestry (LULUCF) sector for the NIR (ECCC, 2021).

Emission factors (EF)

There are no emission factors for agricultural harvests in Canada. The PM₁₀ emission factors proposed by the California Air Resources Board (CARB, 2003) are used to calculate PM emissions from crop harvests. Where not available from CARB (2003), the specific emission factors for some crops are based on an approximation from the closest representation (Pattey and Qiu, 2012).

Tillage Practices (under Crop Production)

Description

Tillage practices produce PM emissions from mechanical disturbances such as seeding, seed bed preparation and cultivation.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5

Agricultural tillage is the common method used by farmers to prepare land for seeding and weed control. Particulate matter emissions are generated from airborne soil particles during tillage operations due to the mechanical disturbance of the soil surface.

Particulate matter emissions from agricultural tillage operations are proportional to the area tilled. They are also dependent on the type of tillage practice as well as the number of tillage events per year. The calculations are described in more detail in Pattey and Qiu (2012).

The number of tillage events per year is dependent on tillage practices. There are fewer tillage events per year for conservation tillage compared to conventional tillage. Therefore, PM emissions from reduced tillage and no-till are lower.

Activity data

Activity data for PM emission estimates from tillage practices rely mainly on a combination of data from the Census of Agriculture and area estimates based on Earth Observation analyses. Activity data on areas of major field crops, including summerfallow, and on tillage practices at an ecodistrict level from 1990 to 2018 are consistent with the data reported in the Cropland Remaining Cropland category of the LULUCF sector for the NIR (ECCC, 2021). Information on the number of tillage events per year for crop type and tillage practices is taken from soil cover indicators (Huffman et al., 2012).

Emission factors (EF)

Emission factors for tillage practices are calculated using the method described in U.S. EPA (1985).

Wind Erosion (under Crop Production)

Description

Wind erosion occurs when wind blows across exposed agricultural land, resulting in PM emissions from the entrained particles.

General inventory method

Pollutant(s) estimated:
TPM, PM₁₀, PM_2.5

Wind erosion emissions from agricultural lands are calculated by multiplying the cultivated cropland area by an emission factor.

Activity data

Activity data for PM emission estimates from wind erosion rely mainly on a combination of data from the Census of Agriculture and area estimates based on Earth Observation. Activity data on areas of major field crops, including summerfallow, and on tillage practices at an ecodistrict level from 1990 to 2018 are consistent with the data reported in the Cropland Remaining Cropland category of the LULUCF sector for the NIR (ECCC, 2021).

Emission factors (EF)

The PM emission factor for wind erosion is calculated using the wind erosion equation (Woodruff and Siddoway, 1965) but considers the impact of soil and crop cover on PM emissions (Huffman et al., 2012). The emission factor for windblown PM emissions from agricultural lands is calculated using the methodology described in Pattey and Qiu (2012).

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