Overview of Estonia’s current Tier 2 approach
Although the total population of livestock has been decreasing since 1990, enteric fermentation from cattle is a key source in the national inventory, accounting for about 95% of methane emissions from livestock (NIR 2017). Manure management methane emissions from dairy cattle are a key category by trend. Estonia began using a Tier 2 approach for cattle enteric fermentation emissions in 2007, and subsequently adopted Tier 2 approaches for manure management methane emissions and methane emissions from pigs in 2010 (Table 1).
Table 1: Overview of Tiers used for livestock methane emissions in Estonia’s national GHG inventories
|Livestock types||Tier used for enteric fermentation (CH4)||Year adopted*||Tier used for manure management (CH4)||Year adopted*|
*Year refers to the year of NIR submission
Description of approach: Estonia implements the IPCC Tier 2 model for cattle. The approach estimates daily gross energy (GE) intake on the basis of animal performance, management practices and environmental factors. GE is converted to methane using a methane conversion factor (Ym), and estimated daily emissions are multiplied by number of days to make an estimate of annual emissions per head. Activity data on the population of livestock of each category are multiplied by the EF to estimate total annual emissions from enteric fermentation for that category of livestock.
Implementation of the approach:
Activity data: Livestock population data is provided each year by Statistics Estonia, which provides population data for each of the 11 counties in the country. Initially, emissions were separately estimated for dairy cattle and 4 other types of cattle in each county (Table 2). Subsequently, a review recommended separate calculations for calves <6 months old, which are now estimated as 50% of the population of calves <1 years old. In 2017, the former method of calculating emissions by county and aggregating results to national level was replaced by a single calculation at national level using the weighted average of activity data from the counties.
Table 2: Livestock categorization in Estonia’s Tier 2 approach
|NIR 2010||Dairy: mature female|
Non-dairy: mature female, mature male, steers, calves <1 year old
|NIR 2017||Cattle >2 years old: dairy cattle, non-dairy mature females, non-dairy mature males|
Cattle 1-2 years old
Calves 6-12 months old
Calves 0-6 months old
|1 calculation at country level using weighted average of activity data from sub-regions|
Estimation of emission factors: Table 3 shows the sources of data used when Estonia first applied the Tier 2 approach (2007) to dairy and other cattle and the sources used in its most recent inventory submission (2017). Estonia’s initial Tier 2 approach for cattle used a mixture of IPCC default values and national statistical data:
- Apart from the standard coefficients in the IPCC model, default values were used for live weight, feed digestibility and the methane conversion factor.
- Subsequently, national data for cattle live weight was obtained from the Estonian Animal Recording Centre (EARC), which also provided data on milk fat content and % of cows giving birth in each year. The EARC collects animal performance data on dairy cattle by breed. A weighted average of live weights is estimated and used as the estimate of live weight in the national inventory.
- The initial estimate of feed digestibility was from the IPCC guidelines. Subsequently, a scientific publication from the country was used as the data source (Kaasik et al. 2002).
For dairy cattle, data on cattle weight, milk yield and fat content, and the % of cows giving birth are updated annually on the basis of data obtained from statistics agencies and the animal recording centre. Estimated GE and EFs thus vary year to year. For non-dairy cattle, live weight estimates, which are derived from IPCC default values and national research, do not vary from year to year.
Table 3: Data sources used for Tier 2 estimate of enteric fermentation emissions for dairy cattle in Estonia
|Model parameter||Data source in 2007||Data source in 2017|
|Average live weight||IPCC 1996||EARC|
|Daily weight gain (kg)||Literature from own country||EARC|
|Coefficient for maintenance (Cfi)||IPCC 1996||IPCC 2006 GL|
|% of time spent on pasture||-*||-*|
|Coeff. for feeding situation (Ca)||IPCC 1996||IPCC 2006 GL|
|Annual milk yield (kg)||Statistics Estonia||Statistics Estonia|
|Average fat content (% fat)||EARC||EARC|
|% pregnant in the year||EARC||EARC|
|Coefficient for pregnancy (Cpreg)||IPCC 1996||IPCC 2006 GL|
|Digestible energy (%DE)||IPCC 1996||Literature from own country|
|Gross energy (GE)||Calculated||Calculated|
|Methane conversion factor (Ym)||IPCC 1996||IPCC 2006 GL|
* indicates no data source cited.
Source: NIR 2007, NIR 2017
Manure management (Methane)
Approach used: IPCC approach (T2 for cattle and swine), T1 for other livestock.
Implementation of the approach: Livestock population data are taken from national statistics, using the same sources as are used for enteric fermentation. In Estonia’s initial Tier 2 approach for methane emissions from cattle manure management, the default values from the IPCC 1996 Guidelines (Reference Manual) were used for all parameters. Estonia continues to use default values for ash content, the maximum amount of methane able to be produced from that manure (Bo) and the methane conversion factor (MCF). Country-specific data are now used for feed digestibility, and the proportion of manure managed in different systems is estimated using expert judgement to replace the IPCC default MMS values.
Table 4: Data sources used for Tier 2 estimate of methane emissions from manure management in Estonia
|Model parameter||Data source in 2010||Data source in 2017|
|%DE||IPCC 1996 defaults||Literature from own country|
|Ash content||IPCC 1996 defaults||IPCC 2006 defaults|
|Bo||IPCC 1996 defaults||IPCC 2006 defaults for E Europe|
|Proportion of manure managed in different systems (MMS)||IPCC 1996 defaults||Expert opinion from Estonian Environmental Research Centre|
|MCF||IPCC 1996 defaults||IPCC 2006 defaults|
Estonia has no country-specific estimates of the uncertainty rates of activity data. Estimates were obtained from an Austrian publication (Rypdal & Winiwarter, 2001), where uncertainties of livestock population data from Austria, Norway, the Netherlands and USA are presented. Estonia assumes activity data uncertainty is the same as the Austrian uncertainty estimate. Uncertainty of emission factors is estimated using the IPCC default values.
Table 5: Estimated uncertainty values in Estonia’s livestock inventory
|Livestock populations||±10%||Rypdal and Winiwarter, 2001|
|Enteric fermentation (cattle, pigs)||±20%||IPCC 2006 Vol 4 Ch 10, p.10.33|
|Enteric fermentation (sheep, goats, horses, fur animals)||±40%|
Source: Estonia NIR 2017
Kassik A, Leming R, Remmel T. 2002. Nutrient losses (N, P, K) in dairy-and pig production. Journal of Agricultural Science.
Rypdal K, Winiwarter W. 2001. Uncertainties in greenhouse gas emission inventories—evaluation, comparability and implications. Environmental Science & Policy, 4(2-3): 107-116.