1. Overview of existing excretion factors
Gerard Velthof

2. Aim of this Task
Make an overview of the different methodologies used in Europe to calculate N and P excretion factors
Create a database with the excretion factors used in different reporting systems

3. Need for excretion factors
Greenhouse gas emissions: UNFCCC
Ammonia emissions
Gothenborg protocol: UNECE
NEC Directive: EC
Manure production: EC Nitrates Directive
Agri-environmental indicators, including nutrient balances: Eurostat, EEA, DG’s
Models used for evaluations: GAINS, CAPRI, MITERRA

4. UNFCCC
Countries report emissions of greenhouse gases to the UN Framework Convention on Climate Change
Methods to calculate greenhouse gas emissions based on the IPCC guidelines
Intergovernmental Panel on Climate Change
N excretion factors needed to calculate N2O emissions from housing, manure storage and soils

5. IPCC Guidelines: Tiered approach
Tier 1. Default excretions rates in units of N excreted per kg of animal per day
Typical average animal mass values are available
Tier 2. Calculation of N excretion from N intake and N retention data
Typical N retention data are available
Tier 3. Country-specific methodology

6. Example IPCC Tier 1 excretion factors

7. Methods in 2011 reports to UNFCCC

8. Excretion factors dairy cattle in NIR 2011

9. Excretion factors pigs in NIR 2011

10. Gothenborg protocol and NEC Directive
Obligations to report ammonia emission to UNECE and EC
EMEP/EEA air pollutant emission inventory guidebook
Includes methods to calculate ammonia emission
Tiered approach

11. EEA/EMEP Guidebook
Tier 2 excretion factors
Tier 1. Default NH3 emission factors in kg per animal.
Tier 2. Defaults values
Tier 3. Country-specific approach. More categories than Tier 2.

12. Comparison IPCC and EEA/EMEP factors

13. Nutrient balances Eurostat and OECD
Both nitrogen and phosphorus
Different approaches used
Combination of new and existing factors, e.g. excretion factors reported for UNFCCC
Excretion factors also used for other Agri-environmental indicators: ammonia and greenhouse gas emissions

14. GAINS model (IIASA, Vienna)
Used for studies for EC, including NH3 emission
Default values for excretion, except dairy cattle
equation in which excretion depends of milk yield

15. CAPRI model (university of Bonn)
Economic model used for Common Agricultural Policy
Excretion is calculated as the difference between N intake and N retention of animals
Based on feed statistics (FAO, Eurostat)
Available feed in a region distributed over animals, based on energy and nutrient requirements

16. Nitrates Directive Maximum application of manure: 170 kg N per ha
Estimation of manure N production (net excretion):
Net excretion = gross N excretion - gaseous N losses in housing and storage
Defaults: EU or country specific
Calculation: farm specific
Both excretion factors and N emission factors
Calculated/measured manure amount
or volume and N content
Defaults or measurements

17. Nitrates Directive
Guidelines to calculate manure N production are available:
Ketelaars and van der Meer (1999): “Establishment of criteria for the assessment of the nitrogen content of animal manures”
Used in some member states (e.g. UK and Italy), but most member states use other approaches
Also recommended in HELCOM in 2003

18. Nitrates Directive

19. Differences

20. Causes for differences
Different methodologies:
from defaults to country specific approaches
but even defaults differ (e.g. IPCC and EEA/EMEP)
sometimes not clear (e.g Nitrates Directive)
Sometimes only aggregated excretion figures for animal categories are reported
Differences in age, weight, feeding systems, young animals and unit (per animal or per animal place)
Lack of feed data; assumptions have to be made

21. Recommendations
Need for a harmonized procedure to calculate excretions:
Harmonization of animal categories (e.g. FSS)
Recommend a set of methodologies (Tier approach) to estimate the excretion for each category
To be used for all policies and reporting systems

22. Thank you