Rothamsted Research examines the sources and impacts of ammonia, nitrous oxide, and methane emissions in UK agriculture, highlighting that agriculture is responsible for a significant portion of these greenhouse gases. The document discusses the influence of management practices, particularly in cattle farming, on emissions and emphasizes the importance of effective mitigation strategies, including diet changes and manure management. It concludes that while there are mitigation methods to reduce emissions, there will always be variability in production systems, necessitating ongoing research to improve efficiencies.

1. Rothamsted Research
where knowledge grows
Rothamsted Research
where knowledge grows
Ammonia and Greenhouse Gas Emissions
– who emits more?
Tom Misselbrook
Rothamsted Research, North Wyke

2. Overview
 Sources and impacts – ammonia, nitrous oxide, methane
 Current emission estimates
 Influence of management practices
 Potential mitigations

3. Ammonia - overview
Air quality pollutant
Particulate formation, eutrophication, acidification
Agriculture is major source – c. 90% for UK
NH3 emissions from UK agriculture

4. Ammonia - cattle
41%
19%
28%
12%
Housing
Manure storage
Manure spreading
Grazing
Managed manure is the major emission source

5. Ammonia – influence of management
Annual emission per dairy cow
Extended grazing systems will have lower NH3 emissions
BUT … potential for increased N2O and nitrate leaching
How efficiently are manure nutrients used?

6. GHG from agriculture - overview
Nitrous oxide and methane are potent GHG (c. 300 and 25x CO2)
Agriculture accounts for 84% N2O and 44% CH4 in UK
GHG emissions from UK agriculture (CO2e)

7. Enteric methane – influence of management
Production system – large, high yielders vs small, lower yielders
105
110
115
120
125
130
Large, high Medium Small, low
EFkgCH4/head
0
5
10
15
20
25
105
110
115
120
125
130
Large, high Medium Small, low
gCH4/kgmilk
EFkgCH4/head
EF (kg/hd/yr) g/l milk
Based on AC0114 proposed inventory methodology

8. GHG – influence of management
• Diet and body weight – relatively small effect
• Production level has a greater effect
• Other considerations – longevity, fertility, health
110
115
120
125
130
135
140
450 500 550 600 650
EFkgCH4perhead
Live weight
5,000 Milk yield 10,000
25% Concentrate level 75%

9. Mitigation – diet, lower N intake
Lower losses
throughout the system

10. Mitigation - diet
How low can we go? – Defra project AC0122
How to achieve in largely forage-based systems

11. Mitigation – manure management
Band spreading Slurry injection
Rapid incorporation
 Very effective NH3 emission
reduction
 Potential increase in N2O

12. Mitigation – nitrification inhibitors
-50
0
50
100
150
200
250
300
350
400
DailymeanN2Oflux(gN2O-Nha-1d-1
Autumn urine application
Control
Urine
Urine + DCD
 Economics – limited evidence of yield benefit
 Delivery mechanism
0
20
40
60
80
100
Spring Summer Autumn
%reduction
GT
NW

13. Summary and conclusions
 Cattle farming is a significant source of NH3, N2O and CH4
 Ammonia emissions primarily from managed manure
 Methane primarily from enteric fermentation
 Nitrous oxide primarily from soils
 Management practices influence magnitude of emissions – but
potential trade-offs
 Mitigation methods exist – particularly for ammonia
 Accept that there will always be a variety of production systems
 Research to improve nutrient use efficiencies/develop mitigations
within given systems
 Particularly for more precision in grazing/grassland-based systems

14. THE
END
!
Thanks!