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Agricultural ammonia emission mitigation: principles and practices - Jeremy Wiltshire
- 2. 2© Ricardo-AEA LtdRicardo Energy & Environment in Confidence
From Defra 2018: Code of Good Agricultural Practice (COGAP) for Reducing Ammonia Emissions
Why does ammonia emission matter?
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Agriculture emits around
87%
of ammonia from the UK
Latest data for 2017
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• The UK has agreed ammonia emission limits under the 1999 Gothenburg Protocol
• The UK estimates and reports ammonia emissions annually
Policy context
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Agricultural sources (ref: Inventory of Ammonia Emissions from UK Agriculture, 2017)
Beef cattle
24%
Dairy cattle
23%
Poultry
15%
Pigs
8%
Sheep
4%
Horses
1%
Fertiliser
application
18%
Digestate
application
5%
Sewage sludge
application
2%
- 6. 6© Ricardo-AEA LtdRicardo Energy & Environment in Confidence
Agricultural sources (ref: Inventory of Ammonia Emissions from UK Agriculture, 2017)
Housing
27%
Manure
application
25%
Fertiliser
application
18%
Manure
storage
9%
Grazing/
outdoors
7%
Hard
standings
7%
Digestate
application
5%
Sewage sludge
application
2%
- 7. 7© Ricardo-AEA LtdRicardo Energy & Environment in Confidence
Ammoniacal N content of manures
Exposure to air
• Grazing vs housing
• Spreading management and environment
Filtration
pH
Urea fertiliser breakdown (hydrolysis)
Principles governing emission and mitigation
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• Manures contain ammoniacal nitrogen, which is ‘available’ for emission to air
• N content (and NH3 content) of manures can be influenced by diet
• Decreases in protein content and change in amino acid balance leads to important
decreases in ammonia emissions
• Ammoniacal N content of manures affects emission throughout the manure handling
chain
Ammoniacal N content of manures
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Manure:
• mix of faeces and urine (plus bedding)
• Contains ammoniacal N
• Moves from housing to storage to spreading
N ‘flows’ through the system, from housing to storage to spreading
Relevance to mitigation:
• If N is ‘saved’ in storage, more flows through to spreading, so more is available to be
lost at spreading
N-flow concept in housed livestock systems
Housing
27%
Manure
application
25%
Fertiliser
application
18%
Manure
storage
9%
Grazing/
outdoors
7%
Hard
standings
7%
Digestate
application
5%
Sewage sludge
application
2%
- 11. 11© Ricardo-AEA LtdRicardo Energy & Environment in Confidence
• Minimising exposure to air
minimises emission
• Most exposure to air happens
in housing and at spreading
• Minimise housing
Exposure of manures to air
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• Spreading techniques can reduce exposure to air
• Around 40% of the readily available nitrogen content of manures is often lost following
surface application to land
• Windspeed and temperature are important factors
• Time from spreading to incorporation is important
Exposure of manures to air
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Source: Defra 2018. Code of Good Agricultural Practice (COGAP) for Reducing Ammonia Emissions.
https://www.gov.uk/government/publications/code-of-good-agricultural-practice-for-reducing-ammonia-emissions
Exposure of manures to air
- 14. 14© Ricardo-AEA LtdRicardo Energy & Environment in Confidence
• Reduced emission spreading techniques
Source: Defra 2018. Code of Good Agricultural Practice (COGAP) for Reducing Ammonia Emissions.
https://www.gov.uk/government/publications/code-of-good-agricultural-practice-for-reducing-ammonia-emissions
Exposure of manures to air
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• Capture /filter at point of emission from
buildings
• Only possible in buildings with forced
ventilation – pigs and poultry
Potential for filtration
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• Decreasing the pH
from (e.g.) 7.5 to 5.5
shifts the balance
between NH3 and NH4
+
• Acidification is used in
Denmark and interest
in the UK is increasing
• Relatively expensive
• Abatement 40-50%
overall depending on
pH reduction
pH of manures
- 17. 17© Ricardo-AEA LtdRicardo Energy & Environment in Confidence
• Urease enzymes catalyse the hydrolysis of urea
• urea + water ammonia + carbon dioxide
• Per kg fertilizer N ammonia emissions are reduced by c. 80% by using ammonium
nitrate instead of urea
• This is among the most cost-effective means of reducing ammonia emissions
• Urease inhibitors can be added to urea - reduces ammonia emissions by 70%
Urea hydrolysis
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Uptake potential is difficult to estimate
• Uptake depends on policy and economic drivers
• Further uptake depends on extent of current implementation
Uptake of most mitigation actions is limited by cost to the farmer
Uptake of some mitigation actions is limited by practical considerations
• Covering solid manure stores
• Covering some slurry stores
How long does it take to implement mitigation actions?
Practicalities in the farming industry