Welcome to our guide on manure storage systems tailored to UK farming practices. Whether you're running a dairy, beef, pig, sheep, or poultry operation, this guide helps you:

• Identify your current or planned manure management system
• Gain practical insight into emissions and environmental trade-offs

Important Note on Emissions Reporting

This page focuses only on emissions during manure storage, not those from application to land.

Emissions from manure application (e.g. ammonia, nitrous oxide) are handled separately in the Organic Fertility section, where factors like timing, method, and manure type influence impact.

Even short-term storage contributes to emissions and should be accounted for.

Examples for estimating storage emissions:

• If slurry is used throughout the year and emptied every 3 months, select a 3-month storage system for the entire year.
• If slurry is only produced for half the year and emptied every 2 months, select the 3-month storage system and apply it to 50% of the year’s emissions.

This ensures accurate reporting without overestimating or double-counting emissions.

Anaerobic Digestion (AD)

Definition: Controlled breakdown of manure by microbes without oxygen, producing methane-rich biogas and digestate.

Emissions:
CH₄: Very low — gas is captured for energy.
NH₃: Slight — may release from uncovered digestate.
N₂O: Slight — depends on digestate handling.

Composting Systems

In-Vessel Composting

Definition: Composting in enclosed units with controlled aeration.

Emissions:
CH₄: Low — aerobic conditions inhibit methane.
N₂O: Low — stable temperature and air reduce emissions.
NH₃: Moderate — nitrogen loss through volatilisation.

Windrow Composting

Definition: Manure in outdoor rows; may be turned (intensive) or static (passive).

Emissions:
CH₄: Low (intensive); higher (passive) — less oxygen in passive heaps.
N₂O: Low — good aeration reduces it.
NH₃: Moderate — drying and disturbance increase losses.

Static Pile Composting

Definition: Heaps with no turning; rely on passive aeration.

Emissions:
CH₄: Higher — anaerobic pockets form easily.
NH₃: Moderate — nitrogen escapes from surface exposure.

Farmyard Manure (FYM) – Solid Storage

Standard FYM

Definition: Manure with bedding stacked outdoors, not actively managed.

Emissions:
CH₄: Moderate — develops in compacted core.
NH₃: Moderate — volatilises from surface.
N₂O: Possible — from aerobic/anaerobic zones.

With Additives or Bulking

Definition: Additives bind nitrogen; bulking agents improve aeration.

Emissions:
CH₄: Lower — better airflow prevents methane.
NH₃: Varies — more surface can increase losses.
N₂O: Reduced — microbial activity suppressed.

Covered/Compacted FYM

Definition: Covered or compacted heaps to reduce emissions or leaching.

Emissions:
CH₄: May rise — less air.
NH₃: Lower — covers block volatilisation.

Deep Bedding

Definition: Manure and bedding build up in housing until removed.

Short-Term

Emissions:
CH₄: Moderate — limited anaerobic zones.
NH₃: Moderate — nitrogen exposed.
N₂O: High if disturbed — oxygen triggers release.

Long-Term

Emissions:
CH₄: Higher — long storage favours anaerobes.
NH₃: Higher — more nitrogen, more time to volatilise.

Daily Spreading

Definition: Manure spread within 24 hours of excretion, no storage.

Emissions:
CH₄: Minimal — no time for anaerobic breakdown.
NH₃: Moderate — high exposure to air.
N₂O: Not during storage — but can form in soil.

Dry Lot

Definition: Outdoor, hard-surfaced pens where manure is periodically scraped.

Emissions:
CH₄: Moderate — wetter patches can go anaerobic.
NH₃: Moderate — exposed waste emits nitrogen.

In-Field Manure (Grazing)

Definition: Manure deposited directly on pasture by grazing livestock.

Emissions:
CH₄: Low — quick exposure to air.
N₂O: Possible — weather and compaction dependent.
NH₃: Variable — urine can volatilise, especially in warm weather.

Liquid Slurry Systems

With Natural Crust

Definition: A surface crust forms over stored slurry, reducing gas loss.

Emissions:
CH₄: High — anaerobic microbes thrive.
NH₃: Reduced — crust acts as a barrier.

With Cover (Rigid or Floating)

Definition: Storage is sealed to limit emissions, often for compliance.

Emissions:
CH₄: Still high — unless gas is captured.
NH₃: Lower — physical cover limits loss.

Without Crust or Cover

Definition: Open slurry tanks or pits.

Emissions:
CH₄: High — no oxygen allows methane production.
NH₃: High — gases escape freely.

Pit Storage Below Animals

Definition: Manure stored in pits under housing, short- or long-term.

Emissions:
CH₄: High — warm and anaerobic.
NH₃: Moderate — rises with disturbance.
Spikes: Emptying may release stored gases.