Frequent removal of manure to outside storage
System: Pigs
Mainly applicable for: Low outdoor temperature, liquid manure systems, farms with an anaerobic digester
Not or less applicable for: High outdoor temperature, or low temperature inside the livestock barn
Description
Frequent removal of manure to outside storage with a lower temperature than inside the livestock barn. This can be achieved by a vacuum system, slanted walls, scraper, or backflushing. Frequent removal, or another method of reducing methane emissions from slurry in barns, may be needed to allow anaerobic digestion to operate effectively. See the separate information sheet on anaerobic digestion for pig farms.
Mechanism of effect
The temperature of outside storage is generally lower than inside livestock barns. At lower temperature the methanogenic microbial activity in stored slurry is lower, and hence less methane is produced. In general, slurry temperatures higher than 20 C have shown high CH4 emissions which are reduced significantly under 15 C (Sommer et al., 2007). Lowering the temperature of slurry from above 25 C to less than 15 C results in less or no N₂O emissions due to inactivation of microbial processes in slurry. Removal to an outside storage is only effective when the external storage temperature is cooler than the inhouse pits.
Reference situation
Storage of manure inside livestock barns.
Legend
| ● – Small effect (<5%) | o – No effect | o – no effect |
| ●● – Medium effect (5-20%) | ● – Unfavourable effect | N/A – unknown effect |
| ●●● – Large effect (>20%) | ● – ● – Variable effect (depending on farm characteristics or way/level of implementation) |
Effect on total greenhouse gas (GHG) emissions (LCA)
| Mean effect and range in kg CO2-equivalents | per kg product | per farm (absolute) | Level of evidence | ||
| Mean | (min-max) | Mean | (min-max) | ||
| Frequent removal to outside storage | ●● | ●–●●● | ●● | ●–●●● | Low |
Effect per emission source
| Mean effect on emission from | Manure | Animal | Feed and forage production | Barn & farm inputs | |||
| CH4 | N2O | CH4 | CO2 | N2O | LUC | CO2 | |
| Frequent removal to outside storage | ●●● | ●● | #N/A | ● | |||
*risk of an adverse effect (see ’cause of variable or unfavourable effect’)
Cause of variable or unfavourable effect
Frequent removal to outside storage
The effect of frequent removal is larger with a larger difference between the temperature inside and outside the barn (effects being larger in winter), a higher frequency of slurry removal and a higher removal efficiency (less residual slurry left in the pit). Different methods (e.g. vacuum system, scraper, backflushing) have different effects.
| Literature references | Frequent removal to outside storage |
|---|---|
| Ambrose et al., 2023 | Additives and methods for the mitigation of methane emission from stored liquid manure |
| Petersen et al.; 2024 | In-vitro method and model to estimate methane emissions from liquid manure management on pig and dairy farms in four countries |
| Ma et al., 2023 | Frequent export of pig slurry for outside storage reduced methane but not ammonia emissions in cold and warm seasons |
| Hilgert et al., 2022 | Methane Emissions from Livestock Slurry: Effects of Storage Temperature and Changes in Chemical Composition |
| Misselbrook et al., 2016 | Greenhouse Gas and Ammonia Emissions from Slurry Storage: Impacts of Temperature and Potential Mitigation through Covering (Pig Slurry) or Acidification (Cattle Slurry). |
| Wang et al., 2021 | NH3, N2O, and NO emissions from digested pig slurry stored under different temperatures: Characteristics and microbial mechanisms |