Cattle slurry is a significant source of nutrients for grass growth. To reduce ammonia and greenhouse gas emissions as well as retain maximum nitrogen from the slurry, chemically amending the slurry can be useful.
Overview
Slurry additives are chemicals that are added to slurry during storage to alter the composition of slurry in such a way that nitrogen retained within the slurry is increased thus reducing GHG losses to the atmosphere.
Why should farmers consider chemically amending their slurry?
Treating slurry with chemicals yields the following benefits:
- More nitrogen will be retained from the slurry thus reducing demand and costs associated with chemical fertiliser.
- Gaseous nitrogen losses will be reduced resulting in lower greenhouse gas emissions associated with slurry.
- The treated slurry will have a less pungent smell.
In the following video, a Teagasc researcher discusses the treatment of slurry with chemical amendments during storage.
How do you chemically amend slurry?
- The slurry additives would reduce greenhouse gas emissions without increasing the loss of other nutrients such as phosphorus into water bodies or increasing ammonia in the atmosphere.
- Slurry chemical amendments used for trials are not yet fully authorized for commercial use.
Economic and Environmental Benefits
Treating manure with chemicals such as Glasabate reduces the loss of carbon resulting in fewer emissions. More nitrogen is retained in the manure thus reducing the demand for chemical nitrogen fertiliser and the reduction in fertiliser cost.
In order to quantify the environmental and economic benefits, a case study for a farm with 93 cows housed for 18 weeks during winter was used as shown in the Table below.
Net costs of slurry additives and reduction in emissions
| Scenario1 Amend 50% of slurry | Scenario2 Amend 100% of slurry | |
| Quantity of slurry amended (m3) | 226 | 552 |
| *Amendment cost (€) | -452 | -1104 |
| Environmental impact | ||
| Total emissions(kg CO2-eq / kg FPCM) | 0.935 | 0.911 |
| Reduction in emissions (%) | 2.56 | 5.10 |
93 cow herd, soil drainage is moderate
* Estimated amendment cost is 2€/m3 of slurry
Net savings/ cost are the savings or cost per year for the farm
Research
Research at Farm Zero C
Work at FZC investigated the use of a chemical additive- GasAbate supplied by Glasportbio, on greenhouse gas emissions stored slurry. The results showed that treating stored slurry with GasAbate could reduce methane emissions by 80%. The treatment also had increased biogas output. Shinagh was one of the first dairy farms to implement this technology which provides evidence of the technology being scaled to a commercial farm.
Other Research
Key findings from previous research on the use of Slurry Chemical Amendments have yielded different results:
- Acidification of slurry has consistently shown a reduction in GHG emissions during storage (Emmerling et al., 2020).
- Applying cattle slurry pre-mixed with the nitrification inhibitor dicyandiamide (DCD) during anaerobic storage was shown to potentially reduce nitrous oxide losses (Kavanagh et al., 2021).
- More research is required to ascertain soil health impacts and long-term grass productivity when treated slurry is used.
Links to more research
- Amendment of cattle slurry with the nitrification inhibitor dicyandiamide during storage
- The Effect of Chemical Amendments Used for Phosphorus Abatement on Greenhouse Gas and Ammonia Emissions from Dairy Cattle Slurry: Synergies and Pollution Swapping.
- Mitigating ammonia and greenhouse gas emissions from stored cattle slurry
Regulations
Chemically amending slurry helps in reducing nitrogen losses from slurry thus helping farmers in adhering to the following regulations.
Suppliers
While most chemical amendment additives are not yet available commercially, the following company is working to further develop these additives: