Fertiliser use is responsible for 30 to 35% of the total agricultural emissions. Straight fertilisers such as Calcium Ammonium Nitrate (CAN) are high nitrous oxide emitters whereas urea emits more ammonia. When farmers use protected urea, they can reduce overall nitrous oxide and ammonia emissions from the fertiliser.
Overview
Protected urea is urea treated with a urease inhibitor to minimise ammonia and nitrous oxide losses. Protected urea can be applied in spring, summer, autumn just CAN.
Why should farmers use protected urea?
- Farmers can use protected urea to reduce nitrous oxide and ammonia emissions.
- Protected urea costs less per kilogram of nitrogen than CAN.
The following video provides all the information on the use of protected urea.
How does protected urea work?
- Urea is not readily available to plants and initially needs to be converted into ammonium.
- This is done by urease enzymes in the soil that binds to the urea.
- Urease inhibitors temporarily bind to the urease enzymes so they can’t bind to the urea, preventing the localised spike in pH and reducing the losses of ammonia.
Economic and Environmental Benefits
Most farmers use a combination of CAN and Urea for their nitrogen requirements. Table 5 shows the net annual savings and emission reductions from replacing a combination of CAN and Urea with Protected Urea.
Table 5 Reduction in emissions and fertiliser costs
| Scenario 1 50% CAN 50% Urea | Scenario 2 100% Protected urea | |
| Price /kg Nitrogen (€) | 2.41 | 2.17 |
| Savings /farm(41ha) (€) | 2460 | |
| Net savings/ha (€) | 0 | 60 |
| Environmental impact | ||
| Total Emissions (kg CO2-eq / kg FPCM) | 0.95 | 0.91 |
| Reduction in emissions (%) | 0 | 4.21% |
Farm size is 41ha applying 250kg/ha fertiliser 84 cow herd, soil drainage is average
The 2022 fertiliser prices of €750/t for CAN, €950/t for Urea and €1000/t Protected Urea were used.
Net savings/ cost are the savings or cost per year for the farm
Research
Research at Farm Zero C
At FZC, protected urea has been used to replace CAN since 2020 and life cycle assessment is being done to ascertain the level of emissions reduced by replacing CAN with protected urea.
Other Research
Key findings from previous research are as follows:
- Protected urea resulted in a significant reduction in ammonia in both grass and tillage cropping when compared to standard urea.
- When compared to CAN, protected urea had a significant reduction in nitrous oxide losses in grassland (Forrestal et al., 2019).
- Urea treated with NBPT could reduce N₂O emissions to levels similar to unfertilised control without reducing the yield of grass in Johnson Castle (Krol et al., 2020).
- There is a very low risk of the inhibitor(NBPT) residuals in milk if animals are fed with grass fertilised with protected urea (Nkwotwa et al., 2021; van de Light et al., 2021).
Links to more research
- Protected urea: what is it, does it work, and is it cost-effective?
- Reducing nitrous oxide emissions by changing N fertiliser use from calcium ammonium nitrate (CAN) to urea-based formulations
- Nitrogen fertilisers with urease inhibitors reduce nitrous oxide and ammonia losses while retaining yield in temperate grassland.
Regulations
Switching to protected urea would help farmers in achieving the following climate targets and regulations.
European Communities (Fertiliser) Regulations 2005–
Ag Climatise roadmap 2020– The following actions of the roadmap towards climate neutrality promote the use of protected urea.
- “Action 2: Replace 50% of the straight CAN used on Irish grassland with protected Urea by 2030 and replace all urea with protected urea.”
- “Action 4: Maximise production of grazed grass.”
Suppliers
Some of the suppliers for protected urea are listed below.