A new proposal could offer Irish dairy farmers face rising pressure from strict nitrogen limits aimed at protecting the environment a fresh way to manage nutrients and reduce costs, Teagasc has said.

Currently, according to Teagasc, Irish dairy farmers are facing increasing restrictions as a result of the Nitrates Directive, which limits the amount of organic nitrogen (N) that can be applied to land from livestock manure.

The standard limit is 170kg of organic N per hectare per year.

Some farmers can avail of a derogation to go higher; however, recent changes mean that, depending on your herd’s average milk yield, the N excretion rate per cow is now 80kg, 92kg, or 106kg N per year.

For many dairy farmers, this pushes their farms over the 170kg/ha limit, breaching the legal limit as per the Nitrates Directive.

Any stocking rate above this is in derogation territory.

The derogation, which allows higher limits, has been extended until at least 2028, but Teagasc has highlighted that its future remains uncertain and the rules are tightening.

Slurry exports problem

Currently, if a farm exceeds the 170kg/ha limit, the main options are to:

Export slurry to another farm that is under the limit;
Reduce cow numbers;
Rent or lease additional land.

The problem is, according to Teagasc, exporting slurry means losing valuable nutrients.

In addition, under current rules, if farmers export slurry to an anaerobic digestion (AD) plant, they cannot bring the resulting digestate back to their own farm if you are already at the organic N limit.

This forces them to buy chemical fertiliser to replace the lost nutrients, breaking the circular nutrient cycle and increasing costs. 

What is ReNure?

ReNure (Recovered Nitrogen from Manure) is a new proposal from the European Commission.

It would allow certain types of processed manure - specifically, digestate from AD plants that has undergone further treatment - to be classified as a chemical fertiliser rather than organic manure.

This means it would not count towards the 170kg/ha organic N limit, and could be used to replace chemical N fertiliser on your farm.

If Ireland were to adopt this proposal, ReNure would allow farmers to:

Export slurry to an AD plant;
Receive back processed digestate (if it meets ReNure standards);
Use up to an additional 80kg N/ha of this processed digestate as if it were chemical fertiliser.

According to industry insight from Teagasc, it must be clear that qualifying ReNure is a fertilising product, not just organic manure.

Engagement through discussion groups is seen as the first phase of this education.

On-farm separation is viewed as a key part of the plan, offering derogation farmers the options to maximise their organic fertiliser usage while returning ReNure at a lower cost and improved carbon intensity.

What digestate qualify as ReNure?

According to Teagasc, not all digestate will qualify.

"To be classified as ReNure, digestate must be further processed – for example, by ammonia stripping, membrane filtration, or chemical precipitation, to produce products like ammonium salts, mineral concentrate, or struvite."

These processes make the nitrogen in digestate more plant-available and similar to chemical fertiliser.

Is AD necessary or can ordinary manure that undergoes ammonia stripping also qualify?

It is not absolutely necessary to have AD. But, ammonia stripping is a capital-intensive process, and to achieve the economy of scale needed for viability, plants will have to be very large scale.

Because of this, ammonia stripping is best suited as an add-on to large-scale AD plants rather than a standalone treatment.

What about the costs involved in qualifying to be a ReNure assured product?

Teagasc has said capital costs will likely require an independent certification process, which demands an economy of scale for implementation.

Industry estimates suggest that BioBased ReNure costs will sit below current fertiliser processing costs before carbon taxes.

Practical implications

Farmers can replace a large portion of chemical N fertiliser with ReNure digestate, saving money and reducing their carbon footprint, according to Teagasc.

Digestate must be further processed to meet ReNure standards, which may increase costs and require investment in AD infrastructure.

"Phosphorus management remains a challenge, as most P stays in the solid fraction. Record-keeping, soil testing, and compliance with spreading rules will be essential," Teagasc said.

The European Commission’s Nitrates Committee endorsed the ReNure proposal on September 19, and it is now with the European Parliament and Council for final approval.

They have a three-month window for observations. If adopted, it will be up to Ireland to implement the rules and support the necessary infrastructure.