An ambitious circle: from pollution to solution

Slurry separation is not a new concept, and the process of separating the liquid and solid fractions has multiple benefits. The liquid goes back into the slurry tank, which now has more space without the heavy particles. The mixing and spreading of that liquid is easier, particularly when using low emission slurry spreading kit. It also retains the good nutrients required to feed the soil when spread. The separated solids that are removed contain high levels of phosphorus, a problematic agricultural run-off nutrient.

Lough Neagh

In Northern Ireland (NI), agricultural run-off has contributed to an ecological disaster with the extensive pollution of Lough Neagh, which supplies more than 40 per cent of Northern Ireland’s drinking water. The lake has a surface area of 392km², is approximately 31km long and 14km wide.
According to a report published last year titled, The Lough Neagh Report: Blue Green Algae and Water Quality in Northern Ireland, ‘Lough Neagh is NI’s most important natural resource and is of huge economic significance for those who depend on it for drinking water, its fishing and eel industries’. Lough Neagh’s agricultural pollutants have co-offenders in the form of human sewage and wastewater treatment works but agriculture is the biggest contributor. In 2023, toxic blue green algae was detected at Lough Neagh, and the problem persists today. Eel fishing is currently prohibited there for the rest of this year.
It that same report mentioned earlier, directly NI’s agriculture minister, Andrew Muir, described Lough Neagh as an example of ‘a collective failure to deal with the environmental challenges’ faced in Northern Ireland. And, he added that ‘regulatory and policy frameworks have failed to adequately protect water quality, the Lough Neagh ecosystem and wider environment’.
In an effort to address this, a 37-point action plan was devised, one of which involved the launch of a small business research initiative (SBRI) project by the Department of Agriculture, Environment and Rural Affairs (DAERA). This aimed to improve the ‘sustainable utilisation of slurry’ (SULS) and remove excess phosphorus from the environment.

Collaboration

Cue the Mid-Ulster Biorefinery and Circular Economy Cluster, a collaboration between various companies and organisations in NI to, ultimately, construct a 10-megawatt biomethane facility in the region. The starting – and most important – point on this journey is Lough Neagh and ensuring that phosphorous run-off is stopped. Along the journey are important stages such as: separating the slurry that is causing the run-off, removing the phosphorous-rich solids, using this to feed an anaerobic digestor to produce biomethane, pyrolysing (heating to a very high temperature) the digestate (byproduct of biomethane production), and creating greener construction products such as bricks and paving slabs from this.

The SBRI-sponsored project carried out by this Mid Ulster Biorefinery and Circular Economy Cluster is at the pilot stage of separating the slurry on farm. A custom-built separator led by Dr James Young, C for C project technical lead, and fabricated by Vogelsang, has recently been acquired for the purpose. The separated solids then undergo analysis and this is where Alltech comes in. Patrick explains: “We are obviously an agricultural company with a strong history of biotechnology and analytical chemistry. We bring a lot of the experience that we have in science to the agriculture industry.” He continues: “So, regarding the slurry, what we’re trying to do on the analytical side and biotech side is see how much we can improve the separation – via enzymatic or chemical or mechanical process – to extract even more of the phosphorus [from the liquid]. Typically, you can have 60 per cent [phosphorus] in the solid fraction, and 40 per cent in the liquid fraction. We’re trying to increase that [solid percentage].”
A number of farms are involved in the pilot and Patrick explains how it works: “The liquid fraction stays with the farmer. It’s still rich in nitrogen and potassium and it has some other nutrients and minerals, and it will still have some phosphorus – that’s not all removed,” he explains. Samples are then analysed at Alltech’s European Bioscience Centre in Dunboyne, and tested for dry matter, volatile solids, and total phosphorus, for example. Samples are simultaneously analysed at Queen’s University Belfast. The Dunboyne facility has a biochemical methane potential laboratory, so scientists there are also investigating how to optimise the anaerobic digestion process. Patrick explains: “This involves us taking the separated solid, putting it under anaerobic conditions – whatever conditions we think would be best for the anaerobic digester that we are aiming to set up, or for people who are taking the material – and we’re able to quantify the amount of methane that is produced from samples.So then we can build that into our business model of how we’re going to optimise the digester based on the separate slurry solids.”

Positive message

This is a positive story about turning a waste product into a wanted product. “The project, so far, has not been about utilising any crop-based material,” explains Patrick. “So we’re not going to be utilising grass for it. There’s enough waste material from pig slurry, cattle slurry, even poultry manure, to go into a digester in that mid-Ulster area. And our focus is to optimise that,” he says.

Future plans

While a feasibility study has been carried out with KPMG, the success of this project is dependent on separating even more solids from the slurry. Patrick explains: "We are at the early stages because we are still trying to optimise this feedstock and if we can improve it by 10-20 per cent, it will make a big difference to how we decide to proceed.”
Crisis breeds opportunity. That is what Alltech founder, Dr Pearse Lyons used to say, Patrick recalls. “This is a crisis. But we have tools now to solve that crisis. It’s an opportunity to utilise these agricultural byproducts and waste streams as a power source, not just to generate clean energy for Northern Ireland, but also to remove as much phosphorus as we can from waterways and land.”