Anaerobic digestion (AD) has been a hot topic in Ireland, with the sector facing numerous challenges both past and present.

A lack of policy implementation to drive progress, coupled with a fragmented planning system, has led many to believe that this industry is not advancing.

Nephin Renewable Gas and John Sheridan's proposed plant in Ballinrobe, County Mayo. Source: Nephin Renewable Gas

However, few realise just how much progress has been made. Dozens of large-scale, modern plants are currently navigating the planning process or awaiting policy support to begin construction.

Some 18 plants have already secured 20% of the required capital costs from the Department of Agriculture, but there are more which have missed the window and intend to apply for the next phase of funding in 2025/26.

While there are several planned and operational facilities handling food waste, sewage sludge and commercial waste, a significant portion of the projects in development focus on agricultural and agri-business waste.

This article will highlight the new projects expected to begin construction within the next 12–18 months.

Nephin Renewable Gas – Mayo

Nephin Renewable Gas, a company vying to become Ireland’s largest AD developer, has several projects in the planning stages. It is a subsidiary of Nephin Energy, the largest shareholder in the Corrib gas field, and is owned by Canada Pension Plan (CPP) Investments, a fund that had net assets in 2023 in excess of €398bn.

The company’s first project was submitted for planning in Ballinrobe, Mayo, in July, in partnership with pig farmer John Sheridan on an 11ac site adjacent to the piggery.

The proposed AD plant will require 18,000 tonnes of cattle slurry, 9,500 tonnes of pig slurry, 12,000 tonnes of poultry manure, 20,000 tonnes of wholecrop silage and 5,000 tonnes of grass silage annually, all sourced from local farmers.

The plant will also process residues from the food, dairy and beverage industry.

Evergreen Agricultural Enterprises will be the country’s largest AD plant, located in Monasterevin, Kildare. Source: Evergreen Agricultural Enterprises.

The biomethane gas produced will be exported to the national gas grid. The digestate will be turned into a bio-based fertiliser and the CO2 captured and sold. Mayo County Council has asked for more information before making a decision.

Nephin Renewable Gas – Waterford

Nephin’s second AD project is situated in Carrick-on-Suir, Waterford. It is being developed in collaboration with farmer James Foran on a 19ac site.

Similar to their Mayo facility, the Waterford plant is designed to process 90,000 tonnes of feedstock annually. This feedstock will comprise 9,000 tonnes of cattle slurry and manure, 26,000 tonnes of pig slurry, 12,000 tonnes of poultry manure, 14,000 tonnes of wholecrop silage and 9,000 tonnes of grass silage. It will also process residues from the vegetable, food, drink and dairy production.

The biomethane will be injected directly into the gas grid, while the digestate will be converted into a bio-based fertiliser. Captured CO2 from the process will be sold as a by-product.

Waterford County Council has requested further information before reaching a decision on the planning application.

Nephin Renewable Gas – Cork

Nephin has also submitted an application for a large-scale AD plant in Mitchelstown and is planning another site in Macroom, Cork. At the time of writing, it is understood that the plant design, layout, and feedstock composition will be similar to their facilities in Mayo and Waterford.

Carbon AMS – Meath

Managing multiple plants across Northern Ireland and Scotland, Irish developers Carbon AMS are now set to develop their first new-build biomethane project in the Republic of Ireland, located in Duleek, Meath.

In collaboration with farmers Donal Hartford and Brugha Duffy, the plant will process 4,000 tonnes of maize silage, 8,000 tonnes of beet, 8,000 tonnes of farmyard manure, 10,000 tonnes of cattle slurry, 1,500 tonnes of pig slurry, 4,000 tonnes of distillers’ grains and 10,500 tonnes of grass silage annually.

The AD plant, which has received full planning permission, will be constructed adjacent to Donal’s farmyard. It will export biomethane to the national grid via a newly installed gas pipeline.

The plant will also capture and sell CO2, while processing digestate into biofertiliser.

Curragh Biogas – Meath

Located in Carnaross, Meath, Curragh Biogas is a partnership that includes farmers Christopher Gibney and Colm Carpenter, along with former Irish Farmers’ Association chief executive Pat Smith.

The 50GW AD project has secured full planning permission and is actively seeking investment from farmers and co-operatives. The facility aims to produce biomethane for grid injection, along with by-products such as CO2 and digestate. Situated on a 10.5ac site, the plant will process 70,000 tonnes of agricultural manures, slurries and silage annually.

Stackallen AD – Meath

Located just outside Slane in Meath, on the grounds of Stackallen House, businessman Martin Naughton has applied for planning permission to construct an AD plant on a 12.5ac site.

The proposed facility aims to process 22,000 tonnes of grass silage, 6,000 tonnes of cattle slurry, 2,000 tonnes of farmyard manure, 9,000 tonnes of hybrid winter rye and 6,000 tonnes of beet annually.

The plant is designed to produce biomethane for off-site export, while also capturing CO2 and generating biofertiliser as by-products.

The planning application has been submitted, but Meath County Council has requested additional information before making a decision on the proposal.

Nephin Renewable Gas and James Foran's proposed plant in in Carrick-on-Suir, Waterford. Source: Nephin Renewable Gas.

Evergreen Agricultural Enterprises – Kildare

Mooted to be the largest AD plant in the country so far, the Evergreen Agricultural Enterprises AD plant will process mainly spent grains and wastes from the distilling and brewing industry.

The project, which is just outside Monasterevin, Kildare, will process upwards of 165,000 tonnes of feedstock per year, producing biomethane for grid injection. The project will be developed on a 20ac site, and a commencement notice has been issued.

Nua Bioenergy – Tipperary

Currently navigating the planning system, Nua Bioenergy is a new AD project proposed for the former Lisheen Mine site in Thurles, Tipperary.

Plans for Stackallen AD, Slane in Meath.\ Source: Stackallen AD

Situated on a 13.5ac site, the plant is designed to process 98,000 tonnes of feedstock annually, comprising 8,000 tonnes of wholecrop silage, 30,000 tonnes of farmyard manure, 30,000 tonnes of bellygrass sludge, 15,000 tonnes of dairy sludge and dewatered manure and 15,000 tonnes of broiler manure. If approved, the biomethane gas produced will be exported to the grid.

Lisglennon AD – Mayo

Dairy farmer John Gilvarry received approval from An Bord Pleanála earlier this year for a 60,500-tonne AD plant near Ballina, Mayo. The facility will process 18,000 tonnes of cattle slurry and 42,500 tonnes of grass silage annually, sourced from nearby farmers. The plant will connect to the grid via a new gas pipeline.

Other notable projects

Other notable projects include NaringTech, located in Derryville, Tipperary, which will process 40,000 tonnes per year of organic waste. Another notable project is Roadstone’s proposed plant at Killough Quarry, Tipperary, which is exploring the use of grass silage, maize silage, cattle slurry and chicken manure.

Bio Agrigas, located in Mullingar, Westmeath, will process 20,000 tonnes per year of slurries, energy crops, food processing waste and category 2 ABP material. There are also multiple smaller projects around the country, as well as existing plants upgrading their capacity or switching to produce biomethane.

Multiple large developers such as Greengate Biogas and CycleØ are proceeding with projects but have not submitted planning yet.

The author Stephen Robb is currently involved in a family/community proposal for an anaerobic digestion facility in Co Donegal.