Despite all the hype surrounding Ireland’s emerging anaerobic digestion (AD) industry, there still remains a significant knowledge gap about how it will actually function. Arguably, we won’t know the finer details until the first handful of projects are operational and integrated into the community. However, we have a good understanding of how similar plants operate in other countries, as well as insights from the Government as to how it envisages the sector will operate.

The Irish Farmers Journal’s Renewable Roadshow series aims to shed some light on this matter. The event, which kicked off earlier this week in Cork, will feature a dedicated session on AD and its implications for farming.

The anaerobic digestion process. Source: EBA

What is anaerobic digestion?

The final session of each evening at the roadshows will focus on AD. For those unfamiliar, AD is the natural breakdown of organic material (such as slurry, crops, and food waste) by microorganisms in the absence of oxygen.

During this breakdown, biogas is released, which is made up of around 55% methane, 40% carbon dioxide and 5% other gases. This process can be controlled and managed in purpose-built, sealed metal or concrete tanks, known as AD plants, where the biogas is collected and used.

Biomethane is produced through the removal of carbon dioxide and other gases, concentrating methane to around 97% or higher. Chemically identical to natural gas, biomethane serves as a renewable alternative and can be used in existing gas appliances. The CO2 can also be captured, liquefied, and sold to industry.

What goes into an AD plant must come out in the form of digestate, which is the organic material remaining after the digestion process. Digestate is higher in available nutrients when compared to slurry.

Over 140 new AD plants are needed over the coming years.

Why now?

The Irish Government has set a target of 5.7 terawatt-hours (TWh) of biomethane production by 2030 under the Climate Action Plan, aiming to supply 10% of Ireland’s gas needs.

Achieving this target would require the development of 140 to 200 large-scale AD plants. Currently, we only stand at 0.001% of biomethane in our gas mix, so the challenge ahead is great.

These targets are driven by broader sectoral and national emission reduction targets and, if met, the AD sector could potentially save an estimated 2m tonnes of CO2 emissions per year.


It’s the Government’s stated aim to make biomethane production a suitable diversification option for farmers. It wants farmers to be able to own, operate, or supply feedstock to AD plants. However, for many farmers, the latter option will be the most immediate. Agricultural feedstock will be essential for supplying the network of AD plants.

The Renewables Roadshow will delve into what types of feedstocks are required and the potential benefits to farmers in supplying plants. For example, an AD plant could create a new export market for slurry, helping farmers in meeting their nitrate obligations.


Digestate will play an important role in helping farmers reduce chemical fertilisers, while also assisting in a more balanced spread of nutrients across Ireland. AD can facilitate the movement of nutrients from where they are not needed to where they are needed.

Slurry will be an important feedstock for AD.

The model

While the draft National Biomethane Strategy failed to excite, the final version of the Government’s roadmap to AD development is expected to contain answers to some significant questions. We’ll delve into the types of support needed to kickstart this industry and what has been committed so far.

Case studies

Finally, we’ll be joined by Barry Caslin, energy and rural development specialist with Teagasc, and Sean Finan, CEO of the Irish Bioenergy Association, to run through two case studies on AD:

  • Case study one – building an anaerobic digestion plant.
  • The first case study will examine the economics of constructing and operating an AD plant in Ireland. It will compare a modern commercial biomethane project with a small-scale farm-based project.

  • Case study two – how farmers can get involved.
  • The second case study will explore how farmers can get involved with AD other than through project development. This will include an indication of the economics involved in supplying an AD plant with grass silage, crops, manure, or slurries, as well as using digestate to reduce chemical fertiliser requirements.

    Grass silage and wholecrop will be key feedstock for AD plants.

    Still time to register

    The Irish Farmers Journal Renewables Roadshow will continue its tour next week and the remaining events will take place on:

  • 16 April at the Newpark Hotel Kilkenny.
  • 23 April at the Errigal Country House Hotel, Cavan.
  • 30 April at the Athlone Springs Hotel, Athlone.
  • The roadshows are evening events, with doors open from 6.30pm. The session kicks off at 7:30pm sharp and will run until 10pm. Tea, coffee and sandwiches will be available. To register, simply open your camera and scan the QR code to access the registration link, or go to

    If you have any questions about renewable energy options for your farm, business or household, feel free to send us your enquiries ahead of the events at

    The roadshow is being delivered in partnership with FBD, the Irish Farmers Association and Bord Gáis Energy.