What is anaerobic digestion?

Anaerobic digestion is a biological process in which microorganisms break down organic material in the absence of oxygen. It produces biogas, which can be upgraded to biomethane and injected into the gas grid, and digestate, which can be used as a fertiliser or soil improver.

Biomethane is biogas that has been upgraded to remove carbon dioxide and other impurities so that it meets the quality standards of the natural gas grid. It is a renewable substitute for fossil natural gas and can be used for heating, industry and transport.

What is digestate and how is it used?

Digestate is the nutrient-rich material left after anaerobic digestion has broken down the feedstock, and it is a valuable resource in its own right. Because digestion stabilises the material, digestate carries far less odour than raw slurry or manure, which makes it easier to store and to spread near homes and communities. It is also a good fertiliser: the nitrogen, phosphorus and potassium from the feedstock remain in a form crops can readily take up, returning nutrients straight to the soil. Every tonne spread displaces synthetic fertiliser, much of which is manufactured from fossil gas, so digestate helps Irish farms cut their emissions and their reliance on imported, fossil-derived inputs.

How does anaerobic digestion reduce methane emissions?

By capturing methane from organic waste that would otherwise decompose in open lagoons or landfill, anaerobic digestion prevents uncontrolled methane release. The captured biogas is then used as a renewable energy source, displacing fossil natural gas.

What feedstocks are used in Ireland?

Common Irish feedstocks include cattle slurry, pig slurry, crop residues, grass silage and food waste. The right mix depends on availability, transport distance, digestor design and the regulatory rules that apply to each material.

How is biomethane injected into the gas grid?

Biogas is upgraded to biomethane at the AD plant, then compressed and injected into the local gas network at a grid entry point. Gas Networks Ireland operates the network and sets the technical and commercial rules for injection.

Lush green grassland in Ireland, representative of the feedstocks used in anaerobic digestion.

Research and Knowledge Transfer

Anaerobic Digestion in Ireland

Anaerobic digestion underpins Ireland’s plan to scale biomethane, cut emissions from farming and strengthen energy security.

Authored by: Katherine Casey
Published by: Climaticus
Published: 20 July 2026

The Irish AD Landscape

In Ireland, anaerobic digestion is emerging as a central technology for meeting climate targets, managing agricultural residues, and building a circular bioeconomy. It sits at the intersection of energy, agriculture, environmental regulation and rural development.

Biogas is produced via anaerobic digestion and can be used directly to generate heat and electricity, or upgraded to biomethane and injected into the gas grid. The digestate retains valuable nutrients and can be returned to land as a fertiliser substitute, closing a loop between agriculture and energy.

Ireland currently produces only a small fraction of its 5.7 TWh biomethane target for 2030. Closing that gap requires new anaerobic digestion capacity, reliable feedstock aggregation, and the infrastructure to upgrade and inject biomethane into the gas grid.

Most Irish AD projects are expected to be farm-based or cooperative in scale, drawing on slurry, grass silage and agricultural residues. Larger centralised plants are also being developed where feedstock density and grid access make them viable. Each model has different implications for farmers, communities, developers and offtakers.

Who Anaerobic Digestion Matters For

For Farmers and Landowners

Anaerobic digestion turns slurry, crop residues and other organic materials into a revenue stream. Farmers can supply feedstock under long-term contracts, receive digestate back as a fertiliser substitute, and participate in cooperative hub models that keep value in the local area.

Farmers and Landowners →

For AD Developers

Ireland needs new AD capacity to meet its 5.7 TWh biomethane target. Developers need feedstock aggregation, planning and consent pathways, offtake contracts, and verification systems that satisfy regulators and gas buyers.

AD Developers →

For Biomethane Offtakers

Biomethane offers a route to Scope 3 emissions reductions and renewable gas procurement. Consumers need verified supply, traceable origin, and contracts that align with RED II and corporate reporting requirements.

Biomethane Offtakers →

Policy and Market Drivers

Several policies are converging to create demand for anaerobic digestion and biomethane in Ireland. The Climate Action and Low Carbon Development (Amendment) Act 2021 sets legally binding carbon budgets and sectoral emissions ceilings. The National Biomethane Strategy establishes a 5.7 TWh production pathway by 2030.

At EU level, RED III raises renewable energy targets and tightens sustainability criteria. The EU Methane Regulation requires monitoring, reporting and verification of methane emissions across the energy sector. The Nitrates Directive and Water Framework Directive continue to shape how nutrients are managed on farmland.

Corporate buyers are also driving change. CSRD, CSDDD and Scope 3 reporting obligations mean large companies need verified data on the emissions profile of their supply chains. Biomethane with traceable origin and independent verification is well placed to meet that demand.

Read more about the market opportunity and regulatory landscape on The Biomethane Market page.

Frequently Asked Questions

Explore the Biomethane Opportunity

Whether you are a farmer with feedstock, a developer planning capacity, or a gas consumer looking for verified biomethane, Climaticus can help you take the next step.

The Biomethane Market Contact Climaticus