Northern Ireland was once regarded as a leader in anaerobic digestion (AD) on the island, with 84 operational plants. Practically all of these AD plants are producing electricity and exporting it to the national electricity grid, generating some 52MWe of electricity per year.

The Anaerobic Digestion and Bioresources Association (ADBA) presented these figures at its Northern Ireland (NI) conference last week and show how responsive the sector can be when credible policy supports are put in place.

The Northern Ireland Renewables Obligation (NIRO) scheme provided a credible pathway to AD development, with plants receiving State support for 20 years.

The scheme encouraged farm-scale plants, typically those under 500kWh, which are largely supplied with farm slurries, crops and commercial food waste. The digestate produced is also used on farmland, although this presents its own set of challenges.

While the support scheme and model have proven effective, the methods of financing the construction of these plants varied, and, over time, not all financing packages have been as successful as others. Indeed, the terms of the finance package agreed upon, and the ability or inability to refinance, have determined the financial success of many of these plants today.

Nevertheless, AD in Northern Ireland is considered a success story, and the focus is now firmly on phase II – developing a biomethane industry.

Biomethane

While leaders in producing electricity from biogas, NI lags behind the rest of the UK and the Republic of Ireland in biomethane production.

Biomethane production has a distinctly different business model than electricity production.

It typically involves multiple extra steps to remove the CO2 from the biogas, which can be captured and sold, as well as removing a number of other gases. The concentrated biomethane must then be directly injected into the gas grid or transported to injection sites.

These additional steps generally increase the size, cost and operational complexity of the plants.

There are a small number of AD plants producing biomethane in NI, but all of these are supplying generators to produce electricity.

One plant in Granville is directly connected to the gas grid and, in theory, could meet all the gas requirements for Dungannon, Tyrone.

However, it has proven uneconomical to do so thus far.

That said, the biomethane sector is expected to develop significantly in NI, playing a role in meeting 2050 net zero targets while also addressing the nutrient challenges in the region. This means that there will need to be new AD plants built, specifically designed to produce biomethane, as well as upgrading existing AD plants.

A general theme in the conference was that NI is well placed to develop a biomethane industry. Firstly, it has a healthy indigenous market for natural gas, which will need to switch to renewable alternatives such as biomethane.

The NI gas network provides gas to three major power stations, which are responsible for 55% of the demand; to 25,000 businesses, which account for 25% of the demand; and to 525,000 homes, which together account for 20% of the demand.

This gas network is modern and connecting AD plants directly to it is entirely possible. Secondly, NI has an abundance of the raw materials to use as feedstock for AD. These are manures from the dairy, poultry, pig and drystock sectors and crops such as grass silage.

A 2022 Queen’s University Belfast led research project calculated that the methane from NI’s housed livestock manure plus silage could produce 6.1TWh (terawatt hour) of biomethane, or 90% of the gas distribution network demand.

For reference, the Republic of Ireland’s 2030 target is 5.7TWh or 10% of gas demand. Most importantly, the vast majority of this feedstock – 83% – is located within 10km of the NI gas distribution network. We will delve deeper into the potential of NI nutrients and AD next week.

Finally, there is significant demand from farmers and developers to build a new biomethane industry. In an exercise carried out by the gas grid operators in NI, 84 AD operators and developers said they were interested in expanding or building new biomethane projects.

Around one-third of these respondents are in advanced stages with projects.

What policies are needed?

As discussed throughout the day, NI has significant catching up to do. The conference outlined the three main steps needed to advance the sector in Northern Ireland.

Securing planning permission: the elephant in the room

One of the biggest challenges facing the development of the sector is securing planning permission for extensions and new developments, primarily due to issues related to ammonia and nutrient management. The conference heard that results from the flagship Small Business Research Initiative, which focuses on slurry separation, will help address these challenges. There will be more details in next week’s paper.

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