In order to begin meeting the country’s 2030 biomethane target, the Republic of Ireland is aiming to develop large, centralised anaerobic digestion (AD) plants, supplied with manures, wastes or crops to produce renewable gas as a replacement for natural gas.

The scale of the project required to make this model work, assuming the enabling policies are in place, will make it difficult, if not impossible, for the vast majority of farmers to build, own and operate an AD plant. This is an option available to many farmers across Europe.

However, under the National Biomethane Strategy published last year, this is not the only chosen model. The strategy outlined that its preferred approach is a combination of large AD plants and smaller, on-farm plants, typically one quarter to one sixth the size of those currently being developed around the country.

The intention behind this is that large plants would produce the bulk of the gas, while smaller plants would offer a way for farmers and communities to get involved and support the adoption of the technology.

Small-scale

The current challenge with AD is making it financially viable. This is even more difficult with small-scale plants, which cannot benefit from the economies of scale required to produce biomethane gas. Recognising this, the strategy stated that greater incentives to support smaller plants will be required and committed to assessing the potential for an appropriate small-scale finance scheme.

This action was assigned to the Department of Agriculture, with support from stakeholders including the Biomethane Implementation Group, the Irish Strategic Investment Fund (ISIF), and the Strategic Banking Corporation of Ireland (SBCI). It was due to be completed by Q4 2024.

More research

Like many of the major policy commitments in the strategy, the industry has heard few updates on this to date. When questioned by the Irish Farmers Journal, the Department of Agriculture (DAFM) said it has engaged with ISIF regarding a potential funding model for smaller-scale AD.

“As a result of these discussions, it was agreed that research should first be conducted to demonstrate the viability of smaller on-farm AD plants. This research has been funded by DAFM through Carbon Tax Funds and is currently underway by Teagasc,” the statement read.

“A potential funding model will then be explored via ISIF if the research demonstrates that certain technological solutions are feasible at farm level,” it stated.

The DAFM also said it has engaged with the SBCI regarding the inclusion of eligible investments in AD under the Government-backed Growth and Sustainability Loan Scheme (GSLS). The SBCI has confirmed that the GSLS Green Checker includes investment in AD. The scheme provides up to €3m in low-cost loans for up to 10 years from participating institutions.

Alternative model

However, even with a low-cost finance scheme in place, all of the systemic problems facing the AD sector apply to projects regardless of their scale. Planning permission, gas grid connections, the absence of a market, policy uncertainty and licensing delays all make projects unbankable – and these challenges affect small-scale plants aiming to produce biomethane just as much as large ones.

However, there is a growing movement to develop an alternative model in Ireland, aimed at farmers who produce a lot of slurry and use a significant amount of energy. Arguably, it is not a new concept – in fact, it is the original model for AD, developed nearly 40 years ago.

The idea is that a farmer could build a micro or small-scale AD plant, consisting of an insulated tank or covered slurry store or lagoon, and use fresh slurry or manure produced on the farm to feed it. Biogas is then produced and combusted through a small engine, with the electricity and heat used solely on the farm, see graphic below.

While this may sound similar to the model used in Northern Ireland or across Europe, the vast majority of those plants are supported by a long-term support tariff, where much of the electricity is exported to the grid. This new model would rely on no support tariff, with the return on investment coming from the replacement of imported electricity and fossil fuel used to generate heat.

The difference

The difference between this model and the small-scale model being explored by the Government is that it’s much more realistic for farmers. There is no need for expensive gas upgrading equipment, grid connections, grid entry units, compressors, pasteurisers (if using on-farm slurry and manure only) and the many other pieces of equipment and infrastructure that add millions to the cost of an AD biomethane project.

This alternative model is much simpler and could be rolled out on practically any farm with reasonably high energy use that produces slurry and manure. If designed correctly, a small-scale AD plant could essentially make the farm energy independent, potentially even allowing for a small amount of electricity to be exported back to the grid, while also adding another tool to the toolbox for managing slurry on the farm.

This very model has been tested in the IrBEA Small Biogas project, which we will learn more about in the coming months.

Not biomethane

Of course, the elephant in the room is that if this model were rolled out, while we would see an emissions saving from reduced fossil energy use on farms and slurry/manure having methane gas removed, this model wouldn’t contribute to our 2030 biomethane target. This means that under the DAFM’s €40m capital grant scheme, a project like this wouldn’t have been eligible, even though much of the grant will go unspent and may be sent back to Europe by the end of this year. Some would argue this model may reduce the pool of feedstock available for actual biomethane production. However, others will say that this is how most farmers can meaningfully get involved with AD, and that in time, plants could be expanded for biomethane production.

While this model will require significantly less investment than a biomethane plant, it will still require capital grant aid for most farmers to make a reasonable return on investment. Perhaps this is where TAMS could come in, combined with the GSLS scheme. As we understand, this model currently isn’t being explored by the Government.