While there has been a lot of talk about anaerobic digestion (AD) plants connecting directly to the gas grid and injecting biomethane to replace natural gas, only one plant on the island of Ireland has actually managed to do it.

Last month, the first molecules of biomethane produced by Tyrone-based Granville Eco-Park flowed into the national gas grid.

The Irish Farmers Journal recently attended the launch event at the plant to see how it works.

Granville Eco-Park

Granville Eco-Park is a well-known food-waste AD plant, processing upwards of 90,000 tonnes per year in Granville, Dungannon.

The plant was built in 2014 and has a production capacity of 40,000 MWe per annum. The plant is part of the Bio-Capital group, which owns and operates eight AD plants across the UK, including two in Northern Ireland.

David McKee, Bio-Capital.

Biogas is extracted from food waste and is cleaned to produce biomethane.

Until now, the biomethane was used to run four combined heat and power plants (CHPs) onsite to generate electricity for export, supported under the Northern Ireland Renewables Obligation.

They also compress and transport the biomethane to a range of CHPs located in businesses around Northern Ireland via specialised trailers and have a gas vehicle refuelling station onsite.

Gas to grid

Despite being well-serviced by a gas grid around Dungannon, it wasn’t possible to connect the plant to that grid and inject the renewable gas into it.

However, over the past few years, the team has been working closely with the grid operator, Evolve, the Northern Ireland Utility Regulator, and various government departments and bodies to develop a direct-grid injection connection, essentially serving as a demonstration project for other plants in Northern Ireland.

After securing planning permission and regulatory approval in September, they took delivery of a Thyson grid entry unit, which was installed onsite.

The Thyson Grid Entry Unit.

The grid entry unit monitors the biomethane quality before entry into the network, with multiple sensors in place to shut off the flow in the event the gas doesn’t meet the spec.

The biomethane is also odorised to give it the distinctive gas smell for safety reasons before it enters the grid. They also had to install propane tanks onsite, while an additional 200 metres of new gas pipeline was laid to connect the unit to the network.

They have the capability to supply much of Dungannon’s gas needs. They are able to inject upwards of 1,100 m3 of biomethane per hour at two-bar pressure; but as they produce around 1,600 m3 per hour, they will still be operating their network of CHPs.

When generated from organic waste and used for heat, biomethane could produce greenhouse gas savings of up to 92% compared to natural gas.

The total investment represents £1.2m (€1.4m), and while significant, £40m (€46.6m) is already invested on the site.

Future plans

The plant also produces significant amounts of organic fertiliser in the form of digestate. The digestate has a nutritional value of around £17 (€19.75) per tonne; however, they plan to further upgrade this to make a fertiliser product that can be sold.

Around 9,000 tonnes of CO2, which is removed from the biogas, is currently vented, but they now plan on capturing and selling it to the market in Ireland.

The island of Ireland has a demand for 45,000 tonnes of CO2, and with the closure of fertiliser factories in particular, Ireland and GB markets are now importing much of their CO2 requirements.

Northern Ireland injection process

With one or two exceptions, practically all new AD projects on the island will be producing biomethane. Therefore, having a streamlined, affordable gas grid connection process is essential.

Northern Ireland has three distribution gas operators: Evolve, Phoenix Natural Gas, and Firmus Energy, and the same grid connection process has been adopted by all three operators, so other developers will be following the same steps.

The vast majority of existing plants in Northern Ireland are agricultural plants, producing 500kWh of electricity through a CHP.

Given their small scale, the economics of switching these plants to produce biomethane for grid injection would be extremely challenging and would require significant investment.

While the connection process is now in place, it still needs tweaking to make it easier and more cost-effective for AD developers.

The project at Granville has been a real pathfinder project, as they had to work closely with the departments and regulators to find a way to inject into the grid.

In total, 14 companies were involved in the project, seven of which are based in Northern Ireland.

This was evident by the number of officials from various departments, as well as industry professionals and politicians, who were in the same room at the launch event, proving that biomethane is both cross-sectoral and cross-departmental, and that collaboration is needed to make projects happen.