A biogas plant which will produce biomethane to power 10 trucks is set to go live in Northern Ireland in July, following a substantial expansion, Weltec Biopower has announced.

The plant is owned by Northern Irish food logistics company McCulla Transport and is currently undergoing an expansion undertaken by Weltec Biopower and partner companies.

At the site in Lisburn, 10km south of Belfast, 450m³ of biogas will be processed into biomethane/ renewable natural gas (RNG) every hour.

With this amount, the logistics company can operate 10 new compressed natural gas (CNG) trucks, which are refueled directly at the company's new biomethane filling point.

The substrates for the production of the green fuel come from the 41 Lidl supermarkets in Northern Ireland, following a deal struck with the supermarket giant.

Original plant

Ashley McCulla, chair of McCulla Transport, was able to commission the first stage of his biogas plant from Weltec Biopower back in January 2017.

The intention at the time was to utilise the residual materials from his own agricultural business and to create synergies through the use of renewable electricity and heat in the refrigerated warehouse at their main logistics depot.

McCulla explained:

"By digesting slurry, agricultural residues and grass silage from our farm, we were able to produce green energy ourselves with a 500kW CHP plant and use it on our company premises. Ultimately, this has significantly improved our carbon footprint.

The expansion to biogas upgrading, HGV fuel and becoming "Ireland’s greenest fleet" was the logical next step of this good experience with the anaerobic digestion (AD) plant and their network in the food industry.

Plant expansion and Lidl deal

Under the arrangement with Lidl, with the conversion of the biogas plant, 17,500t per year of food leftovers from Lidl stores will substitute the agricultural residues as substrate for the HGV fuel production.

Under the motto “Goodbye Diesel - Hello Biofuel”, the 10 new bio-CNG trucks will transport Lidl food deliveries with renewable gas, the chairman said, claiming:

"Every lorry that runs on the green fuel emits 93% less carbon emissions than a diesel truck.

Weltec Biopower outlined its plans for the construction of the biogas plant, noting that four pits are available for the pre-storage of the substrates.

The subsequent anaerobic digestion takes place in two digesters made of stainless steel with a diameter of 23.03m, a height of 6.30m and a capacity of 2,625m³ each.

The digestate is stored in a 3,432m³ stainless steel gas-tight storage tank. To fully exploit the energy potential of the food waste, Weltec equipped the 80m³ dosing feeder in combination with the Multimix pre-feed system.

In it, food leftovers are shredded and homogenised. In addition, the Lidl waste is automatically unpacked and pasteurised at the biomethane plant.

Weltec sales manager Dr. Kevin Monson noted: "Our biology department guaranteed a trouble-free substrate changeover, more than doubling output from the original 500kWe plant without further investment in digestion space, by switching from grass silage and slurry to food wastes."

The biogas upgrading system comes from Pentair Haffmans. The "tried and tested" module separates carbon dioxide and other components of the biogas from methane using membrane technology.

This creates biomethane that is similar in its properties to natural gas, but is significantly more climate-friendly, Weltec claims.

Despite processing 450 standard m³ of biogas per hour, the 500-kilowatt CHP continues to run, because McCulla can use the electricity and heat for his headquarters and the cold store.

Following on from the plant expansion, McCulla chairman Ashley McCulla has announced that the sustainable transport model will be applied to his entire truck fleet over the next five years.