A £23 million (€26 million) anaerobic digestion (AD) plant in Ballymena has become one of the first of its kind in the world to be fuelled solely by poultry litter.

The first few loads of poultry manure arrived at Stream BioEnergy’s Tully Biogas plant in October; however, the unit has only just reached full operational capacity within the last three weeks.

AgriLand gained exclusive access to the site along with the firm’s development manager Morgan Burke to find out what’s involved in the running of such a mammoth project.

Biosteam Tully AD plant, Ballymena, anaerobic digestion

A pioneering process

Already the plant has picked up major awards for its innovative approach to AD, having been named best Energy Generation project at the 2017 Sustainable Ireland Awards.

Morgan Burke said: “It’s technically a very difficult thing to do because normally conventional AD plants would only have a very small amount of poultry litter going in as feedstock – because there’s a lot of nitrogen in poultry litter.

“So to actually get an AD process which can work with 100% poultry litter is quite hard to achieve.

“We reduce the nitrogen content in the chicken litter and then use conventional AD,” he said.

The plant employs 12 full-time members of staff, many of whom previously worked at the Michelin factory in Ballymena which has been ear-marked for closure.

Many additional off-site jobs have also been created through the range of contracting and professional services that it requires.

The litter is supplied by just over 100 Moy Park contracted broiler farmers.

Biosteam Tully AD plant, Ballymena, anaerobic digestion

40,000t a year of poultry litter

The plant generates 3MW of renewable electricity from 40,000t a year of locally-sourced manure by combining conventional anaerobic digestion with nitrogen-stripping technology.

Once it arrives on site, the litter is fed into two industrial-sized hoppers which break up the material and control the feeding into the digesters. The digestion process takes around 45 days.

Digestion is a two-stage process with two primary digesters – where most of the digestion takes place – and then two secondary digesters where the process finishes.

The four digesters combined are capable of handling around 20,000m³ of material at any one time.

Outputs from this stage are biogas and digestate.

The biogas produced by the plant is fed into two 1.5MW gas engines that generate electricity on site which is then sold to the National Grid.

The digestate is pasteurised to create a safe nutrient-rich fertiliser that can be used by farmers.

Burke said: “The plant produces enough sustainable energy to power the equivalent of 4,000 homes, diversifying Northern Ireland’s fuel mix and reducing the country’s reliance on fossil fuels – as well as the emission of greenhouse gases into the atmosphere.

The plant is delivering other benefits to the community in the form of local jobs and investment and through the recycling of nutrients.

“It is also making a significant contribution to the challenge of managing poultry manure in a more environmentally friendly and sustainable way thereby supporting the local poultry sector.”

Construction of the Tully Biogas Plant was completed in just 15 months.

The plant was developed by Dublin-based renewables firm Stream BioEnergy and uses pioneering technology from Xergi, a Danish firm specialising in the design of large-scale AD plants.

Local companies in Northern Ireland were appointed to deliver engineering and construction services – with Maghera-based company BSG Civil Engineering engaged as principal contractor.