Anaerobic digestion (AD) is a technology that is very much on the front foot in Northern Ireland at the present time. Utilising a range of raw materials, including animal slurries, silages and food wastes, the processes involved provide a source of renewable energy. The end product of the digestion processes undertaken is biogas – a mixture of methane and carbon dioxide – which is suitable for energy production. The biogas can then be used to generate electricity and heat to power on-site equipment and the excess electricity then exported to the national grid.
The sector has been further boosted courtesy of the ruling made by the European Commission in 2011, which allowed for an increase in the ROC (renewable obligation certificate) levels for electricity generated from anaerobic digestion from the then two ROCs per megawatt hour for all sizes to four ROCs per megawatt hour for generating stations up to 500KW capacity and three ROCs per megawatt hour for stations between 501KW and 5MW.
“These incentives will remain in place until at least 2015,” Moore Biosystems’ Dr Peter Barrett told Energy Ireland. “In 2017, feed-in tariffs will be introduced, which will bring the sector here in Northern Ireland more in line with the rest of the UK, regarding the support arrangements that are in place.
“My understanding is that a consultation process, designed to agree the implementation of the new feed-in tariff arrangements, is to get under way shortly. However, it is still too early to predict if the new measures will provide the same level of stimulus as those currently available.”
AD has proven particularly attractive to agriculture, given the more than significant volumes of slurry produced on local farms and farmers’ ability to produce high quality grass and high dry matter silages, which constitute high energy sources for the micro-organisms at the heart of the digestion processes.
“Increasingly, food wastes will be used as a valuable feed stock in AD plants,” Peter Barrett continued.
“Their use requires the attainment of the relevant licences by the AD operator. However, the technology represents a win-win scenario in this regard as it both harvests the valuable green energy within these materials and converts the potential pollutants into a digestate, which can be used a valuable fertiliser source for farmers and growers.”
But despite its many attractions, Peter Barrett will readily admit that the AD has proven to be a ‘slow burner’, up to now, with the potential it represents remaining relatively untapped.
“Taking a project from the initial design stages through to final commissioning is a very complicated process,” he stressed. “Planning approval can take up to a year to obtain. Large numbers of people have major concerns about the siting of an AD plant in their vicinity. Issues that crop up in this regard include the increase in traffic to and from the facility, the use of food and municipal wastes and the perceived pollution risks.
“As an industry, we must do a lot more to explain how the technology works and the benefits it can offer local communities and the economy as a whole. The reality is that the technology has been proven in many countries across Europe, where AD plants are commonplace in and around rural villages and towns.
It costs approximately £2 million to design and construct a 500 kilowatt AD plant. Under the current support arrangements, a facility of this size should pay for itself in seven to eight years.
“The length of payback period depends on how efficiently the plant operator can utilise both the waste heat and electricity produced,” Peter Barrett commented. “In cases where the heat is fully utilised, on-farm or other adjacent business, the value of the outputs will be optimised. Community heating is again commonplace in Europe and is a desirable export for an AD plant.”
But not too many farmers, or other potential AD operators, would happen to have £2 million sitting in a bank account, which brings up the key question of securing the required finance for such a venture.
Peter Barrett again: “The local banks have been slow to embrace AD. However, there are a number of other institutions that are willing to invest in the technology.” Looking to the future, more mainstream funding options may embrace the technology and with evidence recently coming from the establishment of a Green Investment Bank.
Moore Biosystems, a sister company of the Ballymena-based precast manufacturer Moore Concrete, is currently involved in the development of a number of AD projects at different locations right across Northern Ireland.
“We offer a turnkey service, which includes the initial design process, the procurement of planning and all on-site works,” Peter Barrett further explained.
“Crucially, we also offer clients an ongoing service and management backup, to ensure that their facilities remain fully operational for the optimal period of time.”
Peter went on to confirm that the commissioning of Moore Biosystems’ most recent project is now nearly complete. Located on the Portadown farm of the Hunniford family, the 500 kilowatt plant will utilise a feedstock comprising a mix of cattle slurry plus abattoir and industrial waste materials.
“Full licensing has been secured regarding the utilisation of these products and the plant has ambitions to obtain PAS110 standards for the digestate produced,” Peter Barrett continued. “The specification for the new facility includes a feedstock pasteurisation unit.”
“All of the digestate will be used as a fertiliser on our grassland and cereal acreages,” confirmed Richard Hunniford, who farms with his father, also Richard, and brother Victor.
He added: “Apart from the final commissioning process, all of the work required on the project has now been completed. Everything has gone without a hitch so far.
“We received grant aid from DARD under the remit of the Biomass Process Challenge Fund. This support has helped defray the capital costs associated with the construction of the new plant. ”
Richard concluded: “The business plan for this project is centred on the availability of renewable obligation certificates or ROCs, for the production of green energy. Our ROCs application has been accepted with the final agreement kicking in as soon as we start generating electricity.”