Scottish Executive Funded Sites (Early 2000s)
Seven small on-farm digesters were installed circa. 2004, under a Scottish Executive programme which was administered by the environmental consultant EnvriosAspinwall. The prime reason for installing these plants, which were built with public money at a time when the anaerobic digestion process was considered unproven, was for public health reasons. The intention was to reduce organically contaminated storm water run-off from the farmyards of these seven sheep and cattle/dairy farms into watercourses which led to bathing beaches. At the time the EU Bathing Beaches Directive was being implemented and there was concern that unless action was taken to reduce the faecal indicator organisms (pathogenic bacteria) count in storm water run-off from the seven farms, the nearby beaches would fail to meet the required standards.
Income for tourism to the Solway Firth bathing beaches would have been reduced if the bacterial count in the local rivers had not been reduced. So, the primary function of the seven anaerobic digestion plants was to absorb the farm run-off and treat it so that it would become a useful sanitized crop fertilizer.
The following is a quotation taken from the website (no longer available) of Greenfinch Ltd. in January 2007:
“Farm Biogas Plants
Seven farm biogas plants have recently been built in Southwest Scotland as part of a Scottish Executive research programme into diffuse pollution of bathing waters. The large amount of rainfall in the area, together with high numbers of livestock, impermeable soils and short river lengths all contribute to the risk of faecal indicator organisms (FIO) ending up in the water courses. The biogas plants have been integrated into the farms waste management systems.
(C) Greenfinch Ltd
The slurry is being collected in the dairies where it is pumped into a large reception tank, before entering into the digester. For the farmers, this has not only enhanced their waste management system, but it has also given them two valuable by-products. The gas is burnt in a biogas boiler which heats the digesters with surplus energy used for domestic heating, or running a generator to produce electricity. Digestate, the other by-product, is used by the farmers as a bio-fertiliser. There is a lot of research to be carried out into the use of this liquid by-product, however it is clear that the readily available nutrients will save the farmers money by not having to import such large quantities of mineral fertiliser, and making a carbon saving.”
The locations of these plants were not recorded on the above website, but three are thought to have been located as follows: (1) Sorbie, Saltcoats, Ayrshire; (2) Meikle Laught, Knockrivoch, Saltcoats, Ayrshire; (3) Corsock, Dalbeattie; Southwick, Dumfries. The designer and installer was Greenfinch Ltd (now part of Biogen). The feedstock is thought to have comprised at the time of sheep and cattle manure and slurries. The reactor sizes varied, up to 480 cubic metres. These plants were designed to be operated by each farm. The current operating status of these plants is unknown.
Other Early Biogas Plants in Scotland Before 2010
Food Waste AD Plants
- Rogerstone Biogas Project designed by H2OK consultants. InSource Energy partnered with Premier Foods™ RF Brookes ready meal facility at Rogerstone, South Wales to deliver on-site anaerobic digestion facilities to treat the food waste from the manufacturing process.
- Deerdykes, near Cumbernauld, Glasgow; HBS and Monsal, project in progress for operator Scottish Water Waste Services, feed will be food waste and it was planned to have a throughput of approximately 30,000 tpa.
Municipal Solid Waste AD Plants
Isle of Lewis, Western Isles
Under the Western Isles Integrated Waste Management Facility, PFI Contract awarded to Earthtech, a Linde Technology designed plant is completed. The plant feed is Biodegradable Municipal Waste/ food waste.
Farm/Central AD Plants
The following feasibility studies were thought to be underway pre-2010:
- Isle of Mull – Animal slurry
- Isle of Bute – Animal slurry, dairy waste
- Island of Westray – Orkney; Ris Energy – feedstock animal slurry, and fish waste 0.024 MW.
Note: The author was an acting environmental consultant at the time and was involved in some of the above projects.
More about: UK National AD Plants
Good article. Scotland will be beating England soon.Thanks.
In summary, in Scotland the benefits of anaerobic digestion we conclude these plants lead to reduced sludge and required footprint compared to aerobic treatment.
A biogas plant reduces methane and sludge for resource recovery, it can destroy pathogens depending on the operating conditions.
But, in Scotland drawbacks include that we find that the process is easily upset. It operates best at controlled and consistent conditions, which winter to summer can be hard to find enough feed, and it requires knowledge and skill for operation. Here is a useful page for you:
http://www.ionacapital.co.uk/page/82/bioenergy-market.htm