The North British Distillery has partnered with ENER-G and HydroThane to develop an anaerobic digestion (AD) project to deliver both energy and water savings, while increasing productivity and reducing costs.
Based in Edinburgh, the distillery – a joint venture between Diageo plc and the privately-held Edrington Group – supplies internationally-renowned whiskies, such as The Famous Grouse and Johnnie Walker Black Label.
The £6 million green technology project has reduced the distillery’s carbon dioxide emissions by approximately 9,000 tonnes per year, which equates to the annual carbon saving benefits of a 7,377 acre forest, or removing 3,000 cars from the road.
The project introduced high rate anaerobic digestion to help the company provide a sustainable solution to a bottleneck in the back-end production process. This comprises a by-products plant producing Distillers Dark Grain pellets for animal feed.
Instead of investing in additional energy intensive evaporation capacity to process the liquid by-products from the distilling process, a decision was made to install an anaerobic digestion plant which, conversely, produces renewable energy in the form of biogas.
The AD plant, which was completed in two phases, is capable of treating 27,000Kg of Chemical Oxygen Demand (COD) per day and produces up to 24 000 MW hours of renewable energy in the form of biogas.
A high efficiency 500kW ENER-G combined heat and power system and a 1 000kW steam boiler convert the biogas into steam and electrical energy for use on-site. These two energy streams dramatically reduce the distillery’s reliance on the use of fossil fuel based energy inputs from the national gas and power grids.
By using HydroThane ECSB (External Circulation Sludge Bed) high rate anaerobic digestion technology to process a third of the post distillation liquor, the company has reduced the load on its existing energy intensive evaporation plant – increasing productivity while reducing energy demand.