Bio-energy plants transform whisky distillery sector

Diageo owns 28 malt distilleries and one grain distillery in Scotland. It is leading the industry in terms of creating sustainable energy solutions and it has invested almost £100million to date in using distillery co-products to produce renewable energy.

On-site bio-energy plant

The on-site bio-energy plant was commissioned by a British provider of on-site Anaerobic Digestion (AD) plants, Clearfleau. Diageo and Clearfleau have collaborated closely in developing the Glendullan bio-energy plant and the initial plant at the nearby Dailuaine distillery which has been operational for over three years.  Each on-site plant comprises a high-rate digester, specifically designed to handle liquid distillery co-products, followed by aerobic treatment for water clean-up. 

Clearfleau’s Anaerobic Digestion plant at the Glendullan distillery.

Meeting targets

The Glendullan bio-energy plant will make an important contribution to Diageo’s global environmental targets by reducing annual CO2 emissions by approximately 6,000 tonnes. The company has invested £6 million at the Dailuaine distillery to create a new bio-energy plant which uses anaerobic digestion technology to treat waste water. The use of AD technology to produce electricity for use on-site was a first in malt distilling. This plant uses the liquid residues from the distillation process to generate bio-gas which is then used in a Combined Heat & Power (CHP) plant to generate electricity and steam on-site which is used to power the onsite distillery and the dark grains plant.

The second plant generates 0.5 MW of biogas, providing 40% of electrical demand for the site and reduces CO2 emissions by 250 tonnes. At the end of the process all that is left is clean water which can be discharged without environmental impact and solid bio-fertiliser which are used by farmers.

Clearfleau's AD process at Glendullan

The plant at Glendullan is delivering a 25% reduction in fossil fuel energy demand at the distillery, saving Diageo significant costs and reducing its carbon footprint by 1,000 tonnes of CO2 per year.   The AD plants reduce the incoming COD load by over 95% and minimize further treatment required for the discharge of cleansed water to the river Fiddich and then into the Spey.

SEPA targets

This investment will help Diageo meet the Scottish Environment Protection Agency’s (SEPA) new plans for enhanced resource use - achieving low carbon emissions, improved materials use and energy savings.  It will also enable local farmers to replace fossil-fuel-derived fertiliser with nutrient rich bio-solids. 

Digestion of distillery residues is making a major contribution to Scottish targets for both carbon mitigation and the generation of renewable energy.  The net carbon savings for the two plants, based on replacement of aerobic treatment with the innovative anaerobic bio-energy solution deployed at Dailuaine and Glendullan is about 3 tonnes of carbon a day. 

One year on

The initial 12 months’ results show on-site anaerobic digestion at the Glendullan distillery at Dufftown is converting approximately 1,000m3 per day of malt whisky distillery co-products into valuable renewable energy.  This is about 1 million m3 of biogas per year – producing 6000 MW hours of thermal energy for the distillery.

Diageo also took the opportunity to invest in a new pipeline linking the nearby Mortlach and Dufftown Distilleries to the bioenergy plant at Glendullan, allowing co-products from all three distilleries to be processed and removing over 15 trucks a day from the local roads.

Carbon savings

If the impact on the transport of co-products is included, the overall saving of carbon for the two sites increases to over 3,000 tonnes of carbon a year – for an expected 20-year period.  If 10 additional, comparable on-site bio-energy plants were to be installed in the whisky sector in the next three years, the net annual saving could exceed 30,000 tonnes of carbon. 

Craig Chapman, Chief Executive of Clearfleau said: “With the distillery sector setting tougher sustainability targets, SEPA’s beyond compliance ‘one planet prosperity strategy’ endorses practical action, such as optimizing energy output from un-wanted co-products.   We are working with Diageo and other distillers to deliver renewable energy solutions that support carbon reduction targets and a more circular approach to resource use.”    

Diageo is committed to being one of the most environmentally sustainable beverage companies across its global operations. The company’s collaboration with Clearfleau at its Speyside distilleries has made a significant contribution towards this goal in its Scotch whisky operations in Scotland.  By boosting distillery efficiency, it is hoped that more Scottish distillers will be encouraged to generate value from the residues of the whisky distillation process.