An innovative new project is using residues from Scotland’s whisky industry in biogas production at Aberdeen’s Nigg Waste Water Treatment Works (WwTW) for the first time.

One of the CHP engines which convert biogas into heat and green electricity at Nigg WWTW

The successful trial involving Scottish Water, Scottish Environment Protection Agency (SEPA) and major distiller Chivas Brothers is using distillery residue at the WwTW with promising results.

The trial was made possible by close collaboration between the industry, SEPA and Scottish Water. It was led by the publicly owned water company’s commercial subsidiary, Scottish Water Horizons.

The residues from distilleries and breweries in the area can be added to sewage sludge in a co-digestion process at Nigg, as part of a system which produces biogas – an alternative fuel used to run the site’s boilers and Combined Heat and Power (CHP) engines.  

The facility already has a process to turn sludge produced during waste water treatment into biogas – this is then used on site instead of oil or diesel. Since October 2021 the sludge treatment centre has trialled co-digestion to process residues brought in from Chivas Brothers’ distilleries and breweries alongside the sludge – and this has noticeably increased the amount of biogas being produced.  

With the addition of the distillery and brewery residues, the plant saw a saving of 58 tonnes of carbon over the 12-week trial period, which equates to 250 tonnes per year.

Chief Scientist Elise Cartmell said:

“We’re very pleased with the findings which show that the trial boosted biogas production and significantly reduced the site’s need for oil to power its on-site boiler. Just as importantly, there was no adverse impact on the operation of the site or on the quality of the biosolids that are also produced for recycling to land.

“We believe there is excellent potential for this approach to be used at Nigg in the future and for it to be rolled out to other sites across Scottish Water.”

Through collaborative working and close monitoring throughout the Nigg trial, the teams involved have laid the groundwork to explore further opportunities in the future to support businesses and green energy production across the country through co-digestion.

The team at Chivas Brothers approached the water company because the various residues created as part of the distillery process are often rich in energy and they were keen to find alternative outlets to capture and use it.

Chivas Brothers’ Environmental Sustainability Manager Ronald Daalmans said:

“The trial with Scottish Water has shown that residues from our effluent treatment process still have an energy value that can contribute to a more circular and sustainable economy and provide an alternative outlet for distillery residues when other routes are full.  

“We hope the trial will open up further opportunities for collaboration between the Scotch Whisky sector and utility operators.”

Elise Cartmell continued:

“It’s turning out to be a win-win for both parties: the distilleries are provided with an outlet for treatment which helps this key regional industry become more sustainable, while we at Scottish Water benefit from a boost in production of green energy at our site, which reduces our reliance on fossil fuels and helps our journey to net zero.”