Wastewater from distilleries could be used to generate sustainable green hydrogen, according to studies by scientists at Edinburgh's Heriot-Watt University.

Academics have developed a way to use distillers' wastewater – generated from processes including cooling and cleaning – to produce green hydrogen, a process powered by renewable energy which currently consumes more than 20 billion litres of fresh water a year.

Whisky distilleries in Scotland alone produce an estimated one million litres of wastewater every year; for the global distilling industry, this figure is thought to be close to one billion litres.

A team led by Dr Sudhagar Pitchaimuthu, a materials scientist in Heriot-Watt’s School of Engineering and Physical Sciences, have developed a nanoparticle called a nickel selenide. This nanoparticle treats the wastewater to clear it of substances that can inhibit the electrolysis process by which hydrogen is generated. In the team's research, the treated wastewater produced similar or even slightly higher quantities of green hydrogen compared with fresh water.

Dr Pitchaimuthu explained: “It takes 9kg of water to produce every 1kg of green hydrogen. Meanwhile, every one litre of malt whisky production creates about 10 litres of residue. To help protect the planet, we need to reduce our use of fresh water and other natural resources, so our research focused on how to use this distillery wastewater for green hydrogen production with a simple process that removes waste materials present in the water.”

The research is published in the Royal Society of Chemistry journal, Sustainable Energy & Fuels, in a paper entitled "From brew to clean fuel: harnessing distillery wastewater for electrolysis H2 generation using nano scale nickle selenide water oxidation catalysts". The paper is authored by Dr Pitchaimuthu’s PhD student, Michael Walsh, who played a key role in conducting the research.

“About one billion litres of wastewater a year is produced from the distilling industry, so the potential of this process is huge,” Dr Pitchaimuthu said. “Using industry wastewater means we can reduce the extensive freshwater footprint associated with green hydrogen production. Our research also shows how we can use the world’s resources more sustainably to produce clean energy.”

The next steps for the research team include developing their own electrolyser prototype, scaling up production of their nickel selenide nanoparticles, and analysing the distillery wastewater to discover whether other valuable materials could be salvaged from it, alongside hydrogen and oxygen.

The research was funded by Heriot-Watt’s School of Engineering and Physical Sciences and completed in collaboration with the University of Bath’s Department of Chemical Engineering and the Scotch Whisky Research Institute, which supports applied research across the Scotch whisky production process.