Recycling in the Scottish Whisky Industry

Proven for centuries

The first Whisky distillers in Scotland were farmers. They were looking for the perfect way to store their surplus grain. While stored barley easily begins to mold in a humid environment, the Whisky distilled from barley malt can easily be kept in oak barrels for decades.

The improvised solution quickly turned into a wide-ranging supply for Whisky, which became very popular. But not the whole grain of barley is turned into malt and finally into Whisky. A lot is left behind. To speak of waste in this context is not correct indeed even wrong, one speaks of by-products.

After leaching out the malt sugar with hot water in the Mash Tun, the shells and other substances remain in the so-called draff. This draff is rich in proteins and minerals and is very suitable as concentrated feed for animal fattening.

Since this hot draff accumulates before fermentation and does not yet contain alcohol, it is very prone to bacterial attack and spoilage. Therefore farmers pick it up by truck shortly after the Mash Tun is emptied. What cannot be fed immediately is usually mixed with silage for later use and thus increases its nutrient content.

This draff can also be preserved. For this purpose it is dried to a residual moisture of less than 10%. It is then pressed into pellets and bagged. However, this procedure requires a lot of energy and is becoming less and less profitable. Numerous plants were closed due to the rising oil and gas prices in the past decades.

The problem is greater than one might imagine at first glance. The Scottish Whisky industry has grown massively since the 1990s. Around 500,000 tons of draff are produced every year. Where to put it? The livestock industry has grown as well, but not to the same extent.

Nowadays, the draff that is not purchased by farmers is usually converted into heat and electricity in cogeneration units. First, the water is pressed out of the draff to facilitate the combustion. In some power plants, bark, sawdust and wood chips from the wood industry are burned along with the draff. There used to be a draff pellet plant in the municipality of Rothes in Speyside (Glen Grant, Glenrothes, Glen Spey, Speyburn). Today it has become a large Rothes CoRDe LTD cogeneration plant, using 115,000 tons of wet draff from local Whisky distilleries and 60,000 tons of wood chips per year.

With the help of steam turbines, the plant generates 7.2 megawatts of electricity, which is sufficient for 9,000 households. However, such a plant always has a negative aftertaste: even though food is not burned, feed for food production is.

But back to Whisky. After the production, pot ale is left over. These are the heavier substances that accumulate in concentrated form during distillation, which ultimately do not end up in the Whisky and are left behind with the water. This liquid also contains valuable components, even though the pot ale, as concentrated as it accumulates at the bottom of the pot stills, is toxic to humans. In the past, more than one worker suffocated from the fumes while manually cleaning the pot stills. Today the pot ale is drained automatically. Then the pot still is cleaned automatically by spray nozzles and afterwards rinsed with clear water. This waste water goes back to the manufacturers of the cleaning products. If today a Pot Still has to be entered through the manholes for maintenance, a second man with a safety line outside the Pot Still is mandatory.

But what happens to the pot ale? It is rich in minerals and therefore suitable as a fertilizer for the fields. The soil is given back a part of what was taken from it with the harvest. This cycle has also proved its worth for centuries

The electrical energy of the biomass power plant is not everything. Diageo, the largest Whisky producer in the world with several dozen malt and grain distilleries in Scotland, has integrated these draff power plants into its distillery complexes. The company operates its own biomass power plant at the Glenlossie-Mannochmore distillery. This means that not only the electricity but also the waste heat can be fed into the Whisky process via cogeneration. This leads to large savings in gas and oil.

The most modern and best-integrated plant of its kind is located in the Roseisle distillery near the small town of Forres, which was built in 2009. Here, the biomass power plant was planned along with the construction of the distillery with its astonishing 10 million litres annual capacity. 60,000 tons of draff per year supply the distillery with electricity and operate the mashing and distillation with process steam.

In ancient times, Whisky distillers produced their Whisky with what they found on the spot. The energy was supplied by the peat, which was used to dry the malt as well as to fire the mash tuns and the pot stills. Today, the distilleries are supplied with the necessary energy from the by-products of Whisky production, thus becoming less dependent on oil and gas.