July 26, 2021

I, Science

The science magazine of Imperial College

Little Miss Muffet
Little Miss Muffet has been eating too much whey, not enough curds it seems

Body builders have got a lot to answer for.  The protein shake manufacturing process is leaving dairies with vast amounts of waste whey, and they don’t know what to do with it. Could turning the whey into biogas be a sustainable answer?

Greek scientists have assessed an anaerobic biogas reactor to see if it can get rid of the problematic waste, whilst making financial sense by reducing dependence on fossil fuels.  Their results, published in Renewable Energy journal, are encouraging: dairies could be saving hundreds of thousands of Euros in just a few years.

Globally, 34 tonnes of cheese is produced every minute.  Whey is the bit that’s left over when the curds are removed for compression into hard cheese. Traditionally, this highly nutritious liquid was fed to pigs. However, since the explosion of bodybuilding, whey is now ‘ultra-filtered’ to catch every last protein molecule for use in muscle shakes.

After ultra filtration, all that’s left is a watery solution of 5% lactose – a type of sugar. This liquid can be processed further to extract lactose for use in pharmaceuticals, but that’s beyond the means of many dairies. “The equipment needed for lactose extraction is very expensive,” says Dr Tassos Stamatis, co-author of the research. “Moreover, the dairies will need to find clients in the pharmaceutical industry, which is completely out of their scope.”

Dairies have resorted to desperate measures. “Some small size dairy plants illegally dump it in rivers,” says Tassos, “it’s one of the most important environmental problems facing the industry.”

The intriguingly-named Upflow Anaerobic Sludge Blanket (UASB) reactor could be a solution.  Whey is fed into one end of the system and heated to 35⁰C. It then passes through four processing tanks; each containing different species of bacteria that digest the whey without the need for oxygen. Out the other end comes biogas and water. A bit of gas is burned to warm up the whey as it’s fed in and the rest can be used wherever it’s needed in the dairy – instead of natural gas.

UASB reactors cost over €2 million, but the team from Greece’s University of Thessaly found that a reactor installed at a decent-sized dairy would pay for itself after just six years – that’s including interest on loans taken out to buy it in the first place. After a decade, with a vastly reduced need for expensive natural gas, the plant would have saved over €100,000.

The technology is gaining interest in the US and across Europe. Dr Stamatis thinks that with a few simple tweaks, the system might be made up to 20% more efficient and could be set to revolutionise the dairy industry. “Dairy plants in Greece are now thinking seriously about investing on this technology,” he says.