Alcohol-free beer is getting ever more popular.

But that leaves brewers with a problem: what to do with all the booze removed from their beers?

Now AB InBev thinks it's found a solution.

It's teamed up with detergent maker Ecover to turn the leftover or 'rest' alcohol into washing-up liquid:

David De Schutter is AB InBev's European head of innovation:

(SOUNDBITE) (English) INBEV EUROPEAN INNOVATION AND TECHNICAL DEVELOPMENT DIRECTOR, DAVID DE SCHUTTER, SAYING:

"In the beginning, when we were producing non-alcoholic beer, we had very little quantities of rest alcohol. So there was no real partners to find (to upcycle). But as those amounts were growing the brewery was asking us 'ok, what can we do with the alcohol, because it's piling up."

The alcohol comes from AB InBev's Leffe and Jupiler brands.

It makes up about a quarter of the resulting detergent.

EcoVer developed the upcycling technique.

Head of Innovation Tom Domen says there was one big problem:

(SOUNDBITE) (English) ECOVER HEAD OF INNOVATION, TOM DOMEN, SAYING:

"There's still a little bit of the beer smell that was in the alcohol. So this for us was also a challenge in, how can we mask that smell to make sure our product still smells nicely when you're doing your dishes. You don't want the kind of beer smell on your dishes."

Now the brewer is finding other uses for its waste.

About 1.3 million tonnes of leftover grains go the cattle industry for feed.