06 May 2020| Dutch sustainable solutions| Loes van Driel

Rotterzwam: circular oyster mushrooms

Food can be grown on waste instead of soil. Rotterzwam grows mushrooms on locally collected coffee grounds. And what do you think of their new, local vegetarian ‘bitterbal’?

A local, unique product grown on locally sourced coffee grounds: that is what Rotterzwam has created. Since first taking Rotterdam by storm, they’ve opened a bigger mushroom farm in the city. Rotterzwam also works with farmers and Wageningen University & Research centre on closing agricultural cycles using urban waste. They are also working to scale up their concept by encouraging members of the public individuals as well as national and international partners to grow mushrooms using local waste.

Working with people and organisations

Rotterzwam offers a DIY toolkit for anyone who wants to turn their coffee grounds into home-grown mushrooms. Organisations in the region that use at least 100 kg of coffee per month can partner up and contribute their coffee grounds. Rotterzwam collects the coffee grounds one to three times a week by electric bus. They also offer a welcome package, information posters and a good feeling because with each kilogram of reused coffee grounds collected, a few kilograms of carbon emissions are avoided and a valuable raw material is repurposed.

Products

Rotterzwam oyster mushrooms are mostly sold to Rotterdam-based companies. Working with pastry chef Van der Heijden, Rotterzwam has also created a vegetarian version of the ‘bitterbal’, a deep-fried ragout ball much loved as a snack by the Dutch. They can be ordered in some Rotterdam bars and restaurants, and are sold via wholesalers at 40 local Rechtstreex pickup points, or each Friday at the Rotterzwam nursery.

A bigger movement

This concept can be implemented anywhere. To close the cycle and make optimum use of resources, Rotterzwam also holds workshops, helping others to create more sustainable oyster mushroom farms, tours and team outings. The concept of growing food on waste is being developed in collaboration with other companies, governments and research institutions so as to maximise its impact in relation to sustainable goals.