“Used coffee grounds still contain 99% of their nutrients”


Finding a new awareness and balance not only leads to new connections but also new ideas. This is how Rotterzwam was born, a circular concept for upcycling coffee grounds to produce oyster mushrooms.

Five million kilos of coffee grounds
Seeking meaning in life, wanting to contribute to a better society and to ecological sustainability, that’s what this company stands for, says account manager Dick Rensen: “Rotterzwam aims to find a solution for an existing waste stream that is not reused; coffee grounds. After making a cup of coffee, we normally throw away the coffee grounds while they still contain 99% of their nutrients. In Rotterdam alone, there are five million kilos of coffee grounds per year as a residual flow, while it forms the perfect basis for growing oyster mushrooms. That’s how Rotterzwam was born.”

Beer and bitterballs
Rotterzwam’s focus is twofold; both businesses and consumers are included in their strategy. Together with local partners, they collect coffee grounds from companies including de Bijenkorf, which they use to grow their oyster mushrooms in an ecological way after which they sell them locally to restaurants, supermarkets, and people at home. “Among other things, we work with an artisan bakery in Rotterdam who makes croquettes and bitterballs from our oyster mushrooms, and we work with a local brewery that makes beer from them. This way we create a local chain which ensures more impact.” On the other hand, Rotterzwam also encourages consumers to make an impact themselves. The trend to grow mushrooms at home increased during the corona crisis, which exactly matched the concept of Rotterzwam, states Dick: “We saw a bigger interest in our grow kit, with which people can grow oyster mushrooms at home. A very good thing, especially when considering that we drink four times as much coffee at home.”

Creating a collective awareness
Apart from providing an upcycled, circular product, for Rotterzwam it is mainly about creating a collective awareness among the people they work with. “We are not anonymous garbage collectors at the back of a company solving a problem, but we tell the whole story at the front of the company. We always provide knowledge and awareness alongside our product and services, with practical tips. We create impact certificates that transparently show what the positive effects are and we organize inspirational sessions at companies where we collect coffee grounds, to show them what they can do themselves. That’s how we ultimately can make the biggest, positive impact.”



Lara Oliveri



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