Coffee Grounds for Mushrooms

Who would have thought coffee grounds could be circular? In fact, they are ideal as a fertile substrate for growing oyster mushrooms. Rotterdam-based rotterzwam collects the coffee grounds from local pubs, large corporations and restaurants. They cultivate the mushrooms and sell the produce to customers in the Rotterdam area.

Bitterballen van rotterzwam

Bitterballen made from rotterzwam's oyster mushrooms

Image: Rotterzwam

Rotterzwam mixes the coffee husks and mushroom and spawns them in a bag that is hung in a special grow room. The grow room is in Blue City, a new hub for the circular economy. It is located in an old, disused riverside swimming pool in the center of Rotterdam.

The oyster mushrooms are fully grown and harvested in 6 weeks. Up to 50 kilos of mushrooms can be picked every week. Most of the produce is sold to restaurants, shops and private customers in the local area.

The entire process is sustainable and local - an outstanding example of the circular economy.

Sustainable snacks

One of rotterzwam's popular products are the typical Dutch ‘Bitterbal’ snack. Normally this snack contains meat, but rotterzwam created a vegetarian version made from mushrooms. Substituting the main ingredient beef with mushrooms saves 50 to 90 liters of fresh water per bitterbal in the production process. Making it healthy, delicious and environmentally friendly at the same time.

Sharing know-how

Rather than shun the competition, rotterzwam is keen to share their know-how actively with others and encourage everyone to take up mushroom cultivation. Rotterzwam host a free webinar on a wide range of mushroom topics every month. The company wants to educate other entrepreneurs and encourage them to start cultivating mushrooms. Their goal is to spread their innovative idea and inspire others.

Mushroom Learning Network

The Mushroom Learning Network is an event co-hosted by rotterzwam. Its goal is to educate would-be growers and have experienced planters share their knowledge at the same time. The event takes place in a northern European city every year. During this two-day meeting, participants can exchange ideas on various topics concerning mushroom cultivation - from the growing process to its financial and business side.

Although rotterzwam’s mushrooms are grown and sold locally, their idea is shared globally. The company's goal is to partner up with the world and create sustainable collaborations for the circular economy.