Rotterzwam is a company from The Netherlands that grows Oyster mushrooms. Not that special in itself, but they use old coffee ground and coffee peels to grow them on. They go around Rotterdam, a city in The Netherlands, and pick up old coffee ground from local bars and café’s. What was normally waste, now becomes a fertilizer for delicious mushrooms which they sell to hospitality businesses or directly to consumers. Their latest product is a grow kit for consumers so that everyone can start using their coffee waste and it turn into nutritious food.