Rotterdam Showcases Circular Economy with Urban Mushroom Farm
An initiative in Rotterdam called "rotterzwam" is being highlighted as a model for the urban circular economy. The farm grows mushrooms on coffee grounds collected from local businesses, a significant urban waste stream. The spent substrate is then returned to the city as compost, demonstrating a closed-loop system that integrates waste valorization, urban agriculture, and local food production.
- Inspired by Gunter Pauli's book, "The Blue Economy," co-founders Siemen Cox and Mark Slegers started rotterzwam in 2013 to create local food supply and minimize urban waste. The social enterprise operates on a for-profit basis but prioritizes a balance between profit and social impact. - The farm is located in the former Tropicana, a disused subtropical swimming paradise, using spaces like the old dressing rooms for its 1500 m2 production area. This practice of using abandoned real estate is a core part of their model of growing on the "waste of the city." - In 2022 alone, rotterzwam repurposed 69,366 kg of coffee grounds, which prevented 31,339 kg of CO2-equivalent emissions and produced 2,608 kg of mushrooms. Beyond coffee grounds, the farm also utilizes coffee husks, a waste product from the bean roasting process, as a substrate ingredient. - The business model is diversified, with revenue generated from mushroom sales to wholesalers and local restaurants (20%), and sales of their home "Growkits" (20%). A significant portion of their income (40%) comes from educational workshops and paid internships that teach their cultivation methods. - Rotterzwam actively promotes an open-source philosophy, sharing its knowledge and business case through the "Mushroom Learning Network" to encourage similar initiatives in other cities rather than shipping their own products long distances. - The initiative is part of Rotterdam's broader ambition to become a fully circular city by 2050, a goal which aims to create 3,500-7,000 new jobs and reduce the use of primary raw materials by 50% by 2030. - This urban farm aligns with the Dutch national government's goal for the Netherlands to have a completely circular economy by 2050. The government's "Vision on Circular Agriculture" specifically aims for the country to be a global leader in the field by 2030 by optimizing resource use. - Beyond mushroom cultivation, the enterprise extracts enzymes from the spent mushroom substrate, which can be used to increase the yield of biofuels from wastewater treatment. The final remaining substrate is then composted by worms and sold back to the city.
