Innovation

The main innovation of Rotterzwam is in the circular “closed-loop” system. They collect coffee grounds from local businesses, such as restaurants and coffee bars, and mix it with other ingredients to create a substrate. This substrate is used to grow mushrooms in specially converted, conditioned sea containers located in Rotterdam-West. This approach not only enables mushroom cultivation, but also allows them to tackle the significant issue of urban waste. Besides coffee grounds (of which they collect around 70,000 kilos annually), their process also incorporates other organic waste like wood waste and spent grains (a byproduct of the beer brewing process).

Rotterzwam’s innovative solution contributes directly to multiple UN SDGs. By using coffee grounds to cultivate food, they significantly reduce CO2 emissions, which directly supports SDG 12 (responsible consumption and production) and SDG 13 (climate action). Since they produce local foods, it also aligns with SDG 2 (zero hunger) and SDG 11 (sustainable cities and communities), since transport emissions are reduced and urban food security is strengthened. They also support SDG 9 (industry, innovation, and infrastructure), since their core business model is based on the circular economy by transforming waste into a valuable resource, which is a key factor of SDG 9. Besides these environmental benefits, Rotterzwam also creates local employment opportunities and engages in social partnerships, which contributes to SDG 8 (decent work and economic growth). Unlike most businesses, Rotterzwam embraces an open-source business model, actively encouraging others to replicate its sustainable practices. As Fabian explains: “Our whole narrative is that we are open-source. We're not afraid to let people see what we’re doing, even if that means they might copy it or eventually outcompete us.” To support this mission, they offer workshops, training programs and starter kits. This open-source ethos contributes to SDG 4 (quality education) and SDG 17 (partnerships for goals).

Inspiration

Rotterzwam began as an idea sparked by a book. One of the company’s founders was inspired by The Blue Economy, a book that presents numerous concepts for contributing to a circular economy, written by the Belgian author Gunter Pauli. As Fabian explains, “In that book, he provides a lot of ideas of how to contribute to a circular economy. And one of the ideas is growing mushrooms on coffee.” While the book didn’t offer detailed instructions, it planted the seed that became the core of Rotterzwam’s innovation.

Inspired by this concept, the founder began researching how to implement it himself. He soon discovered someone already experimenting with growing mushrooms on coffee grounds inside an old swimming pool in Rotterdam, part of an initiative called BlueCity. “There were like three or four entrepreneurs active within the building.” It was in this setting that Rotterzwam took shape, through a collaboration between the founder and others already active in the space.

The company officially started around 15 years ago. After facing the challenge of their original location burning down, they were able to come out stronger and focus on growing. That initial spark of inspiration from circular economy theory evolved into a hands-on enterprise that continues to grow, educate, and innovate. Fabian was inspired to join the company and with his background in biology he pointed out that “...we can learn a lot from nature, because, in nature, there is no word such as waste.” 

Overall impact

Rotterzwam’s innovation has had measurable environmental, social, and systemic impact. In the short term, the company has diverted tens of thousands of kilos of coffee grounds from incineration, significantly reducing CO₂ emissions and creating a sustainable, plant-based food source. In 2022 alone, they repurposed 69,366 kg of coffee grounds, preventing 31,339 kg of CO₂-equivalent emissions and producing 2,608 kg of mushrooms, equivalent to 286,731 snacks. Compared to meat-based alternatives, this saved over 8.6 million liters of water. While most visible in Rotterdam, Rotterzwam’s influence extends through workshops, guided tours, media outreach, and community engagement.

In the long term, Rotterzwam has helped reshape public attitudes toward food, fungi, and waste. As Fabian explains, “People in the West still have a very weird relationship with fungi. Anything in your fridge that has fungi on it smells and is not nice.” Through education and grow-at-home kits, they help people reconnect with where food comes from and recognize waste as a resource. “Food doesn’t just come from the supermarket,” Fabian adds. 

Furthermore, Rotterzwam’s open-source approach has inspired entrepreneurs beyond the Netherlands. While many underestimate the effort required to replicate the concept, the company actively lowers this barrier by openly sharing their knowledge and offering training. This commitment has fueled growing international interest, with visitors from regions such as Asia visiting their farm to learn from their model. With their spin-off, Sporo, focused on substrate production, they are now preparing to scale the concept across metropolitan regions. Looking ahead, success means building urban farms, creating jobs, and embedding circular thinking into mainstream food systems.

Business benefit

Sporo will take over the production of making the substrate from the different products. Sporo will supply the substrate to Rotterzwam, and other companies who are interested. This shift will allow Rotterzwam to focus purely on cultivating the mushrooms. As the work at Rotterzwam will become more streamlined, they are looking to hire people with a distance to the labour market. They also believe that their mission and vision attracts a different kind of employee. “The people that come here are not the people who want to make the big bucks, but they are people that really want to do something with their hands.”

As pioneers in their field Rotterzwam believes they have changed the market by demonstrating how to be more circular and succeed. Their example has encouraged other companies to take action and improve on their environmental image. In order to expand their impact, they shifted from being 100% sustainable to being 50% sustainable so they could maintain the business, attract more customers, promote circular principles and create a bigger impact. They are excited for the future. Fabian points out: “Doing new tests on organic waste materials excites me. Furthermore, we are developing a lot of new mushrooms. So we're not only looking at edible mushrooms, but also mushrooms that you can use within supplements.” By expanding their product range and exploring new applications, they aim to reach new markets and increase their relevance. Moreover, Rotterzwam is looking into expanding their business to other cities and creating a larger community. 

Social and environmental benefit

Rotterzwam’s innovation contributes meaningfully to both environmental sustainability and social progress. By transforming local organic waste into food, their model strengthens the circular economy at a city level. Instead of treating used coffee grounds and other organic byproducts as waste, Rotterzwam turns them into a productive resource. This not only cuts waste but also enriches the soil after use and reduces the need for imported farming materials. This circular approach reduces emissions while also promoting the development of localized, low-impact food systems that align with SDG 12 (Responsible Consumption and Production) and SDG 13 (Climate Action). 

Beyond its environmental benefits, Rotterzwam also has very strong social benefits as it plays a strong educational and social role. Rotterzwam actively engages the public in sustainable practices through workshops, training programs, and open-source knowledge sharing (SDG 4). These initiatives build ecological literacy and offer people concrete ways to take action, whether by starting their own circular project or simply changing how they view food waste. This fosters the mindset shifts necessary for long-term systemic change. In addition, Rotterzwam is committed to inclusive employment. As they scale up, they intentionally seek to create jobs for people with a distance to the labour market, helping translate environmental innovation into broader social benefit. Their work also helps simplify fungi, challenging cultural stigmas and promoting mushrooms as a smart, nutritious solution in sustainable food systems. In doing so, they close the loop, transforming waste into taste.

Interview

Florian de Deugd, Coordinator