How a certification turned sewage sludge from an undesirable waste to a demanded good

Reducing the disposal of wasted materials and increasing their usage has been argued by international organizations like the UN to be pivotal for sustainable production and consumption. Sewage sludge is such a material that could replace mineral fertilizers and increase humus in the soil. However, research on sewage sludge (and other waste) utilisation has identified that the main barrier is to raise demand and establish a market. This paper focuses on the remarkable increase in agricultural use of sewage sludge from 6% to 60% between 2002 and 2024 in Sweden. The hypothesis is that the establishment of a certificate (Revaq) for wastewater treatment plants played an important role in marketing sewage sludge. Based on minutes from the Revaq steering board, the paper uses qualitative analysis to scrutinise how exchange, representation, and normalisation of sewage sludge were practiced. The hypothesis is partially confirmed, where the establishment of the certificate’s stricter rules gained farmers’ support. However, and more importantly, it is not by establishing the certificate alone that support increased, but through relationship building and negotiations to bridge the tensions between market-shaping practices. Revaq had to balance the number of treatment plants with the strictness of rules, a human excrements-only norm with societal embeddedness, and supporting increased agricultural use while enforcing certified sludge as the only option. Understanding how a certificate can enhance waste-derived materials marketing is key to reducing the dependence on new raw materials. • Establishing a certificate can enhance the construction of a sewage sludge market • A certificate needs to address limit values and rules, but also relations and trust • Practices of representation and the actual exchange collide with norms and rules • The certificate becomes an arena to balance opposing market-shaping practices