What Should We Do With Sewage Sludge? Public Preferences for Biosolids Management in Australia

Biosolids are a solid byproduct of municipal wastewater treatment systems. Conventionally, because of their nutrient and carbon content, most biosolids have been applied to agricultural lands in Australia. However, growing concerns over methane emissions, ongoing management and transportation costs and contaminants of emerging concern, such as per‐ and polyfluoroalkyl substances (PFAS) and microplastics, are calling conventional approaches into question. Water utilities are therefore exploring alternative options and new infrastructure investments to manage biosolids, considering wide‐ranging financial, environmental and social outcomes. We survey 3135 Australian residents and use an anchored best–worst scaling experiment to elicit public preferences for alternative biosolids management strategies. Results suggest the public is generally supportive of all biosolids management approaches, but that the reuse of biosolids to build roads, to create energy and for construction is most preferred. Using latent class analysis, we also uncover significant preference heterogeneity and some polarisation, especially for the use of biosolids in the food system. Together, our results emphasise the importance of developing effective soft infrastructure, like policy and engagement processes, to build public confidence and support the implementation of new hard infrastructure to improve biosolids management outcomes.