The preconditions for increasing phosphorus recycling from sewage systems in Sweden : a study of factors influencing Swedish farmers´ willingness to use phosphorus fertilizers produced from sewage sludge

Abstract: The Swedish government (2018) is currently investigating options for prohibiting direct application of sewage sludge on arable fields and replace it with techniques capable of precipitating phosphorus from sewage sludge and turn it into refined phosphorus fertilizing products. The investigation is part of the government´s ambition to increase the recycling rate of phosphorus available in sewage sludge and thus turn the sludge into a greater agricultural resource than it is today (ibid). The success of refined phosphorus fertilizers is primarily contingent on farmers´ willingness to use them, making the factors influencing this willingness crucial to be aware of. However, these factors are not explicitly mentioned as being taken into consideration in the government´s investigation (ibid), and no previous research exists on this topic. For this reason, this thesis has focused on investigating the factors influencing Swedish farmers’ willingness to use refined phosphorus fertilizers produced form sewage sludge. It has done so by conducting semiBstructured interviews with nine Swedish conventional farmers. Their answers have been analysed using inductive thematic analysis. The analysis identified three themes, or factors, influencing farmers’ willingness to use refined phosphorus fertilizers produced from sewage sludge; (1) Scientific understanding about the products, (2) Features of the products, and (3) Price of the products. The first factor, Scientific understanding about the products, is about farmers expressing a need for a widespread scientific understanding about the refined phosphorus fertilizers and the technologies used to produce them. This in order to avoid that phosphorus fertilizers produced from sewage sludge become subjected to the same controversy surrounding the safety of using them as directly applied sewage sludge is perceived as being subjected to today. The second factor, Features of the products, is about phosphorus fertilizers produced from sewage sludge needing to have physical and chemical features similar to the mineral fertilizers farmers use today. The third factor, Price of the products, is that the prices for phosphorus fertilizers produced from sewage sludge should not exceed those for phosphorus mineral fertilizers, and that society has a responsibility to keep prices at a level where phosphorus fertilizers produced from sewage sludge are economically feasible for farmers to obtain. The thesis concludes that the Swedish government should implement technologies and refined phosphorus fertilizing products that accommodate the identified factors to the extent possible. This in order to improve the preconditions for an increased recycling rate of phosphorus available in sewage sludge.