Sludge biochar in the Halland region – phosphorus reuse, regulation, localization and economic feasibility Thermal treatment of municipal sewage sludge has gained interest in Sweden in recent years. With respect to smaller wastewater treatment plants, an investment in thermal treatment may be more attractive if a collaboration between utilities is formed and treatment is performed regionally. This study investigated the feasibility of sludge pyrolysis in the Halland region, southwest Sweden. The current sludge volumes in Halland were mapped, the potential benefits of using sludge biochar in agriculture were investigated, the regulations relevant to sludge pyrolysis and use of sludge biochar were investigated, and lastly the economic feasibility of sludge pyrolysis and associated sludge logistics were investigated. The analysis was based on data collected from utilities in the region and technology providers, as well as literature data. The logistics assessment was based on current sludge volumes produced in Halland and the average distances to final site of disposal. The economic feasibility was calculated in terms of net present value (NPV) and payback period. Based on its phosphorus content, sludge biochar is interesting as a phosphorus fertilizer; however, the plant availability of phosphorus needs to be considered. Other potentially positive effects of using sludge biochar in agriculture is the increased nutrient retention capacity of the soil as well as the liming effect. Further, literature data indicates that sludge biochar has lower toxicity compared to dewatered sludge. Regulations for sludge biochar are expected to evolve during the coming years. The logistics assessment indicated that four separate sludge pyrolysis plants (including drying) would be more transport efficient compared to one centralized pyrolysis plant. This was expected since drying and pyrolysis greatly decreases sludge mass. However, the economic feasibility assessment indicated that one central pyrolysis plant would be preferable. Conservative baseline assumptions indicated that sludge pyrolysis would not reach pay off within 20 years (NPV of -96 mSEK). With a projected increase in alternative sludge disposal cost, the NPV was calculated to be 57 mSEK, with a payback period of ~16 years. It is important that the choice of sludge management takes alternative future forecasts into account in order to identify the most suitable solution to invest in. Key factors in the future forecast are upcoming requirements for the quality of wastewater products used on arable land, as well as requirements for the recirculation of plant nutrients. These are expected to have great significance from an economic point of view.