Comparative study of struvite quality produced in European Wastewater treatment plants

Sammanfattning

P fertilizers are made from phosphate rock, which is a finite resource. It was added to the EU list of critical raw materials in 2014. The phosphorus in P fertilizers could potentially be substituted by a substance called struvite, which can be recovered from sewage sludge. In 2019, the EU updated and included struvite into fertilizer regulation 1009/2019 which made distribution of struvite possible. This thesis aims to: 1. assess the suitability of different types of struvite as a fertilizer in terms of heavy metal content and compare it to conventional fertilizers and sewage sludge, 2. estimate the market price of struvite based on nutritional content and compare it to realized market price of struvite today. Although limited in sample size, the result of this study supports previous findings of struvite’s superior quality in terms of heavy metals. Heavy metal content in struvite is roughly only a hundredth fraction of that of sewage sludge and a tenth fraction of that of commercial P fertilizers. Estimated market price of struvite based on nutritional content was determined to $280- 502/ton. Despite promising results, participating wastewater treatment plants reported selling prices of €50/ton and €90/ton – considerably lower than the estimation. The literature study also revealed polarizing results, as some wastewater treatment plants had to cease production of struvite due to it not being sellable, while one technology provider reports as high price as €1000/ton. However, the former seems to be the typical experience. This is attributed to the limited knowledge of nutrient delivery of struvite, as well as the unconventional fertilizer properties of struvite which might initially deter consumers of fertilizers. The limited production quantities of struvite might also discourage fertilizer producers from utilizing struvite in their products.