Assessment of granulated fertilizers from waste materials

Abstract

Waste materials such as fly ashes and sewage sludges have properties that can be exploited in various applications e.g construction, energy recovery, etc. These residues contain nutrients (P, N, S, ca) that make them attractive substitutes for synthetic fertilizers in forestry and agriculture. Nevertheless, the use of these materials is often limited due to the presence of potentially toxic elements and substances. Moreover, spreading of loose ashes can lead to rapid wash out of nutrients as well as cause difficulties of spreading itself (e.g due to the dusting) It is therefore necessary to assess and modify properties of these and similar waste materials in order to take advantage of their beneficial properties. This study focuses on the comprehensive characterization of fly ashes and sewage sludges collected from various incinerators and wastewater treatment plants in northern Sweeden in terms of mineralogical and chemical composition. Leaching tests and selective extractions will be performed to identify the differences in element behaviour in individual materials as well as in their mixtures. The obtained results will be used to identify the key mechanisms responsible for element leaching and determine properties that need to be modified in order to have a higher-value material.