Evaluation of fly ash in terms of its suitability for fertilizer purposes by type of combustion and feedstock - literature review

Abstract Fly ash, as waste generated from the combustion of coal and other solid fuels, is an important topic in the context of a circular economy in any industry. There are many variables that affect the amount of waste generated, including the type and quality of fuel and the efficiency of dust collection systems. Statistics on the consumption of coal and lignite in Poland, as well as other sources of waste (such as municipal and sewage sludge) indicate a significant amount of fly ash produced. According to the waste hierarchy, fly ash can be recycled or subjected to other recovery methods with the objective of using it as a sealing material, an ingredient in mortars and adhesives, and in geotechnics. For hazardous waste, the preferred recovery methods are cementation, geopolymerization and vitrification. The trace-element content of ash varies depending on the source and type of material burned. This is a key issue for determining the feasibility of further ash management. Due to the content of macro- and micronutrients beneficial for plants and soil, fly ash can be used for fertilization purposes following the examination of its chemical properties, with particular attention to the concentration of heavy metals and other contaminants.