Repurposing Fly Ash Derived from Biomass Combustion in Fluidized Bed Boilers in Large Energy Power Plants as a Mineral Soil Amendment

This research involved studying the physico-chemical parameters of fly ash derived from the combustion of 100% biomass in bubbling and circulating fluidized bed boilers of two large energy plants in Poland. Chemical composition revealed that ash contains substantial amounts of CaO (12.86–26.5%); K2O (6.2–8.25%); MgO (2.97–4.06%); P2O5 (2–4.63%); S (1.6–1.83%); and micronutrients such as Mn, Zn, Cu, and Co. The ash from the bubbling fluidized bed (BFB) was richer in potassium, phosphorus, CaO, and micronutrients than the ash from the circulating fluidized bed (CFB) and contained cumulatively less contaminants. However, the BFB ash exceeded the threshold values of Cd to be considered as a liming amendment. Additionally, according to our European Community Bureau of Reference (BCR) study Pb and Cd were more mobile in the BFB than in the CFB ash. Except for a low nitrogen content, the ash met the minimum requirements for mineral fertilizers. Acute phytotoxicity revealed no inhibition of the germination and seed growth of Avena sativa L. and Lepidium sativum plants amended with biomass ash. Despite the fact that low nitrogen content excludes the use of biomass fly ash as a sole mineral fertilizer, it still possesses other favorable properties (a high content of CaO and macronutrients), which warrants further investigation into its potential utilization.