Content, association, modes of occurrence, and significance of potassium in biomass and biomass ash

Potassium is an unreplaceable element in phytomass and zoomass, because it has a crucial role for their normal cellular function. The demand, scarcity, quality, and prices of natural K resources are future challenges for manufacture of K materials and alternative K resources are required. An overview on the content, association, modes of occurrence, and significance of K in biomass and biomass ash (BA) was conducted based on reference and our own chemical, mineralogical and leaching data. Potassium is enriched in biomass (commonly 1-2%) and occurs as various and dominantly water-soluble (normally 50-80%) organic and inorganic forms. Potassium oxide has very high contents in BA (typically 15-30%) as the modes of K occurrence in BA include more than 89 species represented by glass, char and numerous discrete minerals among silicates, phosphates, sulphates, carbonates, oxyhydroxides, and chlorides. The bioavailable K proportions in BA (commonly 20-45%) are lower in comparison with biomass due to the formation of less mobile K phases during biomass combustion. It was identified that various technological and environmental issues are connected with the specific modes of K occurrence in biomass and BA and they include: volatilization, particle emissions, slagging, and corrosion during biomass combustion; use of biomass or BA for production of fertilizers, soil amendments, different K materials, and recovery of K and critical elements; sequestration of atmospheric CO 2 ; and occurrence of hazardous K compounds. Potassium in biomass and BA is a huge alternative and prospective renewable and C-neutral resource that can substitute the traditional and non-renewable K resources. • Contents of K in biomass and biomass ash (BA) were characterized. • Modes of K occurrence in biomass and BA were described. • Technological and ecological significance of K in biomass and BA was evaluated.