Abstract

Biomass is one of the most important renewable energy sources in the energy industry. It is anticipated that burning biomass will supply 33–50 percent of the world's energy needs by 2050. Similar to how biomass burns, conventional fuels also produce fly ash and other combustion byproducts. As a result, interest in biomass as an energy source is also growing, as is the annual production of ash, a byproduct of combustion. According to estimates, the burning of biomass has the potential to produce approximately 476 million tons of ashes annually. The amount of ash produced by heating wood ranges from 0.4 to 3.9% of the dry fuel mass, while the dry wood mass's calorific value typically falls somewhere in the 18.5 MJ kg 1 range. However, it is particularly challenging to identify biomass ash due to the wide range in chemical composition between biomass and combustion technology. Additionally, despite the fact that it may contain combustible substances like polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs), as well as toxic compounds that are harmful to the environment like heavy metals, this waste is a valuable ingredient that can be utilized in fertilizers. It contains calcium (Ca) and potassium (K) among other nutrients and microelements. The majority of PAHs and VOCs are produced when coal and wood are incompletely burned in unstable low-power boilers. However, incomplete combustion may also contain substances that are formed as a result. However, it is essential to keep in mind that a number of analyses must be carried out before the fly ash can be utilized as an additive to building materials or fertilizer for cultivation in a variety of industries (such as zeolite synthesis, the recovery of rare earth metals, or the production of plastic). Utilizing combustion byproducts is the goal here. Tests should be conducted on organic compounds, chlorides, heavy metals, sulfates, micro- and macroelements, grain and phase composition, and other factors. Instead of being disposed of in landfills, where it will lose its valuable properties, such ash should be used for agriculture and land reclamation if its pollution levels are low. This review aims to discuss the characteristics of biomass combustion ashes produced in Poland and around the world, the factors that influence their composition, and the possibilities for their reuse in various industries and the environment.