Chemical and Physical Analysis of Different Ash Fractions from Small Biomass Boilers

Due to the growing number of small biomass boilers in residential buildings, the ash amounts from these plants are increasing. In order to find a beneficial use for these ashes, chemical and physical analyses were carried out on different ash fractions of different boilers. The results enable a comparison of the used boilers and fuels. As a result, it was shown that the chemical composition and physical properties strongly depend on the type of the ash, the fuel, and the boiler. The main focus of the investigations was on assessing whether the ashes were to be classified as fertilizer or waste. Accordingly, the results of the analyses were compared with the respective limit values for these cases. In addition, further possible applications were evaluated with regard to their suitability, and related current problems were identified.