Characterization of Poultry Litter Ash in View of Its Valorization

The overall aim of this research was to evaluate the valorization potential of the poultry litter ash produced in the biomass power plant of BMC Moerdijk (the Netherlands), since the ash contains phosphorus (P) and potassium (K), which are both essential nutrients. As a first step, the ash was characterized by means of chemical analysis. Ash collected in the superheater section of the boiler had the highest P concentration (10.6%). Furthermore, the P concentration in the ash decreased as it was collected further downstream in the boiler and flue gas cleaning part of the installation. K showed an opposite concentration trend, that is, its concentration was the lowest in the superheater ash (9.4%) and increased to 15.5% in the electrostatic precipitator ash. Based on the results of the chemical analysis, different valorization options could be considered. Although poultry litter ash has the same heavy metal/P ratio as poultry litter and is free of pathogens and toxic organic substances, its recycling as a P/K fertilizer is hindered by legal constraints. Furthermore, the use of the ash in/as animal feed is not straightforward because of its origin (animal feces) and waste status. Besides P and K, other ash elements such as calcium, silicon, magnesium, iron and aluminum can also be valorized, for example by using the ash as building material or in cement production. However, in these applications the high P and K concentration of the ash can be a technical obstacle rather than a benefit. In this regard, it can be interesting to separate the fertilizer elements, that is, P and K, from the rest of the ash by means of for example a wet chemical extraction after which the remaining solid residue better meets the composition requirements for building material or raw material for cement production. Graphic