Characterisation of poultry litter ash in view of its valorisation

The overall aim of this research was to evaluate the valorisation potential of the poultry litter ash produced in the biomass power plant of BMC Moerdijk (the Netherlands). This poultry litter ash contains phosphorus (P) and potassium (K), both essential nutrients. Chemical characterisation showed that ash collected in the superheater part of the boiler had the highest P concentration (10.6%). Furthermore, the P concentration decreased as the ash was collected further downstream in the boiler and flue gas cleaning part of the installation. K showed an opposite concentration trend, i.e. its concentration was the lowest in the superheater ash (9.4%) and increased to 15.5% in the electrostatic precipitator ash. However, even if 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. Besides P and K, also other ash elements such as calcium, silicon, magnesium and aluminium can be valorised e.g. by using the ash as building material or in cement. However, in these applications the high P and K concentration of the ash can rather be a technical obstacle than a benefit. In that regard, it could be interesting to separate the fertilizer elements, i.e. P and K from the rest of the ash by means of e.g. a wet chemical extraction after which the remaining solid residue better meets the composition requirements for building material or raw material for cement.

Publication year:2018