A study to define the physicochemical characteristics of biochar from manure generated on 3 different livestock farms in Malta

Abstract

The amounts of livestock manure produced in Malta surpasses the application rate as stipulated by the Nitrates Directive with the consequence of having an accumulation on farms. In such cases, manure becomes a liability instead of a benefit, incurring significant risk in creating environmental pollution. Pyrolysis of manure is an interesting alternative to land application, as it has the ability to render organic nitrogen into inert nitrogen gas and reduces manure biomass volumes. This technology utilises high temperature, thereby destroying any potential pathogens that may be present in the manure, has the potential of extracting useful energy and generates potentially high value products, e.g. biochar. The functions and application of biochar when used as a soil amendment to improve soil physical, chemical and biological properties depend on its structural and physicochemical properties. Such understanding is crucial for its sustainable use and application. Manure feedstock originating from large ruminant, small ruminant and poultry operations were subjected to a pyrolysis process at 570◦C. The starting nitrogen (N) content was repartitioned into inert N2 (59%), whilst 38% was retained within the biochar structure. The biochar physicochemical properties relating to electrical conductivity (EC) values, the accumulation of zinc and the alkaline nature, render the application of this biochar on Maltese soils challenging. Alternatively, this biochar could be used as a solid fuel to dry the incoming manure biomass, and the resulting ash utilised to extract potassium and phosphorus.