Thermochemical Valorisation of Waste : Pyrolytic Conversion of Horse Stable Residue Into Biochar

In this study, horse stable waste (horse manure, peat and wood sawdust) was processed under pyrolytic conditions. The chemical and physical properties of biochar obtained from different mixtures of horse stable residues were compared. All measurements followed an experimental design using a mixture model. This approach allowed the properties of any combination of ingredients to be predicted and the influence of each component on the final value to be estimated, with very good agreement between predicted and observed values. The results of the analysis of pH, polycyclic aromatic hydrocarbons (PAH), specific surface area (SSA) and CHNSO (carbon, hydrogen, nitrogen, sulphur and oxygen) showed that all possible combinations of materials can be used as soil amendments, since: an alkaline pH (>7) prevents soil acidification and a concentration of PAH below the limit (ΣPAH<12mg/kg) does not pose a risk to human health. A high SSA value (>180 m2/g) and a different particle size distribution (PSD) provide habitat for microorganisms, increase water retention capacity and reduce greenhouse gas (GHG) emissions from the soil.