Changes in Some Chemical Properties of Various Organic Materials after Converting in Biochar and Hydrochar

Biochar and hydrochar are carbonacious solid materials that produced through carbonization of biomasses, resulting in carbon sequestration and soil fertility improvement. The aim of this study was converting different biomasses including sewage sludge, poultry manure, sugar beet tailing, wheat straw, and apple wood wastes to biochar and hydrochar and investigating their chemical properties. Also, using a factorial experiment on the basis of completely randomized design with three replications, ‎the effects of the apple wood biochar and hydrochar were studied in the presence and absence of monocalcium phosphate fertilizer‎ on soil pH and EC and available P, K, and Na. A slow pyrolysis process with a temperature of 500 ºC for 1 h was employed to produce the biochar and a hydrothermal carbonization process with a temperature of 180 ºC and pressure of 11 bar for 12 h was applied to produce the hydrochar. After conversion of biomasses to biochar and hydrochar, yield percentage of the biochars and hydrochars and pH, EC, ash percentage, and concentrations of N, P, K, Ca, Mg, Na, Fe, Mn, Cu, and Zn in initial biomasses, biochars, and hydrochars were measured. The results showed that the ash percentage and elements concentrations in biomasses, biochars, and hydrochars of poultry manure and sewage sludge were greater than those of sugar beet tailing, wheat straw, and apple wood. The pH of all biochars was more than 7, and the pH of all hydrochars (except for the poultry manure-derived hydrochar) was less than 7. Application of wood biochar increased soil pH and the integration of P-fertilizer with hydrochar decreased soil pH. The soil pH and EC in presence of hydrochar were lower than those of biochar with and without P-fertilizer. The P-fertilizer had synergistic interactions with biochar and hydrochar‎ in terms of soil available-P. The effects of biochar, hydrochar, and P-fertilizer application on soil available- potassium and sodium were not significant. Regarding the acidic pH of the studied hydrochars and increased concentrations of some nutrients in the investigated biochars and hydrochars, the applications of biochar and hydrochar accompany with P-fertilizer could be recommended in calcareous soils.