Characterization of soil amendment potential of 18 different biochar types produced by slow pyrolysis

Abstract

Feedstock type is the most dominant factor influencing the physical characteristics andchemical composition of biochar. The main purpose of this study was to characterize andcompare some of the physical and chemical properties of biochars produced by slowpyrolysis of 18 feedstocks, which are locally available agricultural residues. Moreover,elucidating the potential agronomic benefits of these biochars was the other objective of thestudy. Biochars were produced at 500 oC in an ingeniously developed reactor. The biocharswere characterized for specific surface area (SSA), field capacity (FC), wilting point (WP),plant available water content (AW), pH, electrical conductivity (EC), cation exchangecapacity (CEC), total carbon (C) and nitrogen (N), plant available phosphorus (P) andpotassium (K) concentrations. Considerable variation of characteristics among biocharsindicates the dominant impact of feedstock type on physical properties and chemicalcomposition of biochars. Total C contents were highly variable with values up to 91.9% forpine sawdust. Phosphorus and K in feedstocks were concentrated in the biochars and weretwo to four times higher in the biochars. The CEC of biochars varied from 79.5 cmol kg-1(pepper residues) to 5.77 cmol kg-1 (poplar sawdust). The CEC and SSA had a significantnegative correlation (P