This article deals with slow pyrolysis of agricultural residues such as olive husk, corncob and tea waste at high temperature (950–1250K) in a cylindrical reactor batch reactor. The aim of this study was to experimentally investigate how different residues utilizing strategies affect the treatment conditions such as temperature, particle size, and lignin and inorganic matter contents on bio-char yield and reactivity. When the pyrolysis temperature is increased, the bio-char yield decreases. The bio-char yield increased with increasing particle size of the sample. A high temperature and smaller particles increase the heating rate resulting in a decreased bio-char yield. The higher lignin content in olive husk results in a higher bio-char yield comparison with corncob. Bio-char from olive husk was more reactive in gasification than bio-char from corncob because of the higher ash content.