Preparation and characterization of agricultural waste biomass based hydrochars

In this study hazelnut shell and olive residue were hydrothermally carbonized in a stainless steel autoclave. Chemical, structural and physicochemical properties of obtained hydrochars were investigated in dependence of the reaction parameters and characterized by use of various techniques. Reaction temperature was found to have a much stronger influence on hydrothermal carbonization (HTC) of biomass than reaction time after 2 h. Hydrochar samples consist of spherical/semi-spherical particles in nano to micron size with aromatic framework. Hazelnut shell based hydrochars have higher number of O-containing reactive functional groups compared with the olive residue based hydrochars. Because of the knowledge gaps in hydrochar characterization, more comprehensive product characterization and reporting are needed to advance our understanding of HTC processes, products and applications. By the help of the results of this study, it will be possible to choose the appropriate hydrochar characteristics in various applications of hydrochars.