This paper compares and evaluates the physicochemical characterization and thermal analysis of different agricultural lignocellulosic biomasses namely: olive pomace (OP), argan shells (AS), date palm seeds (DS) and hydrochar (HC), obtained from the hydrothermal carbonization (HTC) of OP, in order to identify a good potential fuel for thermochemical conversion systems. Several physicochemical and thermal characterization methods were used. The aforementioned biomasses are mainly composed of cellulose, hemicellulose and lignin as shown by the FTIR and XRD analysis. From energy point of view, the hydrochar (HC) has the highest value of the higher heating value (HHV) (27.86 MJ/kg). These results make (HC) a very good candidate for thermochemical energy conversion technologies. Thereafter, thermal analysis (DSC and TGA) was conducted in an inert atmosphere to analyze the thermal behavior of the samples under well-defined thermal conditions. Right after, two kinetics models were used to estimate pyrolysis kinetic parameters (the activation energy (E) and pre-exponential factor (A)) of the four biomasses. Among those are, for example, olive pomace has (E = 200.104 kJ/mol; A = 7.14E + 21 s−1) and (E = 199.053 kJ/mol; A = 3.58E + 21 s−1) according to KAS and FWO models, respectively. Consequently, pyrolysis of (OP) requires less energy to occur, which promotes its energy performances.