Thermogravimetric characteristics and pyrolysis kinetics of Alga Sagarssum sp. biomass

•Systematically study and the first attempt of pyrolysis for Macroalge Sagarssum sp.•Determination of global kinetic parameters including activation energy from TG analysis.•Influence of pyrolysis temperature and residence time on product yields and compositions.•Calculation of kinetic parameters from a lumped kinetic model. Alga Sagarssum sp. can be converted to bio-oil, gas, and char through pyrolysis. In this study, the pyrolysis characteristics and kinetics of Sagarssum sp. were investigated using a thermogravimetric analyzer and tubing reactor, respectively. Sagarssum sp. decomposed below 550°C, but the majority of materials decomposed between 200 and 350°C at heating rates of 5–20°C/min. The apparent activation energy increased from 183.53 to 505.57kJmol−1 with increasing pyrolysis conversion. The kinetic parameters of Sagarssum sp. pyrolysis were determined using nonlinear least-squares regression of the experimental data, assuming second-order kinetics. The proposed lumped kinetic model represented the experimental results well and the kinetic rate constants suggested a predominant pyrolysis reaction pathway from Sagarssum sp. to bio-oil, rather than from Sagarssum sp. to gas. The kinetic rate constants indicated that the predominant reaction pathway was A (Sagarssum sp.) to B (bio-oil), rather than A (Sagarssum sp.) to C (gas; C1–C4).