Influence of microalgae on synergism during co-pyrolysis with organic waste biomass: A thermogravimetric and kinetic analysis

The synergistic influence of microalgae on the two forms of organic waste biomasses, namely biomass wastes (BW) and its digested form (DBW), during co-pyrolysis was evaluated based on the thermal decomposition behaviour, gas yields, extent of thermal decomposition and reaction kinetics. The biomasses and their blends were co-pyrolysed at three different heating rates (10, 15 and 20 ⁰C min-1) in a thermogravimetric analyzer coupled with a mass spectrometer. Initial assessment, based on TG-DTG data, revealed that the thermal degradation can be divided into three zones (50-150 ⁰C, 150-550 ⁰C and 550-800 ⁰C) for all the biomasses and their blends. The thermogravimetric data was used to evaluate the kinetic triplet, which include apparent activation energy (Eα), pre-exponential factor (A) and reaction mechanism, f(α). Semi-quantitative method was used to quantify the gas species, H2, CO2 and CO were dominant species, implying the water gas reactions and oxidation reactions were predominant. The synergistic influence of microalgae was clearly evident in terms of reaction kinetics, as noted in the reduction in the apparent activation energy and increase in the total gas yields. The obtained kinetic triplet and thermodynamic parameters are expected to facilitate the design and optimization of co-pyrolysis of microalgae with other forms of organic wastes.