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The investigation on combustion characteristic and kinetic parameters of Tetraselmis chuii microalgae was carried out under thermogravimetric analyzer. The sample of microalgae has prepared by the Center for Brackish Water Aquaculture (BBPBAP) Jepara, Indonesia. The drying out the water content in the sediment was performed by an oven at temperature 80 °C as long as 24 h. The dry sample then the crushed and followed by sieving to be mesh size of 60. The thermal decomposition of Tetraselmis chuii microalgae was investigated by a thermogravimetric apparatus, in which the 10 mg of sample was heated up in the temperatures range of 25-900 °C with an atmospheric airflow rate of 50 mL/min and a heating rate of 15 °C/min. The mass loss during temperature expansion was recorded by a computer to be a thermogravimetric (TG) graph and used to evaluate the thermal characteristic of the sample. The kinetic parameters were evaluated in the active combustion zone by the Arrhenius method, resulted in the respective values of reaction order (n), logarithmic frequency factor (log A), and activation energy (E) were 1.24, 9.0 min−1 and 101.05 kJ mol−1 for stage II, and 2.38, 33.31 min−1 and 502.88 kJ mol−1 for stage IV. [ABSTRACT FROM AUTHOR]

The prospect of microalgae Spirulina platensis-synthetic waste mixture (SPSW) as alternative energy to replace fossil fuels was investigated in terms of the elemental composition changes during the combustion process. The microalgae Spirulina platensis (SP) sample was achieved from BBPBAP Jepara, Central of Java, Indonesia. While synthetic waste (SW) sample was taken from a temporary shelter in Malang City. A quantity of 30% of SP and 70% SW were mechanically mixed to warranty the uniform mixture in sample’s powder. SPSW sample was tested its chemical content by using Energy-dispersive X-ray (EDX). To understand the stage of thermal decomposition, the samples firstly were tested under the thermogravimetric (TG) instrument. The combustion has been performed at a heating rate of 10 °C/min at the temperature range of 25–1000 °C, under 100 ml/min constant flow rate of air atmosphere. From this experiment’s result could be specified the temperature of onset and end of the decomposition stage. In accordance with these temperature parameters, the new samples were heated up in the furnace with the similar TG’s condition. The residuals leftover at every stage then were analyzed their elemental composition to evaluate the changes of their content. The TG result showed that SPSW combustion occurred in five stages. Started with initial devolatilization at the temperature range of 25–302 °C, the main thermal decomposition which separated into two zones (302–435 °C and 435– 505 °C), transition stage stretched out between 505–613 °C, the combustion of char at range of 613–710 °C, and the last stage was the slow-burning reaction of residual char at 710–1000 °C. The EDX analysis result showed that organic contents of C and O and inorganic elements of Cl and Ca were encountered as the most elements in the parent and residual materials in the sample at each decomposition stage during combustion. The raw material sample of SPSW contained C and O that were 10.97 and 5.86 mg, respectively. At the temperature of 302 °C, the amount of C and O elements were decreased. At the range of 435–505 °C occurred the major mass loss, indicated the plenty of organic content of C and O were released in a short time. The residue of SPSW at the temperature of 710 °C, designated by the elemental composition including C, O, Cl, and Ca that was 0.50, 0.80, 0.40, and 0.60 mg, in that order. [ABSTRACT FROM AUTHOR]