The Elemental Composition Changes of Spirulina platensis-Synthetic Waste Mixture during the Combustion Analyzed by Energy-dispersive X-ray.

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]