Basic properties of microalgae Spirulina sp and its two model components of carbohydrate and protein for considering its potential as a fuel feedstock

The basic properties of microalgae Spirulina sp have been characterized and compared with its two model components of carbohydrate and protein. The Spirulina sp samples were cultivated by the Brackishwater Aquaculture Development Center, Situbondo, Indonesia. The two pure carbohydrate and protein models were each represented by starch and glycine, each obtained from Sigma Aldrich (Singapore) and HiMedia India, respectively. The ultimate and proximate tests were performed to explore their chemical and physical properties. The adiabatic bomb calorimeter was employed to understand their heating value. It was observed that carbon is the component that makes up the majority of Spirulina sp, the value of which is 45.56 (wt%,db), whereas in the two model components of starch and glycine, the most dominant ingredients were oxygen, which are that of 49.37 and 40.51 (wt%,db), respectively. The proximate analyses showed that volatile matter presented as the largest constituent for the overall sample; 76.76, 94.29 and 88.62 (wt%,db), each for Spirulina sp, starch, and glycine. From these ultimate and proximate datasets, it is clear that most of the carbon content in Spirulina sp formed the volatilized matter during the thermal processes, whereas a small portion would be fixed carbon. The gross calorific values of Spirulina sp, starch, and glycine were tested according to the ASTM D 5865-19 standard, resulting in the respective values of 4971, 0, and 3870 kcal/kg. These results confirmed that the starch had less significance in determining the heating value, and protein was probably more prominent in this role. To complete this analysis, the role of lipid as the remaining primary component in microalgae that is yet to be presented in this paper would have to be explored in-depth in future work.