Sukarni Sukarni, Uun Yanuhar, I. N. G. Wardana, Sudjito Sudjito, Nurkholis Hamidi, Widya Wijayanti, Yusuf Wibisono, Sumarli Sumarli, I. M. Nauri, and Heru Suryanto

DOI: 10.14456/sjst-psu.2018.178

pp. 1456 - 1463

Abstract

The cellular macromolecular and mineralogical content changes during the combustion of Nannochloropsis oculata
biomass have been investigated. A Fourier transform infrared spectroscopy (FTIR) analyzer was used to investigate the cellular
macromolecular content changes of biomass at every stage of decomposition during heating to 1200 ˚C. From ambient temperatures to 190 ˚C, similar spectra were obtained, indicating relatively little change in the chemical structure of the biomass
material. Changes in the spectra are very noticeable from 190 to 1200 ˚C. The combustion process begins with thermal cracking
of the –OH groups of silanol that escape together with moisture at temperatures up to 190 ˚C. Subsequent temperature increase
decreased intensity of the spectrum, indicating thermal degradation of the organic compounds derived from lipids, proteins, and
carbohydrates. These processes occur up to 800 ˚C. The X-ray diffraction (XRD) results showed that the mineral constituents of
biomass degraded during the combustion process, and a portion reacted to form new compounds such as melilite (Ca₆Na₂O₁₅Si₄).
The SEM images show a morphological distinction between biomass and its residue at 1200 ˚C, due to the decomposition and
rearrangement of the mineral content during heating. Fragmentation of the samples also occurred during heating, characterized
by more uniform residue at 1200 ˚C.