Exploring the prospect of marine microalgae Isochrysis galbana as sustainable solid biofuel feedstock

Abstract

Among the renewable biomass fuel alternatives, microalgae are the most important future choices owing to its fast growth rate and great capability for CO2 fixation. There are various species in the world, in which each species has its characteristics. This work presents a prospect of marine microalgae Isochrysis galbana for renewable fuel feedstock regarding its biomass abundance, physicochemical properties, and thermal characteristic. The seawater medium in the Erlenmeyer flask was used for the algal culturing. The biomass abundance, in term of specific growth rate and doubling time, was assessed by calculating the culture medium cells number with a hemocytometer and optical microscope. Harvesting was done by precipitating biomass with caustic soda, subsequently filtering, and washing it with distilled water. The biomass sediment had been sun-dried for three days, and then dried biomass was crushed by using the mortar to be a powder. The proximate analysis was arranged by conducting an experiment in according to the test method of ASTM D 3173-11, ASTM D 3175-11, ASTM D 3172-13 and ASTM D 3174-12 for specifying the content of moisture, volatile matter, fixed carbon, and ash of the sample, respectively. The heating value was estimated by using adiabatic bomb calorimeter. The chemical composition of biomass was determined by Energy-dispersive X-ray (EDX) spectrometry. The biomass cellular macromolecular compounds were also evaluated by Fourier transform infrared (FTIR) spectroscopy and compared with its residue. Through eight days observation, it was noticeable that Isochrysis galbana has a specific growth rate of 0.18 d-1 and a doubling time of 3.85 d. The respective moisture, volatile matter, fixed carbon, and ash content were 12.98, 40.10, 7.47, and 39.45 (%, air-dried basis). The energy content algal biomass was 16.22 MJ kg-1. This current investigation encourages that Isochrysis galbana can be viable as one of a future sustainable solid biofuel feedstock.