Authors: Somayeh Daneshvar, Koji Otsuka, Yasuaki Maeda, Feridoun Salak
Abstract—Liquefaction of green macroalgae, Codium fragile (C. fragile), has been investigated in subcritical ethanol medium. The effects of liquefaction experimental parameters (i. e. reaction temperature and time) were evaluated on the yield of water soluble materials, ethanol soluble materials, and residual solids. The aqueous phase showed a maximum total organic carbon (TOC) content at 190 °C after 10 min reaction time, due to decomposition and solubilization of mainly cellulosic part as well as other organic molecules of the algae. As a result, water soluble sugars and organic acids (as result of hydrolysis of cellulose) were identified in the aqueous phase. The quality of bio-oil extracted under subcritical ethanol conditions was examined by GC-MS. The results showed that bio-oil extracted or obtained by liquefaction of macroalgae in alcohol at higher temperatures are mainly composed of variety of fatty acid ester compounds. Investigation of the residual solid phase after treatment showed that with increasing reaction temperature and/or time, the amount of total residual solid declined and finally reached a minimum amount at around 200 °C and 15 min residence time. The remained solid at higher temperatures is mainly attributed to the inorganic/carbonized composition of the algae sample. However, it is possible to have the un-reacted algae at relatively lower temperatures as well. In order to evaluate the energy density of the remained solids, we evaluated and compared the higher heating values (HHVs) of the residual solid and initial sample base on ultimate analysis. FTIR analysis was also carried on in order to investigate and compare the structure of residual solid with those of pure cellulose.
Keywords: Codium fragile; Fatty acids ester; Green macroalgae; Liquefaction; Subcritical ethanol