Behavior of Organics in Kelp during Hydrothermal Pretreatment: Fundamental Characteristics and Effect of Salt

Abstract

Kelp (Laminaria japonica) was treated in a batch reactor under hydrothermal conditions over a temperature range of 150-190 °C, and the resulting liquid and solid products were analyzed. The effect of salt on the hydrothermal pretreatment of kelp was also investigated. We found that more than 80 % of total organic carbon moved into the liquid phase, leaving only about 10 % in the solid phase. Thus, the effectiveness of the hydrothermal pretreatment on the dissolution of organic compounds was studied. Mannitol, the primary monosaccharide present in kelp, was extracted into the liquid phase; however, the high target temperature resulted in a slight decrease in the yield of mannitol.Formic acid and acetic acid were also produced.The effect of salt was not observed, which indicated the effectiveness of direct treatment of kelp under hydrothermal conditions without the need for desalination.