Utilization of Sub and Supercritical Water Reactions in Resource Recovery of Biomass Wastes

Abstract

Abstract.Recently, the utilization of sub and supercritical water has been proposed to recover waste substances from biomass. This is important not only for prevention of environmental issues, but also for rational utilization of natural resources. Sub and supercritical water treatment is one of the most effective methods for this, because water at high temperature and high pressure behaves as a reaction medium with remarkable properties. This sub and supercritical water treatment process can promote various reactions such as oxidation, hydrolysis, and dehydration. Therefore, sub and supercritical water can be used for the conversion of organic wastes to useful chemical compounds, as well as for oxidizing hazardous waste into CO2 or harmless compounds. This paper presents the concepts of sub and supercritical water and their application in organic waste recycling at temperatures of 423 -673 K for substances such as lignin and its derived compounds.

Processing of Biomass with Hydrothermal and Supercritical Water

“…Concentration of degradation products furfural, 5-HMF, and formic acid [73]. alcohol, and sinapyl alcohol are connected by ether and carbondcarbon bonds [4,74]. The ether bond in lignin between one propyl side chain of a hydroxyphenylpropane unit and the hydroxy group attached to a benzene ring of another hydroxyphenylpropene unit is a major feature of the structure.…”

“…Therefore, disassembly of ether bonds and carbondcarbon bonds is important in the degradation of lignin. Hydrolysis occurs at ether and ester bonds, cleaving them by the addition of one molecule of water for every broken linkage, a process which is accelerated by the high ion product of water [61,74,82,83]. mechanism is complicated by the fact that every compound can be obtained through different reaction pathways.…”

“…Hydrolysis is a key reaction that promotes the degradation of natural polymers. In parallel, formation of char due to repolymerization occurs at the same time, which may be the main reason why the yield of chemicals is low for lignin conversion [74]. Degradation of lignin was studied in high-temperature and supercritical water at temperatures of T ¼ 623 and 673 K in batch experiments.…”

Integrated volarization of spent coffee grounds to biofuels

“…Cellulose is considered as a major source of volatile content in the biomass, while lignin serves as a natural binder in the biomass (Biswas et al, 2011;Wahyudiono and Goto, 2013). Although the SCG contain relatively high lignin content, the addition of a binder, like glycerin, is expected to enhance combination of biomass particles well.…”

Synthesis of Polyhedral Magnetite Particles by Hydrothermal Process under High Pressure Condition

“…This method utilizes the solubility of inorganic substances in water at subcritical conditions. Due to the change structure of water under elevated temperatures and pressures, it is able to play an important role in the transformation of precursor material and subsequent precipitation of the material dissolved in the fluid [12][13][14]. The particle products were characterized by SEM and XRD after drying.…”