Ecotopia Science

Hydrogen gas has successfully been produced from biomass by hydrothermal gasification. Various alkaline additives have been found to increase the hydrogen yield. However, studies have not yet been done on pollutants that would be produced in the hydrothermal gasification with real biomass waste containing hetero-atoms such as S, N, and P elements. Studies have also yet to be done on finding ways to suppress the formation of pollutants. For this purpose, L-cysteine containing hetero-atoms S and N, and O-phospho-DL-serine with P, were selected as pure test samples. The objective was to determine the optimum conditions for the suppression of the pollutants produced in the hydrothermal gasifications, while effectively generating hydrogen. Phosphate ion was found in the liquid phase after the gasification of O-phospho-DL-serine with and without additive at 400°C. Phosphorus compounds were not detected in the gas phase. When a large quantity of Ca(OH) 2 was added, phosphorus compounds were precipitated in the solid phase. Hydrogen gas yields were increased and other gases were suppressed by using the additive. These results were same as those of chicken manure. The test samples were used to determine the optimum conditions of 400°C, 21 MPa, and the Ca(OH) 2 additive. NH þ 4 was mainly produced in liquid phase by using the model sample of L-cysteine. With the addition of Ca(OH) 2 , the yields of SO 2 and H 2 S are significantly decreased. NO À 2 and NO À 3 were detected at trace levels. The main gas produced was hydrogen and the generation of CO 2 gas was efficiently suppressed. These optimum conditions were then applied to real biowastes, cow dung. Hydrogen production increased and was found to be mainly in the gas phase, while there was negligible generation of pollutants, with these were in the gas phase. H 2 S were detected at trace levels. NO was not recorded, and production of other gases were suppressed by using the additive. Nitrogen in the sample was trapped as NH þ 4 in the liquid phase.

Hydrogen gas and the valuable material hydroxylapatite have successfully been produced from biomass wastes by hydrothermal gasification. However, it was expected that toxic compounds might be produced through the reaction. It was therefore important to clarify whether toxic compounds were synthesized in hydrothermal gasification of biowastes since dioxins are categorized among the most toxic compounds for humans. This is particularly true of biomass wastes containing hetero-atoms in organic matrices. In this study, formation of the dioxins polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and certain dioxin-like polychlorinated biphenyls (PCBs) were examined. Chicken manure and cattle manure were tested as real biowastes for hydrothermal gasification and the produced compounds in the liquid and solid phases were analyzed for detection of dioxins by gas chromatography/mass spectrometry (GC/MS). The total toxic equivalent quantities (the total TEQ) of dioxins produced by the hydrothermal gasification were found to be much lower than regulation levels in Japan require and therefore the products require no additional post treatments.

Production of hydrogen gas and/or valuable material has successfully been made from biomass wastes by hydrothermal reactions in supercritical water. However, it is expected that toxic compounds might be produced through the reactions. It is therefore significant to clarify whether toxic compounds are synthesized or not in hydrothermal reactions of biomass wastes (biowastes), particularly of biomass wastes containing hetero-atoms in organic matrices. In this work, formation of Dioxins (Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxinlike polychlorinated biphenyls (DL-PCBs)) was examined since Dioxins are categorized among the most toxic compounds for human being. Chicken manure was tested as a real biowaste for hydrothermal reactions, the produced compounds in the liquid and solid phases were analyzed for detection of Dioxins by GC/MS. It was confirmed that total TEQ of Dioxins produced by the hydrothermal reaction was much lower than that regulation levels in Japan and the products requires no additional post treatments.

Production of hydrogen gas and/or valuable material has successfully been made from biomass wastes by hydrothermal reactions in supercritical water. However, it is expected that toxic compounds might be produced through the reactions. It is therefore significant to clarify whether toxic compounds are synthesized or not in hydrothermal reactions of biomass wastes (biowastes), particularly of biomass wastes containing hetero-atoms in organic matrices. In this work, formation of Dioxins (Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxinlike polychlorinated biphenyls (DL-PCBs)) was examined since Dioxins are categorized among the most toxic compounds for human being. Chicken manure was tested as a real biowaste for hydrothermal reactions, the produced compounds in the liquid and solid phases were analyzed for detection of Dioxins by GC/MS. It was confirmed that total TEQ of Dioxins produced by the hydrothermal reaction was much lower than that regulation levels in Japan and the products requires no additional post treatments.