Seong-Gu Hong

Application of Montmorillonite as Capping Material for Blocking of Phosphate Release from Contaminated Marine Sediment

To investigate the applicability of montmorillonite to capping material for the remediation of contaminated marine sediment, adsorption characteristics of PO4 onto montmorillonite were studied in a batch system with respect to changes in contact time, initial concentration, pH, adsorbent dose amount, competing anions, adsorbent mixture, and seawater. Sorption equilibrium reached in 1 h at 50 mg/L but 3 h was required to reach sorption equilibrium at 300 mg/L. Freundlich model was more suitable to describe equilibrium sorption data than Langmuir model. The PO4 adsorption decreased as pH increased, due to the PO4 competition for favorable adsorption site with OHat higher pH. The presence of anions such as nitrate, sulfate, and bicarbonate had no significant effect on the PO4 adsorption onto the montmorillonite. The use of the montmorillonite alone was more effective for the removal of the PO4 than mixing the montmorillonite with red mud and steel slag. The PO4 adsorption capacity of the montmorillonite was higher in seawater than deionized water, resulting from the presence of calcium ion in seawater. The water tank elution experiments showed that montmorillonite capping blocked well the elution of PO4, which was not measured up to 14 days. It was concluded that the montmirillonite has a potential capping material for the removal of the PO4 from the aqueous solutions.

Development and Assessment of a Downdraft Gasifier for Biomass Gasification

A downdraft gasifier was manufactured for biomass gasification. The gasifier was designed based on the principles of gasification presented in previous studies. The pipes of 25mm diameter were used for both supplying air and discharging producer gas. Wood charcoals were mostly used for fuels. The concentration of CO ranged from 25 to 35%, comparable to the values presented in other studies. The temperature outside wall of the gasifier was measured up to , indicating a great heat loss. When glass wool was cover over the wall, some parts of wire mesh located in the bottom of the reactor were molten down. There were several modifications that should be made in order to improve its efficiency and obtain more stable continuous gasification, including insulation, reduction in pressure loss, durable bottom meshes, the optimum length of reaction part, and safety.

Change in Soil Properties after Planting Giant Miscanthus

Miscanthus has received wide attention as an option for biomass production in Korea, recently. New strain of giant miscanthus has been developed and was planted in two large trial sites (184 ha) in the lower reaches of the Geum River. To evaluate the susceptibility of the giant miscanthus as an bioenergy crop for the future, we investigated the influence of the giant miscanthus on the soil properties. The particle size, CEC, pH, EC, T-N, T-P, heavy metal total concentration, and heavy metal fractions of soil samples collected from abandoned field, 1 year old giant miscanthus field (1st Year GM), and 2 year old giant miscanthus field (2nd Year GM) at different depths of 0~15, 15~30, and 30~45 cm in April and August were analyzed. Results showed that the CEC and pH of the soil of the giant miscanthus field were lower than those of the soil of abandoned field. The EC of 2nd GM was lower than that of abandoned field, indicating that the giant miscanthus may facilitate soil desalination process. The organic and sulfide fraction and residual fraction of heavy metals in the giant miscanthus field was higher than in abandoned field, due to the low pH of the giant miscanthus field and the excretion of phytosiderophores by rhizome of the giant miscanthus. This study showed that the giant miscanthus can influence on the soil properties and further study for long term is needed to elucidate the interaction between the soil and the giant miscanthus.

Operational Strategy of Anaerobic Digesters Considering Energy Balance

Anaerobic digestion system is getting more attractive in that it produces biogas in the process of organic waste stabilization. Net energy production is important when biogas production is concerned. In this study, net energy production was evaluated with respect to biogas production and heat losses in a hypothetical digester. Under the condition of digester operation with slurry inflow of 5% of TS, additional fuel is required to maintain digester temperature during the winder season. Substrate therefore, needs to have higher VS contents through co-digestion of silage or food waste that has greater values of methane production rate. Heating input slurry is important in cold season, which covers over 80% of heating requirement. Heat recovery from digestate is valuable to reduce the use of biogas for heating. It seems desirable to minimize slurry inflow when temperature is very low. Psychrophilic digestion may be a feasible option for reducing heating requirement.

Carbon Monoxide Consumption in Digestate and its Potential Applications

ABSTRACT Acetogen acetyl-CoA , , . . . , , . , . . , -. . , . , . Keywords: Acetogens; gasification; anaerobic digestion; fermentation; bioreactor Gasification is a century old technology to produce combustible producer gas from solid fuels including coals, biomass, and municipal wastes. Major combustible components are carbon monoxide and hydrogen in the gas. The producer gas can be used to fuel engines for heat and/or power, or to produce synthetic fuels through chemical processes. In some countries where sufficient amount of biomass is available, gasification plants are in * Corresponding author. Tel.: +81-31-670-5134Fax: +81-31-674-4119E-mail address: bb9@hknu.ac.kr2008 12 172009 2 32009 2 3 operation to provide gaseous fuel for community heating or cooking. However, there are some limitations and problems that should be considered when planning gasification projects. The gas has relatively lower calorific values, about 4-7MJ/Nm 3 from air gasification and 10- 18MJ/Nm