Behaviors of nitrogen compounds were investigated to elucidate the mechanisms of nitrogen (N) removal in a forage rice field applied with liquid cattle waste (LCW). In total, 567 kg-N·ha−1 of NH4-N was applied to the rice field by basal fertilization and three applications of LCW topdressing as supplemental fertilizer during the cultivation period. The N balance (calculated from NH4-N and NO2+3-N leaching, nitrous oxide (N2O) and ammonia (NH3) emissions, nitrogen uptake by rice plant and N adsorption into the soil) showed that almost 80% of the input N was taken up by plants and removed via denitrification during the cultivation period, while 11.7% of input N remained as adsorbed N in the soil at harvest. Increases in NO3-N concentration in the soil solution and N2O fluxes after drainage indicated that the drainage procedure is important for enhancement of nitrification and denitrification. Nitrogen removal rates after LCW application were estimated by the box model and suggested that declining nitrogen uptake rate by rice plants after the 3rd LCW application caused the remnant N in the soil at harvest. These results suggest that an appropriate schedule and amount of LCW application could be effective to reduce remnant N.
Several clean development mechanism projects for bioenergy production have been started in Southeast Asia. However, the effect of these projects on the lifecycle aspect of biomass production is still unclear. This study aimed to evaluate GHG emission of tapioca starch production and the GHG reduction potential of biogas utilization through field investigation in Lampung province, Indonesia. GHG emission was calculated by considering biomass carbon balance, fossil fuel and chemical fertilizer consumption, nitrous oxide emission and methane emission. First, we estimated the biomass carbon balance of tapioca production. The results showed that 42% of cassava carbon was converted to tapioca starch and 16% to wastewater and other for biomass residues. In addition, 34% of wastewater carbon was converted to methane in wastewater treatment pond. Based on these results, this study clarified that GHG emission of tapioca starch production was 1.4 t-CO2eq/t-tapioca. GHG of methane from wastewater treatment accounted for 63% of total GHG emission. Therefore, this study considered GHG reduction by biogas utilization. The results showed that 64% of GHG emission will be cut by biogas utilization, and that GHG emission will be reduced by 0.49 t-CO2eq/t-tapioca.
This study developed a method to predict the water retention curve of a layer packed with soil particles of various sizes from the particle size distribution and the voidage of the packed layer. The results indicated that the predicted water retention curve coincided well with the measured one in the case of a packed layer of spherical particles having a narrow size distribution. Also, the results showed that the developed method could be applied to a packed layer of nonspherical particles like Toyoura sand, which also had a relatively narrow particle size distribution. In the case of soil particles with a wide size distribution, the predicted water retention curve showed much lower water content than the measured one at lower water potential. This indicated that the contribution of larger particles to a change in water content tended to be overestimated in the developed method. The method was therefore modified to reduce the contribution of larger particles, and as a result, the water retention curve predicted by the modified method agreed well with the measured one.
In situ treatment technologies, including chemical treatment by Fenton's reaction, are expected to be effective for site remediation of polluted soil. To get basic data on the decomposition rate of trichloroethylene (TCE) by Fenton's reaction using iron powder, we investigated the influence of pH and dissolved Fe ion concentration on the decomposition rate of TCE in the presence and absence of buffer solution to maintain pH value. The decomposition rate depended on hydrogen peroxide concentration, and the maximum rate was observed around concentration of 88 mol/m3. This finding was explained by the consumption of hydroxyl radicals by a competing reaction with hydrogen peroxide against TCE decomposition by the hydroxyl radicals produced from hydrogen peroxide. Under this condition, the most rapid dissolution rate of iron, i.e., the maximum increasing rate of Fe ion concentration, and the most rapid reduction in pH value were observed. The results with buffer solution showed that dissolution rate of iron was highly dependent on pH, and it was suggested that TCE decomposition was accelerated by the increase of Fe ions, rather than directly by the lowering of pH. The initial lag period in the TCE decomposition with iron powder, in contrast to the rapid initial reaction in the case of Fe solution, was also explained by the relatively slow dissolution of iron and relatively fast rate of Fenton's reaction with ferrous iron to produce hydroxyl radicals. The concentration of Fe ions was estimated and suggested to be much higher and the pH lower in the film around iron powder than in the body of the liquid. Also, the transfer of TCE from the liquid body to the reaction area in the film was suggested to be accelerated by its decomposition.
In recent years, contamination of groundwater by arsenic has become an environmental problem around the world, since arsenic is carcinogenic. It is present in groundwater predominantly as inorganic arsenite (As(III)) and arsenate (As(V)). To remove arsenic from water, adsorption is an effective technology, because adsorptive methods are generally simple to operate at low cost. We performed adsorption experiments with various metal oxides in order to remove arsenic from aqueous solution. The adsorbent γ-Fe2O3, which is inexpensive and safe for human health, was prepared by varying the molar ratio of Fe3+ and Fe2+, and the effect of pH on removal of arsenic was examined with the synthesized γ-Fe2O3. The adsorption of As(III) and As(V) was found to be strongly dependent on pH. As(III) present as a neutral species at below pH 7 is thought to be adsorbed by physical bonding through, for example, van der Waals forces, or by chemical reaction, while the adsorption of As(V) present as anionic species in aqueous solution over pH 1 is affected by electrostatic repulsion at higher pH than its IEP with a change in zeta potential after adsorption. We investigated the adsorption of arsenic at different temperatures and found that the adsorption of As(V) is more strongly dependent on the temperature than that of As(III).
Composite membranes composed of a thin layer of THF clathrate hydrate formed on a porous alumina support membrane were prepared by various methods, namely, dipping, coating, and a combination of dipping and coating. The THF hydrate layer is expected to work as a molecular sieve for gas separation, where only gas molecules that can pass through the small vacant cages of the THF hydrate would permeate through the hydrate layer. In the dipping method, the support membrane was dipped in aqueous solution of THF, and the membrane was cooled to the temperature where the THF solution at the surface of the membrane can be converted into the THF hydrate layer. The composite membrane prepared by dipping showed unstable gas permeation fluxes, and no molecular sieving effect was achieved. In the coating method, an aqueous solution of THF was brushed on the surface of the support membrane a given number of times, and the THF solution layer was converted into the THF hydrate layer by cooling below the hydrate formation temperature. The composite membrane coated by brushing two times showed an unstable gas permeation flux, and the permeation flux of the membrane coated by brushing three times decreased significantly. The thickness of the THF hydrate layer can be controlled by the combination of dipping and coating. The permeation flux of helium was stabilized after curing the membrane for several hours at a temperature above that for hydrate formation. In this case, no permeation of sulfur hexafluoride was observed through the membrane; molecular sieving effect was achieved. However, the observed helium flux was too low for practical application.
Zirconium(IV), which has strong affinity for phosphate ions, was loaded to zeolite for the adsorption and a removal of phosphate ions. At saturation, the amount of zirconium loaded to zeolite reached 1.20 mol/kg. Adsorption of phosphate ions by the zirconium-loaded zeolite was 100% in the range of pH 2–4. At above pH 4, the percentage adsorption decreased. At pH 7, the capacity of Zr-zeolite to adsorb phosphate ions was 0.65 mol/kg, while that of H-zeolite was 0.13 mol/kg. Adsorption of phosphate ions in secondary effluent containing other ions was fast and selective.
Fluid catalytic cracking (FCC) has been the most important and flexible conversion process in petroleum refineries. It is economically beneficial in allowing low-value materials of high molecular weight to be cracked into valuable constituents, such as gasoline, diesel and petrochemicals. Therefore, understanding the reaction mechanism of heavy molecules is a key to increase the selectivity of valuable products. To improve FCC performance, generalization of the main factors affecting catalyst structures, feed properties and operation conditions is crucial. Our work mainly focuses on the metal deactivation behavior of residual fluid catalytic cracking (RFCC) catalysts. Catalyst cracking activity relates amount of metal on the catalyst. If two kinds of deactivation, steam and metal poisoning, are considered, the catalytic property of the equilibrium catalyst in a RFCC unit can be expressed. It can be used, for example, as the RFCC catalyst deactivation reduction ratio in analyses of the influence of the regenerator condition of RFCC unit according to this model. As a result, a circulating fluidized bed reaction system model for estimation of FCC catalyst activity was developed and used to evaluate the effects of regenerator condition on catalyst deactivation.
Effect of irradiated light color on growth of S. platensis was experimentally investigated using four inorganic electro-luminescence sheets. We found that the light intensity profiles of blue, blue-green and orange inorganic electro-luminescence sheets were uniform on the sheets, and those in the horizontal direction decreased exponentially. The maximum specific growth rate and the saturation constant of S. platensis varied with the color of the irradiated light.
Pulverization of woody chip was carried out with a planetary mill, and the effect of particle size and moisture content of wood chips on grindability (pulverized particle size and cellulose crystallinity) in a pulverization process was evaluated. Wood chips were prepared with a cutter mill and sieved into different ranges of particle size. Moisture content of wood chip was controlled at 0–10% in a drier. Enzymic saccharification of pulverized wood was also carried out, and the effect of pre-drying treatment on saccharification ratio was evaluated. Agglomeration of fine particles inhibited the progress of pulverization and cellulose crystal fracture. Cellulose crystallinity of pulverized wood was significantly influenced by the moisture content of woody chip, and cellulose crystals of lower moisture content wood chip was more easily destroyed. Enzymic saccharification ratio was not affected by low temperature pre-drying treatment.