Hidetoshi Kuramochi

Improved biogas production from food waste by co-digestion with de-oiled grease trap waste

The objective of this study was to assess the feasibility of co-digesting food waste (FW) and de-oiled grease trap waste (GTW) to improve the biogas production. A lab-scale mesophilic digester (MD), a temperature-phased anaerobic digester (TPAD) and a TPAD with recycling (TPAD-R) were synchronously operated under mono-digestion (FW) and co-digestion (FW+de-oiled GTW). Co-digestion increased the biogas yield by 19% in the MD and TPAD-R, with a biogas yield of 0.60L/g VS added. Specific methanogenic activity in the TPAD-R was much higher than that in the MD. In addition to methane, hydrogen at a yield of approximately 1mol/mol hexose was produced in the TPAD-R. Alkalinity was consumed more in the co-digestion than in mono-digestion. Co-digestion resulted in more lipid accumulation in each digester. The MD favored the degradation of lipid and conversion of long-chain fatty acids more than the TPAD and TPAD-R.

Dual-fuel production from restaurant grease trap waste: bio-fuel oil extraction and anaerobic methane production from the post-extracted residue.

An effective way for restaurant grease trap waste (GTW) treatment to generate fuel oil and methane by the combination of physiological and biological processes was investigated. The heat-driven extraction could provide a high purity oil equivalent to an A-grade fuel oil of Japanese industrial standard with 81-93 wt% of extraction efficiency. A post-extracted residue was treated as an anaerobic digestion feedstock, and however, an inhibitory effect of long chain fatty acid (LCFA) was still a barrier for high-rate digestion. From the semi-continuous experiment fed with the residual sludge as a single substrate, it can be concluded that the continuous addition of calcium into the reactor contributed to reducing LCFA inhibition, resulting in the long-term stable operation over one year. Furthermore, the anaerobic reactor performed well with 70-80% of COD reduction and methane productivity under an organic loading rate up to 5.3g-COD/L/d.

Estimation of physicochemical properties of 52 non-PBDE brominated flame retardants and evaluation of their overall persistence and long-range transport potential

Non-PBDE (polybromodiphenyl ether) brominated flame retardants (BFRs) used as alternatives to PBDEs should be evaluated in terms of their environmental contamination potential. We first used two well-known estimation tools, EPI Suite and SPARC, to estimate the physicochemical properties of 52 non-PBDE BFRs. We assessed the dependence of the properties on the molecular weight and chemical structure of the compounds. The accuracy of the estimates was evaluated by comparing results with previous experimental data. In the case of EPI Suite, we have recommended an appropriate calculation method for the air-water partition coefficient. Half-lives in each environmental medium were also estimated with EPI Suite. Based on the estimated properties and half-lives, the overall persistence (Pov) and long-range transport potential (LRTP) of the BFRs were calculated using the Organization for Economic Cooperation and Development Pov and LRTP Screening Tool. We selected some POP-like chemicals from among the non-PBDE BFRs on the basis of their Pov and LRTP. From a Monte Carlo analysis of the calculated results for the selected BFRs, we suggest physicochemical properties to be measured in the future.

Prediction of physico-chemical properties for PCDDs/DFs using the UNIFAC model with an alternative approximation for group assignment

The original-type UNIFAC model was used to predict the environmentally important physico-chemical properties of PCDDs/DFs, such as aqueous solubility, Henrys law constant, and 1-octanol/water partition coefficient, through the UNIFAC-derived infinite dilution activity coefficient. In this application, we suggest an alternative approximation that the aromatic ether group AC-O in PCDD/DF molecules is replaced with the aliphatic ether group CH-O, because the AC-O group is not available in the conventional UNIFAC model. With this approximation, the ability of the UNIFAC model to predict those properties was examined by comparing with experimental data. The UNIFAC model provided comparatively good estimation results. From these results, it is shown that the alternative approximation is useful for the UNIFAC estimation of physico-chemical properties for PCDDs/DFs. Furthermore, the predicted solubilities of 2,3,7,8-T4CDD and O8CDD in organic solvents and the co-solvency effect on solubility of PCDDs in methanol/water mixture indicate that the UNIFAC calculation presented here could well predict the physico-chemical properties of PCDDs/DFs in various solution conditions.

Effects of ATP, Mg2+ and a mixture of the two on the formation of large DNA aggregates induced by spermidine.

To investigate the effects of ATP, Mg2+, and a mixture of the two on the formation of large DNA aggregates induced by spermidine, we constructed novel phase diagrams of the spermidine/DNA/Tris-buffer system in the presence of these compounds. These diagrams reveal not only the difference in the inhibition of the aggregate formation between ATP and Mg2+ but also a type of buffering effect whereby the complex formation of ATP and Mg2+ diminishes their individual inhibitory actions. Furthermore, the equilibrium composition of ATP, spermidine, Mg2+, and their complexes in the liquid phase was estimated using the equilibrium constants for the complex formations and their mass balances. From this solution equilibrium analysis, the threshold condition for DNA aggregation is suggested. The phase diagrams and equilibrium analysis presented here are useful to predict the threshold of aggregation in a system similar to in vitro transcription. Finally, we recommend that region b in this paper, where the variation in the concentration of either ATP or Mg2+ had little effect on the DNA aggregation, should be used to establish the initial conditions of in vitro RNA synthesis.

WATER SOLUBILITY OF SOLID SOLUTION OF PHENANTHRENE AND ANTHRACENE MIXTURE

Water solubilities of solid solution forms of phenanthrene and anthracene in water between 283 K and 308 K were measured by the shake flask method. The present experimental results showed that solid composition affected the water solubility of the solid solution as follows: The saturation concentration of a solute decreased with an increase in the amount of the other in the solid phase. In particular, this solubility decrement was remarkable within a low concentration range of anthracene in the solid solution. Within the same range, furthermore, the temperature dependence of the anthracene water solubility increased while that of phenathrene decreased. Finally, we tried to calculate the solubility behavior, based on the fugacity ratio between the liquid and solid phases and an activity coefficient model.

Influence of the type of furnace on behavior of radioactive cesium in municipal solid waste thermal treatment

Municipal solid waste (MSW) contaminated by radioactive cesium (r-Cs) has been incinerated since the Fukushima Daiichi Nuclear Power Plant accident. Eight thermal treatment plants with four different types of furnaces were comprehensively investigated to provide fundamental data to improve our understanding of the behavior of r-Cs in various types of MSW thermal treatment facilities. R-Cs tended to distribute to the fly ash (FA) more than to the residue from the bottom of the furnace (bottom ash, incombustibles or slag). The r-Cs concentrations in the FA depended on the type of furnace and followed the order; fluidized-bed incinerator < stoker type incinerator < gasification melting furnaces. Shaft-type gasification melting furnace separated r-Cs selectively into FA and simultaneously discharged decontaminated slag. The leaching rate of r-Cs from FA was high, 30-100%, and independent of the type of furnace, whereas r-Cs in the residue from the bottom of the furnace scarcely dissolved in water. Heat recovery ash e.g. gas cooler ash was characterized by intermediate r-Cs concentrations and leachabilities compared with bottom residue and FA in stoker type and fluidized-bed incinerator. In the case of shaft-type gasification melting furnace, however, heat recovery ash showed similar property to FA due to a cyclone followed by heat recovery process. We evaluated whether baghouses (air- pollution control equipment) successfully removed r-Cs from flue gas. In all cases, r-Cs in flue gas was below the limit of detection after baghouse. We concluded that different types of furnaces affected r-Cs distributions, but flue gases from baghouse systems of all types of furnaces were safe.

Predicted distribution of 16 short-chain chlorinated paraffins in air, water, soils and sediments

Short-chain chlorinated paraffins are industrial contaminants of great concern due to their persistent and toxic characteristics. The predicted distribution of short-chain chlorinated paraffins in air, water, soils and sediments is unclear because their physiochemical properties are poorly known. Here, we calculated the coefficients that control the partitioning behaviors of 16 short-chain chlorinated paraffins. The results show an increase in partitioning coefficients with chlorine number for short-chain chlorinated paraffins with carbon chain length of 10. Mono-chlorinated short-chain chlorinated paraffins show an increase in partitioning coefficients with carbon number. Short-chain chlorinated paraffins with chlorines at both ends of the carbon chain have relatively lower values of

Hydrodeoxygenation of waste vegetable oil over sulfide catalysts

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