Liquefaction process for a hydrothermally treated waste mixture containing plastics

Most landfilled plastic waste is a mixture or is in the form of composites with incombustible wastes such as glass, metals, and ceramics. After hydrothermal treatment, including a steam-explosion process, the separation of mixed waste (MW) into organic and inorganic substances becomes easy. However, the effect of hydrothermal pretreatment on the subsequent liquefaction of organic substances from MW is not obvious. In this study, the effects on the liquefaction of polystyrene and high-density polyethylene are discussed. Moreover, optimum conditions for the liquefaction of organic substances from hydrothermally treated MW are identified. By means of this hydrothermal pretreatment, including the steam-explosion process, polystyrene and high-density polyethylene can be significantly converted to oil by liquefaction at 300°–400°C. In comparison with liquefaction of hydrothermally pretreated mixed waste (HMW) at 300°–400°C with a batch type reactor, the yield of oil increases significantly on liquefaction using a semi-batch type reactor. It is considered that the radical chain and termination reactions among the radicals from HMW were inhibited in the semi-batch type reactor. On liquefaction of HMW in a semi-batch reactor, the conversion of HMW to oil was enhanced on increasing the liquefaction temperature to 350°C and the holding time to 60 min. Chemical Feedstock Recycling & Other Innovative Recycling Techniques 6     

Water resource management in Japan: Forest management or dam reservoirs?

Researchers and journalists in Japan recently proposed forest management as an alternative to dam reservoir development for water resource management. To examine the validity of the proposal, we compared the potential low-flow increase due to forest clearcutting with the increase due to dam reservoir development. Here, we focused on forest clearcutting as an end member among various types of forest management. We first analyzed runoff data for five catchments and found a positive correlation between annual precipitation and the low-flow increase due to deforestation. We then examined the increase in low-flow rates due to dam reservoir development (dQ_d) using inflow and outflow data for 45 dam reservoirs across Japan. Using the relationship between annual precipitation and the low-flow increase due to deforestation, we estimated the potential increase in the low-flow rate for each dam reservoir watershed if forests in the watershed were clearcut (dQ_f). Only 6 of the 45 samples satisfied dQ_f > dQ_d, indicating that the potential increase in the low-flow rate due to forest clearcutting was less than the increase due to dam reservoir development in most cases. Twenty-five of the 45 samples satisfied dQ_f < 0.2 dQ_d, indicating the potential increase in the low-flow rate due to forest clearcutting was less than 20% of the increase due to dam reservoir development in more than half the cases. Therefore, forest management is far less effective for water resource management than dam reservoir development is in Japan.     

Population genetic structures of the fissiparous seastar Coscinasterias acutispina in the Sea of Japan

The morphological characteristics and the population genetic structures of the fissiparous seastar Coscinasterias acutispina were investigated for eight sites in the Sea of Japan in order to clarify the presence of sexual and asexual reproduction. Morphological observation based on arm length showed that fission was common at all eight sites examined, indicating the likely production of clonal individuals. A random amplified polymorphic DNA (RAPD) marker was used to detect clones arising by fission and to assess gene flow among sites. A simulation approach using RAPD data revealed the presence of clonal individuals at almost all sites, suggesting the existence of asexual reproduction. The result of phylogenetic analysis according to RAPD genotype showed no relationship between genetic and geographic distances. Considering the limited movement ability of seastar species during the adult phase, these observations suggest the existence of marked gene flow among sites, due to dispersal of planktonic larvae produced by sexual reproduction. These observations suggest that multi-locus genotypic compositions depend on the relative amounts of recruitment from sexual and asexual reproduction in each population.     

Prediction of response of zooplankton biomass to climatic and oceanic changes

This paper examines the long-term variation in zooplankton biomass in response to climatic and oceanic changes, using a neural network as a nonlinear multivariate analysis method. Zooplankton data collected from 1951 to 1990 off the shore of northeastern Japan were analyzed. We considered patterns of the Kuroshio and the Oyashio, sea surface temperature, and meteorological parameters as environmental factors that affect zooplankton biomass. Back propagation neural networks were trained to generate mapping functions between environmental variables and zooplankton biomass. The performance of the network models was tested by varying the numbers of input and hidden units. Changes in zooplankton biomass could be predicted from environmental conditions. The neural network yielded predictions with smaller errors than those of predictions determined by linear multiple regression. The sensitivity analysis of networks was used to extract predictive knowledge. The air pressure, sea surface temperature, and some indices of atmospheric circulation were the primary factors for predictions. The patterns of the Kuroshio and the Oyashio demonstrated different effects among sea areas.     

A study on the self-assembly behavior of dark materials from molasses

We have previously demonstrated that dark materials (DM) in acidified molasses are effectively adsorbed to Amberlite XAD7HP resin and are eluted from the resin with 0.1 M sodium hydroxide. In this paper, we have characterized the self-assembly behavior of molasses DM by using dynamic and static light scattering in combination with isoelectric focusing and infrared absorption spectroscopy in order to better understand the resin adsorption mechanism. One of DM derivatives, X-G2, contained carboxyl and hydroxyl groups and had a weight-average molar mass of 9.39?×?10³ to 4.42?×?10⁴ at pH 2.1–11.5. The aggregates retained their spherical shape over the full pH range and the large gyration radius (66.4–80.0 nm) indicated that the inner structure was loosely packed. Furthermore, X-G2 had an isoelectric point of 1.8, and its density increased sharply at pH 5.9 and then approached a nearly constant value under alkaline conditions. In summary, the self-assembly processes of DM are controlled by intermolecular hydrogen-bonding and hydrophobic interactions. The aggregates adsorb to the resin through hydrophobic interactions and are eluted when excess carboxylate anions are generated.     

Photodegradation of the synthetic fragrance OTNE and the bactericide triclosan adsorbed on dried loamy sand--results from models and experiments

Fragrances such as OTNE (marketed as Iso-E-Super®) and bactericides such as triclosan (marketed as Igrasan) are present in waste water and thus finally sorbed to sewage sludge. With that sludge they can reach agricultural fields where they potentially can undergo photodegradation processes. In this study the photodegradation of OTNE and triclosan on dried loamy sand was measured under artificial sunlight conditions in laboratory experiments. These compounds were artificially added with concentrations of 1 μg g⁻¹ on pre-rinsed dried loamy sand. The decrease in concentration with light irradiation was measured for 32 d in comparison to soil samples without light irradiation. The estimated light source intensity was 27 W m⁻². Within the experiment, the apparent half-life was 7 and 17 d for OTNE and triclosan respectively. The decrease did not simply follow first-order kinetics. The apparent rate constant decreased in the latter stage of reaction, suggesting that part of the chemicals were inaccessible for degradation. Two models, i.e., a diffusion-limited model, and a light penetration-limited model, were used in comparison to the measured data to explain the observed degradation limitations in the latter stages of the experiments. Comparing the hereby obtained model parameters with estimated physico-chemical parameters for the soil and the two chemical compounds, the light penetration-limited model, in which the degradation in the soil surface layer is assumed to be limited due to the shading effect of light in the upper thin soil layer, showed to be the most realistic in describing the photodegradation.     

Evaluating households’ preferences regarding reducing power outages in rural areas: cases in the Ganges Floodplain in Bangladesh

This paper investigates household preferences regarding an improved supply of electricity in rural Bangladesh, where the expansion of stable electricity is an urgent policy issue. The paper examines household preferences regarding reductions in the frequency and duration of power outages. It also examines prior notification mechanisms that do not necessarily provide an increased supply of electricity but that allow households to prepare for potential power failures. A questionnaire survey designed as a choice experiment was applied to households to elicit preferences. The econometric analysis reveals that villagers prefer a reduction in both the frequency and duration of power outages and a 1-day prior notification of power outages. There are slight disparities in preferences according to the season and the timing of improvements (e.g., summer or winter and all day or peak hours). Thus, the present study may be beneficial for policymakers when considering the provision of electricity supply improvements in rural areas in exchange for slight increases in electricity tariffs.     

Changes in peak flow with decreased forestry practices: analysis using watershed runoff data

The prevalence of forestry practices such as thinning and pruning have gradually decreased since the 1980s. Researchers have noted an increased flood risk with decreased forestry practices for coniferous plantations in Japan on the basis of infiltration and overland flow measurements at a plot scale (typically several square meters). However, no studies have examined changes in peak flow with decreased forestry practices at a watershed scale (typically several tens or hundreds of square kilometers) even though flood disasters generally occur at this scale in Japan. We examined changes in frequency distributions of daily precipitation (P) and runoff (Q) during the period 1979-2007 at the Terauchi watershed, where forestry practices are known to have decreased. For this purpose, we divided P and Q data into 14 and 15 classes according to the magnitude, respectively, and examined changes in the frequency for each class during the period. We observed no significant increasing trend for any P or Q class. Even when taking into account the effect of interannual variations in precipitation on the frequency for each Q class, there was no significant increasing trend in the frequencies except for two Q classes with moderate Q values. These results suggest that the increase in flood risk due to decreased forestry practices might be less than expected.     

Melting and incineration plants of municipal waste. Chemical and biochemical diagnosis of thermal processing samples (emission,residues)

Control of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in emissions and thermal residues from incinerators has been a cause of public concern for more than one decade. Recently, several studies showed that other persistent organic pollutants (POPs) such as coplanar polychlorinated biphenyls (co-PCBs) also have dioxin-like activity and are released from incinerators. Therefore, the present study was aimed at making a risk assessment about dioxin-like activity in extracts of thermal waste residues (e.g. combustion gas; fly ash, slag) from incineration and melting processes in Germany and Japan. For this purpose, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), coplanar polychlorinated biphenyls (co-PCBs), polychlorinated naphthalenes (PCNs) and polyaromatic hydrocarbons (PAHs) were analyzed by chemical analysis. Additionally, 2, 3, 7, 8-TCDD equivalents (EROD-TEQs) were determined by in vitro Micro-EROD bioassay using rat H4IIE hepatoma cells. EROD-TEQs could be correlated to I-TEQ values (from PCDD/Fs/co-PCBs) analyzed by chemical analysis resulting in a maximal sixfold higher estimate. Our study indicates minor influences of co-PCBs, PAHs and PCNs to the sum of dioxin-like toxicity in the extracts of thermal waste residues as determined here. Furthermore, we showed that the levels of dioxins and co-PCBs contained in slag from melting processes and bottom ashes from incineration processes were lower by 1-2 orders of magnitude than that in fly ash.