Journal of Material Cycles and Waste Management

Imaizumi, Shigeyoshi; Wataru, Masazumi; Takahashi, Naoki; Doi, Yoichi

doi: 10.1007/s10163-009-0256-2pmid: N/A

A design method was proposed to determine the critical ratio of bentonite addition, based on a macro void ratio that considers the swelling property of bentonite. The critical ratio of bentonite addition was defined as the ratio corresponding to a macro void ratio of zero. However, when lightweight soil such as tuff sand is mixed with bentonite, the estimated critical ratio of bentonite addition is too high. Several tests on the water absorbing property of tuff sand and its permeability were conducted to confirm the concept of a revised macro void ratio. The revised macro void ratio, which takes into account the swelling of bentonite and the particle pores of lightweight soil, is much smaller than the former macro void ratio for a given ratio of bentonite addition. The estimated critical ratio of bentonite addition to tuff sand that gives a revised macro void ratio of zero is around 18% and is in good agreement with the ratio of bentonite addition beyond which the value of hydraulic conductivity does not decrease markedly.

Takuwa, Yuya; Matsumoto, Tadao; Oshita, Kazuyuki; Takaoka, Masaki; Morisawa, Shinsuke; Takeda, Nobuo

doi: 10.1007/s10163-009-0257-1pmid: N/A

Because landfill gas (LFG) contains an abundance of methane, the utilization of LFG as a renewable energy source is becoming popular in many countries. LFG, however, contains various trace constituents, some of which may pose problems during utilization. For example, siloxanes and halogenated volatile organic compounds (VOCs) can cause difficulties when present in the fuel of gas engines. In addition, many VOCs and mercury have harmful effects on human health, especially on the health of workers at landfill sites and people living near the landfills. Energy recovery from LFG is expected to make great progress in the near future, particularly in Asia, but we found little information on the trace constituents of LFG in this region. Therefore, we sought to characterize the trace components in LFG generated in two landfill sites in China and one site in Japan, to determine the typical concentrations of these trace components in LFG, and to compare their concentrations among landfill sites in Asia. We concluded that the trace components in LFG at the sites studied were mainly siloxanes generated from sewage sludge and harmful benzene, toluene, ethylbenzene, and xylene compounds from petroleum products.

Wang, Yu; Pelkonen, Markku

doi: 10.1007/s10163-009-0258-0pmid: N/A

Management of landfill emissions, i.e., landfill gas (LFG) and landfill leachate, is an important and resource-intensive task. A long-term demonstration pilot, consisting of landfill simulation reactors (LSRs), was used to study the impact of temperature and the applied liquid/solid ratio (L/S ratio) on landfill emissions, characteristics, and trends. This pilot has already run for more than 1000 days since the end of 2004 and will continue to run for some time. The degradation of waste at different temperatures has impacts on the overall degradation degree and on the length of post-closure care required. Higher temperatures accelerated the degradation, but also resulted in higher leachate chemical oxygen demand (COD) and ammonia concentrations, which prolong the aftercare period. Meanwhile, at a given stabilization degree [e.g., 70 l gas/kg waste (dry)], the total leached nitrogen under psychrophilic conditions was 3.5 times that under mesophilic/thermophilic conditions, which resulted in a higher required effort for leachate treatment. The impact of L/S ratio or simulated annual L/S rates was also evaluated. The results show the significance of efficiently obtaining the targeted L/S ratio in order to achieve low landfill emission potential.

Mersky, Ronald

doi: 10.1007/s10163-009-0260-6pmid: N/A

Vehicle queuing at municipal solid waste (MSW) facilities causes economic and environmental damage. In the United States, typical MSW receiving facilities (transfer, recycling, energy recovery, and landfill) have three queues: one at the entrance weighing station, one at the waste tipping location, and one at the exit weighing station. A common method of determining queue behavior relies on equations that assume exponentially distributed arrival and service times, but there has not been a comprehensive study to determine whether this assumption is valid for a variety of MSW facilities and conditions. In this study, data were gathered from two transfer stations, two energy recovery plants, and one transfer/landfill facility. Among the five facilities there was a variety of queuing styles. The data were plotted as an inverse exponential relationship and linearized. The linearized plots were regressed and R 2 values were calculated. It was determined that the negative exponential relationship can be used to describe arrival times at all three queues and service times at weighing queues. The queuing equations are therefore theoretically supported for use at entering and exiting weighing queues and moderately theoretically supported for use at tipping queues.

Yasuda, Kenji; Yoda, Ikuko; Kawamoto, Katsuya

doi: 10.1007/s10163-009-0261-5pmid: N/A

Surrogate measurements should be low in cost and quick to perform. To examine its feasibility, continuous surrogate monitoring was performed using an organic halogen compound (OHC) analyzer. Surrogates for dioxins (DXNs) from waste incinerators were examined by changing the operating conditions such as the atomized volume of activated carbon added and the temperature at the inlet of the dust collector. OHCs were measured along with DXNs in flue gas at the inlet and the outlet of the dust collector of two waste incinerators over five runs; the fly ash was sampled at the same time. Although the final flue gas concentration of DXNs at the incineration plants was below the regulation criteria, this does not mean complete reduction of DXNs. In addition, the de novo synthesis of DXNs inside the dust collectors was studied by analyzing the mass balance for DXNs concentrations in flue gas and fly ash. Semivolatile chlorinated organic compound concentrations at the outlet of the bag filter were basically well correlated with DXNs levels at the inlet of the bag filter in the test runs. When advanced flue gas treatment is applied by using a bag filter and lime/activated carbon adsorbent, DXNs that may be generated during flue gas cooling processes move to the fly ash, and this amount determines the mass balance of the entire system. It may be useful to monitor surrogate organic halogens for detecting changes in DXN concentrations of both flue gas and fly ash in incineration plants.

Champagne, Pascale; Li, Chenxi

doi: 10.1007/s10163-009-0262-4pmid: N/A

A laboratory bench-scale fixed-bed column study operated as a down-flow configuration was conducted to evaluate Sphagnum peat moss and crushed mollusk shells as natural low-cost adsorbents for the removal of heavy metals from aerated and unaerated synthetic landfill leachate. Columns were packed with 15 cm of prepared peat moss, or 15 cm adsorbent mixtures made up of peat moss and crushed mollusk shells (4.0–4.75 mm) from Lake Ontario at different bed depth ratios. Peat was found to have the best adsorption capacities in columns treating aerated synthetic leachate for cadmium and nickel with 78.6% and 83.8% removal efficiencies, respectively. The removal of chemical oxygen demand (COD) and total nitrogen from the synthetic leachate was also monitored to evaluate the potential effects of biological activity on heavy metal adsorption. Columns receiving unaerated raw synthetic leachates did not show any significant removal of COD and total nitrogen, whereas some reduction in COD and total nitrogen was noted in the columns treating aerated synthetic landfill leachate. The results suggested that biological activity and biofilm growth could positively contribute to heavy metal retention within the fixed-media biosorption columns.

Fuse, Masaaki; Kosaka, Hiroyuki; Kashima, Shigeru

doi: 10.1007/s10163-009-0263-3pmid: N/A

In order to provide the basic information for building an international automobile recycling system, this article attempts to estimate the multilateral trade for used automobiles. First, the problems in evaluation of the used automobile trade were clarified through the trade data obtained from the United Nations database (UN-DB) and the Global Trade Information Services database (GTI-DB). Furthermore, we developed an estimation method for the used automobile trade using the highlighted advantages of the UN-DB and GTI-DB. The reasons for employing this estimation method were to correct the systematic errors in both databases and to sample used automobile data from the UN-DB by using the new and used automobile information in the GTI-DB. The world trade volume for used passenger cars in 2005 was estimated by the method developed. These results indicated that total trade volume was 5.65 × 106 vehicles, and that the exports from Germany, the United States, and Japan comprise 22%, 21%, and 20% of the global total, respectively. Moreover, the results indicate that these countries export used passenger cars not only to developing countries (54%), but also to developed countries (46%).

Nguyen, Duc-Quang; Yamasue, Eiji; Okumura, Hideyuki; Ishihara, Keiichi

doi: 10.1007/s10163-009-0264-2pmid: N/A

In this study, e-waste flows of five large home appliances (color televisions, refrigerators, washing machines, personal computers, and air conditioners) in Vietnam are investigated. A social survey was performed to investigate the situation on using appliances in households as well as on the disposal of appliances by the first users. Future quantities of e-waste were estimated using a model that combines use of the Weibull distribution, the logistic function, and the population balance model. It was forecast that about 3.86 million appliances, or 114 000 tons, will be discarded in 2010, and about 17.2 million appliances, or 567 000 tons, in 2025, showing a rapid increase of e-waste in the near future.

Osada, Shohichi; Kuchar, Dalibor; Matsuda, Hitoki

doi: 10.1007/s10163-009-0265-1pmid: N/A

In the present work, a shaft-type furnace model in which the furnace column is divided into multiple cells was proposed and equilibrium reaction calculation software was used to describe the model. The model was used to study the effects of gasification and melting conditions such as temperature, oxygen partial pressure, and chlorine content on the volatilization behaviors of the low-boiling-point metals Na, K, Pb, and Zn during the gasification and melting process of municipal solid waste in a shaft-type furnace. Consequently, the volatilization ratios of Na, K, Pb, and Zn compounds in the exhaust gas from a pilot plant shaft-type furnace were found to be in good agreement with the calculation results, and the Na, K, Pb, and Zn compounds were volatilized mainly as metal chlorides in the temperature range up to approximately 1173 K. With a further rise in temperature, these low-boiling point metals were volatilized as metallic forms. It was found that almost 100% of Pb and Zn compounds were volatilized regardless of the chlorine content in municipal solid waste; in contrast, the volatilization rates of Na and K increased when the chlorine content increased. Finally, Na, K, Pb, and Zn compounds were converted from reduced metals to metal chlorides such as NaCl, KCl, PbCl2, and ZnCl2 with an increase in the ratio of chlorine to each metal.