Municipal incineration bottom ash treatment using hydrothermal solidification

Solidification of municipal incineration bottom ash (MIBA) has been carried out using a hydrothermal processing method, in which the MIBA was first compacted in a mold at 5-20 MPa, and then hydrothermally cured in an autoclave under saturated steam pressure at 150-250 degrees C for 10-72 h. Experimental results showed that the tensile strength of the solidified body was greatly influenced by the addition of NaOH solution and fresh cement in the MIBA. The hydrothermal curing temperature and time exerted a significant influence on the development of tensile strength of solidified body. The strength development is speculated to be due primarily to the formation of 1.1 nm tobermorite. Laboratory leaching tests were conducted to determine the amount of heavy metals dissolved from the solidified bodies and the results showed that under the hydrothermal conditions of this study the leaching of heavy metals was very low. As such, the hydrothermal processing method may have a high potential for recycling MIBA.     

National implications of a 50% global reduction of greenhouse gases, and its feasibility in Japan

This paper considers three questions concerning a low-carbon society. The first is the implication of a 50% reduction in greenhouse gases (GHGs) by 2050. In the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, released in 2007 (IPCC 2007b; http://www.gtp89.dial.pipex.com/chpt.htm), the suggested limit of increase in average worldwide temperatures is 2–3°C above the current level, but is this consistent with a 50% reduction by 2050? Second, when a 50% reduction in global emissions is envisioned, what is the level of reduction needed in Japan? Should the 50% reduction be uniform for advanced industrial countries and developing countries, or differentiated based on a country’s emissions? Third, how feasible are emission reduction targets in Japan? Even if the emission reduction target set for each country takes into account climate change impact and equity, whether the target is technically, or socially and economically, acceptable is another matter.     

Experimental study on CO2 monitoring and quantification of stored CO2 in saline formations using resistivity measurements

This paper reports CO₂ saturation estimations based on resistivity data obtained from laboratory measurements and induction logging results at the Nagaoka pilot CO₂ injection site. The laboratory experiments put in evidence that the presence of clay content tends to reduce the increase of resistivity caused by the displacement of brine by less conductive CO₂. As a result, CO₂ saturations estimated from resistivity measurements without any correction for the clay effect are considerably lower than the actual saturations. The resistivity index (RI) provides better estimates of CO₂ saturations than the Archie's equation because it requires the determination or assumption of only one rock parameter: the saturation exponent. CO₂ saturations estimated from the induction logging data acquired at Nagaoka are considerably lower than the neutron porosity changes due to displacement between brine and CO₂ in the reservoir. Even in the case of considering the De Witte's equation and the Poupon's to account for the clay effect, it was still difficult to get a good agreement with the neutron logging results. New relations based on the resistivity index with correction factors for the clay effect are developed and implemented in this study. One of these relations has proved to be effective to estimate CO₂ saturations in saline formations with high clay content.     

Simplified heating time calculation using the Schmidt graphical method for PCB-contaminated capacitors undergoing the vacuum thermal recycling process

We discuss the use of the Schmidt graphical method to calculate the time required to heat a polychlorinated biphenyl (PCB)-contaminated capacitor in the vacuum thermal recycling process to the processing temperature of 400°C, and we evaluate the results of the heating time calculation by comparing the calculated values with the corresponding experimental values. The thermal conductivity and specific heat of the insulating paper and the carbonized paper in the capacitor were unknown, so we determined their values from experimental data obtained during the vacuum thermal recycling process. The capacitor element is a multilamination of aluminum foil and insulating paper, so we used an equation for a multilayer plane wall to calculate the value of the thermal conductivity. For the thermal conductivity and specific heat of the insulating paper impregnated with PCBs, we used values calculated from the mass ratios and thermal conductivities and specific heats of the individual materials. In addition, the physical properties vary according to the treatment because of the evaporation of PCBs and the carbonization of the insulating paper, so we modified the values of the thermal conductivity, specific heat, and density at the boiling point of the PCB and the carbonization point of the insulating paper before performing the calculations. Our calculated heating times were almost the same as, or were above, the experimental values, so we concluded that our method can be used as a simple calculation of the heating time.     

The analysis of greenhouse gas emissions/reductions in waste sector in Vietnam

The global waste sector produces, on average, 2–5 % of global anthropogenic greenhouse gas (GHG) emissions. The amount of GHG emissions has grown steadily and is predicted to increase considerable in the forthcoming decades because of the increases in population and gross domestic product (GDP). However, the GHG mitigation opportunities for the sector are still fully not exploited, in particularly in developing countries. A series of initiatives were highly successful and showed that large reductions in emissions are possible. This study aims to propose a holistic quantification model, which can be used for estimation of waste generation and evaluation of the potential reduction of GHG emissions in waste sector for developing countries with a particular application to Vietnam. The two scenarios set for the study were business as usual (BaU) which waste management is assumed to follow past and current trends and CounterMeasure (CM) which alternative waste treatment and management are assessed. Total emissions in the BaU scenario are projected to increase from 29.47 MtCO₂eq in 2010 to 85.60 MtCO₂eq by 2030 and 176.32 MtCO₂eq by 2050. The highest emissions are due to methane (CH₄) released by disposal sites, accounting for about 60 % of the GHG emissions from waste in Vietnam in 2030. This emission is projected to increase significantly (67 % in 2050), unless more of the methane is captured and used for energy generation. The CM scenario gives emission reductions from 25.7 % (2020), 40.5 % (2030) to 56.6 % (2050) compared to the BaU scenario. The highest GHG reduction is achieved through recycling, followed by methane recovery to optimize the co-benefit for climate change mitigation.