This article summarizes the discussion on sustainable landfills by a landfill research group that has been working over the last 10 years. First, the concept of sustainability for landfills is defined based on the expected future of solid waste management. A goal is next proposed, taking into consideration concepts such as safety and planning for after-use. It is important for the design to be looked at from four different angles : type of waste, landfill method, facilities, and location of landfill. Different stabilities are defined in the paper, and the relationship between landfill design and risk minimization methods and stability levels is explained. The second half of the article is devoted to an overview of the topic and an introducing to the development of various strategies related to this special issue.

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Elements in waste that are disposed of are eventually transferred to either of three destinations : into the atmosphere by landfill gas, into the surface water by leachate, or into a solid waste body within a landfill. Past studies indicate that the ratio of elements that remain in a landfill is rather high even twenty years after disposal. And they also found that these elements diminish from the landfill very slowly even when several centuries are taken into consideration. This implies that many elements remain even after intense reaction phases cease and emission drops to a level where no treatment is required. It must be important to guarantee that these residual elements never cause a negative impact, over long-range period of time. Most of the numerical models for simulating substance behavior in landfills have, up to now, mainly dealt with the degradation process and generation of landfill gas. For long-term prediction, especially with regard to hazardous elements, the model which can deal with the formation of the high molecular organic compounds such as humic substances needs to be developed.

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Landfill gas and temperature in landfills are indices that reflect aerobic and anaerobic biodegradation. They are also important for evaluating the stabilization of landfills. Passive landfill gas extraction wells have been newly installed in a completed and closed landfill for the purpose of stabilization and observation of landfill gas components and temperatures. In several of the wells, both temperature and carbon dioxide concentration increase in the process of aerobic biodegradation, however in some of the other wells, anaerobic biodegradation is dominant. The passive landfill gas extraction wells seem to have a limited effect on stabilization of the landfill. The paper presents the results put forward by researchers who have been studying stabilization of landfills through chemical oxidation and aerobic biodegradation. Finally, vertical temperature distributions and temporal change of the temperatures in the landfill are reported, and the importance of temperature as an index for stabilization is discussed.

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Solid waste landfills must be appropriately managed so as to prevent the adverse effects on the surrounding environment. Japan′s compliance leaching test for industrial wastes, JLT-13, is used as a means for judging whether leaching of hazardous substances is an issue at solid waste landfills. This report summarizes the role of JLT-13 and other related issues based on recent findings and information. The leaching test is still a prerequisite for securing the environmental safety of any landfill. Moreover, in order to set into place the concept of a material-sound society, the construction of a basic concept ualization/guideline for environmental safety in soils, recycled materials and wastes must be developed.

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Quality control technologies for landfill MSW on a global scale and C&D waste in Japan were reviewed. A method known as mechanical biological treatment (MBT), which combines mechanical sorting and biological treatments, is being introduced in Europe as a means for developing a technology that will reduce organic materials in MSW. There are two directions MSW disposal can take in Asia : incineration dominant or utilization of combined incineration and biological treatments. The crushing and separation process of mixed C&D waste not only removes organics from landfill waste, but also recovers secondary resources. A technological issue related to this technology will be quality control of sieved residues. The cost benefits of applicable technologies must also be considered. Improvements in flexibility and economic efficiency for adapting to local situations will be necessary in order to universalize intermediate treatment technologies in Japan.

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Municipal governments are required to build low-carbon, recycling-oriented waste treatment systems in order to fulfill their obligation to dispose of the municipal solid waste being produced as a “by-product of human activities.”
This report presents the current overall picture of municipal solid waste treatment and related issues in Japan. The paper presents a novel Recyclable Landfill System (hereinafter referred to as ‘RL System’. The RL System incorporates sustainable environmental technology to reuse landfill sites as desalination facilities that can convert incineration ash into a basic ingredient in cement. In this system, the landfill space can be utilized repeatedly as a resource circulation base, and can also thereby contribute to the realization of low-carbon society.

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Environmental restoration technology being used at illegal waste disposal site is explained.
An illegal storage site where hydrogen sulfide gas and methane are being generated, and an illegal dumping site for hazardous metal compounds are explained using case studies.
Examples are outlined as follows : (1) Investigation Methods ; (2) Strategic Planning ; (3) Safety Measures ; (4) Post-monitoring for Environmental Preservation.
The control method of hydrogen sulfide gas and the analysis method of soil contaminated by heavy metals are also introduced here as effective techniques for developing measures for dealing with this waste.

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Semi-aerobic system holds greater advantages when compared to anaerobic landfill because of the reduction of environmental impacts through purification of leachate, which accelerate waste stabilization, among other things. In addition, there are less construction costs and maintenance is easier. Due to these advantages, we had some application this system in overseas such as Malaysia, China, Iran, Samoa, Italy etc. However, the landfill design and operation in overseas is dependent upon the responsibility of the recipient country. It is therefore important for the transfer of semi-aerobic system to oversea that the concept for this system is well understood and an efficient system set in place. The effects of this system on reducing environmental risks must also consist of methane gas reduction, etc. Investigation into this issue must be continued in order to collect more scientific data and detailed mechanisms must be taken into consideration before semi-aerobic system is recognized as one of the co-benefit CDM technology and eventually introduced on a global scale.

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