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Steps taken to counter the climate change problem have a significant impact on the municipal solid waste management (MSW) sector, which must tackle regional environmental problems such as the shortage of sanitary landfills, especially in Japan. Moreover, greenhouse gas emissions and final disposal have a trade-off relationship. Therefore, alleviation of both these environmental problems is difficult, and Japanese local municipalities are anxious for action to solve these problems and reduce treatment costs. Although ambitious waste management measures have been enacted in many countries, they appear to lack a holistic view and do not adopt a life cycle approach. Therefore, it is important to reconstruct the MSW management system, taking into account environmental and economic aspects. In the present study, life cycle assessment and mathematical modelling were used to seek ways of redesigning the MSW management system in order to minimize environmental impacts and/or reduce treatment costs. One economic block was selected as the study area (Iwate Prefecture in Japan). The life cycle inventory and costs data for every MSW transportation and treatment process in this region were collected and processed. Then, taking account of geographic information, an optimal solution for the minimization of environmental impact or treatment costs was derived. To solve the trade-off problem, a sensitivity analysis was conducted to find optimal reduction targets for climate change and final disposal.

The aim of this study was to use life cycle assessment methods to determine the environmental impacts of manure utilisation by a biogas plant and by a typical manure composting system. The functional unit was defined as the average annual manure utilisation on a dairy farm with 100 cows. The environmental impact categories chosen were emissions of greenhouse gases (GHG) and acidification gases (AG). The GHG emissions were estimated as: 345.9 t CO2-equivalents (e) for solid composting (case 1), 625.4 t CO2-e for solid and liquid composting (case 2), and 86.3–90.1 t CO2-e for the biogas plant system. The AG emissions were estimated as: 10.1 t SO2-e for case 1, 18.4 t SO2-e for case 2, and 13.1–24.2 t SO2-e for the biogas plant system. These results show that a biogas plant system produces low GHG emissions, but comparatively high AG emissions with land application. It is suggested that land application using band spread or shallow injection attachments will decrease AG emissions (NH3) from biogas plant systems.

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