For the purpose of the inventory, data, mainly relevant reference materials were collected. Cost data from the sludge treatment facility, which includes mechanical, architectural, electrical installation and operation phases, were obtained from an earlier report (Masui et al. 2001). The lifetime of the building, equipment, electrical equipment and drainage system was 30 days, 7 days, 15 days and 12 years respectively. Disposal treatment costs were used to collect data for the "Japanese Government Database" (Ministry of Land and Resources, Infrastructure and Transportation, Japanese Government 2002). In this database, sludge disposal treatment costs are directly collected from all sewage treatment facilities in Japan. The environmental impacts of treatment and disposal facilities are calculated using the interindustry relationship table of Japan (Ministry of International Affairs and Communications of Japan, 1995). Calculation of dioxin and heavy metal emissions from sewage sludge treatment studies and regulations ( [ Watanabe et al. 2002], [Anto and Kobayosi, 1994], [Tokyo Sewerage Bureau Technical Survey Annual Report, 2005], [Takatsuki, 1999] [Ministry of the Environment, Government of Japan], [Svanstr?m et al. , 2005], [Fertilizer Control Law No. 111] and [Miyamoto et al. 1997]). Annual loads of carbon dioxide, sulfur dioxide landfill consumption, dioxins and heavy metals come from the literature ([Ministry of the Environment, GoJ 2003], [Weng et al. 1998], [Ministry of Health, GoJ 1999], [Central Environmental Committee of Japan Air Environment Task Force, 1999] and [Takatsuki, 1999]).
In addition, in order to control global warming, some countries in the European Union, such as Sweden, Finland, the Netherlands, and Norway, implemented a carbon tax in the 1990s on carbon dioxide emissions from energy sources into the atmosphere. Carbon taxes on energy products vary greatly between countries because the price per ton of carbon is relatively different from country to country. In this study, the average price of carbon tax in Finland (about 6500 is/tc; $ 62/tC) was used in the European Union (Ministry of the Environment, 1995).