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Reduction of Greenhouse Gas

Outline of Earth Plan - 2004

With the Kyoto Protocol issued in February 2005, international measures have been further intensified for preventing global warming. The greenhouse gas emission from the Bureau of Sewerage amounts to 45% of the emission resulted from the overall activities of the administrative works and projects of Tokyo Metropolitan Government, so that the Bureau bears a big responsibility in preventing global warming. It is important, on the other hand, to promote improvement projects for combined sewer system and to improve the diffusion rate in Tama area in order to improve the water quality in the public water area. With the increase in sludge generation and power consumption, the greenhouse gas emission is expected to increase. Under such background, the Bureau of Sewerage drew up the"Earth Plan-2004"in September 2004 before the Tokyo Protocol was issued to indicate our efforts for comprehensive promotion of measures for prevention of global warming. The roles are clearly indicated also in the"Tokyo Government Plan for Global Warming Countermeasures" announced in August 2005.

1.Objective of Earth Plan - 2004

The Plan aims at reducing the greenhouse gas emission by more than 6% of the FY1990 level by the FY2009.

2.Main Measures of Earth Plan - 2004

Reduction of greenhouse gas emission during sewage (wastewater) treatment

  • High temperature incineration, carbonization, and sludge gasification, etc.
  • Reducing the amount of energy used during the water treatment process (Microbubble diffuser, Energy saving stirrer, etc.)

Switching to renewable energy, and to resources and energy with less emission of greenhouse gas

  • Utilization of renewable energy (wastewater heat, heat supply and power generation using the waste heat from sludge incineration, biomass power generation, etc.)
  • Introduction of new power source (installation of "NaS battery" that uses nighttime power and has low percentage of fossil fuels)

3.Bureau`s Prediction and Reduction Target of Greenhouse Gas for FY2009

Expectations for the Reduction of Greenhouse Gases in Earth Plan 2004

High-temperature Sludge Incineration

Of the greenhouse gas emission from sewerage work, 33% is N2O (dinitrogen monoxide) from the sludge incineration. The N2O emission can be reduced by 70% by raising the sludge incineration temperature from 800℃ to 850℃.

※ The greenhouse effect of N2O is 310 times higher than that of CO2.

Incineration temperature vs N<sub>2</sub>O emission

NaS Battery

The rate of fossil fuel used for power generation is less and the cost is lower in the nighttime, when the power demand is low, than in the daytime. Hence, the following effects can be expected by making use of the power, stored at night in the NaS battery, during the daytime.

  • Cheap power and the leveling of electric-load can contribute to drastic reduction in power cost.
  • Reduction in greenhouse gas emission contributes to reduction of environmental load.

※ The NaS (sodium-sulfur) battery is an effective accumulator capable of storing equivalent amount of electricity in a  volume one-third of the lead battery.

Image of utilization of nighttime power

NaS battery Facility

Installation placeOperationFacility scale
Kasai Water Reclamation Center December 2001 2,400kW
Morigasaki Water Reclamation Center April 2004 8,000kW
Sunamachi Water Reclamation Center May 2005 2,000kW
Miyagi Water Reclamation Center April 2006 2,000kW
Kita-Tama Ichigo Water Reclamation Center April 2007 1,000kW

NaS battery Facility image

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