Tokyo Metropolitan
Government Bureau ofSewerage

Measures Against Global Warming,
Aimed Towards Decarbonisation

Background and Reason for the Project

Project Outline

The Tokyo Metropolitan Government Bureau of

The Bureau has been proactive in addressing global

Sewerage (hereinafter referred to as ‘the Bureau’) iswarming

responsible for public sewerage projects in Tokyo’s

environment to future generations. Ahead of thewards such as sewage treatment and rainwater

Kyoto Protocol, in 2004, the Bureau initiateddiversion, as well as basin sewerage projects thatcomprehensive measures to combat global warmingtreat sewage flowing from municipal public sewers in

by formulating the ‘Earth Plan 2004’, a plan aimed at

the Tama region. In the wards and the Tama region,

preventing global warming in sewerage projects.

20 water reclamation centres and 86 pumping

Subsequently, the targets for reducing greenhousestations operate 24 hours a day, 365 days a year

gas emissions have been gradually raised, and efforts

without a break to ensure the functioning of theto combat global warming, such as energy

sewerage system.

conservation and the use of renewable energy, have

The sewerage projects play an essential role intopassonacomfortableglobalbeen enhanced.

ensuring a safe and comfortable living environment(1) Thorough Energy Conservationand forming a well-functioning water cycle. However,In the water treatment process, the Bureau

sewage treatment requires a large amount of energy

promotes the reduction of electricity usage in thesuch as electricity and fuel, leading to the emission

blowers that supply air to the reactors that treatof carbon dioxide (CO2). Additionally, the sewage

sewage using microorganisms. Specifically, bytreatment process generates nitrous oxide (N2O),

reducing the amount of air supplied through the use

which has 298 times the greenhouse effect of CO2,of fine bubble aeration, which makes the air intoand methane (CH4), which has 25 times thesmall bubbles that dissolve easily in water, thegreenhouse effect of CO2. As a result, the Bureau

Bureau has introduced fine bubble aeration systems

accounts for approximately 36% of the greenhousein approximately 70% of its reactors, which isgas emissions from the Tokyo Metropolitan

expected to reduce electricity usage by about 20%

Government, making it its largest emitter and placing

compared to conventional aeration systems. Ina significant responsibility on it for preventing global

addition to updating the aeration system itself, thewarming.

Bureau has optimized the aeration system bycombining fine bubble aeration systems with highefficiency blowers tailored to the pressure and air1

volume of each system, further enhancing the effect.
In the sludge treatment process, the Bureau is(3) Introduction of Environmentally Friendly
Incinerators

working to reduce electricity usage in the sludge

The Bureau is advancing the practical application andconcentrators and dewatering equipment, which

introduction of energy-efficient and energy self-

account for more than 30% of electricity usage. By

sufficient incinerators, which can significantly reduce

switching from conventional centrifugal force-based

greenhouse gas emissions through joint researchsludge concentrators to energy-efficient gravity-with private companies. By combining these

based filtration concentrators, it is expected toincinerators with high-performance dewatering

reduce electricity usage by about 90%. Currently,

machines that reduce the moisture content of sludge,

energy-efficient concentrators have been introduced

there is no need for fuel during operation.

in approximately 40% of concentrators.

Additionally, by incinerating sludge at temperatures(2) Utilisation of Renewable Energy

above 850°C, nitrous oxide (N2O) emissions can be

The Bureau is promoting the introduction of solar

greatlypower generation on the rooftops of buildings and inincinerators significantly reduce electricity usage by

the upper spaces of treatment facilities, as well as

utilising technologies such as turbochargers that use

small-scale hydroelectric power generation utilisingexhaust gases. Energy self-sufficient incinerators can

the drop in elevation when discharging treated water.

generate

Additionally, it is working to expand the use ofincineration, thus supplying the electricity required

renewable energy by effectively utilising the energy

for operation. Currently, seven energy-efficientof sewerage systems.

incinerators

Specifically, the Bureau is conducting initiatives

reduced.

Furthermore,

electricityand

using

one

energy-efficient

waste

heat

energyafter

self-sufficientincinerator have been introduced.

such as generating electricity by using the methane-廃熱Heat
Wasterich digestion gas generated during the seweragesludge treatment process as fuel, recovering and

未利用の廃熱を活用
Utilising
Unused Waste Heat

utilising the waste heat generated during theincinerationofseweragesludgefor

power

generation, and producing carbonaceous materials

発電機
Generator

from sewerage sludge for use as an alternative fuelto coal in thermal power plants.

Electricity
電力
High-performance
高性能脱水機
Dewatering Machine

Furthermore, it is utilising sewerage heat as a

Incinerator
焼却炉

renewable energy source by using the temperature
characteristics of sewerage, which is ‘cold in summer

Covering
the Electricity
焼却炉の運転にRequired
for Incinerator
必要な電力を賄う
Operation

Figure 1: Energy Self-Sufficient Incinerator

and warm in winter’, as a heat source for heating andcooling in water reclamation centres. In addition,(4) Achievements

sewerage heat is supplied to five office buildings,Since 2004, the Bureau has been systematically

hotels, elderly care facilities, and other facilities inpromoting measures against global warming based

Tokyo. Moreover, initiatives are underway to recoveron the Earth Plan, and in the fiscal year 2021, it

sewerage heat by installing heat exchangers in

reduced greenhouse gas emissions by 27% comparedsewerage pipes by private businesses, etc., and use

to the fiscal year 2000.

the recovered heat as a part of the heat source forheating and cooling in office buildings.

Special Features and Innovations
In recent years, as the climate crisis has becomemore severe, there has been acceleration inmovements

towards

decarbonisation

both

domestically and internationally. In Tokyo, action by
2030 is critical to achieving zero emissions by 2050.
Efforts have accelerated to achieve the ‘Carbon Half’
policy, to cut Tokyo’s carbon emissions to half of2000 levels by 2030.
Based on these new national and municipal
initiatives, the new ‘Earth Plan 2023’ was formulated
in March 2023 to prevent global warming. This plan
integrates measures against global warming andenergy issues based on the characteristics ofsewerage projects, aiming to further accelerate andstrengthen efforts toward decarbonisation. The plansets a goal of reducing greenhouse gas emissions by
50% or more compared to the fiscal year 2000 by thefiscal year 2030. It also outlines a vision forinnovative

initiatives

towardachievingzero

emissions by 2050. In the future, efforts will beintensified not only to accelerate existing initiatives
but also to strengthen efforts such as theintroduction of newly developed facilities and thefurther utilisation of renewable energy.