The Expansion of Biomass
Utilization by Carbonization
and Gasiﬁcation
YOUICHI KOGA*1

TOSHIO YOSHIDA*1

YOSHINORI TERASAWA*2NORIAKI SENBA*2

TAKESHI AMARI*2

KAZUO SATOU*3

In an effort to reduce greenhouse gases, the sewage sludge carbonization facility for Bio Fuel Co., Inc. and the Bureau of Sewerageof the Tokyo Metropolitan Government started operation in November 2007 using carbonization and gasiﬁcation to sludge disposal.
The woody biomass cogeneration facility for Maeda Road Construction Co., Ltd. is also now in the trial stage of operation. Inaddition, a sewage sludge incineration facility equipped with a circulating ﬂuidized bed incinerator developed for the Environmental
Planning Bureau of the city of Yokohama as a next generation sewage sludge incinerator started operation in September 2007. Theequipment used to carbonize and recycle the sludge generated in its plants was developed by Mitsubishi Heavy Industries, Ltd. (MHI),
and this report introduces MHI’s efforts toward the reduction of greenhouse gases in these biomass-using plants.

of Sewerage of the Tokyo Metropolitan Government andthe woody biomass cogeneration facility for Maeda Road
Construction Co., Ltd. as examples of new MHI biomass
carbonization and gasiﬁcation facilities.

1. Background of the development of biomass
carbonization and gasiﬁcation technology
In November 2000, in an effort to eliminate emissions,
MHI developed equipment to carbonize and recycle thesludge generated in its plants. MHI then delivered a facility
in March 20 05 that gasif ies woody biomass for use as
an electric power generation fuel, and has continuously
expanded the application of carbonization and gasificationt o biom a s s . T h rou gh t he s e ef for t s , M H I h a s b e e nincreasing the numbers of facilities that apply carbonizationand gasification to biomass such as woody biomass andsewage sludge, which are carbon neutral and can reducegreenhouse gases. This report describes the sewage sludge
carbonization facility for Bio Fuel Co., Inc. and the Bureau

2. Introduction of biomass carbonization andgasiﬁcation facilities
2.1 Sewage sludge carbonization facility
The sewage sludge carbonization facility for Bio Fuel Co.,
Inc. and the Bureau of Sewerage of the Tokyo Metropolitan
Government is a commercial, coal-fired thermal power
station that is capable of converting 300 tons of sewage
sludge into carbonized fuel per day. This is the world’s ﬁrst
facility that uses an alternative fuel to offset a portion of thecoal input, contributing to a large reduction in N2 O emissions

Pyrolysis gas combustion furnace
Cake measuring feeder
Sewage sludge

Wet-type electrostatic precipitator
Dryer

Exhaust gas

Char hopper
Flue gas treatment tower
Carbonization reactor

Induction blower
White smoke prevention unit

Circulating gas preheater
Fig. 1 Schematic diagram of a sewage sludge carbonization facility
The major equipment for the facility includes a dryer, carbonization reactor, pyrolysis gas combustion
furnace, ﬂue gas treatment tower, and wet-type electrostatic precipitator.
*1 Yokohama Dockyard & Machinery Works*2 Yokohama Research & Development Center, Technical Headquarters*3 Mitsubishi Jyuko Kankyo Engineering Co., Ltd.
70

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)

Woody biomass(construction anddemolition waste)

Air preheater

Gas combustion chamber

To asphalt mixing plantCombustion air fan
Air supplyfan550°CGascooler

Circulation
fanCrusher

High temperature air (600°C)

1100°C

Wood waste

SteamDenitration reactor
NH3Bag filter

150°C

CycloneBoilerScrubber

Pyrolysis kilnCarbide

Steam
Slaked lime
Special reactant
Activated carbon

Induction
fanStack

Boiler equipment(deaeration unit)

Fly ashExhaust gas heater

Crusher Carbide combustion
chamber
Utilization within premises
Selling electric power
Steam turbine generator

Detoxification treatment

Fig. 2 Schematic diagram of a woody biomass cogeneration facility
The major equipment of the facility includes a pyrolysis kiln, gas combustion chamber, boiler, bag ﬁlter, scrubber, and denitration reactor.

(whose greenhouse effect is 310 times larger than CO2 ). Thisfacility started operation in November 2007. As shown inFig. 1, it consists of a dryer for sewage sludge, carbonization
reactor (indirect heating-type rotary kiln reactor), pyrolysis
gas combustion furnace, flue gas treatment tower to treat
exhaust gas, and wet-type electrostatic precipitator.
The advantages of this facility in reducing greenhousegases are as follows.
(1) The facility reduces the N2 O generated from sludge bycombusting pyrolysis gas at 950°C using the pyrolysis
gas combustion furnace, producing an 80% increase in thereduction compared to a conventional incinerator.
(2) CO 2 is reduced by effectively utilizing carbon neutral
sewage sludge carbide, which has a heavy oil equivalentof 2,500 kL per year, as an alternative fuel to coal.
(3) The facility reduces 37,000 tons per year of CO2 throughthe above process. This amount is equivalent to the CO2
absorbed by a forest whose area is about 1.7 t imes
larger than the area encompassed by the YamanoteLine (63 km 2 ).
2.2 Woody biomass cogeneration facility
The woody biomass cogeneration facility for Maeda Road
Construction Co., Ltd. is Japan’s first facility to carbonate
and gasify woody biomass (95 tons per day) and convert
it into hot air as a heat source for heating asphalt or into
electric power for use within the premises. This contributes
to a large reduction in greenhouse gases through the useof woody biomass as a fuel. Figure 2 shows a schematic
diagram of the facility, which consists of a pyrolysis kiln

(indirect heating-type rotary kiln reactor), gas combustion
chamber, boiler, bag ﬁlter to treat exhaust gas, scrubber, anddenitration reactor.
The advantages of this facility in reducing greenhousegases are as follows.
(1) The facility pyrolyzes woody biomass (wood waste) andcleanly combusts the pyrolysis gas at a low air ratio togenerate electric power.
(2) In concert with the operation of an asphalt mixing plant,
the facility burns thermal decomposition residue (carbide)
as a solid fuel to use this material effectively.
(3) With the aim of reducing the usage of fossil fuels (fuelreduction of about 1,400 kL per year) within the premises
through (2) above, the facility reduces CO2 by 3,700 tons
per year, which represents a 45% reduction.

3. Introduction of next generation sewage sludge
incinerator
I n addit ion to t he appl icat ion of ca rboni zat ion a nd
gasiﬁcation to biomass, a sewage sludge incineration facility
for the Environmental Planning Bureau, city of Yokohama,started operation in September 2007 with the aim of reducing
emissions of greenhouse gases through the introduction ofa next generation sewage sludge incinerator—a circulating
ﬂuidized bed incinerator. This facility reduces the emissionof N2 O generated from sludge and uses less power compared
to conventional bubble ﬂuidized bed incinerators by treating
200 tons of sewage sludge per day in the circulating ﬂuidized
bed incinerator greenhouse gas reduction system. As shown
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Technical Review Vol. 45 No. 1 (Mar. 2008)71

Air preheater

Ceramic filter

CycloneCirculating fluidized
bed incinerator

Exhaust gas

Calcium carbonate
Sewage sludge
AshSewage sludge
Dryer (steam type)

Waste heat boiler

Fig. 3 Schematic diagram of the next generation sewage sludge incinerator
Major equipment of the facility includes a dryer (steam type), circulating fluidized bed
incinerator, air preheater, waste heat boiler, cyclone, and ceramics ﬁlter.

in Fig. 3, it consists of a dryer for sewage sludge (steamtype), circulating fluidized bed incinerator, air preheater,
waste heat boiler, cyclone to treat exhaust gas, and ceramicﬁlter.
The advantages of this facility in reducing greenhousegases are as follows.
(1) The N2 O generated from sludge is reduced through theadoption of high temperature stable combustion (constantcombustion at 850°C) and an in-furnace SOx reduction
system (limestone, oxidation catalyst).
(2) In addition to reducing the electric power consumptionof the combustion air blower through the t wo -stage
combustion method of the circulating f luidized bed
incinerator, elect r ic power consumpt ion is f ur ther
reduced through the use of the steam drying system.
(3) The facility uses carbon neutral digested gas as theassist i ng f uel (10 0 % f ree of fossi l f uels when t heincinerators are replaced).
(4) From the above, the facility achieves a CO2 reduction ofabout 23,000 tons per year just for the old incinerators,
which will soon be replaced.

4. Conclusion
The current status of MHI’s carbonization and gasiﬁcation
technology in the ﬁeld of biomass utilization is described inthis report. MHI’s intention is to work continuously on ourdevelopments in this field and promote our efforts toward
reducing greenhouse gases.

Youichi Koga

Toshio Yoshida

Yoshinori Terasawa

Noriaki Senba

Takeshi Amari

Kazuo Satou

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)72