New Biomass Utilization
Technologies such as Methane
Fermentation and Pyrolysis
YOUICHI KOGA* 1

HIROSHI MIZUTANI* 1

SHINYA TSUNEIZUMI* 1

HIROTAMI YAMAMOTO* 1

MASAYUKI TABATA* 2

TAKESHI AMARI* 2Amid mounting concern over the creation of a recycling society and suppression of greenhouse effect gas, Mitsubishi
Heavy Industries, Ltd. (MHI) is developing a methane fermentation technology and a pyrolysis technology for theeffective use of biomass on a practical basis. Methane fermentation technology has long been used for human wastetreatment and sewage sludge treatment. The technology is now also being used in a methane fermentation and treatment facility exclusively for the treatment of food waste, established in Tokyo in March 2006 by MHI. This facility isoperating smoothly, with a capacity to process 110 tons/day. Pyrolysis technology has also advanced, with the construction of a electric power generation facility for wood-base biomass gasification with the capacity to process about
100 tons/day. This plant was completed in Mie Prefecture in March 2005, and is now operating smoothly. MHI has
also received an order to construct a carbonized fuel production facility from sewage sludge in Tokyo. Once completed,by the end of 2007, the facility will have the capacity to process 300 tons/day. MHI will continue to offer technologies
geared to meeting societal needs through the effective use of biomass, including the extension of the treatment objects.

2.1 Features of methane fermentation technology
Methane fermentation is a technology to effectively
produce energy by converting biomasses with high water content, such as sludge, food residue, and so on for
the generation of methane (CH 4 ) and carbon dioxide(CO 2 ) from organic matter via the action of anaerobic
bacteria under the anaerobic condition. Energy is efficiently recovered from the generated methane gas using

gas engines, fuel cells, boilers, and so on.
While extensive operational results with methane fermentation technology have been collected in fields suchas human waste treatment and sewerage treatment, thetechnology has seldom been applied to the treatment offood waste. This has been changing, however, partly
through the effects of the Food Recycling Law, etc. andpartly through the widely recognized success of newplants manufactured by MHI (introduced in the nextParagraph).
2.2 Operational status of food recycling facilities bymethane fermentation
2.2.1 Outline
The Tokyo Metropolitan Government is promoting theSuper-Eco Town Project for several purposes: to solve
waste issues, to promote the industrial orientation of newenvironmental industries, and to accelerate the realization of a recycling society. Private enterprises have been
invited to act as project implementers for the establishment of waste treatment and recycling facilities on land
owned by the Tokyo Metropolitan Government in theTokyo waterfront area. The work is being carried out aspart of the urban renaissance projects promoted by theJapanese Government.
Among many candidates, a food recycling facility proposed by BIOENERGY Co., Ltd. was selected as a projectsuitable for the Super-Eco Town, based on an overall
evaluation of items such as contribution to recycling soc i e t y, s a f e t y, e n v i r o n m e n t a l p e r f o r m a n c e , t h etechnological level, and so on.

*1 Yokohama Dockyard & Machinery Works*2 Yokohama Research & Development Center, Technical Headquarters

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)

1. Introduction
There has been growing interest in the creation of arecycling society in which wastes are steadily reduced andthe suppression of greenhouse effect gases. Recognitionof the importance of technologies to effectively use biomass, a carbon-neutral resource, is increasing through theintroduction of concepts such as the biomass town concept and enactment of laws such as the Basic Law for
Establishing a Recycling-based Society and the Special
Measures Law Concerning the Use of New Energy by Electric Utilities (Renewables Portfolio Standard (RPS) Law).
Biomass is derived from sources of various types, suchas agricultural, forestry, fishery, stockbreeding, andwaste resources, and the technologies to use those various types also vary widely . This paper summarizes therecent status of the methane fermentation and pyrolysis technologies that have been developed in Yokohama
Dockyard & Machinery Works of MHI and applied to copewith the societal needs described above.

2. Methane fermentation technology

1Fuel cells (MCFC)
Gas holder

Food base waste

Desulfurization
tower

1 unit of 250 kW
Gas engines

BiogasCrusher/separatorEqualizing
tankMethane
3fermentation tanks 2 tanks of 1 960m
Digested sludge

Unsuitable refuse(transferred outside the facility)

Nitrification/denitrification
treatment facility

1 unit of 500kW
1 unit of 250kW

Treatedwater
Discharge ofsewage water

Dehydrator
Drysludge
DryerTransferredoutside the facility

Fig. 1 Flow of food recycling facility
The food wastes brought in are processed by methane-fermentation, then the biogas product is effectively
used for electric power generation, etc.

Table 1 Major specifications of the food recycling facility
Items

Major specifications

DestinationBIOENERGY Co., Ltd.

Completion date
Address
Structure andsize of building

Treatment objects

Methanefermentation tanks

Gas holder

March 2006
In Super Eco Town of Tokyo Metropolitan
Government (3-4-4 Jonanjima, Ota-ku, Tokyo)
Steel-frame construction; 3 abovegroundfloors and 2 underground floors(1) Business-activity-related municipal
solid wastes:
Food residues released from hotels,
supermarkets, convenience stores, etc.
in the Tokyo metropolitan area.
(2) Industrial waste: Animal and plant residue
released from food processing plants, etc.
in the Tokyo metropolitan area.

Fig. 2 Appearance of the food recycling facility
The biogas produced in the methane fermentation tank is transferredthrough a gas holder to gas engines and fuel cells in which biogas iseffectively used.
Table 2 Operation situation of food recycling facility(February 2007)

Facility capacity

110 tons/day

Treatment method

Methane fermentation method

Items

Operation data

Electric power
generation facilities

Fuel cells: 250 kW
Gas engines: 250 kW + 500 kW

Brought-in amount of food waste

1 453 tons/month(daily average: about 52 tons)

Planned power
generation capacity

About 24 000 kWh/day

This food recycling facility was recently delivered byFig
MHI (FigFig.. 1 , Fig. 22, and Table 11). Food recycling treatment has proceeded smoothly in the facility since thefacility went into commercial operation in April 2006.
The facility has the following features.
(1) Methane fermentation and treatment facility withthe capacity to process 110 tons of food waste per day,more than any other facility in Japan.
(2) The world's first plant to sell electric power generated from gas engines and fuel cells through methanefermentation.
2.2.2 Operational situation
Table 2 shows the latest status of plant operation, asof February 2007.

Amount of biogas produced

298 030 m3/month(205 m3/waste ton)Amount of biogas used forpower generation

264 550 m3/month

Major constituents of biogas

CH4: about 60 %CO2: about 40 %Power generation

556 200 kWh/month(383 kWh/waste ton)

Electricity consumed within facility

332 668 kWh/month

Sold electricity

223 532 kWh/month

The planned amount of biogas production, about 120
m 3N/waste ton, is considerably surpassed. The improvement has been attributed to the TS concentration of thefood waste brought into the facility, which is higher thanthe planned value. The concentration of CH4, the chief
Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)

2Table 3 Major specifications of wood-base biomass
gasification electric power generation facility
Major specifications

Items

MIE CHUO KAIHATSU CO., LTD.

Destination

1 050 C
1 400 kWo615 C: Kiln temperature: Oxygen concentration inthe combustion chamber

5%

11:00

12:00

13:00

14:00

15:00

March 2005

Treatment objects

Wood chips

Facility capacity

4 000 kg/hPyrolysis method

Indirectly heated rotary kiln

Electric power
generation facilities

Condensing extraction turbine: 1 400 kWoSteam conditions: 3.0 MPa, 300 C(3) Performs complete combustion of the generated pyrolysis gas in the combustion chamber, to use thepyrolysis gas as a heat source for the pyrolysis kiln,boiler, etc.
3.2 Operational status of an electric power generation
facility based on wood biomass gasification
In March 2005, MHI completed the construction of agasification power generation facility capable of processing about 100 tons of wood-based biomass per day. The
facility, ordered by MIE CHUO KAIHATSU CO., LTD.,is the first large wood-based biomass processing facility
Table 3in Japan (T3). Fig. 4 shows variations of the gas
temperature in the combustion chamber, kiln temperature, oxygen concentration in combustion chamber, andturbine generated electricity over time based on operational data collected of November 2006. The gasification
proceeds stably at a kiln temperature of 615 oC, and agas temperature of 1050oC and oxygen concentration of
5% in the combustion chamber. The turbine generatormaintains a rated 1,400 kW output, supplying the electricity to the facilities in the establishment and playing
a role in the biomass use.
MHI is conducting various surveys and tests aiming
at the use of pyrolysis coke as a safe and environmentfriendly fuel.
3.3 Practical application of sewage sludge
carbonization technology
3.3.1 Outline
Local governments mainly dispose of sewage sludge
by incineration and landfill disposal. Now, however,the first attempts have been made to convert sewage
sludge into carbonized fuel (pyrolysis coke) for the generation of electric power. The project is underway as
a collaboration between the Tokyo Metropolitan Government Bureau of Sewerage and Bio Fuel Co., Inc. (asubsidiary of The Tokyo Electric Power Co., Inc.). The
conversion of sewage sludge into carbonized fuel offers important advantages for the local government,
the entity responsible for coping with the released sewage sludge: (1) improvement of the recycling rate of
the sewage sludge, and (2) reduction of the sludge
treatment cost.

: Gas temperature in thecombustion chamber: Turbine-generated electricityoCompletion date

16:00

TimeFig. 4 Operation data on the wood-base biomass gasificationelectric power generation facility
The stable power generation output of 1400 kW and other properties
confirm that stable

constituent of biogas, has been stably maintained at theplanned value. This favorable performance has enabledelectric power generation of 556,200 kWh/month (383kWh/waste ton), enough to cover all the power consumption of the facility and provide surplus electricity for sale.

3. Pyrolysis technology
3.1 Features of pyrolysis technology
Pyrolysis is a process to effectively use and convert
dry and wet types biomasses and wastes into resources.
Pyrolysis gas and coke obtained by baking organic matter in low oxygen conditions can be used as energy
sources such as electricity, heat, etc. MHI uses a pyrolysis system with an indirectly heated rotary kiln. TheFig. 3system works as follows (Fig.
3):(1) Charges biomass and waste into the pyrolysis kiln
with a charging screw, then treats the biomass andwaste in a low-oxygen atmosphere at high temperatures of 500oC or above.
(2) Adopts an indirect heating method and homogeneously heats the biomass and waste by rotating
the internal cylinder, in order to ensure stabilizedquality.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)

3

The electric power company, the entity that utilizes
the carbonized fuel, gains from the project by (3) acquiring a new energy source. MHI has offered technicalcooperation from the very beginning of this project. We
carried out carbonization tests using actual sewage
sludge in an indirectly heated pyrolysis kiln installed inMHI's shop, and we implemented a pulverized coal combustion test to help us realize the technology to convert
the sewage sludge into fuel. As a result, MHI received
an order from Bio Fuel Co., Inc. to construct a facility toconvert the sewage sludge into carbonized fuel. The facility is now being constructed at a site owned by theTable 4 and Fig. 5Tokyo Metropolitan Government (T5).
3.3.2 Features of the facility
The facility has the following features:(1) Stabilized operation
To suppress the effect of fluctuation of dewateredsludge properties on the operation of the sludge carbonization facility, the water content of the sludge
supplied to the pyrolysis kiln is reduced to about 25%
by pretreatment (drying) of the dewatered sludge witha directly heated dryer.
(2) Carbonized fuel quality
By adopting an indirectly heated rotary kiln, thepyrolysis temperature can be arbitrarily controlled toensure the quality of the carbonized fuel. The operation is planned to be carried out at the safety control
5 in order to prevent sponindices as shown in Table 5,taneous ignition of the carbonized fuel.

(3) Suppression of greenhouse effect gases
In the carbonization treatment of the sewage
sludge, the nitrogen content in the sludge remains in
the pyrolysis coke and the pyrolysis gas can be combusted at a high temperature (950oC or higher). The
amounts of dinitrogen monoxide (global warming potential: 310) generated can therefore be reduced tolevels lower than the amounts generated in the incineration method.
3.4 Approach for diversification of raw materials ofpyrolysis coke
3.4.1 Outline
As mentioned above, MHI has already practicallyapplied two pyrolysis technologies: one to effectively use
energy by converting wood-base biomass into pyrolysis
gas, and one to use the sewage sludge in a commercial
boiler as a coal substitution fuel by converting the sludge
into carbonized fuel. MHI will try to further expand therange of biomasses that can be treated, in order toachieve two targets: enable the use of 90% or more ofwaste-base biomass under endowment within the region,and enable the use of 40% or more of unused biomass
under the biomass town concept promoted by the Ministry of Agriculture, Forestry and Fisheries of Japan.
Through these efforts, MHI identified the characteristics to convert the biomass, including food base waste
and municipal solid waste (MSW), into pyrolysis coke,and constructed a database for study of the applicabilityof the pyrolysis coke.

Table 4 Major specifications of sewage sludge carbonization facility
Major specifications

Items

Pyrolysis kiln

Bio Fuel Co., Inc.

Destination
Planned completion

Within 2007 (planned)

Dryer

In Tobu Sludge Plant of Sunamachi
Water Reclamation Center (Koto-ku, Tokyo)

Address
Treatment objects

Sewage sludge (after dewatering)

Sewage sludge
properties

Water content: about 76 %Combustible content: about 81 %Facility capacity

300 tons/dayPyrolysis method

Indirectly heated rotary kiln

Heating value ofcarbonized fuel produced

About 3 000 kcal/kg(representative property)

Greenhouse effectgas amount

About 10000 tons
converted in CO2 annually

Fig. 5 Appearance of the sewage sludge carbonization facility
A sewage sludge carbonization facility now under construction isscheduled to be completed within 2007.

Table 5 Safety control regarding spontaneous ignition of carbonized fuelControl indices

Objects and items of safety control
During production of carbonized fuels

Carbonization temperature

Countermeasures for prevention of spontaneous ignitionHumidification with water

Safety countermeasures during storage

Temperature, gas concentration, etc.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)

4Food base AConcentration(ppm (O212%),%)

Heating value of pyrolysis coke
Low
High

150

Food base B,
food base C,
wood base: Mixing combustion with 5 cal %of MSW pyrolysis coke

100500Sludge, garbage: Combustion of Hunter Valley
coal alone

NOx (ppm)

CO (ppm)

Ignition lossof ash (%)

Fig. 7 Example of test result of basic combustion chamber
We compared the combustion of Hunter Valley coal alone and mixed
combustion with 5 cal % of MSW pyrolysis coke.
SmallBig
In raw material: fixed carbon/ash content

A wide range of useful data was confirmed during thecombustion test by comparing the combustion of Hunter
Valley coal alone and a mixture of Hunter Valley coaland 5 cal % of MSW pyrolysis coke. To put the developed
technology to practical use, we had to determine the actual mixing ratio of the coal and pyrolysis coke inaccordance with the levels of chlorine, etc. contained in
the MSW pyrolysis coke, in consideration of the boiler
corrosion.

Fig. 6 Fixed carbon/ash content in raw material, andheating value of pyrolysis coke
The heating value of pyrolysis coke corresponds with thefixed carbon/ash content in the raw material.

3.4.2 Basic characteristics of carbonization of various
biomasses
We have elucidated the basic characteristics of thecarbonization of various biomasses. The major features
Fig. 66):
are as follows (Fig.
(1) Though the heating values of pyrolysis coke differ
largely according to the materials, the trend of theheating value agrees roughly with the magnitude of
the fixed carbon content in the raw material.
(2) In order to presume the heating value of pyrolysis
coke from the raw material properties, we must consider not only the fixed carbon content, but also thecontained ash content.
(3) High amounts of chlorine are contained in food wastes
such as garbage, and high amounts of sulfur are contained in sewage sludge.
3.4.3 Basic combustion test of pyrolysis coke
We carried out a basic combustion test to investigate
the feasibility of using pyrolysis coke from MSW as fuel.
MSW from Village "K" was rough-crushed and then carbonization-processed in the pyrolysis kiln of Yokohama
Dockyard & Machinery Works of MHI. The pyrolysis
coke produced was crushed in a coal mill in MHI'sNagasaki Research & Development Center after removing unsuitable refuse, then a basic combustion test wasFig. 7
carried out (Fig.
7).

4. Conclusion
This article has summarized the latest status of themethane fermentation technology and pyrolysis technology now being promoted for practical application at theYokohama Dockyard & Machinery Works of MHI. Bothtechnologies are in practical use. MHI will continue tooffer the latest technologies, including technologies toexpand treatment objects, etc., to respond to the social
need for the more effective use of biomass.

Youichi Koga

Hiroshi Mizutani

Shinya Tsuneizumi

Hirotami Yamamoto

Masayuki Tabata

Takeshi Amari

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)5