An Analysis on the Economics of Biogas Generation Using Food Wastes in Japan
著者名(英) Yoshiki Ogawa, Hiroto Nakajima journal or
publication title
The economic review of Toyo University
volume 35
number 2
page range 97‑113
year 2010‑03
URL http://id.nii.ac.jp/1060/00002358/
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東洋大学「経済論集」
35巻2号 2010年3月
An Analysis on the Economics of Biogas Generation Using Food Wastes in Japan
Yoshiki Ogawa and
Hiroto Nakajima＊
Abstract
In this study， we would like to analyze the economics of biogas generation using fbod wastes in Japan．
We would like to pay our attention especially to the relation between the scale of power generation plant and the gathering cost of food wastes． First， we surveyed and checked various kinds of premise data fbr cost estimation in order to install in our simulation modeL Second， we made a series of simulations through this model by changing several parameters such as number of producing points of fbod wastes， number of gath－
ering roots， gathering charge of fbod wastes， scale ofbiogas plant， operation rate of biogas plant， selling price ofelectricity， government subsidy and so on． Third， we analyzed the economics of biogas generation using fbod wastes based on these simuIation results from various kinds of viewpoints． Forth， we also surveyed barriers and problems in the fbod wastes utilization in Japan． Finally， we discussed the possibility of biogas generation using fbod wastes in Japan．
The conclusions of this paper are as fbllows． First， Japan need to establish the effective recycling methods fbr fbod wastes， but the demands of livestock feed and compost produced from f（）od wastes are almost saturated． Therefbre， the biogas generation is an important and effective option for disposing of food wastes as the third pass in Japan． Second， even in the super large city area（Case l）， we can not expect the good economics of biogas generation using fbod waste without any special treatment such as govemmental subsidy． Japan should prepare a governmental subsidy to biogas generation plant and a special dealing on the gathering charge of fbod wastes or selling price of electricity． In the large city area（Case 2）， we need to limit a small scale of biogas generation plant using fbod wastes gathering from just neighboring points，
’Student， Master’s course， Graduate School ofEconomics， T｛）yo University
because the balance between the scale of plant and the scope of gathering points is required more severely．
Third， Japan also needs to consider the elimination of several barriers and problems in order to improve the economics of biogas generation using food wastes and to expand the effective use of food wastes．
L2鋭456
Contents Introduction
Generation and recycling of food wastes in Japan
Simulation on economics of biogas generation using food wastes Estimation on gathering cost of food wastes
Results analyzed by rnodel simulations
Concluding remarks References
1．lntroduction
The first commitment period of Kyoto Protocol started in 2008． The utilization of biomass residues is one of the most important options fbr achieving Japan’s Kyoto target in the first period． In this study， we would like to analyze the economics of biogas generation using food wastes in Japan． We would like to pay our attention especially to the relation between the scale of power generation plant and the gathering cost of f（）od wastes． We also would like to discuss various barriers to expand effbctive uses of fbod wastes in Ja－
pan・
We developed a simulation model for estimating benefits and costs of biogas generation using food wastes．
First， we surveyed and checked various kinds of premise data fbr cost estimation in order to install in the developed modeL Second， we made a series of simulations through this model by changing several pa－
rameters such as number of producing points of food wastes， number of gathering roots， gathering charge of fbod wastes， scale ofbiogas plant， operation rate of biogas plant， selling price of electricity， gove皿ment sub－
sidy and so on． Third， we analyzed the economics of biogas generation using fbod wastes based on these simulation results from various kinds of viewpoints． Forth， we also surveyed barriers and problems in the fbod wastes utilization in Japan． Finally， we discussed the possibility of biogas generation using food wastes in Japan．
An Analysis on the Economics ofBiogas Generation Uslng Food Wastes in Japan
2．Generation and recycling of food wastes in Japan
The total generation offbod wastes is estimated at about 22 millions ton per year according to the report on
‘℃omprellensive strategies fbr Biomass Japan”（Ministry of Agriculture， Forestry and Fisheries［2002D． The 20％of fbod wastes are recycled as compost， livestock feed or fat materials and the remaining 80％are burned or reclaimed at landfill． However， total l l．36 millions ton food wastes， as shown in Fig．1，that is 4．95millions ton伽m the fbod－production industries and 6．41 millions from fbod－distribution， fbod－retail and fbod－sen・ice industries， are considered to be available for recycling in real terms， because the remaining about l l mi11ions ton fbod wastes廿om general households are required to divide into fUrther small classes．
food－
prOduction
food一 賄0』sak∋
food－retail
food－service
0．O
国
灘講［麺
画
國
1．0 2．0 3．0 4，0 food－waste（millions ton）
5．0
（Source）Made from data in“Survey on recycling uses of f｛）od waste resources，”（Ministry of Agriculture， Forestry and Fisheries I2001－06］）
Fig．1 Generation of Food Wastes by Food lndustry in 2006
From 2001， the Law on the recycling uses of fbod waste resources（abbreviated below as‘‘the Food recy－
cling law”）was enfbrced， and a丘er then， the recycling ratio has improved in fbod industries all together， as shown in Fig．2． Especially， the recycling ratio is quite high in fbod－production industries． On the other hand， the recycling ratio is still low fbod－retail and fbod service industries positioned as the down一
⑨tream sector of fbod distribution．
殉9・8・刀6。5。ω3。2。佃
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food．produCtion．
Average
food●s6rvic』
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3，0
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2．5
2．0
1．5
1．0
0．5
0．0 2001 2002 2003 2004 2005 2006
（Source）Made from data“Survey on recycling uses of food waste resources”
eries［2001－06］）
Fig．2－2 Recycling◎f Food Wastes in Food lndustries
■わod－senfce 目bod’retail ■句od・wholesale 口fO（》d－productior1
．．
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Comp◎st Feed Fats Methane （Ministry ofAgriculture， Forestly and Fish一
2．1Problems in the recycling of food－wastes
The following four methods such as feed use， compost use， fat use and fUel methane use are cited and pro一 vided in the Food recycling law as a means of recycling． However， the following problems are crucial fbr feed use and compost use which have a higher priority．
（Feed use）
Regulation on supply to a ruminant due to BSE problem．
Problem on oil content， salt content， etc．
（Cornpost use）
Reduction of cultivated acreage
Strengthened control oflivestock excreta Quality ofcompost
2．2Amendment of the Food recycling law in 2007
The target of recycling ratio of fbod waste was changed from total 20％to target setting by each industry，
through the amendment of the Food recycling law in 2007． Therefore， fUrther strengthened programs fbr recycling of food wastes are required to food－retail and fbod－service industries in which the recycling ratio of food wastes is still low．
However， the recycling of fbod wastes through compost use and feed use is quite difficult in fbod－retail
An Analysis on the Economics of Biogas Generation Using Food Wastes in Japan
and food－service industries because of problems such as the requirements from demand side and the quality of fbod wastes as an input materiaL Therefbre， the necessity to examine power generation plant using biogas produced by methane fermentation as an acceptance point of food wastes from these industries seems more and more likely．
3．Simulation on economics of biogas generation using food wastes
3．10utline of simulation（1）Purpose of simulation
On the basis of an awareness of the above－mentioned issues， as a biomass energy（to put it concretely，
plant which produces electricity from biogas by methane fermentation using gas－fired engine， etc． and gener－
ated electricity is sold to皿tside）， taking account of the gathering and transportation cost of fbod wastes in detaiL
（2）Structure of Simulation
In the economic simulation of this study， as shown in Fig 3， each item on construction cost and operating cost of biogas plant is estimated first of all based on prior researches（Biomass Research Center［2006】， The Japan lnstitute of Energy【2002，2006】， Mizuho lnformation and Research lnstitute［2007］， NEDO［2005］
and Uchiyama， Yoji［2006］） evaluating the economics ofbiomass power generation plant．
G硫ering Price Sel腫ng Pri◎e Disrib
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Revenue Estimation Fig．3
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Structure of Biogas Power Plant Economics Simulation
Second， the special fUture of simulation in this study is that the necessary cost required for gathering of fbod wastes is estimated by the separate model dealing with dispersed excretion points and gathering routes in detail， because food waste are excreted at nurnerous points in the wide area． Third， we presumed the existence of selling revenue ofgenerated electricity and gathering revenue of food wastes．
The economics of biomass energy plant is evaluated by obtaining net profit which is calculated from the balance between revenues and costs piled up from the respective items of each sector． In addition， the number of plant operating days is assumed to be 330 days． Each item required for the economic simula－
tion will be explained in detail in the following section．
3．2Detailed checks of each item necessary for economic simulation
（1）Expense estimation 1）Construction cost
As fbr the construction cost of biogas fermentation and power generation plant， we adopted data in“Sur－
vey report on database construction to support the introduction ofbiomass energy，”（Mizuho lnformation and Research Institute［2007］）and got Equation l，after making a crosscheck with various similar data…announced in different reports．
（Construction cost）＝153．98＊（Size of plant）＾0．7238＊1000000 （Equation 1）
Fig．4shows the curve of construction cost which changes by depending on the input size of food wastes．
We adopted a fixed amount method as a dealing way of depreciation and basically assumed the number of year fbr depreciation as 15 years． But we also made the input structure of simulation model in order that we could set the number ofyear for depreciation optionally．
2）Operating and maintenance cost
The maintenance and repair cost of plant is assumed at 3％of construction cost according to the general way． The operating cost of plant is estimated at 6，240 Yen／ton on the basis of data in‘‘Survey report on database construction to support the introduction of biomass energy”（Mizuho Information and Research Institute［2007］）．
As for the number of workers in a biogas plant， we adopted the following equation from Mizuho lnforma－
tion and Research Institute［2007］after making a crosscheck with various similar data announced in different reports．
An Analysis on the Economics ofBiogas Generation Using Food Wastes in Japan
（Number of workers）＝U852＊｛（size of plant）〈0．4919｝ （Equation 2）
Fig．4also shows the curve of number of workers which changes by depending on the input size of fbod wastes． This curve is plotted also by data in“Survey report on database construction to support the intro－
duction of biomass energy”（Mizuho lnformation and Research lnstitute［20071）． The labor cost ofplant is calculated by multiplying the corresponding number of workers by 5 miliions Yen／person estimated as an earned income in the transportation／telecommunication／public utility industワsector based on data in“Sur－
vey on eamed income in the private sectors，”（National Tax Agency［2001－2007］）
Cofistruction cost（billions Yen） Numberσf w）rkers 14 25
12
10
8
6
4
2
Construction Cost
（Pbnt utilization rate 70％）
20
15
10
5
Number of Workers
（Pbnt uilization rate 70％）
0 0
0 50 100 150 200 250 300 0 50 100 150 200 250 300 1nput－size of food wastes（tons／day） lnput－size of food wastes（tons／day）
（Source）Made from data in“Survey report on database construction to support the introduction of biomass energy，”（Mi－
zuho Information and Research lnstitute［2007］
Fig．4 Construction Cost and Number of Workers Depending on lnput－size of Food Wastes
In this simulation， the residue of fermentation is assumed to be impossible to be handled as liquid fertilizer in the market， and therefbre， is assumed to be treated by diluting with water． We estimated sewage cost by multiplying necessary water amount by the sewer charge of 200 Yen／m3． But， we did not consider the sewage treatment cost required to secure the sewage quality under which the sewage can be discharged into a sewer．
3）Gathering cost
The estimation on the gathering cost offbod wastes is a work to which we gave the highest priority in this
study， but the detailed explanation of this work will be discussed in the next chapter，‘‘4． Estimation on gath－
ering cost of food wastes．”
（2）Revenue Estimation
l）Gathering revenue of food wastes
We assumed the acceptance price of food wastes as 15，000－20，000 Yen／ton based on the actUal results on the gathering of garbage， etc announced by Wastes and Recycling Session［2006a and 2006b】． By adding this acceptance price to the average transportation cost 27，000 Yen／ton， we estimated the gathering price of f（）od wastes as 47，000 Yen／ton．
2）Selling revenue ofgenerated electricity
The selling Price ofgenerated electricity is set up at 7．8 Yen／kWh as a reference point according to data on weighted average acceptance price of electricity generated from biomass in“Survey on trading prices under the RPS law in 2006”（Agency of Resources and Energy［2007aD．
Vゾealso adopted the electricity charge of l O Yen／kWh， that is， special higher voltage charge to industry and
large office sector and that of 14 Yen／kWh， that is， higher voltage charge to ordinary office sector， based on the data in‘‘Survey on electricity demand from the first quarter of fiscal 2004 through the third quarter of fiscal 2007”（Agency of Resources and Energy［2007b］）． In addition， we also referred to the electricity charge of23 Yen／kWh for lightening－purpose in general household sector．
In the end， we estimated the amount of generated electricity using the total calorie of produced biogas（the generating amount is 160m3／ton and calorific value is 5，000 kcal／m3）and the e缶ciency of power generation obtained f十〇m the following equation：
（Generation efficiency）＝（0．4－0．3）／（ln（10000）－ln（50））
＊（ln（size of power generation）－ln（50））＋0．3． （Equation 3）
4．Estimation on gathering cost of food wastes
4．1Structure of gathering modelFor the sake of effective use of dispersed biomass resources， we need to take account of gathering method of these dispersed resources from numerous outlet points in the wide area． If the size of biomass power generation plant becomes larger and larger， we can reduce the construction cost， etc． more and more because of the scale merit． However， the gathering cost of input biomass resources required fbr the size of biomass
An Analysis on the Economics of Biogas Generation Using Food Wastes in Japan
power generation plant increases more and more on the contrary．
In this study， we made a separate simulation model for dispersed outlets of food wastes in order to estimate agathering cost of fbod wastes． As shown in Fig．5， the simulation model is composed of the following components，（i）ring roads spread out in the state of concentric circle centering biomass power generation plant，（ii）outlets of biomass resources which exist on ring road with a certain interval（d）， and（iii）trunk line roads radiating in all direction to connect biomass power generation plant with ring roads．
Using this model， first， we estimated necessary working time in order to gather necessary biomass re－
sources required from the size of biomass power generation plant． Then， the total gathering cost is calcu－－
lated by multiplying this working time by the unit cost of gathering per hour． By this procedure， we can analyze necessary expense for the gathering of food wastes under different conditions．
4．2Distribution of outlets of food wastes
In this model simulation， we assumed the following distribution conditions of biomass resource outlets
（Case l to Case 4 in Fig．5）on the outlet interval on the same ring road（d）and the interval between two ad－
jacent ring roads（x）．
Case 1 0utlet interval（d） 314 m ring road interval（x） 1㎞
Case 2 0utlet interval（d） 628 m ring road interval（x） 1㎞
Case 3 0utlet interval（d） 1，256 m ring road interval（x） 2㎞
Case 4 0utlet interval（d） 2，512m ring road interval（x） 4km The definition ofd and x is also shown in Fig．5．
876543210q234与喝7 876543210咋234与唱ヲ
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Fig．5 Sructure of Simulation Model for gathering of Food Wastes
一
3 4 5 6 7 8
In order to check the suitability of this gathering model， we compared the distribution density of biomass outlets in the model with the distribution density of convenience stores per inhabitable area in respective prefectures． The results are as follows．
Case l 10．26／㎞2 Tokyo Pref． 12．27／㎞2
Case 2 5．09／㎞20saka Pref 6．20／km2 Kanagawa Pref．6．53／㎞2 Case 3 1．27／㎞2 Shizuoka Pref．1．38／km2 Nara Pref． 1．23／㎞2 Case 4 0．32／㎞2 Hokkaido Pref．0．35／km2 Shimane Pref O．38／㎞2
We can easily understand that the area having the same density of convenience store as the density as－
sumed in Case l to 4 is actually existing．
An Analysis on the Economics ofBiogas Generation Using Food Wastes in Japan
4．3Estimation of the unit gathering cost per hour
Outlets of food wastes presumed in this study are convenience stores． The excreting amount of food wastes from one convenience store is assumed at O．02 ton／day． The vehicle fbr gathering food wastes is assigned to packer vehicle having the maxirnum load capacity of 1．5 tons． The assumed work procedure of a packer vehicle is as f｛）llows． This packer vehicle visits excreting outlets one by one with running veloc－
ity of 30 km／hour and goes back to the biomass power generation plant when the load amount of food wastes reaches to l ton。
The time of gathering work at each outlet is assumed to be one minute． After visiting 500utlets（this means the finish of l ton loading of fbod wastes）， the time of unloading work at biomass power generation plant is assumed to be three minutes．
We can obtain total working time fbr gathering l ton fbod wastes by summing up the following four fac－
tors：（a）the running time from the plant to the first outlet via the trunk Iine road，（b）the running time from the first outlet to the 50th outlet and the loading time at each outlet，（c）the running time from the 50th outlet to
the plant via the trunk line road， and（d）the unloading time at the plant． The gathering expense of l ton f（）od wastes are calculated by mu】tiplying the above－mentioned total working time by the unit gathering cost per hour．
We estimated the unit gathering cost per hour of food wastes on the basis of the unit gathering cost per hour ofcombustible garbage by the local governrnent shown in Table L
Table 1 Unit Gathering Cost per hour of Combustible Garbage by Local Government （Case example oflchikawa city in Chiba Pref．）
Amount ofcombustible garbage gathered Commission fee to the private companies
Unit gathering cost per l ton of combustible garbage Amount of combustible garbage gathered per day by 2 ton packer vehicle
Working time per day by 2 ton packer vehicle
89，818ton 834，743，000Yen 9，294Yen／ton
6．698ton
5hours
The unit gathering cost per hour of combustible garbage is estimated as 12，450 Yen／hour using the data shown in Table 1． We assumed the unit gathering cost per hour of food wastes would be the same， that is，
12，450Yen／hour．
5．Results analyzed by model simulations
5．1Result on the base case simulationWe made a various kind of model simulations in this study in order to analyze economics of biomass power generation using fbod wastes． One of the representative results obtained from these analyses are shown in Fig．6． This result is obtained under the following conditions；（a）47，000 Yen／ton gathering price of fbod wastes，（b）7．8 Yen／kWh selling price of generating electricity，（c）70％utilization rate of pOwer gen－
eration plant，（d）15 years depreciation period and（e）no subsidy to constnlction cost（initial investment）．
Case l to Case 4 shown in Fig．6are corresponding to distribution cases on excretion outlet of food wastes，
respectively， which is discussed in detail in the preceding section，‘‘4． Estimation on gathering cost of fbod wastes．，，
We can get the fbllowing implication and consideration廿om this result． First， we compared the eco－
nomics of biogas generation by changing number of producing points of fbod wastes． The results showed that the economics of biogas generation using food wastes is better in the super Iarge city area（Case l）and large city area（Case 2）which has a high density on producing points of fbod wastes than in the small city area（Case 3）or rural area（Case 4）which has a low density on producing points of food wastes．
Second， we analyzed the relation between the scale of biogas generation plant and the scope of gathering points of fbod wastes． In the super large city area（Case 1）which has a high density of gathering points， the biogas generation plant dealing 40 through 100 ton fbod wastes per day showed the best and similar eco－
nomics． The economics of the plant dealing less than 40 ton become worse because of the economics of scale and the economics of the plant dealing more than l OO ton become worse because of the increasing gathering cost． This means that there is the most suitable size of plant where both of the scale merit of plant size and the increase of gathering cost are well－balanced．
Third， even in the case of‘‘Case 1”having the highest density of excretion outlets of fbod wastes， the eco－
nomics of biogas power generation plant can not show a positive net benefit without special supports． This result supports the present situations where some introductions of biogas power generation plant in the pri－
vate sector are apPearing with some special supPorts・
（1、OOOYenfton）
000821 0064 1
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1
0
An Analysis on the Economics of Biogas Generation Using Food Wastes in Japan
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100 150 200 250 300 0 50 100 150 200 250
｜nputsize◎f plant（tonlday） lnputsize of plarlt（tonlday）
Base Case Simulation Results on the Econ◎mics of Biogas Power Generation Plant
300
Forth， in the small city（Case 3）or mral area（Case 4）which has a quite low density of gathering points，
the biogas generation plant dealing 5 through 15ton fbod wastes per day showed the highest but large nega－
tive economics． The economics of the plant dealing more than l 5 ton become worse rapidly because of the increasing gathering cost．
Fi食h， the most suitable plant size is also lowered rapidly fそom about 60 ton in Case l，about 40 ton in Case
2，about 15 ton in Case 3 to about 5 ton in Case 4， as the distribution density of excretion outlets of fbod wastes is lowered． We can easily understand that biogas power generation in lower density area is unprof二 itable because the influence ofgathering cost is quite large．
5．2Simulation results on improvement of profitability by eXternal supports
We analyzed the pro行tability of biogas generation plant in the preceding section． Even in the super large city area（Case 1）which has a high density of gathering points， we can not get the positive profitability of biogas generation plant without special treatments such as government subsidy， special charge or price and so on． In addition， in the large city area（Case 2）， the small city area（Case 3）and the rural area（Case 4）which has a low density of gathering points， we can get large negative results on any scale of biogas generation plant without special treatments．
In this section， we made several model simulations related to special external supports to Case l（the super large city area）in order to observe the improvement of profitability brought by them． These simulation
results are shown in Fig．7． The simulations is made for the following four external supports；（a）govem．
ment subsidy to construction cost（initial investment），（b）increase of plant utilization rate，（c）support to gathering price of fbod wastes， and（d）support to purchase price of generated electricity．
The results show that the economics of biogas plant in Case l is improved from negative to positive if the more than 50％of construction cost is subsidized by govemment． The economics of biogas plant is also improved from negative to positive ifthe gathering price is increased to more than 53，000 Yen／ton． How－
ever， the negative economics of Case l is not easy to be tumed to positive by increase of plant utilization rate and by supPort to purchase price ofgenerated electricity・
The economics ofbiogas plant is improved from negative to positive if the plant utilization rate reaches to lOO％． The economics of biogas plant is changed from negative to positive if the purchase price of gener－
ated electricity reaches to 23．8 Yen／kWh which is the similar level ofelectricity charge in the household sec－
tor．
（1，000YerLtton）
（1，000Yentton）
Chage8 in SUbsidy to
6．0 6、0
4、0
2．0
0．0
一2．0
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一6．0 0
（1．oeOYentton）
6．0
4．o
2．0
0，0
一2．0
一4．0
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Fig．7
50 100 150 200 250 1nputsize of plant（ton／day）
Support to
300
0 50 100 150 200 250 1nputsize of ptant（tontday｝
300 4．0
2．0
0．0
一2．0
一4．0
一6．0
0
（1，COOYeniton）
6．0
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250 300
0 50 100 150 200 1nputsize of ptant（tenlday｝
250 300
lmprovement◎f Profitability by EXternal Supports in Case 1（the super targe city area）
An Analysis on the Economics of Biogas Generation Using Food Wastes in Japan
5．3Suitable combination of external support
Considering the simulation results described in the preceding section， the support by a single option is not areasonable tool even for Case l（the super large city area）． Therefore， we need to consider the suitable combination of extemal support options as a next step． Figure 8 shows simulation results on some combi－
nations ofexternal support options such as govemment subsidy， special charge or price and so on．
As shown in Fig．8， we can conclude that the fbllowing two combinations of extemal supports would be suitable and reasonable for the improvement of the profitability on biogas power plant in Case l（the super large city area：（1）30％government subsidy to construction cost（to initial fixed cost）and increase ofgather－
ing price from 47，000 Wton to 50，000 Wton， or（2）30％gove㎜ent subsidy to construction cost（to initial fixed cost）and increase of purchase charge of generated electricity丘om 7．8 Yen／kWh to l 3．8 Yen／kWh which is the electricity charge level in the commercial sector．
（1，000Yeniton｝ （1，0eOYenlton）
5 5
0
一5
一10
一15
30％subsidy
＋31000Yenlton
0
一5
一10
一・P5
50％subsidy
＋9，000Yen！ton
＋6．O Yen／kWh
50％subsidy
＋6，000Yen／ton
一20 －20
0 50 100 150 200 250 300 0 50 100 150 200 250 300 1nputsize of plant（tonlday） lnputsize of plant（tonfday｝
Fig．8 Suitable and Reasonable Combination of External Supports in Case 1（the super large city area）and Case 2（the large city area）
On the other hand， as fbr Case 2（the large city area）， we can not find a satisfactory solution， for example，
by the combination ofexternal supports such as 50％government subsidy to construction cost and increase of gathering price from 47，000 Yen／ton to 53，000 Yen／ton， also as shown in Fig．8． We can get a positive economics under the combination of extemal supports such as 50％govemment subsidy to construction cost，
increase of gathering price from 47，000 Yen／ton to 56，000 Yen／ton and increase of purchase charge of gener一
ated electricity from 7．8 YenfkWh to 13．8 Yen／kWh at last． However． we can not conclude that this final result would be a suitable and reasonable solution which should be adopted．
Needless to say， as f（）r Case 3（the small city area）and Case 4（the rural area）， we cannot find any suitable and reasonable support methods to improve profitability．
6．Concluding remarks
The conclusions of this paper are as follows． First， Japan need to establish the effective recycling meth－
ods for food wastes， but the demands of livestock feed and compost produced from fbod wastes are almost saturated． Therefbre， the biogas generation is an important and effective option for disposing of food wastes as the third pass in Japan．
Second， even in the super large city area（Case 1）， we can not expect the good economics of biogas genera－
tion using food waste without any special treatment such as governmental subsidy． Japan should prepare a governmental subsidy to biogas generation plant and a special dealing on the gathering charge of food wastes or selling price of electricity． In the large city area（Case 2）， we need to limit a small scale of biogas gen－
eration plant using food wastes gathering from just neighboring points， because the balance between the scale ofplant and the scope of gathering points is required more severely．
Third， Japan also needs to consider the elimination of several barriers and problems in order to improve the economics ofbiogas generation using food wastes and to expand the effective use of food wastes．
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