- Email: [email protected]
Methane production from animal wastes and its prospects in Japan
METHANE
PRODUCTION FROM ANIMAL ITS PROSPECTS IN JAPAN
WASTES AND
K1YONOR1 HAGA, HIROSHI TANAKA & SHIGEMITSU HIGAKI
Department of Feeding and Management, National Institute of Animal Industry, Ministry o/ Agriculture and Forestry, Chiba-shi 280, Japan
ABSTRACT
Animal waste accumulation, due to #Ttensivefarming, and the energy shortage prompt a reappraisal of methane fermentation of animal wastes in terms of juel and fertiliser production as well as waste management in Japan. Initial experiments on methane fermentation of pig wastes were performed using a 200-litre digester and extension work is being conducted in several Prefecture Livestock Experiment Stations. The prospects for methane fermentation of animal wastes in Japan are discussed in this" paper and potential gas production is assessed.
INTRODUCTION
The recent world energy shortage necessitated the development of alternative energy sources to replace fossil fuels which will be depleted in the near future. This is a very urgent problem, especially in Japan where the energy dependence on imported fuels reaches about 88%. Among the alternatives, bioconversion of organic wastes through methane fermentation into fuel gas seems to be most feasible. In addition, animal wastes, which amount to about 56 million tons per year in Japan, are causing serious pollution problems. Therefore, methane fermentation of animal wastes is attracting considerable attention not only in terms of waste management but also in terms of production of both energy (biogas) and liquid fertiliser (digested slurry). We will in this paper review work on methane production from animal wastes in Japan and describe its current status and future prospects, referring particularly to our own work. As gaseous fuels are more convenient than conventional solid ones, many people have been interested in producing methane from organic wastes. Various types of 45 Agricultural Wastes (1) (1979)--© Applied Science Publishers Ltd, England, 1979 Printed in Great Britain
46
KIYONORI HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI
digester for an individual farm have been designed and some of them are still being operated. According to an investigation by Ono (1963), patents and working models for methane fermentation presented from 1926 to 1960 amounted to 48 and 178 cases, respectively. However, the wastes used for these digesters were mostly kitchen rubbish, etc. and animal wastes and night soil were scarcely used, as is shown in the review by Ono. He made a comprehensive compilation of such projects, and designed the digester for animal wastes shown in Fig. 1, which, it was suggested, would provide enough energy for cooking, heating washing water and space heating for a farm. The system was moderate in construction and maintenance expenditure Gas ( - - ~
(Floating cover ~Weight ~, g
--'1 _. ~Outletl~
Gas
...
wo,,e, k
" ~ @ < A .... " / /
/
k
Digester Fig. 1.
Old-type facilities for methane production (Ono, 1963).
and was widely used in many farms around the 1960s. The gas production, however, was poor in cold winter weather when more energy is demanded and the maintenance was rather tedious. Thus, when L P G became available at low price, sooner or later most facilities were abandoned and replaced by LPG. Recently, the animal industry in Japan has expanded rapidly with the increasing demand for animal products resulting from the increase in Japanese living standards. This expansion is characterised by a rapid increase in numbers of animals and by a drastic decrease in the number of farms. For example, the average number of pigs per farm in 1977 was about 11-6 times that in 1962, as shown in Table 1. Increasing confinement of animals results in the accumulation of wastes in limited areas as well as an increase in pollution problems (Tables 2, 3 and 4). TABLE 1 CHANGES IN THE NUMBEROF PIGS AND PIG FARMS
Year
1962
1967
1972
1977
Number of pigs (thousands) Number of pig farms (thousands) Pigs perji~rm
4030 1030 3"9
5980 650 9"2
6980 340 20-6
8132 179 45.4
47
METHANE PRODUCTION FROM ANIMAL WASTES TABLE 2 CALCULATED ANIMAL WASTE PRODUCTION
Animal
Number of head (thousands)
Pig Layer Broiler Dairy cattle Beef cattle
8132 120810 103330 1888 1987
Total
(1977)
Faeces Urine Total (thousand tons per year) 5580 6062 2835 18609 10460
6541 3989 2415
12121 6062 2835 22598 12875
43546
12945
56491
TABLE 3 SELECTED STATISTICS ON LAND USE ( 1 9 7 5 )
Items
Area (thousand ha)
Total land area Land in farm Paddy field Arable land (except paddy field) Orchard field Forage field Other cultivated field
37748 5674 3172 2402 628 485 1289
TABLE 4 POLLUTION PROBLEMS CAUSED BY ANIMAL WASTES ( 1 9 7 6 )
Number of problems
Percentage (~!~)
Kinds of problem Odour Miscellaneous
Animal
Water pollution
Total
Pig Poultry Dairy cattle Beef cattle Miscellaneous
2242 263 902 465 6
2279 1397 1448 655 26
32 31 27 9 3
3937 1549 1969 935 31
Total
3883
6205
102
8421
Pig Poultry Dairy cattle Beef cattle Miscellaneous
56.9 17.8 45-8 49.7 19.4
68.0 90-2 73.5 70.1 83-9
0.8 2"0 1.4 1"(1 9-7
(46-7) (18"4) (23"4) ( 11.1 (0.4t
Total
46.1
73.7
1.2
(100)
48
KIYONORI HAGA, HIROSH! TANAKA, SHIGEMITSU HIGAKi
However, animal wastes are rich in nutrients for crops and can be considered as valuable resources if only they are treated properly. Therefore, the most desirable solution for pollution problems due to animal wastes should involve proper treatment on the assumption of the application of the wastes to land. The situation of the animal industry in Japan has thus prompted us to reappraise methane fermentation of animal wastes to produce both fertiliser and energy. Research and development in this field is briefly described in the following section.
METHODS AND RESULTS
Basic e.¥periments (Agric. Forest. Fish. Research Council, 1975) The initial studies on methane production from animal wastes were carried out using a cylindrical digester (Fig. 2) made from F R P (Fibre-glass Reinforced Plastic). The scale of the digester (200 litres) was suitable for the waste from one pig and it contained about 150 litres of waste slurry. The temperature was kept at 35 °C by circulating hot water through a coil in the slurry. The digester was insulated by a 5 cm layer of glass fibre. Inlet
Stirrer lWater pipe for heating
Gas
o0,,0,
g
Water Digester (200 Iitres ) Fig. 2.
Gas meter
Gas holder (2001itres)
Experimental facilities for methane production.
A methane fermentation was developed from a mixture consisting of 44 kg of fresh pig faeces and 88 litres of tap water with 30 litres of anaerobically-fermented cow dung as seed for the fermentation. After the development period with intermittent loading as shown in Fig. 3, an ecosystem where pig wastes were smoothly converted into biogas was attained and then daily loading of the substrate into the digester was started. The daily loading was 7.5 litres of slurry consisting of 2-5 kg of pig faeces and 5 kg of tap water (3-2 kg
49
METHANE PRODUCTION FROM ANIMAL WASTES
•
lifres/dQy 80
pH
~5
160 4
Gas production
t /
~I~¢"
ppm 60 n
CH4 % 50 t n L t t--nH2Sl t t, 10 20 :30 40 50 60 70 80 90 days
Fig. 3.
Progress of acclimatisation for methane production (arrows: charging wastes).
organic matter metre -3 digester d a y - l ) . Digester temperature was 35°C and stirring was at a rate of 60 rpm, 15 min h - ~. In the established digestion 170-200 litres d a y - ~ of biogas which contained, on average, 62.2 °~ilmethane, 37-8 ~o carbon dioxide and 150 ppm hydrogen sulphide was produced. The digested slurry is useful for fertiliser (Table 5) and has a much less offensive odour than swine faeces (Table 6). After one year of operation, it was felt that the complexity of having both stirring and heating systems might not be necessary. Thus, to simplify the system, we put a submersible pump (165 W), operated by a timer, into the digester and succeeded in TABLE 5 CHARACTERISTICS OF
PIG FAECES S L U R R Y BEFORE A N D AFTER DIGESTION
( 1) Pig fiwces slurry bejore digestion Total ~solids (",)
Organic matter (%)
Volatile [~ltty acid ( VFA ) (mg litre-1)
7-73
6.31
2048
(2) Digested slurry Total solids (%)
Organic matter (%)
VFA (rng litre 1)
TKN
5"20
3"68
79
6"19
NH,~-N P20 5 ( %, Dr)" basis) 1"29
7'58
K20
2-70
50
KIYONOR1 HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI TABLE 6 R E M O V A L OF M A L O D O R O U S C O M P O U N D S T H R O U G H M E T H A N E F E R M E N T A T I O N
TO a Indole, #g Skatole, ttg p-Cresol, m g N H 3, m g (CH3)3N,/~g V F A C2, m g C 3, rag iC4, rng C4, m g C5, mg
Pig faeces (400 ml)
Slurry, digested (400 ml)
10000-20000 520 1000 4-2 61 290 96 68 14 52 44
2000-5000 1 980 0.3 170 90 38 1-5 0.1 0.3 O-1
a T O = threshold odour.
maintaining the temperature of the digester at 35 °C without any problems for two years (Fig. 4). The above results enabled us to build the following pilot plants, which are now in operation.
Extension work (National lnstitute of Animal Industry, 1978) Several Prefecture Livestock Experiment Stations are carrying out pilot-plant scale experiments in co-operation with us. Kagawa Prefecture Livestock Experiment Station: The type of digester is the same Timer
~nlet
Ii -~.Gas(sameasFig2. ) !../×..>~/,-/.f. v//'-;//..'/) I~.' •//.~, ).././/,.~.,~-'..
/ ~'X,.~
I
z/t/ Ostes
I
1/
" -
L XSubmersible Fig. 4.
Digester operating with a submersible p u m p performing both stirring and heating (modification from Fig. 2).
METHANE PRODUCTION FROM ANIMAL WASTES
5]
Digester (5 m3) mode of FRP
Storage tank
Inlet
i
1734ee
Outlet -
I
Temperatun controller Submersible
Switch box
Gas meier Fig. 5.
Ground level
Facilities for methane production at Kawaga Prefecture Livestock Experiment Station.
_
,,,,,~ Vmylhouse
Gas
Y Piggery
]~
~
]L6~ressuregauge~ t
] III II~esulphurisation IWIII
reagent
-fi~ii II
-I~
II
"~~ ~ " - ~ i l G o s meier Gasho,der ~as
t)I
Storage ta,nk
Ill II /'A
Submersible k'l
Digester (41,5 m ~ ) made of concrete Fig. 6.
Facilities for methane production at Kochi Prefecture Livestock Experiment Station.
52
KIYONORI HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI
as ours but the scale is 16 times larger (3 m 3) (Fig. 5). The digester is equipped with a submersible pump (0-4 kW) and is operated under mesophilic conditions (35 °C). Biogas generated from pig wastes is stored in a gas holder (1.8 m s) and is used for the experiment of running a modified gasoline engine (5 hp per 2000rpm), which consumes 24.6 litres of biogas in 1 h. Kochi Prefecture Livestock Experiment Station: A septic tank used for pig wastes was converted into the digester by making the modification shown in Fig. 6. The digester runs under mesophilic conditions at around 30°C. The gas is being supplied to two brooders for 500 chicks in winter and to a grass drier at other seasons. Ehime Prefecture Livestock Experiment Station: A bag-type digester made from vinyl or polyethylene film is now under construction and will be used for mesophilic fermentation of pig wastes with the aid of a submersible pump and direct solar radiation. Nagano Prefecture Livestock Experiment Station." The digester (220m3), constructed under the housing for 30 head of dairy cattle, is now in operation (Fig. 7). Wastes from the dairy cattle are introduced by gravity into the digester with two
\ I
Housing for .30 head of dairy cattle Partly slotted floor .
.
.
.
.
.
.
.
.
.
.
.
.
.
~" L~'~';"-,~" ""-"v'"": w"J -'" " ~-~l'~t'~ "Gutter rJ
.
.
.
.
Wastes .
~
I I
I Gas
.
"~"-'~' ~ " Gas
Waste slurry
'" ~'!! "~'" ~;I I rIOutl^t -
~,-,
c
[~[
.I,II Screen
Fig. 7.
Submersible p u m p s ( 3,7 k W ) " ...... """~
Facilities for methane production at Nagano Prefecture Livestock Experiment Station (verticalsection view).
submersible pumps for stirring and heating. The pumps are surrounded by screens which prevent clogging caused by coarse organic material. The gas produced is to be used to generate steam and provide hot water.
Hiroshima Prefecture Livestock Experiment Station--Department of Poultry." Experiments on methane production from poultry wastes are being carried out by using a digester (290 litres) very similar to ours, and biogas is obtained at a rate of 378 litres kg-~ Total Solids added.
Hiroshima Prefecture Livestock Experiment StationlDepartment of Pigs." Systematic experiments with a larger installation are being performed at this station (Fig. 8). Wastes from 200 head of pigs are mixed with 2-3 volumes of tap water and
>.,
g
~J
2 E
o
o
.o
.-~ .E ,J o~
E
o
o
E 0
J~
,©
!.
o.
©
©
o
\ ~n
c-..
J=
E \, \
,©
E
i (.9~, (.9
~ r-.-~
i~
r~
~7
~o g o
54
KIYONORI HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI
charged into two digesters every day. The digesters, with polyurethane insulation, are kept under mesophilic conditions by submersible pumps and produce enough gas to run air-conditioning facilities for about 8 h each day. In the Department, investigation on methane production from pig wastes, utilisation of the gas, effects of air-conditioning on pigs, fertiliser value of slurry digested, economic aspects of the system, etc., are now being studied.
DISCUSSION
The procedures for methane production from animal wastes have been almost established but problems of handling, transportation and charging of the wastes, utilisation of the gas produced and the slurry digested and designing efficient facilities at reasonable prices are still to be solved. Various types of digester are being operated at several Experiment Stations as mentioned above and which type of digester is most satisfactory in Japan will become clear in the near future. As noted by Morris et al. (1975), the important benefits of anaerobic digestion of animal wastes include stabilisation of the organic matter, reduction of offensive odour and production of useful fuel gas, without decreasing the fertiliser value of the wastes. Plant nutrients such as N, P205 and K20 contained in animal wastes produced in Japan correspond to about 70 ~ of the amount of chemical fertiliser used in Japan. Moreover, organic matter in the digested slurry favourably affects soil condition. Liquid slurry wastes, however, are more difficult to transport or to handle than solid wastes in the agricultural system of Japan. This bottleneck for utilisation of digested slurry as fertiliser has to be solved by stimulating the distribution of liquid manure. If the total amount of animal wastes could be subjected to methane fermentation, the following amount of biogas and energy would be yielded. Animal Wastes
5.6
X
l0 T ton year-
matter content: 10 ~o t'--].(organic 300 m 3 of biogas ton- 1 of org. matter 1.68
I Biogas produced
x 10 9 m 3
year-
, .... 6000 kcal m-3 of biogas 1-01
Energy produced
t
x
1013
kcal year -~
- --107 kcal klitre- ~ of petroleum
Petroleum equivalent to the energy
1-01
x 10 6
klitre year 1
METHANE PRODUCTION FROM ANIMAL WASTES
55
A l t h o u g h the energy obtained from biogas is no more than 0.27 ~o o f the annual c o n s u m p t i o n o f energy in J a p a n (about 3.8 x 10 is kcal year-1), it is nevertheless a b o u t 18 ~o o f the agricultural c o n s u m p t i o n o f petroleum (about 5.5 x 106 klitres y e a r - 1). On the other hand, as an average Japanese family uses 7 0 m 3 o f fuel gas per m o n t h , the biogas from animal wastes could supply 2 million families.
REFERENCES AGRICULTURE, FORESTRY AND FISHERIESRESEARCHCOUNCIL, MINISTRY OF AGRICULTUREAND FORESTRY
(1975). The Report on Research and Development of the Techniques for Animal Waste Management 1974. Tokyo, pp. 197-216. (In Japanese.) MORRIS,G. R., JEWELL,W. J. & CASLER,G. L. (1975). Alternative animal waste anaerobic fermentation designs and their costs. In: Energy, agricuhure and waste management (Jewell, W. J. (ed.)), Ann Arbor Science, Michigan. NATIONAL |NSTITUTE OF ANIMAL INDUSTRY, MINISTRY OF AGRICULTURE AND FORESTRY (1978). Research
subjects of Prefecture Livestock Experiment Station, Chiba. (ln Japanese.) ONO, J. (1963). Principles and practices of methane production. Bungado, Tokyo. 271 pp. (In Japanese.)
PRODUCTION FROM ANIMAL ITS PROSPECTS IN JAPAN
WASTES AND
K1YONOR1 HAGA, HIROSHI TANAKA & SHIGEMITSU HIGAKI
Department of Feeding and Management, National Institute of Animal Industry, Ministry o/ Agriculture and Forestry, Chiba-shi 280, Japan
ABSTRACT
Animal waste accumulation, due to #Ttensivefarming, and the energy shortage prompt a reappraisal of methane fermentation of animal wastes in terms of juel and fertiliser production as well as waste management in Japan. Initial experiments on methane fermentation of pig wastes were performed using a 200-litre digester and extension work is being conducted in several Prefecture Livestock Experiment Stations. The prospects for methane fermentation of animal wastes in Japan are discussed in this" paper and potential gas production is assessed.
INTRODUCTION
The recent world energy shortage necessitated the development of alternative energy sources to replace fossil fuels which will be depleted in the near future. This is a very urgent problem, especially in Japan where the energy dependence on imported fuels reaches about 88%. Among the alternatives, bioconversion of organic wastes through methane fermentation into fuel gas seems to be most feasible. In addition, animal wastes, which amount to about 56 million tons per year in Japan, are causing serious pollution problems. Therefore, methane fermentation of animal wastes is attracting considerable attention not only in terms of waste management but also in terms of production of both energy (biogas) and liquid fertiliser (digested slurry). We will in this paper review work on methane production from animal wastes in Japan and describe its current status and future prospects, referring particularly to our own work. As gaseous fuels are more convenient than conventional solid ones, many people have been interested in producing methane from organic wastes. Various types of 45 Agricultural Wastes (1) (1979)--© Applied Science Publishers Ltd, England, 1979 Printed in Great Britain
46
KIYONORI HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI
digester for an individual farm have been designed and some of them are still being operated. According to an investigation by Ono (1963), patents and working models for methane fermentation presented from 1926 to 1960 amounted to 48 and 178 cases, respectively. However, the wastes used for these digesters were mostly kitchen rubbish, etc. and animal wastes and night soil were scarcely used, as is shown in the review by Ono. He made a comprehensive compilation of such projects, and designed the digester for animal wastes shown in Fig. 1, which, it was suggested, would provide enough energy for cooking, heating washing water and space heating for a farm. The system was moderate in construction and maintenance expenditure Gas ( - - ~
(Floating cover ~Weight ~, g
--'1 _. ~Outletl~
Gas
...
wo,,e, k
" ~ @ < A .... " / /
/
k
Digester Fig. 1.
Old-type facilities for methane production (Ono, 1963).
and was widely used in many farms around the 1960s. The gas production, however, was poor in cold winter weather when more energy is demanded and the maintenance was rather tedious. Thus, when L P G became available at low price, sooner or later most facilities were abandoned and replaced by LPG. Recently, the animal industry in Japan has expanded rapidly with the increasing demand for animal products resulting from the increase in Japanese living standards. This expansion is characterised by a rapid increase in numbers of animals and by a drastic decrease in the number of farms. For example, the average number of pigs per farm in 1977 was about 11-6 times that in 1962, as shown in Table 1. Increasing confinement of animals results in the accumulation of wastes in limited areas as well as an increase in pollution problems (Tables 2, 3 and 4). TABLE 1 CHANGES IN THE NUMBEROF PIGS AND PIG FARMS
Year
1962
1967
1972
1977
Number of pigs (thousands) Number of pig farms (thousands) Pigs perji~rm
4030 1030 3"9
5980 650 9"2
6980 340 20-6
8132 179 45.4
47
METHANE PRODUCTION FROM ANIMAL WASTES TABLE 2 CALCULATED ANIMAL WASTE PRODUCTION
Animal
Number of head (thousands)
Pig Layer Broiler Dairy cattle Beef cattle
8132 120810 103330 1888 1987
Total
(1977)
Faeces Urine Total (thousand tons per year) 5580 6062 2835 18609 10460
6541 3989 2415
12121 6062 2835 22598 12875
43546
12945
56491
TABLE 3 SELECTED STATISTICS ON LAND USE ( 1 9 7 5 )
Items
Area (thousand ha)
Total land area Land in farm Paddy field Arable land (except paddy field) Orchard field Forage field Other cultivated field
37748 5674 3172 2402 628 485 1289
TABLE 4 POLLUTION PROBLEMS CAUSED BY ANIMAL WASTES ( 1 9 7 6 )
Number of problems
Percentage (~!~)
Kinds of problem Odour Miscellaneous
Animal
Water pollution
Total
Pig Poultry Dairy cattle Beef cattle Miscellaneous
2242 263 902 465 6
2279 1397 1448 655 26
32 31 27 9 3
3937 1549 1969 935 31
Total
3883
6205
102
8421
Pig Poultry Dairy cattle Beef cattle Miscellaneous
56.9 17.8 45-8 49.7 19.4
68.0 90-2 73.5 70.1 83-9
0.8 2"0 1.4 1"(1 9-7
(46-7) (18"4) (23"4) ( 11.1 (0.4t
Total
46.1
73.7
1.2
(100)
48
KIYONORI HAGA, HIROSH! TANAKA, SHIGEMITSU HIGAKi
However, animal wastes are rich in nutrients for crops and can be considered as valuable resources if only they are treated properly. Therefore, the most desirable solution for pollution problems due to animal wastes should involve proper treatment on the assumption of the application of the wastes to land. The situation of the animal industry in Japan has thus prompted us to reappraise methane fermentation of animal wastes to produce both fertiliser and energy. Research and development in this field is briefly described in the following section.
METHODS AND RESULTS
Basic e.¥periments (Agric. Forest. Fish. Research Council, 1975) The initial studies on methane production from animal wastes were carried out using a cylindrical digester (Fig. 2) made from F R P (Fibre-glass Reinforced Plastic). The scale of the digester (200 litres) was suitable for the waste from one pig and it contained about 150 litres of waste slurry. The temperature was kept at 35 °C by circulating hot water through a coil in the slurry. The digester was insulated by a 5 cm layer of glass fibre. Inlet
Stirrer lWater pipe for heating
Gas
o0,,0,
g
Water Digester (200 Iitres ) Fig. 2.
Gas meter
Gas holder (2001itres)
Experimental facilities for methane production.
A methane fermentation was developed from a mixture consisting of 44 kg of fresh pig faeces and 88 litres of tap water with 30 litres of anaerobically-fermented cow dung as seed for the fermentation. After the development period with intermittent loading as shown in Fig. 3, an ecosystem where pig wastes were smoothly converted into biogas was attained and then daily loading of the substrate into the digester was started. The daily loading was 7.5 litres of slurry consisting of 2-5 kg of pig faeces and 5 kg of tap water (3-2 kg
49
METHANE PRODUCTION FROM ANIMAL WASTES
•
lifres/dQy 80
pH
~5
160 4
Gas production
t /
~I~¢"
ppm 60 n
CH4 % 50 t n L t t--nH2Sl t t, 10 20 :30 40 50 60 70 80 90 days
Fig. 3.
Progress of acclimatisation for methane production (arrows: charging wastes).
organic matter metre -3 digester d a y - l ) . Digester temperature was 35°C and stirring was at a rate of 60 rpm, 15 min h - ~. In the established digestion 170-200 litres d a y - ~ of biogas which contained, on average, 62.2 °~ilmethane, 37-8 ~o carbon dioxide and 150 ppm hydrogen sulphide was produced. The digested slurry is useful for fertiliser (Table 5) and has a much less offensive odour than swine faeces (Table 6). After one year of operation, it was felt that the complexity of having both stirring and heating systems might not be necessary. Thus, to simplify the system, we put a submersible pump (165 W), operated by a timer, into the digester and succeeded in TABLE 5 CHARACTERISTICS OF
PIG FAECES S L U R R Y BEFORE A N D AFTER DIGESTION
( 1) Pig fiwces slurry bejore digestion Total ~solids (",)
Organic matter (%)
Volatile [~ltty acid ( VFA ) (mg litre-1)
7-73
6.31
2048
(2) Digested slurry Total solids (%)
Organic matter (%)
VFA (rng litre 1)
TKN
5"20
3"68
79
6"19
NH,~-N P20 5 ( %, Dr)" basis) 1"29
7'58
K20
2-70
50
KIYONOR1 HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI TABLE 6 R E M O V A L OF M A L O D O R O U S C O M P O U N D S T H R O U G H M E T H A N E F E R M E N T A T I O N
TO a Indole, #g Skatole, ttg p-Cresol, m g N H 3, m g (CH3)3N,/~g V F A C2, m g C 3, rag iC4, rng C4, m g C5, mg
Pig faeces (400 ml)
Slurry, digested (400 ml)
10000-20000 520 1000 4-2 61 290 96 68 14 52 44
2000-5000 1 980 0.3 170 90 38 1-5 0.1 0.3 O-1
a T O = threshold odour.
maintaining the temperature of the digester at 35 °C without any problems for two years (Fig. 4). The above results enabled us to build the following pilot plants, which are now in operation.
Extension work (National lnstitute of Animal Industry, 1978) Several Prefecture Livestock Experiment Stations are carrying out pilot-plant scale experiments in co-operation with us. Kagawa Prefecture Livestock Experiment Station: The type of digester is the same Timer
~nlet
Ii -~.Gas(sameasFig2. ) !../×..>~/,-/.f. v//'-;//..'/) I~.' •//.~, ).././/,.~.,~-'..
/ ~'X,.~
I
z/t/ Ostes
I
1/
" -
L XSubmersible Fig. 4.
Digester operating with a submersible p u m p performing both stirring and heating (modification from Fig. 2).
METHANE PRODUCTION FROM ANIMAL WASTES
5]
Digester (5 m3) mode of FRP
Storage tank
Inlet
i
1734ee
Outlet -
I
Temperatun controller Submersible
Switch box
Gas meier Fig. 5.
Ground level
Facilities for methane production at Kawaga Prefecture Livestock Experiment Station.
_
,,,,,~ Vmylhouse
Gas
Y Piggery
]~
~
]L6~ressuregauge~ t
] III II~esulphurisation IWIII
reagent
-fi~ii II
-I~
II
"~~ ~ " - ~ i l G o s meier Gasho,der ~as
t)I
Storage ta,nk
Ill II /'A
Submersible k'l
Digester (41,5 m ~ ) made of concrete Fig. 6.
Facilities for methane production at Kochi Prefecture Livestock Experiment Station.
52
KIYONORI HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI
as ours but the scale is 16 times larger (3 m 3) (Fig. 5). The digester is equipped with a submersible pump (0-4 kW) and is operated under mesophilic conditions (35 °C). Biogas generated from pig wastes is stored in a gas holder (1.8 m s) and is used for the experiment of running a modified gasoline engine (5 hp per 2000rpm), which consumes 24.6 litres of biogas in 1 h. Kochi Prefecture Livestock Experiment Station: A septic tank used for pig wastes was converted into the digester by making the modification shown in Fig. 6. The digester runs under mesophilic conditions at around 30°C. The gas is being supplied to two brooders for 500 chicks in winter and to a grass drier at other seasons. Ehime Prefecture Livestock Experiment Station: A bag-type digester made from vinyl or polyethylene film is now under construction and will be used for mesophilic fermentation of pig wastes with the aid of a submersible pump and direct solar radiation. Nagano Prefecture Livestock Experiment Station." The digester (220m3), constructed under the housing for 30 head of dairy cattle, is now in operation (Fig. 7). Wastes from the dairy cattle are introduced by gravity into the digester with two
\ I
Housing for .30 head of dairy cattle Partly slotted floor .
.
.
.
.
.
.
.
.
.
.
.
.
.
~" L~'~';"-,~" ""-"v'"": w"J -'" " ~-~l'~t'~ "Gutter rJ
.
.
.
.
Wastes .
~
I I
I Gas
.
"~"-'~' ~ " Gas
Waste slurry
'" ~'!! "~'" ~;I I rIOutl^t -
~,-,
c
[~[
.I,II Screen
Fig. 7.
Submersible p u m p s ( 3,7 k W ) " ...... """~
Facilities for methane production at Nagano Prefecture Livestock Experiment Station (verticalsection view).
submersible pumps for stirring and heating. The pumps are surrounded by screens which prevent clogging caused by coarse organic material. The gas produced is to be used to generate steam and provide hot water.
Hiroshima Prefecture Livestock Experiment Station--Department of Poultry." Experiments on methane production from poultry wastes are being carried out by using a digester (290 litres) very similar to ours, and biogas is obtained at a rate of 378 litres kg-~ Total Solids added.
Hiroshima Prefecture Livestock Experiment StationlDepartment of Pigs." Systematic experiments with a larger installation are being performed at this station (Fig. 8). Wastes from 200 head of pigs are mixed with 2-3 volumes of tap water and
>.,
g
~J
2 E
o
o
.o
.-~ .E ,J o~
E
o
o
E 0
J~
,©
!.
o.
©
©
o
\ ~n
c-..
J=
E \, \
,©
E
i (.9~, (.9
~ r-.-~
i~
r~
~7
~o g o
54
KIYONORI HAGA, HIROSHI TANAKA, SHIGEMITSU HIGAKI
charged into two digesters every day. The digesters, with polyurethane insulation, are kept under mesophilic conditions by submersible pumps and produce enough gas to run air-conditioning facilities for about 8 h each day. In the Department, investigation on methane production from pig wastes, utilisation of the gas, effects of air-conditioning on pigs, fertiliser value of slurry digested, economic aspects of the system, etc., are now being studied.
DISCUSSION
The procedures for methane production from animal wastes have been almost established but problems of handling, transportation and charging of the wastes, utilisation of the gas produced and the slurry digested and designing efficient facilities at reasonable prices are still to be solved. Various types of digester are being operated at several Experiment Stations as mentioned above and which type of digester is most satisfactory in Japan will become clear in the near future. As noted by Morris et al. (1975), the important benefits of anaerobic digestion of animal wastes include stabilisation of the organic matter, reduction of offensive odour and production of useful fuel gas, without decreasing the fertiliser value of the wastes. Plant nutrients such as N, P205 and K20 contained in animal wastes produced in Japan correspond to about 70 ~ of the amount of chemical fertiliser used in Japan. Moreover, organic matter in the digested slurry favourably affects soil condition. Liquid slurry wastes, however, are more difficult to transport or to handle than solid wastes in the agricultural system of Japan. This bottleneck for utilisation of digested slurry as fertiliser has to be solved by stimulating the distribution of liquid manure. If the total amount of animal wastes could be subjected to methane fermentation, the following amount of biogas and energy would be yielded. Animal Wastes
5.6
X
l0 T ton year-
matter content: 10 ~o t'--].(organic 300 m 3 of biogas ton- 1 of org. matter 1.68
I Biogas produced
x 10 9 m 3
year-
, .... 6000 kcal m-3 of biogas 1-01
Energy produced
t
x
1013
kcal year -~
- --107 kcal klitre- ~ of petroleum
Petroleum equivalent to the energy
1-01
x 10 6
klitre year 1
METHANE PRODUCTION FROM ANIMAL WASTES
55
A l t h o u g h the energy obtained from biogas is no more than 0.27 ~o o f the annual c o n s u m p t i o n o f energy in J a p a n (about 3.8 x 10 is kcal year-1), it is nevertheless a b o u t 18 ~o o f the agricultural c o n s u m p t i o n o f petroleum (about 5.5 x 106 klitres y e a r - 1). On the other hand, as an average Japanese family uses 7 0 m 3 o f fuel gas per m o n t h , the biogas from animal wastes could supply 2 million families.
REFERENCES AGRICULTURE, FORESTRY AND FISHERIESRESEARCHCOUNCIL, MINISTRY OF AGRICULTUREAND FORESTRY
(1975). The Report on Research and Development of the Techniques for Animal Waste Management 1974. Tokyo, pp. 197-216. (In Japanese.) MORRIS,G. R., JEWELL,W. J. & CASLER,G. L. (1975). Alternative animal waste anaerobic fermentation designs and their costs. In: Energy, agricuhure and waste management (Jewell, W. J. (ed.)), Ann Arbor Science, Michigan. NATIONAL |NSTITUTE OF ANIMAL INDUSTRY, MINISTRY OF AGRICULTURE AND FORESTRY (1978). Research
subjects of Prefecture Livestock Experiment Station, Chiba. (ln Japanese.) ONO, J. (1963). Principles and practices of methane production. Bungado, Tokyo. 271 pp. (In Japanese.)