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In which Q = rate of heat loss, (energy/ time) U = overall coefficient of thermal conductivity, (energy/time-area-temperature) A = area normal to the direction of heat flow Tl = mixed-liquor temperature T2 = air temperature outside the digester 5.2.2 Influent Heating The heat required raising the temperature of the raw manure influent to the digester operating temperature is calculated by: Q, = W*C*(T 1 -T 1 ) ............................................................(3) In which Q 1 = rate of heat transfer to raw manure influent, (energy / time) W = weight of influent added C = specific heat of influent, (energy/weight-temperature) T 1 = mixed liquor temperature T 1 = influent temperature Calculation for digester with composite structure For composite wall, roof and floor materials made of structural material and a layer of insulation, the overall coefficient of thermal conductivity, U, is a function of the unlil-surface conductance inside and outside plus the thermal resistance of each of the materials as described by, In which x = materials thickness, (length) k = materials coefficient of thermal conductivity, (Energy/time-length-temperature) h 1 and h 0 = inside and outside unit-surface conductance, (Energy/time-length-temperature) , k a = coefficient of conductivity of air and gas, (Energy/time-length-temperature) 5.3 TREATMENT OF BIODIGESTER IN COLD CLIMATE 5.3.1 Biological and Enzymatic Treatment Much of the current interest in bio-conversion technologies has been focused on the conversion of cellulose material to readily useable fuel products such as ethanol or methane. These technologies have traditionally been two-step processes in which the cellulose material is first hydrolyzed to glucose monomers and is then biologically converted to the final fuel product. Since the efficiency of the biological conversion process is highly dependent on the feedstock supplied to the organism, various hydrolyzing techniques on improving the yield of readily metabolization of the feedstock into simple sugars have been focused. The application of enzymatic hydrolyses into the anaerobic digester helps degrade the material rapidly into biogas. There are number of methods for hydrolysis of the substrates. 37
i Microorganisms play a vital role in the process of production of biogas. There are mainly three types of microorganisms categorized according to their habit of growth temperature. They are as follows: ■ ■ ■ Physophillic bacteria, which grow below IO°C; Mesophilic bacteria, which grow between 25°C - 35°C; and Thermophylic bacteria, which grow within the range of 45°C - 55°C. In 1947-49 an American biologist K.C. Hartlrode, who had long experience in the treatment of water in purifying the pollution, succeeded to develop a biological compound in a dried form from natural elements and he call it Actizyme. To-day this improved compound industrially produced by Actizyme CO. U.S.A. contains per gram more than ten billion bacteria obtained and selected through successive mutation matched with their biological catalyscrs, high quality enzymes and co-enzymes. A trail of Actizyme was made In Nepal at Dandapakhar on the road from Lamosangu to Jiri at an altitude of 1800 m. Actizyme was mixed with slurry and was introduced into the pit. Within a few days gas began to form, and soon the plant was in full operation (Biogas Newsletter, Number 1, 1979). Apart from biological methods, external heating of the substrate (e.g. slurry) inside biodigester has been tried for maintaining thermophylic condition. It can also be achieved by using a part of biogas for heating biodigester. 5.3.2 Solar Energy a. Solar Hut Solar hut is a simple way of preserving solar energy inside the simply made green house. Especially for the cold climate, a black plastic hut is built over the dome of the biogas digester in order to absorb and conserve the solar heat on the dome in view of increasing the temperature inside the digester. Figure 5.1: Polythene Hut Erected over the Biodigester 38
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BIOGAS As Renewable Source of Energ
Page 4 and 5: FOREWORD I have the pleasure to go
Page 6 and 7: EDITORS NOTE Since its inception fr
Page 8 and 9: IBS IEIA IOE INGO IQC IRR JBT KfW K
Page 10 and 11: TABLE CONTENTS FOREWORD EDITOR'S NO
Page 12 and 13: 13.5 Long-term Government Policy 11
Page 14 and 15: List of Tables Table 1.1 Table 1.2
Page 16 and 17: Figure 5.6 Figure 5.7 Figure 5.8 Fi
Page 18 and 19: CHAPTER I CHARACTERISTICS OF BIOGAS
Page 20 and 21: Figure 1.1 clearly indicates that t
Page 22 and 23: CHAPTER II DESIGN CONCEPT AND RELAT
Page 24 and 25: Chinese model fixed dome biogas pla
Page 26 and 27: 2.2.4 Other Designs Figure 2.4: Dee
Page 28 and 29: Anaerobic Filter: The anaerobic fil
Page 30 and 31: ■ Suitable foundation condition -
Page 32 and 33: Solution: From Table 2.2: 1 cow yie
Page 34 and 35: 2.6.2 Volume Calculations for Chine
Page 36 and 37: The resultant force is as follows:
Page 38 and 39: CHAPTER III MICROBIAL ACTIVITIES IN
Page 40 and 41: substances are solubilized into sim
Page 42 and 43: 3.4 FACTORS AFFECTING MICROBIAL ACT
Page 44 and 45: CHAPTER IV VARIOUS USES OF BIOGAS A
Page 46 and 47: Figure 4.5: Sketch of Ujeli Biogas
Page 48 and 49: The volume of water form the 5 HP p
Page 50 and 51: . Availability of Fertilizer Cattle
Page 52 and 53: d. Needs Match Sticks More matchsti
Page 56 and 57: . Integration of Solar Energy Integ
Page 58 and 59: 5.4.1 Biogas Reactor at Lukla/Mosi
Page 60 and 61: Figure 5.8: The Flat View of the Pi
Page 62 and 63: CHAPTER VI BIOGAS IN RELATION TO OT
Page 64 and 65: Table 6.1: Impact of Biogas on vari
Page 66 and 67: Chinese experience shows that if th
Page 68 and 69: 7.2 NITROGEN CYCLE Bio-slurry is ri
Page 70 and 71: 7.4.2 Nutrient Content of Bio-slurr
Page 72 and 73: To avoid the loss of ammonia (NH 4
Page 74 and 75: Experiment with Bio-slurry on Maize
Page 76 and 77: stated that cucumber yielded double
Page 78 and 79: 7.8.5 Philippines In the Philippine
Page 80 and 81: Cross Section—B-B Figure 7.4: Mod
Page 82 and 83: CHAPTER VIII BIOGAS PRODUCTION FROM
Page 84 and 85: ■ ■ ■ Excreta available /day
Page 86 and 87: It is to be noted that the settling
Page 88 and 89: 8.43 Operation of Biodigester After
Page 90 and 91: 9.1.2 Raw Materials Utilized for Fe
Page 92 and 93: help design large anaerobic digeste
Page 94 and 95: Inlet and outlet of the biodigester
Page 96 and 97: CHAPTER X IMPLICATIONS OF BIOGAS ON
Page 98 and 99: 10.43 Substitution of Agricultural
Page 100 and 101: 10.8 CARBON EMISSION SAVED FROM THE
Page 102 and 103: industrial, military or other organ
Page 104 and 105:
apidly. The techniques that have fo
Page 106 and 107:
11.2.7 Contingency Approach The ess
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have to deal not only with one leve
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REFERENCES [1] CES/IOE (2001) Role
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. Internal rates of return (IRRS) a
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Other assumptions made while calcul
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Table 12.1: Summary of Financial Ra
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Table 12.4: Summary of Financial Ra
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Table 12.7: Financial Rates of Retu
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IRRs are higher when increased nutr
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CHAPTER XIII BIOGAS POTENTIAL AND F
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would be available since the number
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13.2 FUTURE PERSPECTIVE IN NEPAL 13
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13.3.1 Institutional Strengthening
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■ ■ Reducing dependency on impo
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CHAPTER XIV ROLE OF VARIOUS ACTORS
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■ ■ ■ To construct 13,000 bio
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utilization of bio-slurry as fertil
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and NBPG. Sometimes a company may b
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CHAPTERXVI IMPACT OF BIOGAS ON USER
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of dung, On the other hand, 33 perc
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CHAPTER XVII IMPACT OF BIOGAS ON HE
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Figure 17.1: Perceived Reduction in
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27 percent of households with bioga
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Majority of biogas households (95.5
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Table 18,1: Sampling of Biogas Hous
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as the probable reasons for non-ope
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Table 18.7 shows that majority of t
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variations. Assuming that 1 hour of
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Status Table 18.15: Comparison of t
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contributes to the saving of Rs. 6.
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Table 18.22: Kerosene Replacement a
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The survey results on Carbon emissi
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CHAPTER XIX WORKLOAD OF WOMEN AND G
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Looking into the division of activi
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19.3 STUDIES OF BIOGAS USERS WITH F
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co-operative manner so that the wea
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Biogas user women perceived that bi
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20.1 INTRODUCTION CHAPTER XX FINANC
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portion of the construction cost of
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CHAPTER XXI CONSTRAINTS AND PROBLEM
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21.6.4 Mosquito Breeding after Biog
Page 188 and 189:
(FAOm:P/Nep/4451-T). [33] CMS (1996
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