Post on 03-Jan-2016
BiogasBiogas
Somporn Somporn JenkunawatJenkunawat
Biogas is gas produced from the fermentation of manure or organic matter by microorganisms in the anaerobic. Biogas is a mixture of gases such as methane (CH4), carbon dioxide (CO2) nitrogen gas (N2) and hydrogen sulfide (H2S), mainly composed of methane and combustible.
Biogas is produced from the wastewater treatment of Agricultural products and livestock plants by anaerobic digestion such as cassava, crude palm oil mill , fruit production factory swine farm, alcohol factory and so on.
Anaerobic Biological Digestion ProcessAnaerobic Biological Digestion Process
Bio-gas Bio-gas
Undigested
Solids & Water
Undigested
Solids & WaterAcetogenesisAcetogenesis
MethanogenesisMethanogenesis
HydrolysisHydrolysis
OrganicWaste
OrganicWaste
Organic MatterOrganic Matter
CH4 + CO2CH4 + CO2
beforebefore afterafter
Laboratory results on high solids digestionLaboratory results on high solids digestion
Properties of biogas as the fuel gas, depending on the amount of methane (CH4), which is igniting the gas in the atmosphere. The heating value of about 600 BTU / cubic foot (for methane gas to heat 1,000 BTU / cubic foot).
Pure methane gas is colorless, odorless when burned will give CO2, water and energy 5,000-6,000 Kcal/M3 at 15 oC. 735 cm of Hg pressure. While the H2S is mixed in will give smelly odor and corrosion. But when it is burned it smells less. The condensation point is -164.4 oC
Why Methane is suitable for renewable
energy source ?
The use of methane as an energy source.1. No blast occur.2. Have a slight odor so if leak will get the smell. 3. No toxic to human.4. Heat get could boil 18 liters of water in 9-10 minutes..
Factors influence on producing
biogas
1. Temperature 2. pH 3. Alkalinity 4. Nutrients 5. Inhibiting and Toxic Mate
rrrrr 6. Organic matter 7. Types of rrrrrr rrrrr
Effect of temperatureAnaerobic digestion is strongly influenced by temperature and can be grouped as: 1.Psychrophilic (0–20°C) 2.Mesophilic (20–42°C) 3.Thermophilic (42–75°C) Changes in temperature are well resisted by anaerobic bacteria, as long as they do not exceed the upper limit as defined by the temperature at which the decay rate begins to exceed the growth rate. However, an important characteristic of anaerobic bacteria is that their decay rate is very low at temperatures below 15°C.
Effect of pH and Alkalinity
The optimal pH range for methane producing bacteria is 6.8–7.2 while for acid-forming bacteria, a more acid pH is desirable .
In general, sodium bicarbonate is used for supplementing the alkalinity since it is the only chemical, which gently shifts the equilibrium to the desired value without disturbing the physical and chemical balance of the fragile microbial population .
Effect of nutrients
The bacteria in the anaerobic digestion process requires micronutrients and trace elements such as nitrogen, phosphorous, sulphur, potassium, calcium, magnesium, iron, nickel, cobalt, zinc, manganese and copper for optimum growth. . The required optimum C:N:P ratio for enhanced yield of methane has been reported to be 100:2.5:0.5.
Effect of organic loading rate
In anaerobic wastewater treatment, loading rate plays an important role. In the case of nonattached biomass reactors, where the hydraulic retention time is long, overloading results in biomass washout. This, in turn, leads to process failure. Fixed film, expanded and fluidized bed reactors can withstand higher organic loading rate.
Organic loads of anaerobic Organic loads of anaerobic digestersdigesters
Anaerobic lagoon Anaerobic lagoon 0.1 to 2 kilo 0.1 to 2 kilo COD/mCOD/m33/d/d
Anaerobic contact Anaerobic contact 1 to 5.5 kilo 1 to 5.5 kilo COD/mCOD/m33/d/d
Anaerobic filterAnaerobic filter 10 to 15 kilo 10 to 15 kilo COD/mCOD/m33/d /d
Fluidized bedFluidized bed 30 to 40 kilo 30 to 40 kilo COD/mCOD/m33/d/d
UASBUASB 15 to 25 kilo COD/m 15 to 25 kilo COD/m33/d/d Multiplate digesterMultiplate digester 9 to 15 kilo 9 to 15 kilo
COD/mCOD/m33/d/d IC reactorIC reactor 30 to 40 kilo COD/m30 to 40 kilo COD/m33/d/d
Inhibitor
The inhibitors commonly present in anaerobic digesters include:AmmoniaSulfideLight Metal ions
Aluminium Magnesium Calcium Potassium SodiumHeavy metal
Advantages• Get biogas
• Cost of construction is lower
• Daily expense is lower
• Eliminate chemical odor at least 90
percent• Using of biogas is
apart of reducing emission of greenhouse
Disadvantages
Need more area not suitable for factory that have limited area.
Microorganism for producing biogasThe production of biogas large molecular organic materials is decomposed into smaller molecule and turn to be inorganic matter and gases by bacteria in the anaerobic digester.
Anaerobic Digestion Process
11. Hydrolysis
Carbohydradtes Sim ple sugar + Alcohol
Proteins Pepti de + Amino acid
Fats Glycer ol + Fatty acid
Microorganisms : -Fat decomp osing microorganism, Cellulos
- e decomposing microorganis mand - Protein decomposing or
ganism
1. Liquefaction stage
12. Acid formation stage
r rr rrrr rrrrrrrr Organic acid + CO
2
Microorganism :Acid formers
2. Gasification stage
r rrrrrr rrrr rrr Organic acid
CO 2 + CH4
Microorganism : Methanogenic bacteria
Raw materials
Carbohydrate
Protein Fat
Propionic acid
Acetic acid
Acetica acid+inert organic residue
(digested sludge)
Butyric acid
CH4 + CO2
Reactions
Methanogenic Reactions
CH3COOH
CO2 + H2
CH4 + CO2
CH4
acetate carbondioxide
methane
methanecarbondioxide
hydrogen
acetoclasticmethanogenesis
autotrophicmethanogenesis
Changing of organic matter by anaerobic reaction
PROPINIC
ACID
COMPLEX
WASTE
OTHERINTERTMEDI
ATES
ACETICACID
CH4
15% 20
%
65%
17%
13%
35%
15%72
%
METHANEFERMENT
ATION
ACID FORMATIO
N
Compositionvolume (%) Methane
-4560
Carbon dioxide -4060
Nitrogen -25Oxygen -25Sulfide, disulfide, mercaptane
-010Ammonia -0110. .Hydrogen -002.Carbon monoxide -002.Other gases
-00106. .Temperature ,◦F
-100120
Specific gravity-102106. .
MoistureSat ur at edHigh heating value,BTU/M3
-400555
Doubling Time Cell Yield Cell Activity ksdays g VSS g-1 COD g COD g-1 VSS d-1 mM
Active Sludge (sugar)Aerobic Bacteria 0.030 0.40 57.8 0.25
Acidification (sugar)Fermentative Bacteria 0.125 0.14 39.6 ND
Acetogenesis (fatty acids)Acetogenic Bacteria 3.5 0.03 6.6 0.4
MethanogenesisAutotrophic (H2) 0.5 0.07 19.6 0.004Acetoclastic (acetate)Methanosarcina 1.5 0.04 11.6 5.0Methanosaete 7.0 0.02 5.0 0.3
More Details on the More Details on the Digestion ProcessDigestion Process
Volatile Solids (VS)
Volatile organic acids
Acid forming bacteria
Methane, carbon dioxide, water, trace gases
Methane formingbacteria
Odor
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1 . Rod shape of methanog en bacteria
1 .1 non sporulating- rod shaped cells
Methanobacterium solmgenii
Methanobacterium formicicum
Methanobacterium propionicum
-12. sporulating rod s haped cells
Methanobacterium omelianskii
Bacterial Shapes
2 Round shape of Met hanogen bacteria 21. Cell not sarcina
arrangement
Methanococcus vaniellii
Methanococcus mazei
22. Cell in sarcina arra ngement
Methanosarcina met hanica
Methabosarcina barkerii
Anaerobic Sludge Granules (SEM)
Acetate as Substrate (Methanosaeta)
Sucrose as Substrate (mixed culture)
1 Slow digestion or solid digestion
11. fined dome digester
12. floating drum digeste r or Indian digester
Biogas Plants
1 Slow digestion or solid digestion
13. plastic covered ditchor pppp pppp pppppppp
2 Fast digestion or wastewater treatment digester
21. Anaerobic Filter: AF
22. Upflow Anaerobic Sl udge Blanker: p ppp
Principles of microbial degradation of organic matter in the absence of oxygen and agglomeration, float up to the top with biogas. When contract with obstacles gas will rise while the microorganisms will fall to the bottom. This is suitable for wastewater with low suspended solids.
Upward-flow Anaerobic Sludge Blanket
influent
effluent
biogas
sludge bed
gas cap
settler
baffles
sludge granule
gas bubble
weir3 phaseseparator
Influent
EffluentRecycle
SludgeBed
Effluent settler
gascap
biogas
gasbubble
sludgegranule
Expanded Granular
Sludge Bed
rrrrr rrrrrr
The principle is to cover the pond with blanket to prevent the smell spreading and allows microorganisms to decompose organic substances in wastewater in the anaerobic condition. It takes at least 20 days, the investment is low but the amount of gas produced is less than other systems.
UASB - Internal Circulation (IC Reactor)
Brewery (Switzerland), 20 m height
UASB - Internal Circulation
Kraft Paper Mill Foul Condensates, Alabama