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CP301.pptx very good biogas I want you to study
1. Generation of Biogas from Cow dung
CP301 Design Project
Group 3
Hitesh Kumawat(2019chb1046)
Jai Singh(2019chb1047)
Gauransh Kanwat(2019chb1333)
Pankaj Verma(2019chb1054)
Anukul meena(2019chb1041)
Under the guidance of Dr. Sarang and Dr. Navin
1
2. Problem
In villages most of the villagers burn woods after cutting the trees to use them for cooking
as there is less availability of LPG cylinders in rural areas and in villages there is huge
amount of cow and Buffalo dug present which needs to be used.
Also in gaushala there is huge amount of dung produced everyday and only 2 times a year
it is used for crops, otherwise it is just a waste.
Mostly probably in rajasthan such system is not used in many villages and there are
abundant cows here so we would like to introduce this plant if they like it.
3. Solution
To solve the problem we discussed, we will create a project in which we will design a
plant in which production of the biogas from Cow dung will take place and also how to
supply the biogas to the nearby houses . Biogas is flammable and can be used for
cooking. We will first collect the sample of a village by which we will estimate how
much dung is produced per day and how much gas it can produce etc.
Process
The process of biogas production is through anaerobic digestion. it takes place in two
stages. In the first stage a group of the acid forming bacteria present in the dung acts
upon the biodegradable complex organic compounds present in the waste materials to
make organic acids. In the second stage, groups of methanogenic bacteria
[methanobacterium, methanobacillus]act upon the organic acids to produce methane
gas.
4. Components of biogas plant
● Mixing tank - Firstly we will collect Dung in the mixing tank then we add some water and
then mix the material thoroughly till a homogeneous slurry is formed. Dung:water ratio
should be 2:1
● Inlet pipe - Through the inlet pipe/tank the substrate is discharged into the digester.
● Digester - Inside the digester the slurry is fermented and biogas is produced through
bacterial action.
● Gas holder or gas storage dome - The gas holder collects the biogas in it, which holds the
gas until the time of consumption.
● Outlet pipe - Either through the outlet pipe or the opening provided in the digester the
digested slurry is discharged into the outlet tank .
● Gas pipeline - We carry the gas to the point of utilization such as a stove or lamp through
the gas pipeline.
5. Biogas
● Biogas is produced after organic materials (plant and animal
products) are damaged through microorganisms in an
oxygen-free environment, a technique referred to as
anaerobic digestion.
● Biogas structures use anaerobic digestion to recycle those
natural materials, turning them into biogas, which
incorporates each energy (gas), and treasured soil products
(drinks and solids).
● Biogas contains roughly 40-75 percent methane, 15-60
percent carbon dioxide, and trace amounts of other gases.
● Biogas, once purified by removing CO2, can be used as a
renewable, low-carbon fuel for power generation and
transmission.
General composition of chemical in bio
mass
6. Why biogas is useful:
● The raw material used could be very cheap, and to farmers, it is almost free.
● The biogas may be applied for many family and farming applications.
● The effluent received from the digester is a great fertilizer for crops.
● Now no longer having misplaced any of the nutritional fees of the unique uncooked
material, however, is odorless and generally germ-free.
● The burning of biogas does now no longer produce dangerous gases, so it's far
environmentally clean.
● The generation is especially easy and may be reproduced on a huge or small scale with
the aid of using many human beings without the want for a huge preliminary capital
investment .
7. Properties of Biogas:
● Average calorific value of biogas is 20 MJ/m3 (4713
kcal/m3).
● The chemical composition of biogas is as follows: 40–75%
CH4 (methane); 15–60% CO2 ; H2 , N2 and H2S form the
rest.
● The biogas heating power depends on the methane
concentration in biogas.
● Optimum temperature of digester for biogas production is
35°C.
● As temperature decrease from 34 to 25 °C resulted in a
decreased biogas production .
● Carbon dioxide decreases the content of other gases(
mainly methane)which decreases the heating power of
biogas .
8. Properties of Cow dung:
❖ The following physico-chemical characteristics were observed for cow dung:
humidity 43%, dry matter 20.83%, organic matter 57%, density 625 kg/m3,
carbon content 31%, nitrogen content 1.46%.
❖ Being a mixture of faeces and urine in the ratio of 3:1, it mainly consists of
lignin, cellulose and hemicelluloses.
❖ It also contains 24 different minerals like nitrogen, potassium, along with
trace amount of sulphur, iron, magnesium, copper, cobalt and
manganese(Indian cow also contain higher amount of calcium, phosphorus,
zinc and copper )
❖ Cow dung harbours a rich microbial diversity, containing different species of
bacteria (Bacillus spp., Corynebacterium spp. and Lactobacillus spp.),
protozoa and yeast (Saccharomyces and Candida).
9. Properties and uses:
❖ Cow dung in India is also used as a co-product
in agriculture, such as manure, bio fertilizer,
biopesticides, pest repellent and as a source of
energy .
❖ Cow dung cake Calorific Value 6000-8000
kJ/kg and heat of combustion is 3240 kcal.
❖ The moisture content of fresh cattle manure was
85.12 ± 1.5 wt%.
❖ For cow manure pH was 8.5.
10. Process of making biogas in fixed dome type digester
● The various forms of biomass are mixed with an equal quantity of water in the mixing tank.
This forms the slurry.
● The salary is fed into the digester through the inlet chamber.
● When the digesters personally filled with the slurry, the introduction of the salary stopped and
the plant is left unused for about two months.
● During these two months in anaerobic bacteria present in the salary decomposes or ferments
the biomass in the presence of water.
● As a result of anaerobic fermentation, bio gas is formed which starts collecting in the dome of
the digester.
● As more and more biomes. Starts collecting, the pressure exerted by the biogas forces the
spent slurry into the outlet chember.
● From the outlet Chamber, this spent slurry overflows into the overflow tank.
● The spent slurry is manually removed from the overflow tank and used as manure for plants.
● The gas valve connected to a system of pipeline is opened when a supply of Bio gas is
required.
● To gain a nonstop supply of bio gas, a performing factory can be fed continuously with the set
slurry.
11. Steps involved in making biogas
The cow dung is rich in nutrition. It contains the ratio of nitrogen phosphorus,
potassium as 3:2:1 and about 65% methane. 1kg of biogas can be produced
from around 22 kgs of dung. The C/N should be between 20-35.
Waste Collection
Pre - Treatment
Mixing
Anaerobic Digestion
Waste feeding into
anaerobic tank
Biogas Utilisation
Biogas Production
Waste (can be used in
agriculture)
12. Process study
We will use fixed dome type digester ( in this type of digester ,the amount of
substrate available per day and the number of heads in the household are the
main important parameters that determine the size of the digester)
because it has below advantages
● Requires only locally and easily available.material for constructions
● Inexpensive
● Easy to construct
13. For 1 kg of Biomass how much cow dung is required
● There are several methods to calculate the amount of biogas that can be produced
from a certain substrate.
● We will calculating on the basis of Total Solid (TS ) content.
● One tonne of TS can produce 200 ccm of biogas, so 1 kg of TS will produce 0.2 m3 of
Biogas.
● One Kg of cow dung contains about 20% TS.
● Now, 1 kg of dung which contains 20% TS will produce, 0.2*0.2 = 0.04 m^3 of biogas.
● 1 kg dung will produce 0.04 m3 of biogas.
● Hence, 1/0.04 = 25 kgs is required to produce 1 m^3 of Biogas.
● Density of biogas is 1.15 kg/m3.
● Volume required to make 1 kg biogas = mass ( 1 kg )/ density (1.15 kg/m3) = 0.86 m3.
● Therefore to produce 1 kg of biogas we need 0.86*25 = 21.7 approx 22 kgs of dung.
14. How much biogas produced per day
● Average , a cow produce (10 kg/per day) we consider same for all
category of cows that are present in gaushal.(may be this data slightly
varies)
● 800-1000 kg/per day produce in gaushala.
● Approx 22 kg cow dung produce 1 kg of biogas
● 35-45 kg of biogas per day .
● We can store biogas in storage and supply to villagers or we can use
direct pipe connection to nearby houses.
15. Weekly plan
● Literature study on biogas and uses and its properties.
● Components and process brief study and cost analysis.
● Impact of this process and how we reduce it case studied.
● Dimension analysis of each part of plant also which material is used to make
this part .
● Cost analysis and reduction.
● Waste collection and recycle process analysis
● Pipe selection and supply pipe system to nearby house study.
● Build model of this plant for better prescription.
● Study how many houses get biogas in this particular village case study.
● Finally find out advantages and uses of biogas
16. Sample (Shri Baba Ramdas Gaushala),Singhasan
,Sikar(332027)
Category No. of animals
Calves 30
Bull 2
Heifers 21
Adults cows 47
Pregnant cows 2
Total Animals 102
16
17. Calculations for gas holder tank and digester tank
DATA:
1 kg dung will produce 0.04 m3 of biogas
Average percentage of solid in dung= 20%
Average bulk density of dung = 920 kg/m3
Optimum ratio of dungto water in the slurry = 1:1
Average dung produced by one animals = 10 kg
Retention time = 30 days
17
18. Calculations for gas holder tank and digester tank
● Number of adult animal = 72
● Number of calves = 30 ≈ 15 (adult animal)
● Therefore total number of adult animal = 72 + 15 = 87
● Average dung produced by 87 animals = 87 × 10 = 870 kg/day
● Average biogas produce per day = 870 ✕0.04 =34.8 m3/day
● Average volume of dung available per day = Mass(Kg)/Density= 870/920 =
0.945 m3/day
● Volume of slurry to be prepared per day= 2✕0.945 = 1.89 m3 /day
● Volume of slurry to be accommodated in 30 days = 30✕1.89 = 56.70 m3
18
19. Calculations for gas holder tank and digester tank
● Gas requirement in village is 50% of the
total produced gas. Therefore, 50 % is
stored in the gas holder tank.
● Now volume of the gas over the slurry in
the digester to be accommodated by the
gas holder =34.8✕0.5 = 17.4 m3 (VG)
● Gas holder is hemisphere So, 17.4 =
2/3✕π✕R3
● R = 2.026 m
● D = 2✕R = 4.052 m
● Height = R = 2.026 m
Fixed dome type digester 19
20. Calculations for gas holder tank and digester tank
● Volume of digester (Vd) = Retention time✕Volume of slurry to be
prepared per day = 30✕1.89 = 56.70 m3
● According to KVIC, in fixed dome plants, the volume of digester(Vd)
comes to between 1.5 times to 2.75 times the gas produced per day. ( it
should be between 52.20 m3 to 95.70 m3)
● Let’s take height of the digester (h) = 5 m
● So, Vd = 𝜋/4✕D2 ✕h= 56.70 m3
● Therefore D= 3.801 m
● According to KVIC Height to diameter ratio between 1.0 to 1.3 are
considered ideal for all types of plants
● In our case H/D = 5/ 3.801 = 1.3
20
21. Cow
dung(Gaushala)
AD Vessel
Digestate
Storage
Batch system with a single
vessel
Cow dung
is loaded
into the
AD Vessel
as a batch
The AD Vessel is
sealed for the
duration of the
digestion process
Digestate can be
treated for use
After a specific
retention time, the AD
Vessel is manually
emptied and reloaded
Biogas is produced
continuously throughout
the retention time
Biogas is treated for use
Process flow
21
22. AD Vessel
Cow dung
Digestate
storage
Cow dung is
regularly fed
into the AD
Vessel
Biogas is treated for use
Digestate can be
treated for use
Digested material is
continuously removed
as new organic
material is added to
the AD vessel
Continuous system with a single vessel
22
23. Cow dung
AD Vessel
1
Digestate
Storage
AD Vessel
2
AD Vessel
3
Cow dung
is loaded
into each
AD Vessel
as a batch
Each AD Vessel is
sealed for the
duration of the
digestion process
Batch system with a multiple vessel
Biogas is produced
continuously throughout
the retention time
Biogas is treated for use
Digestate can be
treated for use
After a specific
retention time, each
AD Vessel is manually
emptied and reloaded
23
24. AD Vessel 1
Cow dung
Digestate
storage
AD Vessel 2
AD Vessel 3
Cow dung is
regularly
fed into
each AD
Vessel
Biogas is treated for use
Digestate can be
treated for use
Digested material is
continuously removed
from each AD Vessel as
new organic material is
added to each AD
vessel
Biogas is continuously
collected
Continuous system with a multiple vessel 24
26. Hydrolysis
● This step is very important for the
anaerobic digestion process since
polymers cannot be directly utilized by
the fermentative microorganisms.
● Hydrolysis therefore renders the
substrate accessible for the subsequent
conversion steps.
● In this step insoluble complex organic
matter is broken down into their
backbone constituents in order to allow
their transport through microbial cell
membrane hydrolysis is achieved
through the action of hydrolytic enzyme.
Acidogenesis(Fermentation)
● Fermentation involves the
conversion of the sugars, amino
acids and fatty acids to hydrogen,
acetate, carbon dioxide, VFAs such
as propionic, butyric and acetic acid,
ketones, alcohols and lactic acid by
facultative and anaerobic bacteria.
● Even though a simple substrate such
as glucose can be fermented,
different products are produced by
the diverse bacterial community.
26
27. Acetogenesis
● Acetogenesis is the conversion of certain
fermentation products such as volatile fatty
acids (VFAs) with more than two carbon
atoms , alcohols and aromatic fatty acids
into acetate and hydrogen by obligate
hydrogen producing bacteria in this stage,
acetogenic bacteria, also known as acid
formers, convert the products of the first
phase to simple organic acids, carbon
dioxide and hydrogen
● The products formed during acetogenesis
are due to a number of different microbes.
Methanogenesis
● A variety of methane-forming
bacteria is required in the anaerobic
digestion system, since no single
species can degrade all the available
substrates the methanogenic
bacteria .
● Methanogenesis can also be divided
into two groups: acetate and
H2/CO2 consumers
27
28. Anaerobic Digestion Process Chemistry
● Anaerobic digestion is the efficient conversion of
organic matter into a valuable product which is
called biogas, and methane (CH4) as its main
combustible component.
● The process mainly is dependent on the mutual
interaction of a group of microorganisms which
break down the complex organic matter , they
are converted into soluble monomers such
as fatty acids, amino acids, glycerolsand simple
sugars.
● In Anaerobic digestion If the chemical reactions
are not understood completely, issues such as
alkalinity depletion,accumulation of ammonia
and volatile fatty acids ,high pH, as well as low
pH, can occur.
28
29. Hydrolysis/Liquefaction
● From a chemical perspective, the cleavage of chemical bonds by the addition of water is called hydrolysis.
Hydrolysis is achieved with the help of hydrolytic enzymes.
● Secreted by proteolytic microbes Proteases, convert proteins into amino acids; cellulases and xylanases,
which are produced by cellulolytic and xylanolytic microbes, hydrolyze xylose and cellulose (both complex
carbohydrates) into and xylem and glucose(both sugars).
● Created by lipolytic microbes, lipases convert lipids (fats and oils) into glycerol and long-chain fatty acids.
Hydrolysis/Liquefaction reactions:
Lipids → Fatty Acids
Polysaccharides → Monosaccharides
Protein → Amino Acids
Nucleic Acids → Purines & Pyrimidines
29
30. Hydrolysis can limit the rate of the overall digestion process, especially when solid waste
substrates are used. Hydrolysis is a relatively slow step.
The reaction associated with Hydrolysis is given in Equation below:
(C6H10O5)n + n H2O → n C6H12O6 + n H2
In this reaction breaking of β-1, 4-glycosidic linkages happens, it is an essential step for cellulose
conversion as it opens the possibility of catalytic transformation to occur.
30
32. Acidogenesis
Acidogenesis is the fermentation stage, the soluble compounds formed after hydrolysis are degraded
and converted into CO2 and H2 with the help of the bacteria known as acidogenic bacteria ( fermentative
microorganisms).
Here these equations show the conversion of glucose to acetate, ethanol and propionate.
C6H12O6 → 2CH3CH2OH + 2CO2
C6H12O6 + 2H2O →2CH3COOH + 2CO2 + 4H2
C6H12O6 + 2H2 →2CH3CH2COOH + 2H2O
32
33. ● The acetogenic and acidogenic bacteria belong to a species of bacteria associated with the
diverse group of both obligate and facultative anaerobes.
● These bacterias are able to live under both anaerobic and aerobic conditions with
streptococcus, micrococcus, desulfomonas, peptococcus and escherichia coli among the
species isolated from Anaerobic digestion processes.
● Characteristics of the substrate used as feedstock is the major determinant of the bacteria
that predominates.
33
34. Bacterias used in the process
Hydrolysis bacteria Acidogenesis bacteria
● Pseudomonas
● Hartmannella
● Lactobacillus
● Propionibacterium
Pseudomonas Hartmannella Lactobacillus Propionibacterium
34
36. Factors Affecting Biogasification of Cow Dung in
the Digester (Biogas Plant)
● pH
pH of the dung slurry can be varied from 6.8 to 7.8 and the pH above 8.5 should not be used as it is
difficult for the bacteria to survive above this pH.
● Concentration of C and N
The methanogenic bacteria need both C and N for their survival because they consume C 30 – 35
times faster than N and the optimum ratio of C, N may be taken as 30:1 .
The fermentation should be strictly carried out anaerobically in the absence of oxygen
● Temperature
Anaerobic fermentation of raw cow dung (gobar) can take place at any temperature between 8 and
55 ℃
36
37. ● Proportion of Solid and Water
Anaerobic fermentation or digestion of dung proceeds well if the slurry contains 8 – 9% solid organic matter as the
dung contains 18% solid, dung can be diluted in the ratio, cow dung:water = 1:1
● Retention Time
The retention time of the system refers to the volume of fluid in the reactor (digester) per volume of the fluids
passing into and out of the reactor per day.
● Volumetric Organic Loading Rate
The volumetric organic loading rate is defined as the rate at which the organic waste is supplied to the digester it
can be expressed as a percentage weight of organic matter added each day to the reactor volume.
It is related to the RT and the percentage organic matter present in the feed, according to the following equation:
Reactor loading rate percent = (Percentage of organic matter in feed)/RT
● Nutrients
Methane forming bacteria have particular growth requirements it has been demonstrated that specific metals such
as nickel, cobalt, molybdenum and iron are necessary for optimal growth and methane production also trace metals
play an important role to stimulate methanogenic activity.
37
39. Acetogenesis
● Acetogenesis is the process in which conversion of certain fermentation products such as alcohols,
volatile fatty acids with more than two carbon atoms and aromatic fatty acids into hydrogen and
acetate happens by obligate hydrogen producing bacteria.
● The acetogenesis stage of Anaerobic digestion is very vital because it affects the efficiency of biogas
production as around 70% of CH4 is formed through CH3COO− reduction, which is the main
intermediary product of the Anaerobic digestion process; approximately 25% of CH3COO− and about
11% of H2 are formed in the acetogenesis stage of Anaerobic digestion.
39
40. The reactions associated with this stage of Anaerobic digestion represented by
equations÷
CH3CH2COO− + 3 H2O ↔ CH3COO− + H +HCO3
− + 3 H2
C6H12O6 + 2 H2O ↔ 2 CH3COOH + 2 CO2 + 4 H2
CH3CH2OH + 2 H2O ↔ CH3COO− + 3 H2 + H+
The reactions showing the release of H2 are two-way reactions. The 1st equation shows that acid
phase products are converted to hydrogen and acetate, and it will used by methanogenic bacteria
in the next stage of the Anaerobic digestion process; bacteria such as Methanobacterium
propionicum and Methanobacterium suboxydans actually account for the decomposition of the
acid phase products into acetate and, the Hydrogen which is released in the reaction performs
toxic effects on the bacterias that carry out this process.
40
41. Methanogenesis
● This is the final stage of the Anaerobic digestion. In this stage, bacteria convert Acetic acid and
hydrogen into CO2 and CH4; methanogens are the the bacteria responsible for this conversion they
are anaerobes that are highly vulnerable to oxygen.
● approximately 70% of the methane is produced from acetate, while the remaining 30% is produced
from the reduction of carbon dioxide by hydrogen and other electron donors
41
42. The reactions associated with this stage of Anaerobic digestion are÷
CH3CH2COO− + 3 H2O ↔ CH3COO− + H + HCO3− + 3 H2
C6H12O6 + 2 H2O ↔ 2 CH3COOH + 2 CO2 + 4 H2
CH3CH2OH + 2 H2O ↔ CH3COO− + 3 H2 + H+
The first equation shows the conversion of Acetic acid into CH4 and CO2. The Carbon dioxide formed is
reduced to methane through Hydrogen gas in the second Equation and, third Equation shows the
production of methane by decarboxylation of CH3CH2OH
42
Cycle for
methanogenesis,
showing
intermediates.
43. Calculations for mixing tank:
● The mixing tank has a cuboid shape.
● As a result, the volume of the mixing tank
= Length✕Width✕Height
● The volume of the mixing tank should be
equal to the volume of slurry prepared per
day. In general, we will use L=H.
● As a result, L2✕W = 1.89 m3 /day.
● So, consider various L values.
● Therefore ,Length of mixing tank = 1.5 m
● Height of mixing tank = 1.5 m
● Width of mixing tank = 0.84 m
43
Fixed dome type Biogas Plant
44. Gas Valve Calculations
● The flow rate and expected pressure drop across the valve were both taken
into account when sizing the gas valve.
● Other parameters considered in determining the size of the gas valve were
gas and flow regime dependent.
● Gas flow, laminar or turbulent flow, incompressible or compressible flow,
non ideal gas effect, and outlet velocity limit to prevent shock waves and
noise are all examples of this.
● The ball valve was the type of gas valve used.
● Literature Data: P1-P2(Pressure drop) = 122.6 N/M2 , K(Friction coefficient)
= 0.05, ⍴g(Density of biogas) = 1.15 Kg/M3 , C(gas valve coefficient )=2.24
44
45. Gas Valve Calculations
● The Bernoulli equation was used to calculate the pressure drop expected across the
gas valve based on the flow rate of the gas and the size of the gas valve.
● Here, V1= V2 , Z1 = Z2 Therefore, V2 =(2g/K) ✕((P1-P2)/⍴g)
● (Q/C)2 = ((P1-P2)✕⍴w)/⍴g
● Therefore, We get V= 204.4 m/s, Q= 731.3 m3/s
● Area of gas valve pipe(A) = Q/V = 3.578 m2
● A = πr2L=> r = (A/πL)½ => r = 0.338 m
● Therefore, Diameter of pipe = 0.676 m
45
Gas Valve
47. AD Vessel 1
(First stage)
Cow
Dung(Gaushala)
Digestate
storage
AD Vessel 2
(Second stage)
Cow Dung
is
regularly
fed into
the first
AD Vessel
Biogas is treated for use
Digestate can be
treated for use
Digested solids are
continuously removed
from the first AD
Vessel as new organic
material is added to
system
Biogas produced in
the first AD vessel
is collected for
treatment
Biogas produced in
the second AD
vessel is collected
for treatment
Hydrolysis products and
acids are pumped to the
second AD vessel to
optimize the digestion
process
Effluent is
continuously removed
from the second AD
vessel as new material
is added
Model of plant 47
48. Required Data
Hydrolysis process is the first stage in AD process. This process can be represented as the rate of change of
biodegradable volatile solids (BVS) concentration in the reactor during the AD process.
The process depends on the type of feed material, the feed flow rate, effective reactor volume and reactor
temperature.
Equation represents the hydrolysis process (Haugen, Bakke, and Lie 2012b):
48
52. Cost of bacterias
● Pseudomonas : ₹ 150-200 per Kg
P. fluorescens a psychrophile microorganism which grows at an optimal temperature
of 25-30 ℃.
● Lactobacillus : ₹ 750-800 per Kg
● Methanogenesis bacteria : ₹ 400-500 per Kg
52
Some Factors that affect bacteria
● Lower growth rate of methanogenic bacteria in Temp. Range in 12-24 ℃ and Higher growth
rate in Temp. Range in 50-60 ℃
● Acidogenic bacteria require a pH in the range 5.5 – 7.0, Methanogenic bacteria require a pH
value ranging between 6.5 - 8.0.
● Product format: Frozen
53. Cost analysis :-
The costs in building a biogas plant and the necessary
infrastructure including materials,techniques, equipment and
labor are as follows.
● Land
● Type of technology chosen
● Building,Designing and commissioning of the biogas plant
● Laboratory premises and offices
● Process to achieve the desired biogas quality
53
CONSTRUCTION AND INFRASTRUCTURE COSTS :-
54. OPERATING AND MAINTENANCE COSTS OF A
BIOGAS PLANT :-
These costs involve the administration of the biogas plant, such as
maintenance, operation and staff. In particular, this cost categories are
as follows÷
● Manpower for the maintenance and operation of biogas installations
● Equipment maintenance,Spare parts, and repair
● Sale,Transport, or spreading of digestate
● Energy (natural gas,electricity )
54
55. Cost of components:-
According to market survey the cost in constructing these
Assumed components of Biogas is Rs 5800/Cubic meter in India.
● Volume of digester = 56.70 m3
Now, cost of digester is = 56.70*5800 = 3,28,860 rupees
● Mixing tank volume = 1.89 m3
So, cost of mixing tank is = 1.89*5800 = 10,962 rupees
● Gas holder = 17.4
Cost of gas holder = 17.4*5800 = 100,920 rupees 55
57. Materials for Biogas plant and their costs in India.
● Concrete-Concrete, in construction, is a building
material composed of a hard, chemically inert
particle, called aggregate, which is mixed with
cement and water. Concrete Price: Rs. 1.84 per
Cubic meters.
● Cement- Cement is a binder, a material used for
construction that binds, hardens and binds other
materials together. Cement Price:400 Rs. Per 50 kg
bag.
● Bricks/Blocks- Bricks and blocks are mainly used
for the construction of walls. Bricks come in
different shapes, sizes and strengths depending on
different construction requirements.Bricks: 6 to 10
Rs. per Piece.
● Sand- Sand is used for reinforcing, bulking and
other properties of building materials such as
asphalt and concrete. Sand Price: 2200 Rs. Per
Tonne.
57
58. ● Polyvinyl chloride (PVC) pipes- PVC pipes are available
in various qualities with adhesive joints or couplings
(pressure water pipes). PVC pipe should be placed
underground. Price(104mm): 350/ Meter
● Water Traps- Where condensation water cannot return
to the digester, a water trap is required. Cost:
700/piece.
● Valves- A main gas valve should be installed near the
biogas digester. Sealed T-joints must be connected
before and after the main valve. Cost: 940/ piece
● Water- Water is mainly used to prepare mortar for
masonry, concrete and plastering work. It is also used
to soak bricks / stones before use. Water tanker price:
800 per 10000 litres.
● Waterproof cement- Waterproof cement is a portland
cement in which a water-repellent agent is added. Cost:
110/kg.
58
59. Cost Estimation of Digester
The digester of our plant is cylindrical in shape.
Now let us calculate our requirements for each material and estimate the total cost÷
Vol of digester = 56.7, Area of the cylindrical wall= πDh=π×3.801×5=59.6757m2
For our digester:
Area of a brick=0.2×0.1=0.02m
Bricks= = 59.6757/0.02= 2,983. Cost= 2983 ×8= Rs 23,870
Wet volume of the wall plaster required= 59.6757× 0.020=1.193514m3
Dry volume of plaster=1.193514×1.33=1.58737362m3
Now let us calculate amount of cement and sand present in plaster,we can take 1:4 for cement
and sand for a good mortar
59
60. Volume of cement = ⅕ × 1.58737362=0.317474724 m3
Cement weight = 0.317474724×1440 = 457.16360256kg
Sand volume = ⅘ ×1.58737362 = 1.269898896m3
Now we know 0.625m3 of sand= 1 tonne of sand, so 1m3 sand costs= 2200/0.625=Rs3520
Now, cost of sand = 1.269898896×3520 = 4,470.05rupees.
Cement cost =457.16360256 × 400/50 = 3,657.31rupees
Water proof cement :- 2% of the cement weight = 9.14, cost = 110×9.143 = 1,005.76 rupees.
So, the overall cost of construction materials for constructing digester is approximately
33,002 rupees
60
61. Cost analysis of mixing tank :-
For constructing the mixing tank of 1.89 m3 , we have to calculate require Values.
Height of the mixing tank = 1.5m , width of the mixing tank = 0.84m ,And length =1.5m
Size of the area (wall) = (1.5×1.5 + 1.5×0.84)×2 = 7.02m2
Brick’s area = 0.2×0.1= 0.02m2
Required bricks = 7.02/0.02 = Approx 351
Step 1:- volume of the wall plaster = area×thickness = 7.02×0.020 = 0.1404 m3
This is the wet volume
For the dry volume = 1.33×0.1404 = 0.186732 m3
We used 1.33 for the dry volume.
61
62. Step 2:- to calculate the volumes of cement and sand , we have to take 1:4 for cement and
sand respectively.
Volume of cement = ⅕ ×0.186732 = 0.03734 m3
Cement weight = 0.03734×1440 = 53.7788
Sand volume = ⅘ ×0.186732 = 0.1493 m3
Now, cost of sand = 0.1493×3520 = 525.536 rupees.
Cost of bricks = 351×8 = 2808 rupees.
Cement cost = 53.778× 400/50 = 430.224 rupees
Water proof cement :- 2% of the cement weight = 1.07, cost = 110×1.07 = 117.7 rupees.
So, the overall cost is = 525.536 + 2808 + 430.224 + 117.7 = 3881.46 rupees.
62
63. Acidogenesis modeling
● The acidogenesis stage represents the rate at which the concentration of volatile
fatty acids changes during the fermentation process.
● The process is determined by the total volatile fatty acid concentration in the
reactor (feed material type), the feed flow rate, effective reactor volume, and
reactor temperature. The acidogenesis process is represented by the equation
below.
● Where Sv is the total volatile fatty acid concentration in the reactor (kg/m3),
● Svin is the total volatile fatty acid concentration in the reactor feed (kg/m3),
● K2 is the yield factor estimated using experimental data,
● K3 is the yield factor related to methane gas growth rate, and
● Ksc is the Monod half-velocity constant for methanogens (kg/m3). 63
67. Determining the Calorific value
❖ Quadrant Ⅰ : CH4 Fraction of Biogas
❖ Quadrant Ⅱ : Gas Temperature (T)
❖ Quadrant Ⅲ : Absolute Gas Pressure (P)
❖ Quadrant Ⅳ : Relative dampness (F)
67
Calorific Value at different P&T conditions
69. Factors affecting the Mixing
1. Geometric characteristics of containers:
Flow dynamics of mixing process in anaerobic digesters has been analyzed from different
standpoints.Although good mixing can be obtain by the material homogenization and
exchange process between microorganisms and their environment.
Agitation inside the anaerobic digestion containers is carried out mainly in the following
three ways:
● Mechanical Agitation With Impellers,
● Pumped Circulation
● Gas Recirculation
The main type of reactor used in anaerobic digestion is the Continuous Stirred Tank Reactor
(CSTR) from which various geometry investigations have been carried out of flat bottom,
conical, spherical or even egg-shaped reactors.
69
70. Overview of the average velocity gradients for the investigated scenarios
70
The velocity gradient is used to demonstrate the importance of minimally mixed zones in a
digester with computational fluid dynamics (CFD) models indicating that a laboratory-scale
digester experiences local velocity gradients of less than 10 s−1, dependent on mixing speed.
Experimental results indicate that there is a threshold above which increased mixing speed
becomes counterproductive and biogas production falls.
The computation of the average velocity gradients further reveals that the pumped recirculation has no significant
influence on the values of velocity gradients
71. 2. Fluid rheology:
❖ Total solids concentration in digestion fluids, besides having effects on degradation rate of
organic matter, also has direct effects on rheological properties.
❖ Rheological behavior of fluids can be described by a basic diagram of shear rate against
shear stress .
❖ The rheological model application will depend on behavior and trend of experimental data,
as well as the speed ranges achieved by the mixing equipment.
71
Power law model in rheology:
The power law model has been employed to adjust experimental data and to
describe the rheological behavior of anaerobic digestion fluids .
Commercial CFD programs incorporate the power law model function for
viscosity of 4% cow manure and power law model fit to experimental data. Experimental data and power law data
72. Model Making in Aspen (Trial)
Continuous flow stirred tank
Mixture Split Flash
Digester Model
74. Acetogenesis modeling
The third stage of AD process represents acidogenesis process. This process
depends on both concentration of acetogens,type of feed material, feed flow rate,
effective reactor volume and reactor temperature.
The following equation represents the acetogenesis process:
74
where b is the retention time factor estimated using experimental data (Haugen,
Bakke, and Lie 2012b) and Kd is the specific death rate of acetogens (d⁻ 1 ).
77. Temperature and Density Gradient in Fluid
Modeling
Fluid motion can occur on a temperature gradient and, consequently, mass transport
phenomena by convection.Two models are basic for the analysis of this phenomenon:
● Flotation model for natural convection, which considers the variation of density as
a function of temperature.
● The Boussinesq model that has given adequate results
77
where ρ is density, β is the thermal expansion coefficient and T is temperature.
The fluid movement assumes a mixture of liquid, vapor and nonconsumable gases
78. ● Velocity increase at the exit of digester causes a change in mixture viscosity and
consequently its ability to flow .
● Because of the boundary conditions and flow characteristics, temperature distribution and
corresponding density.
78
Fig. Temperature Fig. Density
79. Calculations for Overflow tank:
● The digestate is the mixture of solution and
solids that remains after anaerobic digestion.
● It can be applied directly to agricultural land as a
liquid soil amendment, or it can be blended with
a separation step to separate the solid fraction
from the liquid fraction.
● The liquid fraction is high in nutrients (N, P, and
K), with roughly half of the N being organic and
the other half being mineral (i.e. ammonium,
NH4).
● The solid fraction is high in organic matter and
still has a high concentration of organic N and P.
79
Digestate directly used in agriculture
80. Calculations for Overflow tank:
● Volume of the compensation tank =
Volume of gas holder
● => Vc = VG = 17.4 m3
= —
● Vc = 17.4 = 2/3✕π✕RCT
3 - (RCT - H)2
✕π✕(RCT - (RCT - H)/3)
● By trial and error method , We got
● H = 1.15 m
● RCT = 2.29 m
80
FIXED-DOME TYPE BIOGAS PLANT
81. Cost Estimation of Gas Holder
The Gas Holder of our plant is hemispherical in shape.
Vol of Gas Holder = 17.4, Area of the hemispherical wall= 2πr2=25.778m2
For our Gas Holder:
Area of a brick=0.2×0.1=0.02m
Bricks= = 25.778/0.02= 1,288.868264. Cost= 1,288.869 ×8= Rs 10,310
Wet volume of the wall plaster required=25.778 × 0.020=0.51554m3
Dry volume of plaster=0.51554×1.33=0.686m3
Now let us calculate amount of cement and sand present in plaster,we can take 1:4 for cement
and sand for a good mortar
81
82. Volume of cement = ⅕ × 0.6857=0.1371 m3
Cement weight =0.1371 ×1440 =197.48kg
Sand volume = ⅘ × 0.6857= 0.549m3
Now, cost of sand = 0.549×3520 = 1,930.842rupees.
Cement cost = 197.472× 400/50 = 1,579.78rupees
Water proof cement :- 2% of the cement weight 3.9495 ,
cost = 110×3.95 = 434.44rupees.
Overall cost of construction materials for constructing Gas Holder is approximately
14,254 rupees.
82
84. Methanogenesis Modeling
➢ Methanogenesis stage determines the concentration of methanogens that are used to
produce methane.
➢ The process depends on retention time, the feed flow rate, effective reactor volume,
and reactor temperature.
➢ Kdc is the specific death rate of a methanogens (d1 ).
➢ Xmeth is the concentration of methanogens (kg/ m3 ).
84
87. How to increase efficiency
● We need to control the unwanted compounds such as hydrogen sulfide
(H2S) or ammonia (NH4), water vapour(H2O), CO2.
● These are the chemicals responsible for corrosion, both in the digesters as
well as engines.
● Absorption and Adsorption of Hydrogen Sulfide (H2S), CO2 and water vapour
87
89. Pipe Design
The following factors are taken
into account when selecting the
appropriate material for inlet and
outlet pipes:
● Dimensions and type of
material
● The temperature effect and
thermal expansion
● Installation and ease of
maintenance in terms of
design
● Safety
89
Pipe diameters for the specified length and flow rate
90. Pipe Design
● A 1.1 m PVC pipe inclined at a 28° angle
to the vertical will connect the mixing tank
to the digester tank, while a 3 m PVC pipe
will connect the overflow tank.
Why are we using PVC pipe over other?
● Pipes and fittings made of polyvinyl
chloride (PVC) are inexpensive and simple
to install.
● They come in a variety of qualities and
with either adhesive joints or screw
couplings.
90
Fixed dome type biogas Plant
91. Dead space in mixing vessels
● Mixing dead zones detection is conducted to improve mixing in digesters.
● Recirculation incorporation causes disturbances and material movement inside the
digester and reduces dead spaces, increasing biogas production due to a better
microorganism distribution in the material.
91
Dead space (black area) in different inflow configurations.
92. For calculating the dead space the concept of hydraulic retention time (HRT) has been
used.
HRT=V×Q
where V is total volume of digester and Q is volumetric flow at the digester inlet.
● Volumetric flow (Q) causes the material to have a certain mean velocity within the
digester, whose magnitude is a result of the velocity vector (v→), which has
components in x, y, z (u, v, w)
● Those regions where the velocity is less than or equal to the limit velocity
(v→ ≤ v dead zone) are considered as dead space.
92
93. Cost estimation of labour :-
Area of hemisphere part of overflow tank = 2πR2
2×π×(2.29)2 = 32.9329 m2
Area of cylinder part =2πRh = 4.15265 m2
Now, total area = 59.6757 + 7.02 + 25.778 + 32.9329 + 4.15264
Total area is = 59.6757 + 7.02 + 25.778 + 32.9329 + 4.15264 = 129.55924m2
Meter to feet , so the value is = 129.55924×10.764 = 1394.5756 feet
Total cost of labour is = 1395.5756×14 = 19524.059 rupees approximately.
93
Finding the area of overflow tank
98. Model of biogas reactor for Acidogenesis
98
Acidogenesis simulink model
99. 99
Flow Sheet of Acidogenesis
um XAcid
(Ksc/SV)+
1
Feed / Volume
Integration
Output
Input(1) Adding each
parts terms
Output term for LHS
Math
Operation
s(/,*)
Xmeth
Math
Operation
(-,+)
101. Electric Pumps Requirement to run the Biogas Plant
● Pumps are required to bridge the height difference between the slurry-flow
levels by the biogas unit. They may also be required to mix substrates or to
accelerate slow-flowing substrates.
● Pumps are driven by engines. They are expensive, consume energy and can
disrupt with the filling process.
● There are two predominant types of pump for fresh substrate: centrifugal
pumps and positive-displacement pumps (reciprocating pumps).
● Centrifugal pumps operate on the principle of a rapidly rotating impeller
located in the liquid flow.
● Positive displacement pumps are normally used for substrates with higher
solids content.
101
102. Rotary Pumps
● Rotary pumps work with rotors that
pressurize the fluid against the outer wall of
the rotor chamber. The geometry of the
chamber causes the fluid to push into the
outlet pipe.
● The quantity that is conveyed at a power
input of 8 kW is 4m3 slurry.
● We have total slurry of 1.89 m3 per day so
energy input will be
8×1.89/4=3.78 KJ per day
102
Rotary pump
103. Storage of bio-slurry
● This storage is mainly essential because fertilizers should only be used for the specific
duration of the growing season, while bio-slurry is generally produced continuously.
● The bio-slurry can be separated into a liquid and a solid fraction, which are kept
separately. The solid fraction can be held dry in a similar manner as compost or animal
manure.
● Ideally, the solid fraction can be sold as a useful fertilizer while the liquid fraction is used
fairly near to the digester
103
There exist several systems to store bio-slurry,
❖ Cylindrical above-ground tank with coverage
❖ Concrete slurry store, with or without permeable (weeping) walls
❖ Uncovered tanks
❖ Un-lined earth banked slurry lagoon without cover
104. Losses of nutrient in Bio-Slurry
● Gaseous emissions:
○ Similar to manure, N2O, H2S, NH3 and CH4 gases can be released when storing
digestate in open systems and the emissions are suitable as some of them are
greenhouse gasses but the loss of valuable nutrients is relevant.
○ Losses of biogas (CO2 and CH4) and ammonia (NH3) from stored bio-slurry are
assumed due to its high concentration of undigested volatile solids (VS) and
ammonium (NH4).
○ These gases will be released during the hold but also during the separation into a
solid and a liquid fraction, and during the mixing of the bio-slurry.
○ The amount of loss of nutrients during storage is mainly via volatilisation of NH3
to the air.
104
The losses of nutrients are dependent on environmental conditions, bio-slurry composition and
storage design.
Mainly the losses of nutrient are by:
105. ● Leaching of digestate and pollution of groundwater and surface waters:
➢ Another one is the loss of nutrients during storage via leakage. This is the case for
the storage of solid manure, liquid manure and bio-slurry in an unlined earth bank
storage.
➢ This implies that N and K are sensitive to leaching in case the storage facilities do
not have an impermeable barrier at the bottom.
➢ The high loss at the biogas farms was related to the excessive use of washing water
and the common practice to discharge the liquid fraction of the digestate because
of its low nutrient content
105
❖ To prevent leakage of digestate into the groundwater, we should regulations on organic fertilizer
storage.
❖ Preventing water pollution requires that the storage of digestate is at a certain distance from
watercourses and wells, also the problems with an odour should be minimised.
Preventions for Minimizing these losses:
106. Operating Expenses (OPEX)
Cow Dung cost = 3900/ton
For one year = 3900×365 = 14,23,500 rupees per
annum
Labour cost : (1 skilled and 2 unskilled labours)
Salary of this, for skilled = ₹600
For unskilled = ₹500
So, the cost is = 500×365 + 2×600×365 = 620,500
rupees per annum
106
Annual running (operational) cost :
Type of Labour
107. Electricity cost : Electricity cost per unit is 7.95
rupees
So Electricity cost= 3.78×365×7.95=10,968.615
Rupees per annum
Repair and maintenance cost = 2% of capital cost
So, Maintenance cost =2×70,661/100 = 1413.22
rupees per annum
107
Maintenance
108. Comparison between Bio-slurry and Manure:
● Bio-slurry has a lower organic matter content than manure.
● In bio-slurry, the organic matter is more stable.
● Bio-slurry has a higher ammonium content than manure.
● Bio-slurry has a pH that is slightly higher than manure.
● Bio-slurry and manure contain equal amounts of P, K, Mg,
and Ca.
● If Ammonia volatilization during anaerobic digestion and
subsequent bio-slurry handling is prevented, the overall N
content (on a fresh matter basis) will be similar.
108
109. Impact on Bio-slurry from pH :
● Organic solids are converted to volatile fatty
acids during anaerobic digestion of manure.
● The pH initially tends to decrease as these
organic acids accumulate.
● The organic acids in manure usually have
enough buffering power to keep the pH from
dropping too low.
● The concentration of base cations (e.g., Ca,
K) affects the pH of the digestate; they
buffer the pH because H+ in the liquid phase
can sorb at the solids, releasing cations.
109
Factors affecting pH-value of
digestates
117. Mathematical Model
For simplifying we consider some assumptions:
❖ The digester is a closed reactor
❖ A perfect agitation within the reactor
❖ A biochemical reaction in the reactor and a uniform in the reactor
❖ An established transitional arrangements
❖ The growth kinetics obeys the substrate inhibition model
❖ The factor limiting bacterial growth is the organic substrate
❖ The suspended biomass contributes to the biodegradation of the
substrate
117
118. 118
Qi, Si, Xi Qf, Sf ,Xf
Qg ,Z
Anaerobic Digester
Where,
Qi, Qf : are the input and output flows of the liquid and the flow of the biogas produced, and
Qg respectively(L/ d)
Si , Sf : concentrations of the substrate at the inlet and the outlet (g/L)
Xi ,Xf : biomass concentration at the inlet and the outlet (g/L)
Z : concentration of methane in the biogas (g/L)
V : volume of the digester (L)
119. 119
Mass balance on biomass
QiXi+𝛍XVt = QfXf +Vtdx/dt + KdXVf
input growth output
Accumulation
Detachment
dx/dt = D(Xi-X) + 𝛍X - KdX
Dividing by the Volume of the substrate and assuming a constant rate (Qi= Qf= Q)
and (Xf=X), we obtain the following equation: 𝛍 = 𝛍max1/(1+Ks/S +S/KI)
D = Q/Vt
where, D: is the dilution rate (day-1)
Kd: is the rate of detachment of microorganisms (day-1)
μ : is the rate of growth of anaerobic microorganisms (day-1)
μmax: rate of growth of anaerobic microorganisms (day-1)
Ks : half saturation constant (g/L) and KI : coefficient of inhibition (g/L)
Haldane relationship
120. Mass balance on the substrate
120
QiSi - 𝛍X/Yx Vt - KsxX𝛍Vt - KmxX𝛍Vt= QfSf + Vtds/dt +Vt/YsdccH4/dtVt/Ysdcco2/dt +
Vt/Ysdch2/dt+Vt/YsdcNH3/dt
Where,
Sf=S : (Substrat final is substrate instantaneous S)
Yx: coefficient of production of new cells (g/g)
Ksx : substrate degradation rate required for the growth of microorganisms (g/g)
Kmx : substrate degradation rate required to maintain microorganisms (g/g)
Ys : biogas coefficient (g/g).
ds/dt = D(Si-Sf)- 𝛍X/Yx - KsxX𝛍 - KmxX𝛍 - 1/Ys(dZ/dt +dCco2/dt
+dCh2/dt+dCnh3/dt)
Dividing by the volume Vt , we obtain the following equation:
Input
New cells
production
Growth Maintenance Output
CO2 Production
Accumulation
CH4 Production
H2 NH3
Disappearance Biogas Production
121. Mass balance on the biogas
121
QiZi = QfZf +VtdZ/dt - KVf
input Output Accumulation Production
Where YP is methane production ratio(g/g)
YP𝛍X
organic substrate conversion of
methane
dCo2/dt = YCo2𝛍X dH2/dt = YH2𝛍X dNH3/dt = YNH3𝛍X
For CO2 , H2 and NH3 We can write:
122. Mass Balance
● Feed of Cow dung substrate - 870 kg/day
● Mass of Biogas getting produced - 40.02 kg/day
● Volume of Biogas getting produced - 34.8 m3/day
● The leftover will be the digester rate.
122
Energy Balance
● Each cubic meter of biogas contains the equivalent of 6 kWh of heat energy.
● 34.8 m3 biogas will produce 270 kWh of heat energy.
● Calorific value of cow dung is 5.5 kwh/m3.
123. OPEX :-
Fixed operational cost :-
1. Interest on capital cost 10% per annum = 0.1 × 70,661 = 7,066.1 rupees per annum
Calculated capex :-
Digester cost = 33,002 rupees
Mixing tank cost = 3881.46 rupees
Gas holder cost = 14,254 rupees
Labour cost = 19524 rupees
123
124. Calculated Opex:-
Cow Dung cost = 14, 23,500 rupees per annum
Labour cost (1 skilled and 2 unskilled) = 6,20,500 rupees per annum
Electricity cost = 10,968 rupees per annum
Repair and maintenance cost = 1413 rupees per annum.
124
125. References
125
● Obileke, K. (2020, October 31). Design and Fabrication of a Plastic Biogas Digester for
the Production of Biogas from Cow Dung.
https://www.hindawi.com/journals/je/2020/1848714/
● Sancho, D. (2015). Kv ,Cv Flow Coefficient - Valvias. http://www.valvias.com/flow-
coefficient.php
● Junye Wang (2014). Four steps of anaerobic digestion processes..
https://www.researchgate.net/figure/Four-steps-of-anaerobic-digestion-
processes_fig3_268037650
● Emmanuel Menya (2013). Cost estimate of the biogas plant.
https://www.researchgate.net/figure/Cost-estimate-of-the-biogas-plant_tbl2_281088300
126. ● Civil Sir(2022). Plastering calculation in 100 sq ft & how much cement,sand is
required. Plastering Calculation
● Municipal solid waste management(2018-19). Constructing an Anaerobic fixed dome
digester. https://m.youtube.com/watch?v=OYwUx5eOYEw
● Sadik, K.; Hongtan, L.; Anchasa, P. Heat Exchangers. Selection, Rating, and Thermal
Design; CRC press: Boca Raton, FL, USA, 2020
● Kandasamy, D.; Kalamdhad, A.S. Pre-treatment and anaerobic digestion of food waste
for high rate methane production—A review. J. Environ. Chem. Eng. 2014, 2, 1821–
1830. [CrossRef]
● Gerrit Jan Willem Euverink (2020). Microbiology and biochemistry of anaerobic
digestersoverview.https://www.sciencedirect.com/topics/earth-and-planetary-
sciences/anaerobic-digestion
126
127. ● Energypedia(2022). Pumps for Biogas Plants.
https://energypedia.info/wiki/Pumps_for_Biogas_Plants#:~:text=Pumps%20are%20requi
red%20to%20bridge,speed%20up%20slow%20flowing%20substrates
● Biogas entrepreneurship(2021). Cost given may be little older, may compare with the
present one. https://web.iitd.ac.in/~vkvijay/files/biogas%20 entrepreneurship.pdf
● Thaha Water Solutions (2022). Anaerobic Digester.
https://m.indiamart.com/impcat/anaerobic-digester.html
● Venkata Naga Surya Gunasri Appala, Nitin Naresh Pandhare, Shailendra Bajpai,
Mathematical Models for Optimization of Anaerobic Digestion and Biogas Production,
Zero Waste Biorefinery(2022).
127
129. 129
Parametre Symbol
Initial concentration of the organic substrate So
Initial biomass concentration XO
Maximum specific growth rate μm
Dilution rate D
Detachment rate of microorganisms Kd
Mass transfer coefficient at the substrate-
liquid interface
Ks
Factor inhibition Ki
New cell production ratio Yx
Substrate degradation rate for the growth of
microorganisms
Ksx
Substrate degradation rate for the
maintenance of microorganisms
Kmx
130. 130
Coefficient production YS
CH4 production coefficient YCH4
CO2 production coefficient YCO2
H2 production coefficient YH2
NH3 production coefficient YNH3
Parametre
Editor's Notes
The optimum production of biogas depends upon mesophilic (32–38 °C) and thermophilic (50–55 °C) temperature range. The inability of mesophilic microorganisms to survive in psychrophilic temperature range results in 70 % reduced production of biogas during winters in hilly areas .This may be due to the collapse of cell energy, outflow of intracellular substances or cell lysis of mesophiles at lower temperature
e.g., syntrophobacter wolinii, a propionate decomposer and syntrophomonas wolfei, a butyrate decomposer.
thus, a 20 litres reactor which is fed with a 4 litres volume per day so that the volume inside remains constant, will have a retention time of 5 days
phased
2nd para) Research found out that not only the container shape can influence geometry in the mixing process include but also the shape of elements to generate movement inside the reactors.
the time takes the material to perform the path from inflow to outflow of the digester.(HRT)
In many cases the bio-slurry from the digester cannot be directly used as a fertilizer and thus needs to be stored.
Also, bio-slurry can contain important amounts of residual biogas.
Especially methane (CH4) is emitted during homogenisation of the bio-slurry before application to the field.(last)
Anaerobic digestion might not be fully complete directing to additional digestion during storage with resulting emissions of CO2, CH4 and NH3.
2nd )Most of the P was retained in the solid settled fraction, while approx. 70% of the N and K were found in the liquid fraction.
