2. Indian states leading the pack in
establishing biomass based power supply are Uttar
Pradesh, Maharashtra, Karnataka, Andhra Pradesh,
Tamil Nadu, and Chhattisgarh.
State Capacity (MW)
Haryana 52.30
Karnataka 737.28
Madhya Pradesh 36.00
3. State wise biomass power and cogeneration projects
State Capacity (MW)
Andhra Pradesh* 389.75
Bihar 43.42
Chhattisgarh 264.90
Gujarat 55.90
Haryana 52.30
Karnataka 737.28
Madhya Pradesh 36.00
Maharashtra 1,112.78
Odisha 20.00
Punjab 140.50
Rajasthan 111.30
Tamil Nadu 662.30
Uttarakhand 30.00
Uttar Pradesh 936.70
West Bengal 26.00
Total 4,761.00
*Capacity includes projects of both Andhra
Pradesh and Telangana
Source: MNRE Annual Report 2015-16
4. Programme/scheme wise physical progress
Sector
Achievements (capacity in
MW)
(as on 31.03.2016)
I. Grid Interactive Power (Capacities in MW)
Biomass Power (Combustion, Gasification and
Bagasse Cogeneration)
4,831.33
Waste to Power 115.08
Sub-total Grid Interactive 4,946.41
II. Off-Grid / Captive Power (Capacities in
MWe)
Biomass (non bagasse) Cogeneration 651.91
Biomass Gasifiers
· Rural
· Industrial
18.15
164.24
Waste to Energy 160.16
Sub-total Off-Grid 994.46
Total Biomass Based Power 5940.87
5. Considering the present status of biomass based power
generation and thermal applications, it is expected
that only about 30-35 million tones of surplus biomass
is being used annually for the existing and ongoing
biomass projects. According to the Biomass Resource
Atlas (2002-04) prepared by the Indian Institute of
Science, Bangalore, more than 300 districts in India
have biomass potential between 10-100 MW.
6. Major Barriers and Challenges
Unlike solar and wind, biomass is relatively a much reliable
source of renewable energy free of fluctuation and does not
need storage as is the case with solar. But it is not the
preferred renewable energy source till now, mainly due to
the challenges involved in ensuring reliable biomass supply
chain.
This is because of the wide range in its physical properties
and fluctuation in availability round the year depending on
cropping patterns. Biomass from agriculture is available
only for a short period after its harvesting, which can
stretch only for 2-3 months in a year. So there is a need to
have robust institutional and market mechanism for
efficient procurement of the required quantity of biomass,
within this stipulated short time, and safe storage till it is
finally used.
7. Some of the major barriers faced in faster realization
of available biomass power potential for a variety of
end use applications are:-
(i) inadequate information on biomass availability,
(ii) absence of organized formal biomass markets,
(iii) problems associated with management of biomass
collection, transportation, processing and storage;
problems associated with setting up large size biomass
plants,
(iv) non-availability of cost effective sub megawatt
systems for conversion of biomass to energy in a
decentralized manner, and
(v) lack of capability to generate bankable projects on
account of financial and liquidity problems, etc.
8. Indian states leading the pack in establishing biomass based
power supply are Uttar Pradesh, Maharashtra, Karnataka,
Andhra Pradesh, Tamil Nadu, and Chhattisgarh.
Ironically, many states with agriculture based economy,
despite good biomass power potential, have not properly been
able to utilize the opportunity and figure low in biomass power
achievements.
Only Uttar Pradesh in north India has utilized large part of the
biomass potential, which can be attributed to its sugarcane
industry, with cogeneration power plants.
There is also wide variation in tariff being offered for biomass
power plants in different states. Government policy can play a
big role in enhancing the viability of biomass power plants and
in supporting investment growth in the biomass power sector
in states with high biomass power potential.
12. Biomass
a new source of energy
What is biomass energy?
Which biomass energy source are the most
famous for using and under research?
How does it work?
What is the advantages and the disadvantages of
biomass energy?
What is the limitations of biomass energy?
How is it affecting the environment negatively?
13. Bio Mass
Biomass already supplies 14 % of the world’s primary
energy consumption. On average, biomass produces
38 % of the primary energy in developing countries.
USA: 4% of total energy from bio mass, around 9000
MW
INDIA is short of 15,000 MW of energy and it costs
about 25,000 crores annually for the government to
import oil.
14. Bio Mass from cattle manure, agricultural waste, forest
residue and municipal waste.
Anaerobic digestion of livestock wastes to give bio gas
Digester consumes roughly one third the power it’s
capable of producing.
Fertilizers as by product.
Average electricity generation of 5.5kWh per cow per
day!!
15. What is the use of
biomass energy?
For producing heat
energy
Anything from the
nature which can burn to
heat.
E.g. charcoal, wood,
Mustard oil
For producing
electricity
Using method is same as
oil. Burn it and get
energy either for a state
or a house.
E.g. wood, crop residues,
Mustard oil
16. The various and famous
examples for biomass
Crop residues : burn it
in incinerator to
produce energy.
Burning woods :
burning woods in order
to produce electricity
or heat energy.
Mustard oil : used like
oil for electricity or
diesel
17. How does it work? (1)
CROP RESIDUES -burn
in the incinerator and
produce electricity.
It produces 10% of
electricity of Hawaii and
Brazil.
WOOD - burn as feul to
either produce energy or
heat.
Wood-fired power plants
provide 23% of the
electricity used in Maine.
18. How does it work? (2)
MUSTARD OIL - burn in the engine as diesel for
vehicle or in power plant to produce electricity.
It is under research.
19. India
Sources of ethanol:
Sugarcane
Molasses
Agricultural waste
Low average cost of Rs.18/litre projected
Annual production capacity of 1.5 Billion litres
20. Sources of biodiesel:
Honge
Jatropha
High capital, broad scale production plan initiated
Cost per liter projected at Rs. 27
India (Contd.)
21. The advantages for
biomass energy
Most of them are renewable, e.g., wood, mustard oil
and crop residues.
Solve energy crisis in the future.
Some of them are re-using the waste, e.g.,crop residues,
sewage.
High energy efficiency.
Generally it does not polluted the atmosphere as much
as oil and coal.
22. The disadvantages of
the using of biomass energy (1)
More serious air pollution was found when burning
plants matters, e.g., CO2, CO, solid particulate matter.
Emission more carcinogens into the air.
Emission some toxic gases and ash.
23. The disadvantages of
the using of biomas energy (2)
It takes too much energy to collect, dry and transport
the residues to power plants.
Reduce soil nutrient replenishment.
The source of biomass can use fertilize soil, e.g., crop
residues and animal manure. Cutting too many woods
is a kind of deforestation can cause, soil erosion and
natural disasters
24. The disadvantages of
the using of biomas energy (3)
Raising the price of food, wood and wood products
indirectly.
May cause accident.
It uses large area to grow biomass.
25. The limitations for
using biomass energy
Either high technological level or catalytic combustion
is needed.
Large area is needed to grow plants for biomass energy
use.
When producing biomass fuel, large amount of waste
will also produced.
26. The environmental problems
are caused by biomass energy (1)
It will intensify air
pollution.
It may cause
saltilization and
decrease to total size of
the arable land.
27. The environmental problems
are caused by biomass energy (2)
The source of biomass
can use fertilize soil,
e.g., crop residues and
animal manure.
Cutting too many
woods is a kind of
deforestation can cause,
soil erosion and
natural disasters
28. Waste to Energy Plant
Locked into long term contract: may discourage recycling
Fly ash: Bottom ash: Where collected and transported?
29. Metal in Incinerator Ash
Additional concerns: dioxin from burning of chlorine containing
compounds (plastics,etc.). Dioxin: carcinogen, endocrine disrupter
Fly ash: from electrostatic precipitators. Bottom ash: bottom of boiler
Which is most dangerous??
30. Methods of Biomass to Energy
Conversion
Direct combustion
Pyrolysis( thermochemical decomposition of organic material at elevated
temperatures in the absence of oxygen): thermal decomposition into gas or
liquid Involves high temperatures (500-900°C), low oxygen
Biochemical processes:
Anaerobic digestion by methanogens
Controlled fermentation produces alcohols:
Ethanol (grain alcohol)
Methanol (wood alcohol)
31. Anaerobic
Digester
Converts animal or plant waste
Into methane
Typical wastes:
Manure (feed lots,pig farms, poultry)
Olive oil mill waste
Potato processing waste
Big deal: Agricultural Science Depts
33. ENVIRONMENTAL DISADVANTAGES
•Crop and forest residues often contain high
concentrations of important nutrients
•If the residue is harvested as energy, the
nutrients can be lost to the surrounding
environment.
•Other synthetic chemical nutrients or fertilizers
can later be added
•More plants and trees must be planted,
because they will be used in a higher quantity
34.
35. Converting Biomass to Other
Forms of Energy
• Burning biomass is not the only way to release its energy.
Biomass can be converted to other useable forms of
energy, such as methane gas or transportation fuels, such
as ethanol and biodiesel.
• Methane gas is the main ingredient of natural gas. Smelly
stuff, like rotting garbage, and agricultural and human
waste, release methane gas — also called "landfill gas" or
"biogas."
36. Crops like corn and sugar
cane can be fermented to
produce ethanol. Biodiesel,
another transportation fuel,
can be produced from left-
over food products like
vegetable oils and animal
fats.
37. Wood & Wood Waste
Burning Wood Is Nothing New
The most common form of biomass is wood. For
thousands of years people have burned wood for heating
and cooking. Wood was the main source of energy in the
United States and the rest of the world until the mid-
1800s. Wood continues to be a major source of energy in
much of the developing world.
38. In the United States, wood and wood waste (bark,
sawdust, wood chips, and wood scrap) provide about 2%
of the energy we use today.
39. Using Wood and Wood Waste
About 84% of the wood and wood waste fuel used in the
United States is consumed by industry, electric power
producers, and commercial businesses. The rest, mainly
wood, is used in homes for heating and cooking.
40. Many manufacturing plants in the wood and
paper products industry use wood waste to
produce their own steam and electricity. This
saves these companies money because they
don't have to dispose of their waste products
and they don't have to buy as much electricity.
41. Waste-To-Energy
• Energy from Garbage
• Garbage, often called municipal solid waste (MSW), is the
source of about 10% of the total biomass energy
consumed in the United States. MSW contains biomass
(or biogenic) materials like paper, cardboard, food scraps,
grass clippings, leaves, wood, and leather products, and
other non-biomass combustible materials, mainly plastics
and other synthetic materials made from petroleum.
42. Waste-to-Energy Plants Make
Steam and Electricity
Today, we can burn garbage in special waste-to-
energy plants and use its heat energy to make steam to
heat buildings or to generate electricity. There are
about 90 waste-to-energy plants in the United States.
These plants generate enough electricity to supply
almost 3 million households.
43. Waste-to-Energy Plants Also Dispose of Waste
• But providing electricity is not the major advantage of
waste-to-energy plants. It actually costs more to generate
electricity at a waste-to-energy plant than it does at a coal,
nuclear, or hydropower plant.
• The major advantage of burning waste is that it reduces
the amount of garbage we bury in landfills. Waste-to-
energy plants dispose of the waste of 40 million people.
44. The average American produces more than 1,600
pounds of waste a year. If all this waste were landfilled,
it would take more than two cubic yards of landfill
space. That's the volume of a box 3 feet long, 3 feet
wide, and 6 feet high. If that waste were burned, the
ash residue would fit into a box 3 feet long, 3 feet wide,
but only 9 inches high.
45. Biomass
Composition of Municipal Solid Waste
Energy Retrieval from Recycling
Incineration and Incinerator Ash
Secure Landfills
Efficiency of Conversion of Sunlight into Biomass
Methane Digesters
Alternative Biomass Fuels for Vehicles
Wood Combustion
Energy Plantations
46. Composition of Urban Garbage
William Rathje
Garbologist
When did Arizona
Residents throw out
the most meat?
48. Biogas production
From the decomposition
of wastes in farming
sewage treatment
A bi-product of the
cleaning up of waste
water
Biogas consists of about
40% CO2 and 60% CH4 BEA Dithmarschen
49. Requirements
a fermenter, which is supplied with an innoculum of
bacteria (methanogens and decomposers)
anaerobic conditions
an optimum temperature of 35°C
an optimum pH of 6.5 to 8
This needs to be monitored as the decomposers
produce acids and they work faster than the
methanogens consume the acids
organic waste (biomass) e.g. sewage, wood pulp
50. Methanogens and the greenhouse effect
Half of the methane produced
by methanogens is used up as
an energy source by other
bacteria
Half is lost to the atmosphere
(600 M tonnes y-1) where it
acts as an important
greenhouse gas
As more land is converted to
rice paddy fields and pasture
for grazing animals more
methane will be produced
DAF Shiga Pref.
51. Warming up the brew
As global warming progresses the permafrost with
thaw in the regions covered by tundra
Tundra contains extensive reserves of frozen peat
As the peat warms and melts, it will provide a
source of material for methanogens
52. Recycling Trivia
Americans consume 2.5 million plastic bottles every hour
If you drink 2 cans of soft drink per day in aluminum cans and cans are not recycled,
you waste more energy than is used daily by one human in the lesser developed
countries
Recycling one aluminum can saves enough energy to run a TV for 3 hours
Recycling of all paper used in the Sunday edition of the New York Times would save
75,000 trees per year
53. Fly Ash Dump in Korba India
(from power plant)
No vegetation.
54. Biomass — Renewable Energy
from Plants and Animals
Biomass is organic material made from plants and
animals. Biomass contains stored energy from the
sun. Plants absorb the sun's energy in a process called
photosynthesis. The chemical energy in plants gets passed
on to animals and people that eat them.
55. • Biomass is a renewable energy source because we can
always grow more trees and crops, and waste will always
exist. Some examples of biomass fuels are wood, crops,
manure, and some garbage.
• When burned, the chemical energy in biomass is released
as heat. If you have a fireplace, the wood you burn in it is
a biomass fuel. Wood waste or garbage can be burned to
produce steam for making electricity, or to provide heat to
industries and homes.
56. How Much Biomass Is Used for
Fuel?
Biomass fuels provide about 4% of the energy used in the
United States. Researchers are trying to develop ways to
burn more biomass and less fossil fuels. Using biomass
for energy may cut back on waste and greenhouse gas
emissions.
57. Biogas
• Collecting Gas from Landfills
• Landfills can be a source of energy. Organic waste
produces a gas called methane as it decomposes, or rots.
• Methane is the same energy-rich gas that is in natural gas,
the fuel sold by natural gas utility companies. It is
colorless and odorless. Natural gas utilities add an odorant
(bad smell) so people can detect seeping gas, but it can be
dangerous to people or the environment. New rules
require landfills to collect methane gas as a pollution and
safety measure.
58. Some landfills simply burn the methane gas in
a controlled way to get rid of it. But the
methane can also be used as an energy source.
Landfills can collect the methane gas, treat it,
and then sell it as a commercial fuel. It can
then be burned to generate steam and
electricity.
59.
60. Landfill Gas Energy Projects
Today, there are almost 400 operating landfill gas
energy projects in the United States. California has the
most landfill gas energy projects in operation (73),
followed by Illinois (36), and Michigan (27).
61. Using Animal Waste
• Some farmers collect biogas from tanks called "digesters"
where they put all of the manure, dirt, and waste from
their barns. A biogas digester can convert animal waste
into useable energy. On some dairy farms, the muck from
inside the barn is collected and put into a large digester, or
tank. Inside the digester, methane gas is separated from
the liquid and solid waste. The methane gas can then be
used to generate electricity to light a barn, or to sell to the
electric power grid.
62. Biomass & the Environment
Each Form of Biomass Has a Different Impact
Biomass pollutes the air when it is burned, but not as
much as fossil fuels do. Burning biomass fuels does not
produce pollutants such as sulfur that can cause acid rain.
When burned, biomass releases carbon dioxide, a
greenhouse gas.
63. But when biomass crops are grown, a nearly equivalent
amount of carbon dioxide is captured through
photosynthesis. Each of the different forms and uses of
biomass impact the environment in a different way.
64. Burning Wood
Because the smoke from burning wood contains pollutants
like carbon monoxide and particulate matter, some areas
of the country won't allow the use of wood-burning
fireplaces or stoves on high pollution days. A special
clean-burning technology can be added to wood-burning
fireplaces and stoves so that they can be used even on
days with the worst pollution.
65. Burning Municipal Solid Waste
(MSW) or Wood Waste
• Burning municipal solid waste (MSW, or garbage) and
wood waste to produce energy means that less of it has
to get buried in landfills. Like coal plants, waste-to-
energy plants produce air pollution when the fuel is
burned to produce steam or electricity. Burning
garbage releases the chemicals and substances found
in the waste. Some of these chemicals can be
dangerous to people, the environment, or both, if they
are not properly controlled.
66. Plants that burn waste to make electricity must use
technology to prevent harmful gases and particles
from coming out of their smoke stacks. The particles
that are filtered out are added to the ash that is
removed from the bottom of the furnace. Because the
ash may contain harmful chemicals and metals, it
must be disposed of carefully.
67. Collecting Landfill Gas or
Biogas
• Biogas is a gas composed mainly of methane and carbon
dioxide that forms as a result of biological processes in
sewage treatment plants, waste landfills, and livestock
manure management systems. Methane is one of the
greenhouse gases associated with global climate change.1
Many of these facilities capture and burn the biogas for
heat or electricity generation. Burning methane is actually
beneficial because methane is a stronger greenhouse gas
than carbon dioxide. The electricity generated from biogas
is considered "green power" in many states and may be
used to meet state renewable portfolio standards (RPS).
68. Ethanol
• Ethanol was one of the first fuels used in automobiles, and now
nearly all gasoline sold in the United States contains some
ethanol. The Federal government has set a renewable fuel
standard (RFS) that mandates increasing biofuels use through
2022, most of which will probably be ethanol. Ethanol and
gasoline fuel mixtures burn cleaner and have higher octane than
pure gasoline, but have higher "evaporative emissions" from fuel
tanks and dispensing equipment. These evaporative emissions
contribute to the formation of harmful, ground-level ozone and
smog. Gasoline requires extra processing to reduce evaporative
emissions before it is blended with ethanol. Carbon dioxide, a
greenhouse gas, forms when ethanol burns, but growing plants
like corn or sugarcane to make ethanol may offset these carbon
dioxide emissions because plants absorb carbon dioxide as they
grow.
69. Biodiesel
• Biodiesel was the fuel used in the first diesel engines.
Compared to petroleum diesel, biodiesel combustion
produces less sulfur oxides, particulate matter, carbon
monoxide, and unburned and other hydrocarbons, but
more nitrogen oxide. Similar to ethanol, biodiesel use
may result in lower net-carbon dioxide emissions if the
source of biodiesel are oils made from plants, which
absorb carbon dioxide.
70. Methods of Biomass to Energy
Conversion
Direct combustion
Pyrolysis( thermochemical decomposition of organic material at elevated
temperatures in the absence of oxygen): thermal decomposition into gas or
liquid Involves high temperatures (500-900°C), low oxygen
Biochemical processes:
Anaerobic digestion by methanogens
Controlled fermentation produces alcohols:
Ethanol (grain alcohol)
Methanol (wood alcohol)
71. Biogas - Digester types
In this chapter, the most important types of biogas
plants are described:
· Fixed-dome plants
· Floating-drum plants
· Balloon plants
· Horizontal plants
· Earth-pit plants
· Ferrocement plants
72. Fixed-dome plants
The costs of a fixed-dome biogas plant are relatively low. It is simple as no
moving parts exist.
There are also no rusting steel parts and hence a long life of the plant (20 years
or more)
The plant is constructed underground, protecting it from physical damage and
saving space.
While the underground digester is protected from low temperatures at night
and during cold seasons, sunshine and warm seasons take longer to heat up the
digester.
No day/night fluctuations of temperature in the digester positively influence
the bacteriological processes
Wet Fermentation Plants:-
Fixed-dome plants
Floating-drum plants
Low-Cost Polyethylene Tube Digester
Balloon plants
73. The construction of fixed dome plants is labor-
intensive, thus creating local employment.
Fixed-dome plants are not easy to build. They should
only be built where construction can be supervised by
experienced biogas technicians.
The basic elements of a fixed dome plant (here the
Nicarao Design)
74. Fixed dome plant : 1. Mixing tank with inlet pipe and sand trap.
2. Digester. 3. Compensation and removal tank. 4. Gasholder. 5.
Gaspipe. 6. Entry hatch,
with gastight seal. 7. Accumulation of thick sludge. 8. Outlet pipe. 9.
Reference level. 10.
Supernatant scum, broken up by varying level.
The basic elements of a fixed dome plant
75. Advantages: Low initial costs and long useful life-
span; no moving or rusting parts
involved; basic design is compact, saves space and is well
insulated; construction
creates local employment.
Disadvantages: Masonry gas-holders require special
sealants and high technical skills
for gas-tight construction; gas leaks occur quite frequently;
fluctuating gas pressure
complicates gas utilization; amount of gas produced is not
immediately visible, plant operation not readily
understandable;
fixed dome plants need exact planning of levels;
excavation can be difficult and expensive in bedrock.
76. Mixing pit varies in size and shape according to the nature
of substrate. It is equipped with propellers for mixing
and/or chopping the substrate and often with a pump to
transport the substrate into the digester. At times, the
substrate is also pre-heated in the mixing pit in order to
avoid a temperature shock inside the digester.
Fermenter or digester is insulated and made of concrete
or steel. To optimize the flow of substrate, large digesters
have a longish channel form.
Large digesters are almost always agitated by slow rotating
paddles or rotors or by injected biogas.
Biogas Plant Designs
Digester Types:-
77. Co-fermenters have two or more separated fermenters.
The gas can be collected inside the digester, then usually
with a flexible cover. The digester can also be filled
completely and the gas stored in a separate gas-holder.
Gas-holder is usually of flexible material, therefore to be
protected against weather. It can be placed either directly
above the substrate, then it acts like a balloon plant, or in a
separate 'gas-bag'.
slurry store for storage of slurry during winter. The store
can be open (like conventional open liquid manure
storage) or closed and connected to the gas-holder to
capture remaining gas production. Normally, the store is
not heated and only agitated before the slurry is spread on
the field.
78. Gas use element is in Europe in 95% of the cases a thermo-power unit which
produces electricity for the farm, the grid and heat for the house, greenhouses
and other uses. The thermo-power unit has the advantage, that the required
energy can be produced in any mixture of gas and fossil energy. It can,
therefore, react to periods of low gas production and high energy requirements
or vice versa.
Concrete digester with two chambers (one heated, one unheated
for storage)
79. Concrete digester with integrated plastic gas-holder
Steelvessel fermenter with seperate ballon gas-holder
80. Selection of Appropriate Design
Typical design criteria are:
Space: determines mainly the decision if the fermenter is above-ground or
underground, if it is to be constructed as an upright cylinder or as a horizontal
plant.
Existing structures may be used like a liquid manure tank, an empty hall or a
steel container. To reduce costs, the planner may need to adjust the design to
theses existing structures.
Minimizing costs can be an important design parameter, especially when the
monetary benefits are expected to be low. In this case a flexible cover of the
digester is usually the cheapest solution. Minimizing costs is often opposed to
maximizing gas yield.
Available substrate determines not only the size and shape of mixing pit but
the digester volume (retention time!), the heating and agitation devices.
Agitation through gas injection is only feasible with homogenous substrate and
a dry matter content below 5%. Mechanical agitation becomes problematic
above 10% dry matter.
81. Balloon Plants:-
A balloon plant consists of a heat-sealed plastic or rubber bag
(balloon), combining digester and gas-holder. The gas is stored in the
upper part of the balloon. The inlet and outlet are attached directly to
the skin of the balloon.
Advantages: Standardized prefabrication at low cost, low construction
sophistication, ease of transportation, shallow installation suitable for
use in areas with a high groundwater table; high digester temperatures
in warm climates; uncomplicated cleaning, emptying and
maintenance; difficult substrates like water hyacinths can be used.
balloon plant consists of a heat-sealed plastic or rubber bag (balloon),
combining digester and gas-holder.
Disadvantages: Low gas pressure may require gas pumps; scum
cannot be removed during operation; the plastic balloon has a
relatively short useful life-span and is susceptible to mechanical
damage and usually not available locally. In addition, local craftsmen
are rarely in a position to repair a damaged balloon.
82. Balloon plant
Simple biogas plants. Floating-drum plant (A), fixed-dome plant (B), fixed-dome plant
with separate gas holder (C), balloon plant (D), channel-type digester with plastic
sheeting and sunshade (E).
83. Floating-drum Plants
Floating-drum plants consist of an underground
digester and a moving gas-holder. The gas-holder
floats either directly on the fermentation slurry or in a
water jacket of its own. The gas is collected in the gas
drum, which rises or moves down, according to the
amount of gas stored. The gas drum is prevented from
tilting by a guiding frame. If the drum floats in a water
jacket, it cannot get stuck, even in substrate with high
solid content.
85. The Drum
In the past, floating-drum plants were mainly built in India. A floating-
drum plant consists of a cylindrical or dome-shaped digester and a
moving, floating gas-holder, or drum. The gas-holder floats either
directly in the fermenting slurry or in a separate water jacket. The drum
in which the biogas collects has an internal and/or external guide frame
that provides stability and keeps the drum upright. If biogas is
produced, the drum moves up, if gas is consumed, the gas-holder sinks
back.
Size
Floating-drum plants are used chiefly for digesting animal and human
feces on a continuous-feed mode of operation, i.e. with daily input.
They are used most frequently by small- to middle-sized farms
(digester size: 5-15m3) or in institutions and larger agro-industrial
estates (digester size: 20-100m3).
86. Advantages: Advantages are the simple, easily
understood operation - the volume of stored gas is
directly visible. The gas pressure is constant,
determined by the weight of the gas holder. The
construction is relatively easy, construction mistakes
do not lead to major problems in operation and gas
yield.
Disadvantages: The steel drum is relatively expensive
and maintenance-intensive. Removing rust and
painting has to be carried out regularly. The life-time
of the drum is short (up to 15 years; in tropical coastal
regions about five years). If fibrous substrates are used,
the gas-holder shows a tendency to get "stuck" in the
resultant floating scum.
87. Water-jacket Floating-drum Plants
Water-jacket plants are universally applicable and easy
to maintain. The drum cannot get stuck in a scum
layer, even if the substrate has a high solids content.
Water-jacket plants are characterized by a long useful
life and a more aesthetic appearance (no dirty gas-
holder). Due to their superior sealing of the substrate
(hygiene!), they are recommended for use in the
fermentation of night soil. The extra cost of the
masonry water jacket is relatively modest.
88. Water-jacket plant with external guide frame: 1 Mixing pit, 11 Fill pipe, 2
Digester, 3 Gasholder, 31 Guide frame, 4 Slurry store, 5 Gas pipe[6]
89. Different types of floating-drum plants:
KVIC model with a cylindrical digester, the oldest and most
widespread floating drum biogas plant from India.
Pragati model with a hemisphere digester
Ganesh model made of angular steel and plastic foil
floating-drum plant made of pre-fabricated reinforced concrete
compound units
floating-drum plant made of fibre-glass reinforced polyester
low cost floating-drum plants made of plastic water containers or
fiberglass drums: ARTI Biogas plants
BORDA model: The BORDA-plant combines the static advantages of
hemispherical digester with the process-stability of the floating-drum
and the longer life span of a water jacket plant.
90. Low-Cost Polyethylen Tube Digester
Digester
In the case of the Low-Cost Polyethylene Tube Digester
model which is applied in Bolivia (Peru, Ecuador,
Colombia, Centro America and Mexico), the tubular
polyethylene film (two coats of 300 microns)
is bended at each end around a 6 inch PVC drainpipe
and is wound with rubber strap of recycled tire-tubes.
92. Gasholder and Gas Storage Reservoir
The capacity of the gasholder corresponds to 1/4 of the
total capacity of the reaction tube (figure td1).
To overcome the problem of low gas flow rates, two
200 microns tubular polyethylene reservoirs are
installed close to the kitchen, which gives a 1,3 m³
additional gas storage
