Clean
Energy Series:
INVESTMENT GUIDE ON BIOGAS PRODUCTION
IN NIGERIA
INTRODUCTION TO BIOGAS
Biogas is gas released as
a result of the anaerobic digestion of biomass. All organic matter must by
natural phenomena decompose and when the process occurs in the absence of
oxygen (anaerobic), biogas which is essentially composed of methane, carbon
dioxide, trace hydrogen sulfides and other trace compounds are released.
The replication of this natural phenomenon in a controlled
environment and on a commercial scale leads to the harvest of (1) biogas, a
renewable energy source that could be deployed for domestic and commercial use
and (2) bio-fertilizer, a cheaper and more wholesome farm and horticultural
alternative to chemical fertilizer.
An investor harnesses the biogas from this natural occurrence
by investing on the equipment and resources that enables the phenomenon to be
replicated on a large scale and in a controlled environment and by utilizing
substrates or organic matter that would otherwise be wasted and cause
environmental and health hazards.
These organic matter could be wastes from vegetable or animal
sources like energy crops e.g. cassava peels, corn silages and husks or animal
droppings like chicken droppings, pig droppings, cow dung or human excreta etc.
This piece is focused on the utilization of cow dung and abattoir wastes as the
basic substrates for industrial digestion to biogas and bio-fertilizer.
COMPARISON OF BIOGAS (70% METHANE) AND OTHER ENERGY
SOURCES
Energy Source
|
Calorific Value of
Fuel Per Unit
|
KW Calorific Value of
Fuel Per Unit
|
MJ Price of Fuel Unit
|
Price Equivalent of
1m³ of Biogas
|
Biogas Equivalent Per Fuel Unit
|
Diesel/Kerosene (litre)
|
10
|
36
|
19.5
|
0.69/litre
|
1.44m³
|
Benzene (litre)
|
8.5
|
30
|
25
|
0.82/litre
|
1.44m³
|
Fuel Wood (kg)
|
4.5
|
16.2
|
8
|
1.5/kg
|
0.65m³
|
Dried Dung (kg)
|
5
|
18
|
0.15
|
1.4/kg
|
1.1m³
|
Dry Vegetation Waste (kg)
|
4.5
|
16.2
|
-
|
1.5/kg
|
0.65m³
|
Solid Coal (kg)
|
7.7
|
27.6
|
1.8
|
0.9/kg
|
1.1m³
|
Natural Gas (m³)
|
9.3kw/m³
|
33.5
|
3.1
|
0.75/m³
|
1.34m³
|
Propane in Balloons (m³)
|
12.8kw/m³
|
46
|
13
|
0.54/m³
|
1.84m³
|
Electricity kw
|
1
|
3.6
|
1
|
6.9/kw
|
0.14m³
|
Biogas
|
7
|
25
|
2.8
|
1/m³
|
1m³
|
BIOGAS USES
Biogas achieves a heating
value of 5.5Kcal/M³and
may be utilized for the following purposes:
1.
Electricity
Generation
2.
Heating
resource
3.
Cooking
4.
Replacement
fuel for Diesel Engines
5.
Internal
Combustion Engines.
THE MARKETING CHALLENGE
The business models
recommended in this study are designed to surmount the problems that must
necessarily confront a pioneering business and to emphasize the necessity for
the development of a market for the products as a step prior to investment
decision making. In this wise, the following issues must be concluded before
forward planning for equipment purchases can be made:
A.
Institutional
buyers of electricity generated in the biogas project must be found and price
for purchase of constant electricity supply must be agreed and documents signed
before proceeding towards investment in equipment and machinery procurement.
B.
A
gas bottling and distribution license and all other relevant permits must be
procured from the relevant authorities before proceeding to the next phase of
investment actions.
C.
A
distribution and sales plan for the disposal of the derivable bio-fertilizer
must also be concluded and the market and sales channels activated prior to the
investments on machinery and equipment for the biogas plant.
BIOGAS PROJECT
INVESTMENT ANALYSIS
The profitability of alternative energy investments depend unavoidably
on the price of petroleum products in the world market. The world energy
consumption is so tied to hydrocarbons that the benchmark for determining the
profitability of investments in alternative energy is how lower in price the
energy source is in comparison to hydrocarbon fuels.
The Biogas Project will be the first biogas project in the
region and will by that fact be a major determinant of the future success of
biogas investments in a region noted more for its massive production of
hydrocarbons and natural gas. In order to be adjudged successful, the Biogas
project must be able to achieve costs and production figures cheaper than both
natural and liquefied natural gas and the company must also show a clear capability
of deploying and sustaining uninterrupted supply to large scale strategic
institutional consumers.
The products that will be derived from the installed Biogas
Plant utilizing cow dung as substrates at the biogas project are as under
listed:
1.
Biogas
2.
Bio-fertilizers
3.
Bio-slurries
The uses to which these products can be put will determine
the commercial viability of the Biogas Project and these may be listed as
follows:
A.
Electricity
generation.
B.
Cooking
and heating.
C.
Bio-fertilizers
for farm uses.
D.
Bio-Slurries
for Horticulture.
The benefits to be derived from a profitable biogas
production as presented in this study will be to actualize both the investors’
profit interests as well as achieve the economic and social objectives of the
institutions where the plants are to be situated and all neighborhoods where
cow dung waste is to be collected and evacuated particularly considerations for
improvement in public health and derivable ecological, health and environmental
benefits arising from the removal of odorous and other waste.
ECONOMIC AND SOCIAL BENEFITS OF A BIOGAS PLANT
1.
Low
cost production of energy.
2.
The
ready availability of energy produced from non-depleting renewable sources.
3.
The
improvement in the quantity and quality of agricultural production with
bio-fertilizer.
4.
Improvements
in the quality of life of the people through the use of biogas and
bio-fertilizer.
5.
Creation
of a participatory local energy business and market.
6.
Development
of skills
7.
Employment
generation particularly in the rural areas.
8.
Poverty
reduction.
The deployment of the biogas product for the generation of
electricity will require further investments in electricity generation
machinery and electrical installations. The power output will require dedicated
bulk buyers of electricity particularly institutions or factories in order not
to be entangled in legal and engineering issues associated with public supply
of electricity or infringe on electricity distribution laws.
Biogas that per chance may have to be sold as bottled cooking
gas will also require additional investments in gas bottling and pressure pumps
and equipment as well as a large stock of refillable steel gas bottles to
enable the biogas to access the retail market. It is possible to use hard
plastic bottles to fill and distribute the biogas for home cooking but this
will require investments in research, design and production of the plastic
bottles that would take the required pressure.
Further, a decision to deploy the biogas yields to serve for
both electricity and domestic cooking purposes will require investments in both
facilities i.e. dedicated electricity supply to a given institution or
community and biogas bottling for sale to home users for cooking. This dual
application will require investments in machinery but will provide guarantee a for
ready market and steady sales and income.
Biogas electricity generators ranging in power output from
1kw/h to the massive 2.5mw/h are available for sale in China. (see Picture) China
has developed an advanced biogas production, utilization and equipment sales
market. It will be novel to develop a biogas production and utilization market
in your region and this will require the importation and sale of the biogas
electricity generators as well as the production and sale of the biogas to keep
them in domestic use supplying electricity to homes. Buyers of the biogas
electric generators must be assured of the continuous supply of biogas to keep
the generators working in order to be convinced to buy the generators.
Beyond the assurance of steady supply of biogas to power the
generators and the continuous availability of gas bottles for home cooking, buyers
must also be assured that prices for replacement gas at all times must be
cheaper than bottled liquefied petroleum gas, petrol and diesel and that steady
prices will be maintained. When all these are assured, a steady market
will begin to grow for biogas as a strong alternative to generate electricity
for homes as well as cheaper and cleaner option for home cooking. The bigger
attraction will of course be that the Biogas Project will become a business
prototype ready for replication across the region and thereafter a biogas
industry owned and powered by the people will have taken root in Nigeria.
EQUIPMENT REQUIREMENT:
1.
Biogas
Collection Tank.
2.
Substrate
Feeder Tank.
3.
Dung
Storage Facility.
4.
Slurry
Collection Tank.
5.
Gas
Bottling and Pressurizing Equipment.
A modular design for a Biogas plant is recommended for the
Biogas Project. This will require that basic biogas and factory facilities are
provided in the initial factory design and installation while allowing for
additional digesters and slurry tanks to be added as business develops. The
digester is the processing centre for biogas and the focal point of most
activity at the plant. The capacity and output of the digester determine the
capacity of the biogas plant.
Local fabrication of the biogas plant lowers investment costs
dramatically while also allowing for the development of local skills and
technologies for onward sale to future investors as part of the new income
streams of the Biogas Project.
A locally fabricated biogas plant will require the services
of a Fabrication Engineer or experienced technician to accomplish. The inner
walls of the steel tanks will be of galvanized steel or reinforced plasticin
order to avoid corrosion from hydrogen sulfide for as long as possible.
There is of course the alternative of buying and deploying
the largest possible sizes of plastic tanks. They are of lower capacity but
Purchased in enough numbers they can do well to service an industrial capacity
biogas plant.
If local fabrication of biogas plant will not be considered
as a good option considering the pioneer status of biogas business Nigeria, the
Chinese model will be a more viable and workable option. The advantages of a
Chinese plant purchase are as follows:
1) The Chinese plants have a huge
comparative price advantage.
2) The Chinese model can be acquired
with portable gas holders (membranes and gas storage tanks pp17.
3) The Chinese models are purchased with
filters which remove the smell in the biogas and dry it of all vapors.
4) The Chinese have a bigger and more
active biogas industry and can therefore offer long term support at cheaper
cost.
OPERATION OF A BIOGAS PLANT
The two basic products of a Biogas plant are:
1.
Biogas
2.
Bio-fertilizer
There are other products but the only commercially useful one
is bio-slurry which can be regarded as the liquefied form of bio-fertilizer.
Bio-slurry can be sold to market gardeners and other horticulturists.
BIOGAS PLANT RUNNING
COSTS
(NOTE: A 30 day
stock of cow dung should be kept in the factory yard at all times.)
The internationally recognized guide for the calculation of
the cost of running a biogas plant is to allow a margin of 4% of the cost of
setting up the biogas plant as annual running cost and the elements of the
annual running cost will include the following:
1.
Cost
of acquiring substrates
2.
Water
Supply
3.
Maintenance
and repair of plant
4.
Preparation
and bagging of bio-fertilizers
5.
Gas
bottling storage and distribution
6.
Salary
and wages.
The biogas plant to be located in the hot tropical climate
will not require a co-heating system to achieve the required optimal
operational Mesophilic temperature range 27-40 degrees Celsius in the digester
(recommended operational temperature 35-37áµ’c). Construction cost of the digester
therefore will be cheaper than in the temperate region where pre-heating and
co-heating of the digester will be required to activate the digester microbes
particularly in winter seasons. The basic and cheaper construction cost without
an electric pre-heating system will lower investment and running costs.
The Mesophilic temperature range 27-40áµ’C allows for the optimum release of biogas
from substrates resident in the digester, the preservation of nutrients in the
effluent bio-fertilizers and the destruction of smell and pathogens in the
ensuing effluents particularly the bio-fertilizer. The operation of a biogas
plant will therefore be cheaper as the prevailing climatic conditions provide
the natural temperature range for a more optimum harvest by volume of biogas
and bio-fertilizers. Temperatures lower than 18áµ’C (Psychophilic temperature
range) do not allow for normal bacterial activity that will lead to profitable
release of biogas in the digester, so digesters have to be co-heated. Sustained
temperature levels higher than 40áµ’C (Thermophilic temperature range) on the
other hand stimulate intense bacterial activity leading to higher release of
biogas but results in the destruction of plant nutrients in the effluent bio-fertilizers.
In the course of running a biogas plant under mesophilic temperature
conditions, care must be taken not to allow for wide and sudden fluctuating in
temperature as the process of bio-methenation is very sensitive to sudden
changes in temperature. A temperature fluctuation range of no more than ±1áµ’C
may be allowed under the stated conditions.
SLURRY MIXING TANK
The
slurry tank is the chamber where substrates are mixed in the right
substrate/water ratio to achieve optimum biogas yield. The mixing slurry tank
is also the place where a thorough mixing of substrate to break up lumps and
achieve evenness is achieved. The mixing rate for cow dung for maximum biogas
yield is 85-92% water to solid cow dung.
DIGESTER START-UP CONDITIONS
Cow
dung contains the full range of bacteria and micro-organisms necessary to begin
the digestion process to produce biogas in anaerobic conditions in a new
digester tank as cow dung is ingested with all the micro-organisms in the
bowels of cattle. Cow dung therefore is the best substrate to jumpstart biogas
production in a new plant.
MIXING RATE: Cow dung needs to mix with 85-92% water to
produce the perfect mix for optimum gas release in a biogas plant. A water
supply system and a mixing tank needs to be installed.
TANK OPTIMIZATION: The digester tank needs to be filled to
two-thirds of its volume and the balance one-third left for biogas accumulation
and harvest. For fermentation and the production of biogas to begin, it is
necessary to create anaerobic conditions in the digester tank by ensuring air
tightness in the entire bio-digester and the piping systems. It is also
necessary to ensure the absence of scum and other inhibitors to the digestion
process.
FEEDING SUBSTRATES
Utilising
cow dung as substrate under mesophilic temperature regimes, digester feeding
practices are as follows:
A.
10% of digester
volumes are fed daily. The substrates are divided equally and loaded onto the
digester from the slurry mixing tank every 4-6 hours intervals.
B.
The time needed
to liberate all biogas in cow dung substrates is usually 10-20 days under
mesophilic temperature conditions of 25-40 áµ’C. As substrates are fed in from
the slurry tank through the piping at the bottom of the tank, the older,
resident, digested slurry escape from the piping at the top of the tank.
C.
AGITATION
(Stirring): it is necessary at intervals of the digestion process in the
digester tank to stir either by physical or mechanical means the substrates in
the digester tank. This stirring and mixing action achieves the following
purposes:
i.
Frees already
produced biogas trapped in the slurry.
ii.
Evenly
distributes bacteria in the digester for the inoculation of fresh substrate.
iii.
Preventing the
formation of scum and sediments.
iv.
Ensuring uniform
temperature in the digester tank.
v.
Helps prevent
dead and inactive spaces in the digester and avoid reducing volume and
effectiveness.
Stirring and agitation of substrates in the
digester tank should be carried out every 4 hours approximately.
BIOGAS YIELDS
1. The start-up period of a new plant requires
active bacterial action on the substrates. It is necessary to raise and
maintain a temperature range of 35-37áµ’C in the first two weeks of digester
activity and agitate frequently to intensify bacterial inoculation and spread
within the digester.
2. The initial period of gas production is
characterized by:
i.
Low quality (more
than 60% CO2) and infrequent gas production.
ii.
Smelly gas with
low pH value.
Biogas
may be improved by filtering it through limewater to remove carbon dioxide,
iron filings to absorb corrosive hydrogen sulphide and calcium chloride to
extract water vapour after the other two processes.
COW DUNG BIOGAS YIELDS
Cow
dung is an average yield substrate for biogas production but the low cost of
gathering and the high production from the average animal makes it the
substrate of choice for biogas production. The cost for the acquisition of cow
dung substrate for the Biogas Project will be nil. The raw material cost will
be expended on the gathering and transport of the cow dung to the Biogas plant.
The yield expectations for different substrates are as follows:
TYPE OF SUBSTRATE BIOGAS YIELD METHANE CONTENT
(CUBIC
METRE PER KG) (%)
CATTLE 0.25 – 0.34 65
PIG 0.34
– 0.58 65
– 70
POULTRY DROPPINGS 0.31 – 0.62 60
SHEEP 0.30
– 0.62 70
Approximate
yield values for under listed substrates at moisture content of 85-92%.
1 tonne of cattle manure 40 – 50
cubic Metre of Biogas.
1 tonne of Pig manure 70
– 80 cubic Metre of Biogas.
1 tonne of Chicken droppings 60 – 70 cubic
Metre of Biogas.
VOLUME WEIGHT OF BIOGAS: 1M³ = 1.2kg
BIOGAS PRODUCTION: TECHNICAL DETAILS:
Step 1 MIXING TANK
Cow dung (substrate) is
fed into the slurry mixing tank and the water taps opened to achieve the mixing
rate of 92% water and 8% solid waste mix by volume. With continuous activity
and practice, the approximate mixing rates can be achieved without actual
measurements. For bottom fed biogas plants, mixing tank may not rise higher
than the middle height of the digester. The mixed slurry is then transferred
either through piping or by carts to the feeding tanks.
STEP 2 FEEDING TANK
The daily feeding rate
of mixed slurry is usually 10% of the digester volume and divided into 4-6
parts and pumped into the digester every 4-6 hour intervals. Agitation should
follow immediately after each feeding to create evenness in the tank and to
remove trapped biogas. It is expected that an equivalent volume of digested
slurry should flow through the discharge/outlet pipes at the top of the
digester.
STEP 3 BIO-DIGESTER
The bio-digester is the
processing plant of biogas production and where all chemical and bacteria
inoculation take place to produce biogas and bio-slurry. There are three steps
to biogas production in the digester. These are:
a)
Hydrolysis
b)
Acidification
c)
Methane formation
1. HYDROLYSIS:
The organic matter is enzymolized externally by extracellular enzymes
(cellulose, amylase, protease and lipase) of micro – organisms. Bacteria
decompose the long chains of the complex carbohydrates, proteins and lipids
into shorter parts. For example, polysaccharides are converted into monosaccharide’s.
Proteins are split into peptides and amino – acids.
2. FREMENTATION
Acid producing bacteria, involved in the second step, convert the
intermediates of fermenting bacteria-complex organic compositions (proteins,
fats and carbohydrates) into more simple compounds. At the same time in
fermentation environment, there appear primary products of fermentation -
Volatile organic acids, alcohols, amino acids, carbon-dioxide and hydrogen
sulfide. These organic substances act as nutrients for methane-producing
bacteria that convert organic acids to biogas.
3. METHANE FORMATION
Methane-producing bacteria involved in the third step, decompose
compounds with a low molecular weight for example, they utilize hydrogen,
carbon dioxide and acetic acid to form methane and carbon dioxide. Under
natural conditions, methane producing micro-organisms occur to the extent that
anaerobic conditions are provided e.g. under water (for example in marine
sediments, in ruminant stomach and in marshes). They are obligatory anaerobic
and very sensitive to environmental changes. Therefore from the conditions created
for them depends on how intensively they produce gas.
OPTIMIZATION OF DIGESTION PROCESS:
Acid and methane
producing bacteria can be easily found in natural conditions, particularly in
animal manure: for example in cattle digestive system, there is a full spectrum
of micro-organisms necessary for fermentation of manure and the process of
fermentation starts in cattle bowels.
That is why cattle
manure is often used as primary substrate which is loaded into new digester
where for the fermentation to begin, it is enough to create the following
conditions:
·
Maintenance of anaerobic condition in
digester.
·
Maintenance of temperature regime.
·
Availability of nutrients for
bacteria.
·
Correct choice of digestion time.
·
Timely load and unload of substrate.
·
Observance of appropriate C/N ratio.
·
Correctly chosen proportion of solids
content and proper agitation
·
Absence of inhibitors of the
digestion process.
FEATURES OF BIOGAS FROM COW DUNG
Cow dung biogas is 55-65% methane, 30-35% carbon dioxide,
with some hydrogen, nitrogen and other trace element. Its heating value is
around 600BTU. Per cubic feet. Natural gas
consists of around 80% methane, yielding a B.T.U. value of about 1000. About
one cubic foot of biogas may be generated from 0.45kg of cow manure at around
28 degrees C. This is enough gas to cook a day’s meal for 4-6 people.
About 1.7 cubic metres of biogas equal one litre of petrol.
The manure produced by one cow in one year can be converted to methane which is
the equivalent of over 200 litres of petrol.
GAS HOLDERS (STORAGE): The medium for biogas storage depends on the volume
of gas to be stored and the level of pressure requirement at the site of use.
Higher pressure vessels require steel pipes for delivery and steel storage
tanks. Reinforced plastics with polyester fabric are featuring in modern gas
membranes that are elastic, tough, lightweight and can withstand higher
pressures, easier to transport and fix directly to user inlets. They come in
different sizes and capacities with standardized connecting pipes and valves.
(PICTURE)
BIO-FERTILIZER
Plant
nutrients are not reduced in chemical content as a result of any bacterial
activity in the digester. Plant nutrients, nitrogen, phosphorus, potassium,
magnesium, including vitamins and micro-elements necessary for plant growth are
left whole in bio-fertilizer.
Bio-fertilizer
nutrient content (grams per kg of dry matter)
Feed
|
Phosphate
|
Potassium
|
Calcium
|
Magnesium
|
Nitrogen
|
P₂O₅
|
K₂O
|
CaO
|
MgO
|
Na₂O
|
|
Manure
|
3.05
|
5.64
|
3.25
|
0.98
|
1.75
|
Manure and Vegetation Waste
|
6.37
|
7.98
|
5.15
|
1.95
|
3.37
|
Vegetation
waste
|
6.66
|
8.88
|
5.18
|
2.22
|
3.70
|
BIOFERTILIZER PRESERVATION AND STORAGE
The
nitrogen content of bio-fertilizer can be preserved by storing for a short
period in closed vessels and then applied to soil shortly before ploughing.
Storage can be in any of the following forms:
A.
Liquid: Pipe is
connected to discharge channel from the digester and leads directly to
collection vessels for onward transport to farms.
B.
Drying: A drying
system can be constructed to dry the bio-fertilizer to 15% moisture content or
less. Other drying technologies may include the use of separators and sieves.
Drying offers opportunity for longer preservation but suffers loss of 90% of
inorganic nitrogen which represents 50% of overall nitrogen content.
C.
Composting. To
avoid such massive loss of nitrogen, the bio-fertilizer slurry can be mixed
with dead vegetation and wastes and composted. The bio-fertilizer which has
high contents of nitrogen, phosphorus and other chemicals quickens the
composting activity and kills pathogenic micro-flora.
BIO-FERTILIZER NUTRIENT FACTS:
A.
Experiments
conducted have shown increase in corn yields of 49%” “With single application
of bio-fertilizer during pre-sowing period in quantities of 4 tonnes per
hectare. Farmers have registered increases in corn yield of 1.8 times more than
the normal yield.
B.
Tuberous plants
and vegetables: Researches conducted on different types of crops have proven
that the most dramatic yield effects of biogas are on tuber crops like cassava
and tomatoes.
C.
Bio-fertilizer is
a wholesome environment friendly soil enrichment and support fertilizer that
does not result in soil leaching or degradation unlike chemical fertilizer.
Bio-fertilizer contribute immeasurably to the stability of the eco-system by
stopping the wanton destruction of the forest for firewood and by halting the
leaching into the atmosphere of bio-methane from cow dung that contribute so
destructively to the depletion of the ozone layer.
BIO-FERTILIZER PLANT NUTRIENT FACTS
Cow
dung slurry is composed of 1.8-2.4% nitrogen (N2), 1.0-1.2% phosphorus (P2O5),
0.6-0.8% Potassium (K2O) and 50-70% organic humus.
OTHER USES OF BIO-SLURRY
Bio-slurry
can be used as fodder for livestock and feed for fish. Micro-organisms present
in the solid contents are a rich source of protein when the digested slurry and
dregs are used as fodder. It can be used to feed fish and pigs to speed up
growth and shorten the rearing period by 25%. With its high humic acid content
it can be used to rear mushrooms or earthworms for feeding chicken. Chickens
lay 15-30% more eggs when fed a sustained diet of earthworms.
FABRICATION OF BIOGAS PLANT (NIGERIA)
A
modular design for a Biogas plant is recommended for the Biogas Project. This
will require that basic biogas and factory facilities are provided in the
initial factory design and installation while allowing for additional digesters
and slurry tanks to be added as business develops. The digester is the
processing centre for biogas and the focal point of all industrial activity at
the plant. The capacity and output of the digester systems determine the
capacity of the biogas plant.
Local fabrication of the biogas plant lowers investment costs
dramatically while also allowing for the development of local skills and
technologies for onward sale to future investors as part of the new income
streams of the Biogas Project.
A locally fabricated biogas plant will require the services
of a Fabrication Engineer or experienced technician to accomplish. The inner
walls of the steel tanks will be of galvanized steel in order to avoid
corrosion from hydrogen sulfide for as long as possible.
There is of course the alternative of buying and deploying
the largest possible sizes of plastic tanks. They are of lower capacity but
deployed in enough numbers they can do well to service a 250 cubic metre biogas
plant.
REPAIR AND MAINTENANCE OF BIOGAS PLANT
Blocked Inlet/Outlet Pipe
Possible Reasons:
A.
Fibrous
material inside the pipe
B.
Sinking
layer blocking the lower end of the pipe.
CORRECTIONS
(a) Clean up the pipe with a pole
(b) Remove the sinking layer by
frequent poking through inlet and outlet pole.
Sinking Sludge Level
Possible Reasons
A.
Digester
not water tight (If cracks in the digester do not self-seal within weeks, empty
digester and seal cracks).
B.
Insufficient
gas storage: Gas store not gas tight due to cracks or corrosion.
CORRECTION
I.
Seal
Cracks
II.
Replace
corroded parts
BLOCKED TAPS
A.
Corrosion:
Open and close several times, grease or replace taps.
B.
Gas
pipe is not tight: Corrosion or porosity; insufficient sealing of connections.
CORRECTION: (a) identify leaking parts (b) replace corroded or porous parts (c)
re-seal connections.
SUDDEN GAS LOSS
Possible Reason
Crack in the gas pipe: automatic water trap blown empty.
CORRECTIONS
A.
Open
gas tap
B.
Repair
or replace
C.
Add/refill
water
D.
Detect
reason for over-pressure
E.
Check
dimensioning of the water trap
F.
Close
tap.
THROBBING GAS PRESSURE
Possible Reason
1.
Water
in the gas pipe
2.
Blocked
gas pipe
CORRECTIONS
A.
Check
functioning of water trap
B.
Install
water traps in depressions of piping systems
C.
Or
eliminate these depressions
D.
Identify
the blocked parts (start with gas outlet connections to appliances and bends).
E.
Clean
the respective parts.
MATERIAL AND EQUIPMENT REQUIREMENT FOR FABRICATION OF
A BIOGAS PLANT.
1.
Oil
Storage Tanks in Galvanized Steel Sheets (10 no) Total capacity 250Cubic Metres
2.
Slurry
Mixing Tanks
3.
Steel
or PVC Pipes, Bends etc.
4.
Valves,
Chambers, Locks, Gas Pressure Gauges, Metres etc.
5.
Gas
steel storage tanks or gas plastic membranes, gas holders etc.
6.
Cow
Dung Dump Tanks (or just plain ground)
7.
Bio-Slurry
Tanks (Plastic)
8.
Sieving
Equipment
9.
Drying
Equipment.
10.
Sack
Sewing Machine
11.
Bottle
Filling Equipment
12.
Jerry
Cans, PET Bottles.
13.
Tractors
with Buckets (2 No)
14.
Push
Carts
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