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What is
 biogas plant?
biogas
plant produces biogas and bio-fertilizer
from biological wastes of agricultural
and food industries by means of
oxygen-free fermentation (anaerobic
digestion).
Biogas plant – is the most active system
of biological recycling. This system
performs utilization, recycling and has
shortest payback period. The differences
from the other recycling systems are the
following
1) biogas plant does not consumes power,
but produces it
2) produced electricity is used by the
enterprise and end products of other
recycling systems (dry feed or dry
manure) needs to be sold or recycled.
Following raw materials can be used for
biogas production: cattle manure, pig
manure, chicken dung, slaughterhouse
waste (blood, fat, entrails, and rumen
content), plants waste, silage, rotten
grain, waste water, fats, bio-waste,
food industry waste, malt remnants,
marc, distillery slop, bioethanol plant
slop, brewer’s grain (crushed malt
remnants after wort filtration), sugar
beet and fruit pulp, sugar beet tops,
technical glycerin (after biodisel
production), fiber and other starch and
treacle production, milk whey, flotation
sludge, dewatered flotation sludge from
municipal waste water treatment plants,
algae. Most of the raw materials can be
mixed with each other.
What
are the benefits of
biogas plant?
Waste recycling gives:
main benefits
1.
1.
ecological cleaning
2.
2.
gas,
3.
3.
bio-fertilizer,
4.
4.
investment cost saving (for new enterprises)
additional benefits
1.
1.electricity,
2.
2.heat,
3.
3.vehicle fuel
In
detail about
biogas plant benefits
Ecological cleaning and utilization
Biogas plant can reduce sanitary zone
(distance from the enterprise to
residential area) from 500m to 150m. In
many cases such ecological issues are
vital for some enterprises.
Out-of-date lagoons occupy lots of space
and have bad smell. Biogas plant
requires space that several times less
if to be compared to lagoons and manure
storages. Water in lagoons is bounded by
colloid compounds hence evaporation is
very faint. After treatment in biogas
plant water is separated and easily
vaporized. Digested biomass can be
released to the fields without any time
delays, which can reduce lagoons area up
to 5 times! Investments into lagoon
construction are money thrown down the
drain. By investing into biogas plant
you payback your money with profit and
make land usage more effective. Biogas
plant construction is useful not only
for new farms but for existing as well,
because old lagoons maintenance cost are
considerable.
Some of waste products can be stored in
lagoons while the other require energy
and cost consuming utilization
(slaughterhouse waste), biogas
production looks more attractive in that
respect. Usage of conventional lagoons
and land fills often makes possible
filtrate percolation to the groundwater
that causes health problems to people
and animals as well as sanctions from
state sanitary service and costly
medical treatment. Using biogas plant
system you will avoid diseases, medical
and penalty bills.
Equipped with additional filtration
devices (pressure filter, decanter)
biogas plant can reduce COD and BOD
levels in filtrate so it can be
discharged to sewage system or factory
water treatment facility. COD – chemical
oxygen demand and BOD – biological
oxygen demand. Biogas plant makes
possible removal of most part of
contaminating biological matter (organic
matter content reduced up to 60-70%).
Biogas
What is
biogas?
Biogas is the gas consisting of
approximately 50-70% of methane (CH4)
and 50-30% of carbon dioxide (CO2).
Synonyms for biogas such words as sewage
gas, marsh gas, methane. Different
microorganisms metabolizing carbon from
organic matter in oxygen-free
environment (anaerobically). This
process is known as decomposition or
anoxic fermentation and follows food
chain. In the process of fermentation
biological waste produces biogas. This
gas can be used as natural gas for
technological purposes, heating or
electricity production. It can be
stored, pumped, used as vehicle fuel or
sold to your neighbors. In order to
produce electricity no additional
treatment of biogas is required.
By properties biogas is similar to
natural gas. In case adjustable burner
is used biogas needs only drying,
hydrogen sulfide and ammonia removal. If
the burner is not adjustable the system
of carbon dioxide removal will be
needed.
For vehicle refueling additional gas
treatment system should be used. After
such treatment biogas becomes pure
natural gas analog (90-97% of methane
(CH4) and 10-3% of carbon dioxide (CO2)).
Another by-product of biogas treatment
is CO2.
This
gas used as dry ice, for beverages
production or technological purposes and
can be sold as valuable commodity.
|
Raw material |
Biogas yield m3/t of raw material |
|
Cow manure |
60 |
|
Pig manure |
65 |
|
Chicken dung |
130 |
|
Fat |
1300 |
|
Distillery slop |
70 |
|
Grain |
500-560 |
|
Silage, plant tops, grass, algae |
200-300 |
|
Milk whey |
50 |
|
Fruit and sugar beet pulp |
50-70 |
|
Technical glycerin |
500 |
|
Brewer’s grains |
180 |
Anyone understands that natural gas
price increase is inevitable and
substantial. Gas pipeline broaching
worth millions of dollars, contrarily
biogas plants construction is more cost
effective. After investment into gas
pipeline we have to pay for gas as well,
to be compared with biogas it is nearly
costless (less then RM152 per 1000
m3). Biogas plant is the best solution
for gas supply to remote regions.
Bio-fertilizer
Raw manure or other biological waste is
not applicable as fertilizer for 3-5
years. Anaerobically digested biomass is
a finished and ready for use
high-performance bio-fertilizer. This is
not only ecological issue, but the
matter of profit. In raw biological
waste (manure for example) minerals are
chemically bounded to organics that
complicates their consumption by plants.
For example mineralization in raw manure
is 40% if to be compared to 60% in
digested biomass. Digested biomass is
finished solid and liquid bio-fertilizer
free of nitrites, weed seeds, pathogenic
microflora, helminth eggs and odors. As
a result of balanced bio-fertilizer
application crop yield can be increased
up to 30-50%.
Biogas plant produces high quality
bio-fertilizer. Bio-fertilizer is a
commodity. The quality of bio-fertilizer
is higher then mineral fertilizers and
the net cost almost equals to “0”. As a
commodity it can be sold to anyone.
Investment savings
New enterprises can have
considerable investment savings due to
the possibility to avoid building new
gas pipeline, electricity line,
auxiliary generators and waste storage
facilities. Thanks to the short
digestion period the volume of waste
lagoons can be reduced twice. Investment
cost savings can reach about 30-40% from
biogas plant price.
Electricity
Combustion of 1 m3 produces 2
kWh of electricity. You get fluctuation
free electricity in comparison with
public electricity network. By building
biogas plant you will have electricity
at a fixed price, that makes about
0.01$/kWh.
Heat
Heat from generator cooling or biogas
combustion is used for working premises
heating, technological purposes, steam
generation, seeds drying, firewood
drying, hot water supply and
stockkeeping.
New or existing greenhouse nearby biogas
plant is a perfect solution. Heat can
come directly from biogas combustion or
from generator cooling device. Only
generator cooling device can heat 2 Ha
of greenhouse area. 90% of expenses for
growing greenhouse cucumbers, tomatoes
and flowers are heat and fertilizer
costs. If greenhouse combined with
biogas plant it is possible to reach
300-500% of profitability.
Heat is also used to activate
refrigerator vaporizer and produce cold
for refrigeration of fresh milk at dairy
farms or meat and eggs storage.
Vehicle fuel
After treatment of biogas you
get biomethane (90-95% methane, the rest
is CO2). Biomethane is
complete analog of natural gas by its
properties and quality. The only
difference is the source of the gas.
Such methane can be and should be filled
into vehicle tank.
Huge gas filling station network already
exists. In the circumstances of constant
diesel fuel rice in price, methane usage
becomes more attractive. Green Biogaz builds
biogas plants equipped with biogas
treatment system and methane filling
station. Also we can undertake
conversion of engines to run on methane.
Conversion of one system unit to run on
methane costs RM 11,143.00 all materials
and work included. Methane filling
station payback period is about half a
year.
Net cost of biomethane is RM 102 for
1000 m3, and price for diesel
fuel RM 4,567 for 1000 L. 1 L of diesel
fuel equals 1 m3 of biomethane.
Biogas plant scheme
Operation principle of
biogas plant
Liquid
biological waste is pumped to biogas
plant by sanitary pump or extraction
pipeline. Sewage pumping station (SPS)
is located in a separate service room.
Solid biological waste (manure, dung)
delivered by belt conveyor, in case of
manure or dung storage, delivery made by
tractor. Liquid wastes initially come to
primary tank. In primary tank waste
homogenized and heated (sometimes
cooled) for required temperature. As a
rule such tank has 2-3 days storage
capacity. Solid waste can be loaded to
that tank as well for homogenization or
get into digester through screw charger.
From
homogenization tank and screw charger
biomass (manure, dung or distillery
slop) comes to digester (biological
reactor). Biological reactor is
gas-proof tank made of acid-resistant
concrete. Reactor is heat-insulated. The
heat-insulation is calculated depending
on the biogas plant site climate
conditions. For microorganisms’ vital
activity a constant and even temperature
inside the digester is kept, usually it
is mesophilic temperature mode
(+30-41°Ñ). In some cases termophilic
mode of temperature is used (about
55°Ñ). Biomass mixing inside the
digester is made by several ways and
depends on the type of raw material, its
humidity and other features. Mixing can
be done by slopped mixer, “paddle giant”
type mixer or submersed mixers. Al mixer
types are made of stainless steel. In
some cases mixing device can be
hydraulic instead of mechanical. Such
mixers pump the biomass into the layers
with bacterial clumps. Bioreactors are
built with wooden or concrete dome and
have service life of 25-30 years.
Digesters
are heated by hot water with inlet
temperature about 60°Ñ and discharge
temperature of about 40°Ñ. Heating
system is a network of pipes, which can
be built-in to reactor wall or to be
mounted to interior side of the digester
wall. In case biogas plant equipped with
co-generation unit, digester can be
heated by generator cooling water.
Generator cooling water has temperature
of 90°Ñ and before getting into digester
heating system it is mixed with 40°Ñ
water so that heating system receives
water with 60°Ñ. The water is previously
treated and returnable. In winter time
biogas plant requires up to 70% of heat
from generator cooling device and 10% in
summer time. If biogas plant is purposed
only for gas production hot water is
taken from a special water boiler.
Biogas plant self energy and heat
consumption usually makes from 5% to 15%
of overall produced.
The average
hydraulic retention time of biomass in
bioreactor (depending on the material
type) is 20-40 days. During this time
organic matter is metabolized (modified)
by microorganisms presented in the
biomass. Corn silage hydraulic retention
time is about 70-160 days. The hydraulic
retention time defines the size of the
digester.
The
fermentation process is made by
anaerobic microorganisms, which are
injected into the digester during the
biogas plant start up. Any further
microorganisms injection is not
required. Microorganisms injection is
made by one of three ways: 1)
microorganisms concentrate injection 2)
fresh manure addition or 3) injection of
biomass from operational biogas plant.
As a rule 2nd and 3rd methods are used
being cheapest ones. Microorganisms get
into manure from animal bowels and are
not harmful to human or animal. Moreover
bioreactor is a hermetically sealed
container. That is why bioreactors or
fermenters can be placed near the farm
or production facilities.
As end
products we have: biogas and
bio-fertilizer (composted or liquid).
Biogas is
stored at a gasholder. Inside the
gasholder pressure and biogas
composition is evened. Green Biogaz gasholder
is a high-tensile and distensible EPDM
membrane. The membrane material is
resistant to sunlight and internal
bioreactor sediments and evaporations.
Gasholder service lifetime is 15 years.
Bioreactor hermetically sealed by the
gasholder from the top side and covered
by additional tilt cover. The space
between the gasholder and tilt cover is
pumped with an air in order to form
pressure and heat insulation. Sometimes
gasholder is a multichamber cover.
Depending on the project solution such
cover can be secured by belts on the top
of the concrete dome or to be placed in
a separate concrete tank. Gasholder
volume capacity is 0.5 – 1 operational
day.
From the
gasholder biogas constantly comes to gas
or diesel/gas co-generation unit. Here
heat and electricity are being produced.
1m3 of biogas produces 2 kWh of
electrical and 2 kWh of heat power. Big
biogas plants are equipped with an
emergency flare for instances of engines
malfunction and the necessity to burn
the excessive biogas. Biogas system can
be equipped with ventilation, condensate
extractor and desulphurization unit.
The whole
system is operated by the automatic
control unit. Control unit operates the
work of pumping station, mixers, heating
system, gas automatics and generator.
For operational control only one person
for 2 hours a day is required. This
person affects the control with the help
of computer. After two weeks of training
any person without any special skills
can operate the biogas plant.
Anaerobically digested biomass is
finished and ready for use as
fertilizer. Liquid bio-fertilizer is
separated by separation unit and stored
in a tank. In Germany this liquid
(ammonia water) is used as a fertilizer
due to high ammonia (NH4) content. Solid
fertilizer is stored separately. From
the storage tank liquid bio-fertilizer
is pumped to transportation tanks for
further distribution or sale. As an
option biogas plant can be supplied with
fertilizer packing line (bottles 0.3,
0.5, 1.0 l). In case liquid fertilizer
is of no interest for biogas plant
owner, such plant can be equipped with
additional waste water treatment
modules.
When company
doesn’t need electricity but gas for
vehicle filling, biogas plant supplied
with gas treatment system and methane
filling station. Gas treatment system is
equipment that separates carbon dioxide
from biogas and is based on absorption
and stripper technology. Carbon dioxide
content can be reduced from 40% up to
10% (even 1% is possible if required).
This option is very interesting taking
into consideration diesel fuel high
prices.
For some
types of biological waste above
mentioned operation principle requires
modification. For example it is not
workable with single raw materials such
as distillery slop and brewer’s grain.
In that instance two stage systems with
additional hydrolysis reactor should be
used. The peculiarity of the process is
the support of acidity level in
hydrolysis reactors. This technology
patented by Green Biogaz and is under protection
that makes impossible it’s usage by
other companies.
Biogas plant
self energy consumption is 10-15% in
winter time and 3-7% in summer time. In
order to operate even big biogas plant
only one person for two hours a day
required.
Biogas
plant equipment and facilities
1. Homogenization tank
2. Solid biomass loader
3. Bioreactor (digester)
4. Mixing devices
5. Gasholder (gas storage)
6. Water mixing and heating system
7. Gas system
8. Pumping station
9. Separator
10. Control gauges
11. Control equipment with visualization
12. Emergency flare system and security
system
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