Production of Biogas from Organic Waste and its Utilization as an Alternative Energy Source

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International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-3, May-June- 2018
http://dx.doi.org/10.22161/ijeab/3.3.7 ISSN: 2456-1878
www.ijeab.com Page | 763
Production of Biogas from Organic Waste and
its Utilization as an Alternative Energy Source
Sriharti, Moeso Andrianto, Fahriansyah
Center for Appropriate Technology Development Indonesian Institute of Sciences
Jl. KS. Tubun No. 5 Subang Wast Java Indonesia
Abstract As a result of increase in hu man need for
energy, the source of a new energy is necessary to replace
the role of fossil fuel whose existence is beginning to
scarce. The organic waste used for the production of
biogas is an alternative energy, allowing reducing
environmental pollution. The biogas test has been done by
using digester fixed dome type made of fiberglass capacity
of 5.5 m3, equipped with an inlet for introduction of bio gas
raw material and an outlet for the release of resid ual
biogas fermentation and an elbow iron mixing road. A soft
PVC gas holder has capacity of 5.6 m3. The dig ester is
filled by organic wastes namely cow dung and grasses.
Cow dung and water is added at the ratio of 1:2, then after
methane production was stable, filling with grasses mixed
with water. The results of th e test show that organic waste
get to produce biogas in blu e flame, to be used as fuel to
cook, to operate gas generator and for a infra red drying
fuel. The Water Boiling Tests show that thermal efficiency
is 57.9%, the fire power, 4.0173 watts, th e burning rate
0.0688 gram/minute, the specific fuel consumption, 0.1248
kg/hour.
Keywords agitated digester, biogas production, orga nic
waste, power generation, infra-red dryer
I. INTRODUCTION
The increasingly less reserve of petroleum is leading
to increase in prices of refined fuel oil. Given increase in
prices of refined fuel oil attributable to the upsurge of the
world oil costs, the government is encouraged to deal with
energy issues. One of efforts to tighten the refined fuel oil
is to seek renewable source of alternative energy.
Most of need for fuel for low income population
is satisfied by firewood, dried ups, and they are repeatedly
chopping down trees in off-limits forests, thereby making
natural conservation around the forest area in gradually
danger. Based on the matters, it is necessar y to try to use a
source of renewable alternative energy. Biogas is a source
of alternative energy having been developed, made out of
diverse organic wastes b y means of an anaerobic
decomposition process. In general, the type of the
resulting waste may be divided into two fold : one is
organic waste consisting of kitchen waste, traditional
market r ubbish, livestock feces, agroindustrial waste,
garden rubbish, agricultural waste and plantation. The
second type is organic waste in the form of glass bottles,
paper, cans, and plastics. The organic waste volume is, on
average, more than inorganic waste, covering 60-70% of
total waste volume (1).
Based on information from the Ministry of
Environment, each individual produces, on average, 0.8 kg
of waste per d ay. The average waste per person will
continue to increase with the improved well-being and
lifestyle. Assuming 220 million people in Indonesia, the
waste discharged is at t he rate of 176,000 tons per day,
some 105,600 123,200 tons of them are organic waste.
So far, the management of organic waste is even
using conventional techniques such as open dumping
system management to the landfill, making it compost,
burning it, o r dump it into the river. The management of
waste using those techniques tends to be environmentally
less friendly and economically less valuable. The
management in the open dumping system frequently
creates new problems; i.e., generate pollutant gases such as
H2S and NH3. The management of waste made into
compost tends to be economically less valuable and
burning it will cause the environmental pollution and
respiratory troubles for humans. The management of waste
by discarding it into the river will have direct impact being
source of human diseases such as skin diseases and
infectious diseases, while the indirect impact is a cause of
the flood.
Looking at the drawbacks of such techniques, a more
environmentally friendly management technique that able
to produce products of high economic values is necessar y.
For this purpose, the management of organic waste as a
source of alternative energy should be applied. A potential
method is by applying anaerobic technology to the
production of biogas.
Biogas tech nology was introduced in the 1980s;
however, until now the development has not been
encouraging, the existing obstacles include high
construction costs, biogas digesters are not functioning due
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-3, May-June- 2018
http://dx.doi.org/10.22161/ijeab/3.3.7 ISSN: 2456-1878
www.ijeab.com Page | 764
to leakage, requiring manual management (feeding/remove
the stuffing of digester).
Biogas is gas produced from the fermentation of
organic materials by anaerobic bacteria (bacteria being
exist in anaerob conditions). The components of biogas
are CH4 50-70%, CO2 30-45%, N2 0.2%, H2S 500 ppm,
and 02 < 2% (2). Biogas is a fuel such like LPG which can
be used for cooking a nd for power energy plant. Since it
has a calorific value about 5,000-6,513 kcal/m3 (3), the
biogas is a source of environmentally friendly and
renewable energy. The biogas digester output is slurry or
residual sludge of fermentation which is useful as organic
fertilizer for agricultural or plantation activities.
This study is designed to apply the technology to the
production of house hold-scale biogas by utilizing organic
waste derived from garden waste.
II. METHODOLOGY
A. Biogas Digester
Fixed dome digester used is made of fiberglass, 2.2
meters in height, 1.8 meters in diameter, capacity of 5.5
m3. Fixed dome is a most popular model in Indonesia,
where the installation of digester 3/4 is embedded in the
ground, allowing the conservation of space, maintains the
stability of digester temperature, and support the growth of
methane bacteria.
Digester is equipped with an inlet for t he introduction
of biogas raw materials and an outlet for discharging the
fermentation of residual biogas, made of PVC pipe, inlet
of 31 mm in diameter and 19 mm in height spliced to PVC
pipe of 16.5 mm in diameter, 30 mm in height, outlet of 4"
in diameter, 22 mm in length. The outlet is operated based
on the principles of hydrostatic pressure equilibrium.
Digester is equipped with a mixer, made of angle iron,
2 meters in height, and 1.5 meters in diameter. The
purposes of the mixing are to prevent scum from
formation, to reduce sedimentation, and to improve
productivity. In addition, the mixing is generating exac tly
contact between a substrate and a population of bacteria,
and produce a homogeneous condition and keep solid
matters in suspension (4). Digester 2/3 is embedded in the
ground, allowing the conservation of the land, thereby
making the charging of the raw material easier and the
temperature more stable.
B. Agitated Tank Biogas Material
Cow dung is collected in a plastic bag at capacity of
200 liters equipped with a mixer made of PVC pipe. The
purpose of the mixing is to admix the whole organic waste
cow du ng and water to make the anaerobic digestive
process faster. Manual mixing is made by spinning the
mixer.
C. Safety Valve
This digester is equipped with a safety valve for
regulating the gas p ressure in the d igester. It is made of
PVC pipe, 3" in diameter, and 22 mm in height. This
safety valve is using the principles of T p ipe. When the
gas pressure in the pipeline is higher tha n the water
column, the gas will be coming out through the T pipe,
allowing the reduction of the pressure in the digester.
D. Gas Holder
Gas holdet is made of soft PVC, 3.2 meters in length,
1.5 meters in diameter, and a capacity of 4 m3. Digester is
connected to the gas container by plastic tubing. Gas outlet
is made of ½ inch plastic tubing. The gas container is
placed on a height of 1.5 meters from the surface o f the
ground. The biogas is distributed by using the plastic
tubing to the biogas stove. Furthermore, the biogas took in
the gas container is distributed by using the plastic tubing
to be used as fuel for cooking and generator to p roduce
electricity.
E. The Filling up of Raw Material Biogas
Digester is filled up by cow dung and water is added.
The cow dung is coming from cattle breeding of SMK II
(STMPER) and Cikole. The water is added to the cow
dung at a ratio of 1: 2 in order to obtain a dr y weight about
9%. After the full filling up of digester has been completed
and methane has been produced, the digester is filled with
grasses and water is added at a ratio of 1:2.
F. Measurement of Biogas Production
The biogas produced is measured by a gas meter in
specifications as follows: Qmax 6m3/h, Qmin 40 d m3/h, Pmax
50 kPa, V 0.7 dm3. While the gas meter used to measure
the use of biogas for biogas stove and gas generator are as
follows: Qmax 3 m3/h, Qmin 16 dm3/h, temperature -20oC +
50°C, Pmax 1.5 bar, V 1.2 dm3.
G. Utilization of Biogas for Cooking
The biogas produced is used as fuel for cooking by
using biogas stoves. To take advantage of biogas as a fuel
stove required air pump to increase the pressure biogas.
Air pump used has the following specifications: LP 60;
220 V/240 V; frequency, 50-60 Hz; output, 70 liters/min;
power, 60 watts; and pressure, 0.04 mPa, is necessary.
H. Utilization of Biogas to Run a Gas Generator
The biogas produced is used to run a gas generator.
Gas generator used has the following specifications : AJP
4000 E-type; rate voltage, 220 V; frequency rate, 50 Hz;
rate output, 2.5 KVA; maximum output, 3.0 KVA; po wer
generator, 3,000 watts.
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-3, May-June- 2018
http://dx.doi.org/10.22161/ijeab/3.3.7 ISSN: 2456-1878
www.ijeab.com Page | 765
I. Utilization of Biogas to Run The Far Infrared Dryer
Biogas is used as fuel to run the dryer with t he
following specifications (5) : the type of far infrared dryer
tray cabinet, dimension of len gth 2 meters; wide 2 meters;
and height 2 meters.
Parts of wall made of styrofoam with a 40 mm thick
insulating material to withstand the heat out of the dryer
due to the heat transfer by conduction. Th inside styrofoam
coated 304 stainless steel plate thickness of 1 mm as a
reflector of electromagnetic radiation, while the outer
walls using patterned alumunium plate or ange peel with
thickness of 0,8 mm. Floor section using T block with 20
mm thick and using the same layer as the walls. Dryers
have two pieces of fan in the front and back, 1 piece
exhaust fan, 2 piece of of intake air circulation holes in the
door, 2 shelves and 1 control potel. Fans are used to flatten
the hot air in the drying chamber, while the exhaust fan is
used to absorb water vapor out of the drying chamber. As
the type of heating used gasolec S8 as easily available and
suitable for LPG and natural gas. Gasolec has a capacit 3 ,5
kw/hour with an operating pressure 350 1400 mbar (6).
Infrared dryer is used to run the compressor with the
following specifications maximum working pressure 9
kg/cm2, water test pressure 14,7 kg/cm2, capasity 22 l.
J. Testing the methane content
Testing the methane content is done simply b y means of
flame.
K. Water Boiling Test
The water boiling test is designed to determine the
capability of biogas. The test is established in a biogas
stove at room temperature using biogas to boil 2 liters of
water in a pot. Once the water in the first pot is boiling, the
test is done by replacing the pot in the second phase. The
Water Boiling Test is delivering data on thermal
efficiency, fire power, burning rate and specific fuel
consumption (7).
L. Thermal Efficiency Test
Efficiency is the perce ntage of usable heat than the heat
generated by a cookware during the test, the equation used
is as follows (7) :
(mw.cp + mpa.cpa)(T2 T1) + ms.Hfg
overall =
mf.E
Note:
= Overall efficiency of gas burner
mw
= Mass of water under heat (kg)
mpa
= Mass of pot of water under use (kg)
cp
= Heat of water type (kj/kg)
cpa
= Heat of pot type (kj/kg)
T2
= Temperature of boiling water (oC)
T1
= Initial temperature of water (oC)
ms
= Mass of water under evaporation (kg)
mf
= Mass of fuel under application (kg)
Hfg
= Latent heat of water evaporation (oC)
E
= Low caloric value of fuel (kj/kg.bb)
M. Fire Power Test
This test is designed to determine the amount of power
generated by a stove to cook. The power is derived fro m
the multiplication of the mass of the fuel by caloric value
of the fuel divided by time. Thus, the power generated by a
stove is derived from the mass o f the fuel under
application and the caloric value of fuel (biogas) and th e
length of time to cook (7).
To determine the amount of fire power, the following
equation is used:
mf.E
P = (KW)
∆t
Note:
P = Fire power (KW)
mf = Consumption of fuel during time t (kg)
E = Low caloric value of fuel (kj/kg).
∆t = Time of testing (second)
N. Burning Rate
This is a measure of the rate of fuel consumption while
bringing water to a boil. It is calculate by dividing the
equivalent fuel by the time of the test (7).
fcd
Rcb =
tc
Note :
Rcb = Burning rate (grams / minute)
fcd = Biogas consumed (grams)
tc = Time to boil (minute))
O. Specific fuel consumption
Specific fuel consumtion can be defined for any number of
cooking tasks and should be considered the fuel required to
produce a unit output, wether the output is boiled water. In
the case of the cold start high po wer Water Boiling Test, it
is a measure of the a mount of biogas required to produce
one liter of boiling water starting with cold stove (7).
fhd
SCh =
Pht P
Note :