Name of project: production biogas from kitchen waste.
Full working information of project: The methanogens (methane producing micro-organisms) belong to a group of
bacteria called Archebacteria. They evolved when the earth’s atmosphere did not have
any oxygen. After the evolution of green plants, the oxygen content of the atmosphere
started to rise. Being unable to survive in an oxygen rich atmosphere, the methanogens
retreated to places that were devoid of oxygen. Today they are found in marshes, rice
paddies, at the bottom of water bodies and in the intestines of animals. They survive in
the intestines of animals by eating what the animals eat. The methanogens can easily
digest sugar, starch, fats and proteins. They can also digest cellulose, albeit rather
slowly, but they cannot digest lignin at all. Their digestive mechanism is similar to that of
many other organisms, up to the point of converting the food into acetic acid. In the case
of organisms breathing oxygen, the acetic acid gets converted into carbon dioxide and
water (CH3COOH+2O2 = 2CO2+2H2O), whereas the methanogens convert it into
methane and carbon dioxide (CH3COOH = CH4+CO2). The methanogens, are universally
present in the faeces of all animals, because they are thrown out of the body along with
the faeces. Faecal matter is not their food.
Because the methanogens can digest all forms of human food and also cellulosic
biomass, they are ideal for producing methane from kitchen waste. Because the
metanogens reside in the intestines of animals, they work optimally at temperatures
equal to the body temperature of animals, which is about 38C. They also need a medium
having pH value of around 7. At this temperature and pH, they can convert human food
into biogas within a period of about 24 hours. 1 kg (dry weight) of human food yields
about 1 kg (about 800 litres) biogas. To get the same quantity of biogas from dung, one
needs about 40 kg dung, and a fermentation period of about 40 days. Because of the
lower quantity of feedstock and lesser fermentation time, the size of the kitchen waste
biogas plant is much smaller than that utilising dung. According to theoretical
calculations, biogas should normally contain volumetrically about equal amounts of
methane and carbon dioxide, but actually the methane content is generally around 60%.
Pure methane has the same calorific value as LPG (about 11,000 kCal per kg), but
because of the presence of carbon dioxide, the calorific value of biogas is only about
4000 kCal per kg. Therefore, to get the same heat as from an LPG burner, a biogas
stove is designed to deliver volumetrically about 3 times as much gas per unit time as
LPG.
The waste material to be fed into a biogas plant should contain only digestible
organic material. Other organic products like plastic, rubber, petroleum, bones, hair,
horns, hooves or wood (i.e. lignin), cannot be digested by the methanogens. If highly
lignified material like agricultural waste is to be converted into methane, one has to use a
biphasic digester. In this system, the waste is first subjected to aerobic decomposition,
after which it is leached out with water and the leachate is fed into the anaerobic
digester. The aerobic organisms in the leachate die due to lack of oxygen in the
anaerobic digester and their cells serve the methanogens as food.
Operators of a biogas plant must keep in mind that this is a living system.
Introduction of any toxic or bactericidal material into the biogas plant would kill the
methanogens and the system would stop producing methane. Overfeeding should also
be avoided. A biogas plant harbours several other micro-organisms besides the
methanogens. If the biogas plant receives more feed than the digestive capacity of the
methanogens, the undigested food serves the non-methanogenic organisms as nutrition,
causing the latter to increase their numbers. Increase in the population density of nonmethanogenic
organisms causes reduction in that of the methanogens, inhibiting the
formation of methane.
Required metal and substances:
1. 20 gauge sheet- 48.9 square feet.
2. 18 gauge sheet- 12.6 square feet.
3. Pvc pipe for inlet – Diameter 2.5 inch and Hight 6.5 feet.
4. Pvc pipe for outlet – diameter 2 inch and Hight 1 feet.
5. Pvc pipe for clean waste – diameter 2 inch and Hight 1 feet.
6. Hose pipe- dia 1 cm, length 3.75 meter.
7. Stop nob- 2 pieces.
8. Gas pressure gauge-1 pieces.
9. Funnel- 1 pieces.
10. Albow joint 1 pieces.
11. Gas welding torch and lead.
12. Red oxide – ½ kilogram.
Measurments and calculations:
(A) Inlet pipe:
1. Hight – 6.5 feet
2. Diameter- 2.5 inch
(B) Digester tank:
1. Hight -1.8 meter.
2. Diameter – 0.75 meter.
3. Cover plate- 0.44 square meter
4. Coller – 0.025*2.5 square meter
(C) Gas tank:
1. Hight -0.75 meter.
2. Diameter – 0.35 meter.
3. Cover plate- 0.096 square meter
4. Coller – 0.025*1.09 square meter
(D) Outlet pipe:
1. Hight – 1 feet
2. Diameter – 2 inch
(E) Cleaner pipe:
1. Hight- 1 feet
2. Diameter- 2 inch\
(F) Hose pipe:
1. Length – 3.75 meter
2. Diameter – 1 cm
(G) Nozzel:
2 piece for 1 cm pipe.
Figure of plant:
Making process of plant:
1. At first buy required instruments of plant.
2. To cut sheets form sheet bar by measurment.
3. At first make cylindrical tank by using sheet roller for digester tank.
4. And now make cylindrical tank by using sheet roller for gas holder.
5. Now need to cut two sheet covers and two collars for digester tank .
6. And now also need to cut two sheet covers and two collars for gas tank .
7. Now go to make hole on sheet cover , where need.
8. Now go to make joint on digester tank by seam joint with accessories by acitiline gas welding.
9. And then gas holder tank also joint by same system.
10. Joint inlet pipe with funnel.
11. Joint outlet pipe with tank.
12. Joint cleaner pipe with tank in below hole of tank.
13. Joint inlet pipe in digester tank.
14. Joint control switch with gas transfer pipe.
15. Connect digester tank and gas holder by gas transfer pipe.
16. Connect burner with gas holder.
17. Connect elbow with outlet pipe.
Description chart:
DESCRIPTION
FOR 0.53 CUBIC METER
Maximum food waste that can be accumonded
1-2
Gas production capacity
100 gm LPG equvalant
Water required
12-20 lit per day (if operated by only food waste)
Labour required cost
1500 TK
Approximate cost
12000 Tk
Operating process:
1. Everyday need to throw waste 1.5 to 2 kilogram(kitchen waste) with mixer 12-20 kg pure water.
2. Try to put digester tank in sun ray.
3. It will production gas after 20-22 days of first waste throw.
4. Must have system to bring out old wastes when drum is full.
5. Must need to check pressure of gas tank and use by visit properly.
6. And always check control valbe that open or close by system instruction.
Intentions of plant:
1. In our country even all over the world , fuel power is limited. by the demand for increasing people we are going to fall in great power crises. To protect this crises we can product gas equivalent by needless kitchen waste.
2. By this plant we can discrease over pressure from minerals natural gas.
3. Proper management for housekeeping kitchen waste.
4. Production gas by cheaper cost in house.
5. After product gas in plant, digested waste can be use as fertilizer in agriculture plant.
Advantages:
It generates a clean cooking fuel that can replace LPG.
It also generates organic fertilizer in the form of spent slurry.
It is easy to use and maintain because it is above ground.
There is no smell, mosquitoes, dogs, vermin, flies, etc.
All the organic waste is disposed off at source.
Payback period is expected to be 4-5 years only, whereas the life of the biogas
plant is 20 years.
Disadvantages:
1. If digests are not put in proper time in digest tank, it may not work.
2. After some months, if tank is not be cleaned it may not give proper efficiency.
3. If water is not be enough for adequate kitchen waste ,it may not work good.
Conclution:
At last I want to say that, where fuel federation is fail in trouble to provide enough power to among people ,there this cheaper technology may bring a pure breath.
Production biogas from kitchen waste
Mechanical Technology
Feni polytechnic institute
Name of group members:
Shaiful islam majumder
Roll-465741 Registration- 360427
7th semester 1st shift
Mechanical technology
(Leader of this project)
e-mail:
(shaifulislammajumder@engineer.com)
Mohammad hasan
Roll-465713 Registration- 360440
7th semester 1st shift
Mechanical technology
Mejbha uddin
Roll-465718 Registration- 360427
7th semester 1st shift
Mechanical technology
Abu bakkar siddik
Roll-465749 Registration- 360427
7th semester 1st shift
Mechanical technology
Md.Ilias uddin
Roll-465733 Registration- 360384
7th semester 1st shift
Mechanical technology
