Biogas Assignment
BTC-1 Assignments:
Write any two assignments in 500-800 words: You can refer to any books
and/or websites for information. Kindly mention the source.
* 25 marks for each assignment
1. Find out the number of biogas plants in China, India and Nepal. Add some
information on their size and designs. How much do they cost and what are
their benefits. Give source of information.
Write any two assignments in 500-800 words: You can refer to any books
and/or websites for information. Kindly mention the source.
* 25 marks for each assignment
1. Find out the number of biogas plants in China, India and Nepal. Add some
information on their size and designs. How much do they cost and what are
their benefits. Give source of information.
In 1988, the cost of anaerobic digester in India was Rs 5850 equal to 480 USD (Kalia, 1988).
3.7 million biogas plants are operating in India. Nepal has 140000 biogas plants till 2006 (Sorkin, 2006). The digester sizes ranges fron 4- 20 m3.
12 million households in China use biogas plants. Typical biogas plant has digester volume of around 6-8 m3, and produces around 300 m3 biogas per year, operating for 3 to 8 month per year, and costs around $200–250 depending on the province (At Information: Biogas, 2011)
- According to Gas Storage
The design of biogas digester may vary accordingly to suit the requirements of the owner. This can be divided into three groups, namely: fixed-digester, floating gas holder and bag digester.
• Fixed-Dome Digester
Fixed-dome digester (Figure 9) is the most common type of design. The four major components of the digester which are gas storage, fermentation
- Fixed Dome Type Biogas Plant
Fixed-dome digester (Figure 1) is the most common type of design. It is used in India and China. The four major components of the digester which are gas storage, fermentation chambers, hydraulic tank and inlet tanks are integrated into one structure. Its distinct advantage over the other designs is:
1. All concrete construction, hence, durable and life long investment. Simple structure. Least cost.
2. No moving parts and metal components, thus, easy to maintain.
3. Capable of generating higher gas pressure (on the average 10 times higher than floating gas holder type) and does not use floating tank.
Completely constructed underground, thus save land space. Input materials flow easily into the digester by gravity, hence simplifying operation
China: Family size PUXIN anaerobic digester biogas system (Shenzhen Puxin Science & Technology Co. Ltd , 2010).
Puxin family size biogas system is mainly applied to farmers home. The family size biogas system is composed of a 6 or 10 m3 biogas plant , the pipe system, the gas purify system and the appliances or electricity generator.
Puxin Biogas Plant is of the hydraulic pressure biogas plant type, and is composed of a concrete digester and a glass fiber reinforced plastic gasholder. The digester has a capacity of 6 or 10 cubic meters, and is constituted by a stomach, a neck, an inlet and an outlet. The gasholder is 1.6 m in diameter, 1 or 1.2 cubic meter in capacity. The gasholder is installed within the digester neck, fixed by a component; the gasholder and the digester are sealed up with water.
Puxin family size biogas system is mainly applied to farmers home. The family size biogas system is composed of a 6 or 10 m3 biogas plant , the pipe system, the gas purify system and the appliances or electricity generator.
Puxin Biogas Plant is of the hydraulic pressure biogas plant type, and is composed of a concrete digester and a glass fiber reinforced plastic gasholder. The digester has a capacity of 6 or 10 cubic meters, and is constituted by a stomach, a neck, an inlet and an outlet. The gasholder is 1.6 m in diameter, 1 or 1.2 cubic meter in capacity. The gasholder is installed within the digester neck, fixed by a component; the gasholder and the digester are sealed up with water.
Benefits:
- Easy to build.
- Suitable for vast rapid construction.
- Convenient to replace solid fermentation material; suitable for straw and other solid organic material.
- Easy to maintain and a long service life.
- Excellent airtight function and the high rate of biogas production.
- Excellent safety and easy operation
- Low initial costs and long useful life-span
- No moving or rusting parts involved
- Basic design is compact
- Saves space
- Well insulated
- Construction creates local employment
Disadvantages:
· Masonry gas-holders require special sealants
· 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
· Expensive in bedrock.
Figure1
Source: (Khoiyangbam. et al., 2004)
2. Floating Gas Holder Type Biogas Plant
Figure 2
Source: (Khoiyangbam. et al. , 2004)
Advantages:
· Floating-drum plants are easy to understand and operate
· They provide gas at a constant pressure
· The stored gas-volume is immediately recognizable by the position of the drum.
· Gas-tightness is no problem, provided the gasholder is de-rusted and painted regularly.
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.
3. Separate Floating Gas Holder Type
Figure 3
Source: Design of Biogas Digester
4. Bag Type Gas Holder
Figure 4
Source: Design of Biogas Digester
5. Under Ground Digester
Figure 5: Under Ground Digester
Source: Design of Biogas Digester
6. Semi Buried Digester
Figure 6: Semi Buried Digester
Source: Design of Biogas Digester
Figure3
Figure2
Source:Reddy (2007)
Design of Digester
The fixed dome bio-gas plant buried underground. There are 3 main connecting parts :
1. Mixing chamber: where animal excrement is mixed with water before it is poured into digester chamber.
2. Digester chamber: where excrement and water are fermented. Methane and other gases will be produced in the chamber and these gases will push manure and slurry at bottom of the floor into expansion chamber.
3. Expansion chamber: collects excess manure and slurry.
The plant should not be located further than 5 meters from the enclosure. The digester chamber must be in an open area and should not be near any water source or natural water as animal excrement may seep into underground water. The plant should also be situated on a slope and not on the low land to avoid the danger of floods. The excess manure from expansion chamber should flow into the farmer’s field or the storage tank and not into natural water bodies such as rivers to avoid the risk of pollution.
Formula to calculate the size of the digester:
Fresh manure/day x amount of animal x 2( for cow/buffalo) or x 3 ( for Pig) x Retention time (60 days)
The different sizes of the digester’s are given in the table below:
Livestock | 4.6 m3 | 8 m3 | 12 m3 | 16 m3 |
Milking cows | 2 | 3 | 5 | 7 |
Meat cows | 3 | 6 | 12 | 18 |
Buffaloes | 2 | 3 | 8 | 13 |
Pigs | 10 | 15 | 25 | 38 |
- What is scale of operation in large European farm biogas plants? How much biogas do they generate and how do they utilise the gas?
The biogas plants in Europe are very diverse. Many different systems have emerged depending on the regional framework conditions. In some regions, predominantly agricultural biogas plants that use liquid manure and energy crops from the own production to produce the biogas are found. Other regions have concentrated on the use of biogenous residues and commercially/industrially operated biogas plants. Others again prefer the production of fuels from biogas or the construction of CHP plants to generate electricity and heat. The size of the biogas plants in Europe ranges from very small plants (15 kWel) up to large plants (several MW). Also regionally different are the economic framework conditions. The promotion of electricity from biogas plants takes place either through feed-in-tariffs for the produced or supplied amount of electricity or through green certificates (Rhônalpénergie-Environnement , 2011).
a). Biogas Plant – Ebersdorf, Styria-Austria
The Niederl family operates a pig breeding and pig fattening business (250 breeding pigs) as well as a stable furnishing company in the community of Poppendorf. Since the beginning of 2004 they also operate a biogas plant that uses renewable resources and the liquid pig manure. The biogas plant of the Niederl family is characterised by the two horizontal high performance fermenters (400 m³ each) with paddle stirrers. The produced biogas is stored in two gas holders (400 m³ each) above the two post fermenters and converted into electricity and heat using two gas engines (170 kWel and 330 kWel). The generated thermal energy is used to heat the own business (residential house, agricultural buildings), a further possibility for using the heat is already being planned. The electricity generated through co-generation is fed into the public grid. After the fermentation process, the “biogas manure” is open
enough to be spread on the own fields as well as on areas owned by cooperating farmers (200 ha total) in a nutrient rich and minimal smell nuisance causing way. By doing this the family is able to save commercial fertilisers causing for the cycle to close itself. The amount of gas produced per day is 6500 m3 (Rhônalpénergie-Environnement , 2011).
b). LUTOSA, the Belgian potato processing factory – Belgium
Lutosa is a Belgian family company with expertise in the potato sector going back over four generations. It is a public company and the initial investment cost is 2000000 euros. In 1986, a first biogas installation was set up to reduce the organic charge of factory effluents. The biogas produced from the fermentation of waste from the anaerobic purification station was burned by a flare. In 2002, Lutosa launched the largest biogas cogeneration plant in Belgium, in close co-operation with Electrabel in order to enhance the energy yield of biogas production. Currently, the cogeneration plant is able to cover a big part of the factory's energy requirements. Heat (hot water and steam) are totally re-injected into the factory process. The major part of electricity production is feeding into the public grid. The amount of gas produced is 800-1000m3 per hour or 19200-24000m3 per day (Rhônalpénergie-Environnement , 2011).
c). Biogas plant, GAEC du Bois Joly – France
“GAEC du Bois Joly”, in Vendée, is a French agricultural civil society. It is a farm specialized in rabbit (600 females) and bovine production (50 brood cows). This farm produces solid manure on a discontinuous basis. The dry fermentation unit of “GAEC du Bois Joly” is a Ducellier-Isman system improved. Digesters are built in concrete-corridors. Each has a volume of 185 m3 and covers by an EPDM membrane. The anaerobic digestion of solid manure creates liquid. This liquid is collected in each digester and is used to spray on the manure inside the digester, to keep up the humidity and temperature (it is heated up). The liquid also contains methanogen bacteria. So it is very important at the beginning of a new fermentation to use a liquid from an active fermentation. The produced biogas is directly consumed in a CHP unit. The whole electricity is injected to the grid and sold to EDF. The heat is not only used for the digesters, but also for only one rabbits farm building and for farmer’s house. The amount of gas produced is 675000 m3 per year with an initial investment cost of 270000 euros (Rhônalpénergie-Environnement , 2011).
d). Agriculture biogas plant Thomas Karle, Kupferzell – Germany
It used liquid manure from fattening pigs, leaves of sugar-beets, left over from the fruit juice and organic wastes of lettuce, vegetables and fruits. The initial setup cost of the plant is 1200000 euros and the amount of gas produced is 2.2 Mio m3 per year. The gas produced is used for the thermal power of the gas engine, as an electric power of the engine and the manure produced is used as a fertilizer (Rhônalpénergie-Environnement , 2011)
References
Abdul (2011) Biogas Plant Design and Construction [Online]. Available: http://bio-gas-plant.blogspot.com/2011/04/biogas-plant-digester-types.html [Accessed 10 June 2011].
AT Information: Biogas (2011) History of biogas technologies [Online]. Available: http://www.fluid-biogas.com/?page_id=197&lang=en [Accessed 9 June 2011].
Bio-Technology Ltd. (2010) Construction Manual of Bio-gas Reactor [Online]. Available: http://www.apo-tokyo.org/gp/e_publi/biogas/BiogasGP4.pdf [Accessed 11 June 2011].
Reddy, Dr. (2007) MINI BIOGAS PLANT - SRUSHTI [Online]. Available: http://e-biogas.blogspot.com/ [Accessed 23 March 2011].
Rhônalpénergie-Environnement (2011) Biogas Regions [Online]. Available: http://www.biogasregions.org/shining_examples.php [Accessed 09 June 2011].
Shenzhen Puxin Science & Technology Co. Ltd (2010) Family size PUXIN anaerobic digester biogas system (Family size PUXIN anaerobic digester biogas system) [Online]. Available: http://www.greentradebay.com/Product/481394/Family-size-puxin-anaerobic-digester-biogas-system.html [Accessed 10 June 2011].
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