TD390: Supervised Learning: Study ReportCurrent Status of Household Biogas Plants in Thane District: A Study Submitted By Nidhi Gupta (08d10033)Ajinkya Latkar (08d10037)Under the guidance ofProf. A. B. Rao During May-June 2012 Center for Technological Alternatives for Rural Areas (CTARA) Indian Institute of Technology, Bombay
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Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence
of oxygen. Organic waste such as dead plant and animal material, animal faeces, and kitchen waste canbe converted into a gaseous fuel called biogas. Biogas originates from biogenic material and is a type
of bio fuel.
For household cooking purposes, in rural areas, biogas is produced in small plants which typically come
in two types, fixed dome plants and floating dome plants. Both of these types work on animal excreta
as feed, and may or may not incorporate human wastes into it.
Typically a biogas plant consists of the following parts:
1. Feed inlet, for cowdung and household organic wastes
2. Digester
3. Gas holder (defines fixed dome or floating dome)
4. Outlet for bio slurry
5. Attached toilet for incorporation of human wastes (optional)
Fixed dome type biogas plants:
In this type of biogas plants, the gas holder is a fixed hemispherical slab, attached to the digester and
constructed a few feet into the ground depending on the size of the biogas plant.
The slab/dome is non removable, since it is completely under the ground and hence it extremely difficult
The initial motivation behind the survey that was carried out was to understand the behaviour of rural
household biogas plants, and evaluate the government/panchayat schemes that subsidized theconstruction of these plants. It was also to understand the current status of the biogas plants for
estimating an average behaviour, and explore the possibility of community biogas plants in the villages
of Thane district.
For this survey, first some villages of Wada taluka were surveyed. Following are the villages which we
visited for the same:
1. Gandhre
2. Khanivali
3. Dakivali
4. Ambiste-Khurd
5. Ambiste-Budruk6. Kharivali
7. Bilavali
8. Vavegarh
Figures 3 and 4 show a map of the area, locating the taluka and marking the villages in it.
1. GandhreThis is a village located very close to the main township of Wada. The population density here is very
low, and the houses are located far apart from each other. All the existing biogas plants here are of fixed
dome type, and a majority of them are dysfunctional.
2. Khanivali
This village is located in a plainer terrain than most of the other villages. There have been schemes for
biogas plants since around 1990, and people have made the most of them and got constructed biogas
plants for themselves, most of which are not dysfunctional. The village is also moderately large, and is a
travel transit point of Wada, i.e. there is a tempo stand here.
3. Dakivali
This is a moderately large village, population around 250 people, 75 families, located on the lower
border of Wada taluka. Many schemes for biogas were and are still in play here, but many plants are
dysfunctional. A biogas plant under construction was surveyed in this village, wherein details of material
and financial management were procured.
4. Ambiste-Budruk and Ambiste-Khurd
These are two very densely populated villages located close together in the interior of Wada taluka. The
total population is around 500. These villages had very active schemes towards biogas plant
construction till 2000. Inspite of that fact, most plants are dysfunctional.
5. Kharivali
This is a small village located near Kudus in the southern part of Wada taluka. A majority of the plantshere are dysfunctional. Unlike other villages where the dysfunctional plants were just kept covered, here
the tank was properly removed and cemented to provide extra space in house. Many of the households
sold off their cattle. In general it was observed that the villagers very careless about maintaining their
plants. Efforts like simple pipe replacements and cleaning of tank to circumvent problems were ignored
and not undertaken.
6. Bilavali
This is another small village, located close to Kharivali. This is the only village in this survey that had a
problem of water scarcity. Water scarcity is a major reason for many plants going dysfunctional in this
village. Most of the plants here (functional/dysfunctional) are fixed dome type, with only one r two
being of the floating dome type.
7. Vavegarh
This is a widely spread out village located in the northwestern part of Wada taluka. It has got 6
subvillages or “padas”, each of which has atleast 5-6 household biogas plants. Many biogas plants were
found here, but a majority of them are defunct. Interestingly, the people here are trying to develop
alternative technologies for sustainable energy, like solar energy.
ii) Frequent leakages in the connecting pipes. Repeated replacements made the use of biogas expensive
and hence families discontinued its use.
iii) Water is required in large amount. Shortage of Water lead to dysfunctionality of many biogas plants
in Bilavali which doesn’t has a lake or common well for the villagers.
iv)Few families who were rich and could afford expensive LPG cylinders preferred to shut down their
biogas plant as they didn’t wish to put in long hours of labour daily for the continuous running of the
biogas plant
v) Quite a many families had to sell off their cattle for economic reasons
5. Size and Capacity of Plant:
The common size of the plants are mentioned as follows
i) Fixed Dome: Generally 8-10 feet deep and 3 feet in radius
ii) Floating Dome: The pit is about 10 feet deep and tank is about 3 feet above the ground and about 3
feet in radius.
The input to the plant is according to the feed that the family can collect from its cattle and toilets. The
output is left open and the slurry produced is used by the families as fertilizers for their farms.
6. Cost of building the Plant:
Most of the families built the plant with the Schemes and subsidies available at the Government
(Panchayat) level. Among them, a few families loaned money in order to use the scheme. The rest built
the plants on their own. There is quite a disparity in the opinion of subsidy provided to these families.Some families claim that the entire amount was reimbursed while others claim that only half the
amount was reimbursed. Few families self constructed the biogas plants using the materials provided by
the scheme while others took the help of Mason.
7. Effort spent working on the Plant
On an average, a family needs to spend 1-2 hours daily on the working of the plant. This involves
collecting cow-dung, removing it of non-biodegradable substances and converting the feed into thin
slurry by mixing water. Human excreta directly feed into the tank through the pipes. Output slurry needs
to be collected and then used as a fertilizer. All the families, except a couple of them, don’t use external
labour to carry out these daily activities.
8. Performance Analysis:
In general the efficiency of the biogas plant was almost constant, except for the few maintenance issues.
Mostly the plant produced sufficient gas for cooking or heating purposes. In the worst cases, where
families had few cattle or those who couldn’t maintain the plants well used biogas for just heating or
cooking beverages. It’s observed that the efficiency of the biogas plant is most during the summers. High
The major reason for biogas plant failure was cracking. This issue can be addressed by proper
selection of materials. Material should be able to bear high pressure. Cracking may also take place
due to unwanted expansion of the tank or the dome.
Failure of floating type of tank was observed on a large scale. The tank is exposed to atmosphere
and hence can withstand less pressure in comparison to the fixed dome type which is buried
underground. However in case of floating tank, it is easier to replace the tank in case of some repair;
which in case of fixed dome will result in total dis-assembly of the plant.
Schemes for constructing biogas plant
During few interactions with the villagers, it was observed that many families are willing to have a
biogas plant of a scheme suiting his economic situation. A broad classification of the villagers on the
basis of their annual income should be done. Each type of family can avail the schemes according to
their needs. Banks should lend loans at cheaper rates. This in turn would encourage quick
repayment.
Maintenance of biogas plant
One should prefer fibre based tank rather than iron tanks to avoid rusting. Painting should be done
regularly if iron tanks are used. Feed fed to the plant should be free of non-biodegradablesubstances The feed should be made of very low density by mixing with water. Kitchen wastes can
Firstly, we thank our guide, Prof. A. B. Rao for his valuable guidance throughout this study. We
also thank Mr. Katole and Mr. Patil, from the Wada taluka main panchayat office, for pointing usin the right directions and hence helping us kick start our surveys. A sincere thanks to Mr.
Kaluram, contractor for biogas plants, who accompanied us in some of our visits and gave us
first hand information.
We would like to thank our batch-mate Vaibhav Nasery, a collaborator in this project, for
providing us with all the logistical details we needed for the surveys. We would also like to thank
our colleagues Prashant Jain, Raj Patel and Nikhil Jain (all students of IIT Bombay) for their
constant encouragement and companionship throughout this project.
A special word of thanks to all the villagers who cooperated and helped us around during thesurveys.
Lastly, we thank Prof. Sohoni and the entire CTARA team for providing this great opportunity to
study and interact with various stakeholders involved in the project.