Biogas

1. University of Agricultural Sciences Dharwad
College Of Agriculture Hanumanmatti
AEG 302 -"Renewable Energy and Green
Technology " (1+1)
Submitted By,
Mohmed Juned contractor
III Bsc Agri IIsem
Topic -Methods of Maintaining Biogas Production
Submitted To,
Dr J.K Neelakanth
Professor and Head
Department of Agril.Eng A C
Hanumanmatti

2. Methods for Maintaining Biogas
Production-
•Insulating of the gas plant.
•Composting
•Hot water circulation
•Use of chemicals
•Solar systems

3. Insulating the gas plant-
• For reducing heat losses from the digester, the external
surface of the digester is adequately insulated using
different materials.
• Like mineral wool, aluminum cladding, fire glass, straw
etc.
• For this reason, the Janata type of biogas plants are
usually constructed below the ground Level.
• Conversely, in the floating dome design, almost 54% of
the total heat losses occurs from the top of the gas
holder.
• Therefore simple insulation like readily available dry
agriculture residues (paddy straw mat) on the top of the
gas holder could reduce this loss considerably.

4. Composting-
• The heat released in aerobic composting of agriculture
residues around the annular ring in the upper part of the
digester could be utilized to raise the digester operating
temperatures.
• From experiments performed on biogas plants, it is reported
that a temperature rise of 8-10°C above ambient temperature
even during the coldest season, as a result of heat released
from composting manure and straw.
• Under optimum conditions of moisture, composting is
complete in 3-4 weeks and the released heat varies with time
remarkably. Small quantity of water in the straw around the
digester is added later when the drop in temperature occurs
and therefore the temperature of the composting material and
digester contents can be kept relatively at constant
temperature.

5. Method-
• In this method the whole digester slurry is heated from the
exothermic reaction of the compost .
• And the escape of heat of radiation from the top of the
digester is prevented by providing thick paddy straw mat on
the top of the gas holder.
• In the plant as shown in figure a composed pit 1m x 1m all
round the digester is excavated.
• It is lined with 13 cm thick wall.
• Then it is filled with alternate layers of paddy straw and dung.
• The thickness of each layer is about 15 cm and 5 cm
respectively moisturized by sprinkling water.
• The decomposition of the organic matter and paddy straw will
start within 2-3 days and sufficient heat would be produced
which will raise the temperature of the digested slurry.

7. Hot water circulation-
• This system has been reported to be
efficient for maintaining temperatures of
the fermented slurry at the desired level.
• The cost of system, however comes higher.

8. Use of chemicals-
• Use of chemicals such as urea and urine have
been suggested by some workers to increase
the digester temperature.
• The actual heat gains and the corresponding
economics in raising the temperature have not
been worked out yet.
• Addition of urine of animals was also observed
to enhance the gas production.

9. Solar energy systems-
• The solar heat to the biogas digester could be provided in
two distinct ways namely
• (i) the active
• (ii) the passive means.
• The active systems - involve heating of the digester feed
or direct of the digester contents.
• In the first method, the incoming feed (or water which is
used to dilute the slurry) is preheated using solar energy
during the day and is fed to the digester when it attains
the desired temperature.

10. • The passive method-.
Involves the construction of a “green house”
around the digester to capture the radiant
heat energy.
• In an experiment, a passive green house
built over an under ground digester raised
the temperature by 10°C

11. Thank
You