SYNOPSIS
In India there is a good
sunshine for about 300 days in a year which encourages anaerobic digestion.
Kitchen refuse and other similar garbage present a big disposal problem like
bad odor, insects and rodents causing very dangerous diseases. The kitchen refuse
from canteens, hostels, big hotels and similar garbage sources can be
effectively used for anaerobic digestion to recover the fuel energy as well as
good manure from exhausted slurry. The aim of the present study is to evaluate
bio gas production from kitchen refuse using different seeding materials like
cow dung and digested sludge of septic tank and an attempt has been made to work
out the cost that could be benefited from the probable bio gas production using
kitchen refuse. The two phase anaerobic digester bio gas plant of 20 liters
capacity of each phase was operated at room temperature, using kitchen refuse
of Thrissur Government Engineering College Canteen as feed stock material. The
maximum bio gas produced was found to be as 0.301m³/kg VS added/day, at the
rate of loading of 3.3kgVS/m³ slurry/day when digested sludge of septic tank is
used as seeding material.
SUMMARY AND CONCLUSION
Ø GENERAL
From the experiment it was seen that the bio gas plant using
kitchen refuse from Thrissur Government Engineering College canteen, gave
a maximum bio gas volume of 0.301m³/kg VS added/day at the rate of loading
of 3.3kg/VS/m³ digested slurry/day with digested sludge of septic tank as
seeding material. Since the experiment was carried out in a summer
season in the temperature range of 27-32⁰C, the temperature would not
affect appreciably for gas yield.
As the plant was operated at room
temperature, and got a biogas volume of 0.301m3/kg VS added/day, it
is clear that if the temperature, stirring and uniform feeding are constantly
maintained, the biomethanation can be
increased to 1.009m3/kg VS added/day.
Ø THE FEASIBILITY OF BIOGAS PLANT
It is also seen that
the biogas plant is viable and economical if it is operated on large scale
rather than small scale (i.e., for all hostel blocks of Government Engineering
College, Thrissur).
Ø ENERGY RECOVERY AND ITS INTEGRATED
USE
The exhausted slurry
has good fertility value and this manure could be used for good yield of
vegetables which in turn used for cooking in kitchen, which gives the kitchen
refuse material as “feed stock” for digesters. So this is an integrated scheme of
utilizing the waste material for energy recovery in an environmental friendly
way.
Ø RECOMMENDATIONS FOR FURTHER DEVELOPMENT
AND STUDIES
The following
recommendations are suggested for further development and for future studies.
1.
The digesters can be installed below the
ground level for good temperature maintenance.
2.
A room may be constructed with “Green house
effect” using solar energy for good temperature maintenance.
3.
Proper mixing arrangement, using motor
pump sets or circulating the same biogas with pressure.
4.
Uniform feeding avoiding feast or fast
conditions of microorganisms.
5.
Buffering of pH arrangements, especially
for winter months to avoid souring of digester by much accumulation of volatile
acids.
6.
The arrangements for bio gas cleaning (removing
moisture) and utilising the bio gas within 10m of production source for proper
pressure and without leakage.
7.
A cylindrical shape or egg shape
digester will have lesser scum forming are. Hence it is suggested to design egg
or cylindrical shaped digester.
8.
As far as possible, the plug flow
condition should be maintained and also proper retention time should be given
for digestion to be fully completed.
9.
The exhausted slurry can be dried on
sand bed and mixed with other organic fractions of plant origin for aerobic
composting to be used as manure.
10. The water requirements for the digester
slurry can be met with by using waste water from Hostel blocks. The sewage or
sullage water can be used for this purpose in the place of tap water.
ANNIE
K S ASSISTANT ENGINEER, LSGD
SECTION, VAZHAYOOR, MALAPPURAM.
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