Food is the last thing that comes to mind when one sees rotting and stench-emanating
landfills, overflowing with garbage from all over the city. Not surprising then
that many will be shocked if they were told that it is an important source in
the making of cooking gas.
Of late, there have been experiments to convert the emissions from landfills
or garbage dumps to energy so as to power various applications. Though technologies
exist, they are crippled with inefficient output and operational problems. The
TEAM (T ERI’s enhanced acidification and methanation) technology not only
overcomes existing shortcomings but also promises to be an important parallel
source of fuel for thermal applications, especially cooking.
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| Managing the ever-increasing waste |
Distilling the fuel of the future
Tackling mounting waste (produced as a result of growing urbanization and industrialization)
has been one of the biggest civic concerns in modern times. Working towards
finding a sustainable solution, researchers at TERI zeroed in on biomethanation
as the most desirable alternative for the treatment of solid waste, as it yields
biogas that can replace conventional fuels and provides digested sludge that
can be used as organic manure.
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| TEAM technology in operation at TERI's Gurgaon facility |
TERI’s research culminated in the development of a high-rate digester
for fibrous and semi-solid organic waste. The technology has been put to use
in the waste treatment plant in TERI’s sustainable habitat campus in Gurgaon,
Haryana. The plant has been generating good-quality biogas and manure from organic
wastes since the year 2000.
The innovation
The TEAM process goes through a clean and structured scheme of things. Organic
solid waste is cut into small pieces and fed into the acidification reactor.
The waste bed is kept submerged in water. Organic acids formed as a result of
bed degradation lead to the formation of leachate. This leachate is periodically
recirculated through the bed at a predetermined fixed rate to have uniform concentration
of microorganisms and nutrients through the bed and to wash off organic acids
formed as a result of further bed degradation.
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| The TEAM process |
Once a high COD (chemical oxygen demand) concentration is reached, the leachate
is extracted in the leachate collection tank. The acidification phase has a
retention time of six days; therefore, six such reactors are provided to ensure
continuous operation. Anaerobic conditions prevail inside the reactor during
the whole process. The phase separation provides suitable environment to the
microorganisms in acidification and methanation stages, thus enhancing the activity
(left figure below). The residue inside the acidification reactor is dried in
the sun and then used as manure (right figure below).
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| Granules of microorganisms used to generate energy |
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Manure generated after processing waste |
The final concentrated leachate, after pH correction, is fed into the UASB
(upflow anaerobic sludge blanket) reactor for methanation. This phase has a
retention time of 16 hours. The microbial consortia present in the UASB sludge
destroys 90% of the COD, and forms biogas that comprises 70%–75% methane
(a high calorific value fuel), carbon dioxide, nitrogen, traces of hydrogen
sulphide, and moisture. The biogas production rate is 0.45 m3/kg COD reduced.
Beneficiaries
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| Waste being fed into the acidification
module |
The TEAM technology can turn organic waste dumps into resource
centres and tremendously ease the burden on cities, towns, and even villages.
The technology will be of great relevance to municipal corporations as the TEAM
process is an effective and ecological way of utilizing waste. Sectors that
generate organic waste in large amounts – such as food and fruit processing
industries, hotels, community kitchens, and vegetable markets – can make
the best use of the technology. Other waste generating activities such as coffee
processing, tea processing, and poultry farming will also benefit tremendously.
Applications/benefits
The TEAM process completely eliminates engineering problems such as scum formation,
floating of feed material (it leads to incomplete digestion, blocking of inlet
and outlet pipes, and difficulty in feed flow, which are common in small-scale
plants. The process is better than the conventional single-phase reactors primarily
due to low retention time with high treatment efficiency. Maintenance and operations
are easy because there is no need for mixing and slurry preparation. Also, the
process uses less water as it recycles treated liquefied waste for further extraction.
On the socio-economic front, the TEAM process generates employment; it is enterprise-friendly
and suitable for small-scale units. It can also create work avenues for raw
material suppliers. The cost of the plant depends on the composition of feedstock
to be treated. For mixed feed, the cost is about 20 000 rupees per cubic metre.
Payback period is less than two years.
The biogas produced through this process can be piped and put in use as domestic
fuel, and also be used for thermal application and power generation.
