The
dread of the global warming is spreading its tentacles. Everyday the
media reports are full of possible hazards and consequences of the
global warming. What were the climates of the past like, has been a
daunting the scientists involved with the study of the climate change.
Our planet was born after the gaseous nebula cooled down. Once it was
formed, it is believed that Carbon dioxide controlled the global cooling
and heating. There was a time when our planet was wrapped in an ice
sheet. The earliest record of an ice sheet around the globe is from 750
million years old rocks of Namibia. Imagine the impact of a complete
cover of ice all around on the living being! It leads to a complete
collapse of life. For millions of years all biological activity had come
to a standstill, till volcanic eruptions started warming up the
atmosphere again.
There
were several ice Ages and greenhouse conditions. Of these, two
episodes of greenhouse conditions left their indelible mark on the
flora of our planet. The first greenhouse state started some 500
million years ago (Ma) and lasted for about 145 Ma. In terms of
geologists this is the Ordovician-Devonian global warming. The next
major greenhouse state of the climate started some 203 Ma and lasted
for 138 Ma, known as the Jurassic-Cretaceous global warming.
How did it happen and what were
the consequences is an interesting study.
It was
Arrhenius (1896) who first introduced the term 'hot house' theory which
later became the greenhouse theory. Greenhouse effect is a phenomenon by
which carbon dioxide, water vapor, atmospheric methane, nitrous oxide,
ozone and aerosol trap more solar heat within the atmosphere causing a
global warming. In geological past when the earth had become a giant
deep freeze, the global warming came as a relief for the fauna and the
flora to regenerate and rejuvenate. The frozen life was reactivated when
the gases from the sub aerial volcanic activity started to reach the
atmosphere. This increased the atmospheric CO2 content
tremendously and the global warming started.
In other words the greenhouse state is associated with volcanism and sea
level rise. A.E.J. Engel and C.G. Engel (1964) have shown two peaks of
volcanism in the past. The older one persisted through Late Cambrian
(500 Ma) to Late Devonian (355 Ma) and the other in the Late Jurassic
(135 Ma) to Cretaceous (65 Ma) periods of the earth's history.
Researchers have also established that the CO2 content of the
atmosphere was very low during most of the Ice Ages. However, in
contradiction to this find a very recent study carried out by Thomas
Marchitto and Scott Lehman of CU-Boulder's Institute of Arctic and
Alpine Research, it has been found that the carbon build up in the
oceans during the past millennia was released in two big pulses 18, 000
year and 13, 000 years ago. Their results were published in Science
Daily of 11 May, 2007.
Scientists have been aware that nearly 600 billion metric tons of carbon
was released in to the atmosphere after the last ice age. Half of it was
absorbed by the oceans. The recent study will for the first time help
the climatologists and environmentalists to trace the nature's processes
of release of carbon dioxide in the atmosphere and may be also help to
find the actual impact of carbon dioxide released through anthropogenic
activities! Using Carbon 14 isotopes to trace and track the carbon
content of deep and surface ocean waters and the atmosphere, they
established that carbon added to the upper atmosphere at the end of the
last ice age was 'very old'. Thus suggesting it had been stored in deep
oceans and isolated from the atmosphere. Hot oceanic currents were
responsible for release of this carbon from the vaults of ocean in two
major 'burps' 18000 and 13000 years ago.
Carbon dioxide is one of the most abundant Green House Gases (GHG) that
is rapidly dragging our planet towards a Global warming. World over
efforts are on to overcome the problem of GHGs. The industrial
revolution of 1850 set the ball rolling for augmentation of GHGs in the
atmosphere. Rapid strides in technology brought automobiles on the road;
generation of electricity from coal became the in thing.
Thermal power plants are one of the worst atmospheric polluters. A study
carried out in USA says that a 500 megawatt coal powered plant produces
3.5 kilowatt-hours per year electricity, enough for a city of 140, 000
people. The process requires burning of 1,430,000 tone of coal, consumes
2.2 billion gallons of water and 146, 000 tons of limestone.
Such a plant releases 3.7 million tons of Carbon dioxide (CO2),
a leading GHG and main cause of global warming. This was just one
example. In addition there are scores of other processes that keep on
unleashing CO2 in the atmosphere. Trees (forests) and water
bodies particularly the oceans are the sinks of CO2. Heavy
pollution of the oceans and massive deforestation has made these
ineffective.
The scientists world over have been tinkering with various ideas of
disposal of CO2.
V.K. Sibal, Director General of Hydrocarbons, Government of India and
his team had published a paper in Current Science, proposing dumping CO2
in the coal mines.
Coal Bed Methane (CBM) is now considered a major source of gas
supplementing the production of hydrocarbon gas from petroleum sources,
says Sibal. At present the government has given on contract 16 blocks of
CBM to various agencies for exploration and exploitation. Total CBM
resources in these blocks are estimated to be of the order of 820
billion cubic meters. It is also estimated that these blocks will
produce 20-22 million cubic meters of CBM per day for 20 years.
The contemporary commercial production of CBM depends exclusively on
reservoir pressure depletion. CBM stored in the depths and cracks and
crevices of coal seams is pushed up due to pressure from the reservoir.
As the pressure depletes the recovery of CBM is affected. The method,
says Sibal is simple but ineffective because the total recovery is
generally less than 50% of the gas available.
Sequestration of CO2 of generated from combustion of fossil
fuel has been proposed as a safe method of enhanced recovery of CBM and
also a significant tool to divert the harmful GHG to the deep vaults of
the earth.
Actually the idea has emerged from the fact that the subsurface
formations retaining hydrocarbons have substantial capacity to store CO2.
In fact oil and gas reservoirs not being tapped further can also become
potent producers of CBM, if CO2 is pumped in. The process,
feel Sibal and his colleagues will have double benefit. On one hand it
will be goodbye to CO2 and on the other the productivity of
hitherto considered uneconomic petroleum//gas wells or coal mines would
become economic with the availability of CBM.
The concept sounds wonderful, but two issues, namely, avoiding risks and
the cost of collection, transportation and sequestration of CO2
need to be addressed. Carbon capture and storage are in fact a burning
topic amongst the scientists. In January, 2007 the Department of Science
and Technology (DST), Government of India jointly National Geophysical
Research Institute, Hyderabad organized an international workshop at
Hyderabad, on R&D Challenges in Carbon Capture and Storage Technology
for Sustainable Energy Future. Dr.(Mrs.) Malti Goel, Adviser with DST
and Co-Chair of the Workshop in her presentation laid emphasis on
pre-combustion carbon capture, terrestrial and geological sequestration
modeling studies and monitoring and measuring techniques of CO2
sequestered. Such workshops are of importance and significance, because
the brainstorming therein leads to cost effective innovations.
The
rapid pace of development across the globe has led to increased demand
of energy. Coal accounts for 62% of India's energy supply. A sustainable
development in the use of coal as a source of power needs detailed
research in the Carbon Capture and Storage says Malti. Quoting a STERN
report she says that Economics of Climate Change has come out with the
recommendation that cost of stabilization of greenhouse gas emission is
within our reach and would not exceed 1% of GDP. But again this raises
the need for more research to make the project viable.
It is but natural that CO2 will mix with water in the
subsurface and at any given time it could be a major source of
pollution. The earlier cited case study of the thermal power plant in
USA says that in addition to CO2, the Plant's chimneys belch
10,000 tons of Sulphur dioxide, 10,200 tons of Nitrogen oxide, 500 tons
of particles smaller than 10 microns, 220 tons of Hydrocarbons, 720 tons
of Carbon monoxide, 225 pounds of arsenic, 114 pounds of lead, 4 pounds
of cadmium and many other toxic metals like mercury.
Imagine if all this reaches the subsurface, pollutes groundwater and the
same water is ignorantly used for water supply, what would be the fate
of the people! Therefore first and foremost the technique being proposed
has to ensure that pollutants do not reach the subsurface and if at all
they reach then they are confined in the labyrinths of the abandoned
coal mine only.
The German Federal Ministry of Education and Research has worked out
laboratory models which involves the injection of liquefied CO2
in rock formations that contain Calcium Sulphate. This converts CO2
to Calcium Carbonate, which is environmentally safe.
Next is the issue of cost. First is the cost of catching the CO2
and then comes the cost of transporting it for sequestration. Apart from
coal mines, other places for safe dumping carbon dioxide have also to be
located. For example from the Power plants in the coal mine areas of
Central and Eastern India it may be economically beneficial and possible
to transport the obnoxious gas back to the mines, but the cost of
transporting CO2 from a plant located in Northern India
(Delhi), is anybody's guess!
Technology has advanced through new concepts and ideas only. Time is not
far when it will be feasible to divert the anthropogenic obnoxious
emissions to the subsurface to remain ensconced there till eternity!
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The
dread of the global warming is spreading its tentacles. Everyday the
media reports are full of possible hazards and consequences of the
global warming. What were the climates of the past like, has been a
daunting the scientists involved with the study of the climate change.
The
rapid pace of development across the globe has led to increased demand
of energy. Coal accounts for 62% of India's energy supply. A sustainable
development in the use of coal as a source of power needs detailed
research in the Carbon Capture and Storage says Malti. Quoting a STERN
report she says that Economics of Climate Change has come out with the
recommendation that cost of stabilization of greenhouse gas emission is
within our reach and would not exceed 1% of GDP. But again this raises
the need for more research to make the project viable.