As per the latest news, Indian
scientists are one step away from identifying and quantifying Gas Hydrates,
described as the energy of the future and present in large quantities in Bay of
Bengal and the Indian Ocean.
A
Remotely
Operated Vehicle (ROV) developed by the scientists of Chennai-based
National Institute of Ocean Technology (NIOT) has proved that it can undertake
missions up to 6,000 meters to the sea bottom and identify gas hydrates and
poly metallic nodules.
Gas Hydrates or Clathrate hydrates (or gas clathrates, gas hydrates,
clathrates, hydrates, etc.) are crystalline water-based solids
physically resembling ice, in which small non-polar molecules (typically gases)
or polar molecules with large hydrophobic moieties are trapped inside
"cages" of hydrogen bonded water molecules. These hydrates are formed
at low temperatures and high pressure in the deep sea and contain gases, such
as hydrocarbons. Naturally occurring gas hydrates are a form of water ice which
contains a large amount of methane within its crystal structure, and are thus
very important energy source.
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| Gas Hydrate (Source: www.usgs.gov) |
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|
The schematic drawing of a type of gas-hydrates structure
in which methane molecules
are caged in hydrogen-bonded water molecules (after Mahajan et al., 2006)
According to U.S.
Geological Survey (USGS) data, gas hydratesare available all around the world.
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India also has huge
reserves of gas hydrates along its eastern coast. The initial estimation of the
reserves are said to be at least 1,500 times the country's current fossil fuel
reserves - coal, oil and natural gas put together. The hydrate reserves are
found in Krishna-Godavari basin, Mahanadi basin and Andaman regions.
- Hydrates store immense amounts of methane, with major implications for energy resources and climate, but the natural controls on hydrates and their impacts on the environment are very poorly understood.
- The worldwide amounts of carbon bound in gas hydrates is conservatively estimated to total twice the amount of carbon to be found in all known fossil fuels on Earth.
- The immense volumes of gas and the richness of the deposits may make methane hydrates a strong candidate for development as an energy resource.
- Results of USGS investigations indicate that methane hydrates possess unique acoustic properties
Polymetallic nodules, also called manganese nodules, are rock
concretions on the sea bottom formed of concentric layers of iron and manganese
hydroxides around a core. The core may be microscopically small and is
sometimes completely transformed into manganese minerals by crystallization.
Nodule growth is one of the slowest of all geological phenomena – on the order
of a centimeter over several million years. Several processes are involved in the
formation of nodules, including the precipitation of metals from seawater and
the precipitation of metal hydroxides through the activity of microorganisms.
Several of these processes may operate concurrently or they may follow one
another during the formation of a nodule. These nodules are great source of
metals including those of greatest economic interest such as manganese
(27-30 %), nickel (1.25-1.5 %), copper
(1-1.4 %) and cobalt
(0.2-0.25 %). Other constituents include iron (6 %), silicon (5%) and
aluminium (3%), with lesser amounts of calcium, sodium, magnesium, potassium, titanium
and barium, along with hydrogen and oxygen.
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| Manganese Nodule |
The
ROV fitted with scientific payloads like sensors, and sonar instruments could
identify gas hydrates and poly metallic nodules in the bottom of the sea and will
help India launch deep sea mining for poly metallic manganese nodules in the
1,50,000 sq km region in the Central Indian Ocean Basin allocated to the
country by the International Sea Bed Authority.
As in nature, every positive is almost always associated with negative, this immense
source of energy is also associated with many potential hazards, including
environmental, that we need to consider and technological difficulties that
need to be triumphed over.
Technological
difficulties:
- Absence of representative deepwater gas hydrates field anywhere in the world
- Gas production rate (Gas in the production testing of Mallik well in Canada’s permafrost area have yielded very low production rate and could not sustain more than 7 days of production using thermal and depressurization methods)
- Managing Water production rate (High amount of water is expected to be produced along with the dissociation of hydrates)
Environmental
Problems:
- Sand control since the hydrate reservoirs exist at very shallow depth below sea bed (200-400 mbsf) the sands here would not be consolidated due to absence of overburden pressure and mining of these gas hydrates could lead to landslides
- Methane, a "greenhouse" gas, is 10 times more effective (hazardous) than carbon dioxide in causing climate warming and could lead to global catastrophe
- Nodule mining could affect tens of thousands of square kilometers of deep sea ecosystems. Nodule regrowth takes decades to millions of years and that would make such mining an unsustainable and nonrenewable practice. Humans have little knowledge of the vast number of deep-sea species that occur and their biology, making predictions about the effects of mining extremely uncertain. Thus, nodule mining could cause habitat alteration, direct mortality of benthic creatures, or suspension of sediment, which can smother filter feeders
There is no doubt
that gas hydrates are abundant source of energy, whether we will be able to utilize
this source of energy remains to be seen. We need tread a very cautious and balanced
path. Risk to benefit ratio of such mining along with the economic viability and
technological feasibility needs to be studied at great length. Whether we are
able to use this energy resource or it continues to lie in sea will largely
depend on how well we are able to address the potential concern of global environmental
hazards like greenhouse effect.
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