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Methane Gas
PaterVis Corp - EcoEuropean Living
Methane is the major component of natural gas, about 87% by volume. At
room temperature and standard pressure, methane is a colorless,
odorless gas; the smell characteristic of natural gas is an artificial
safety measure caused by the addition of an odorant, often methanethiol
or ethanethiol.
Methane has a boiling point of −161 °C at a pressure of one
atmosphere. As a gas it is flammable only over a narrow range of
concentrations (5–15%) in air. Liquid methane does not burn
unless subjected to high pressure (normally 4–5 atmospheres).
Early in the Earth's history—about 3.5 billion years
ago—there was 1,000 times as much methane in the atmosphere as
there is now. The earliest methane was released into the atmosphere by
volcanic activity. During this time, Earth's earliest life appeared.
These first, ancient bacteria added to the methane concentration by
converting hydrogen and carbon dioxide into methane and water. Oxygen
did not become a major part of the atmosphere until photosynthetic
organisms evolved later in Earth's history. With no oxygen, methane
stayed in the atmosphere longer and at higher concentrations than it
does today.
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Clathrate Fuel
Methane is important for
electrical generation by burning it as a fuel in a gas turbine or steam
boiler. Compared to other hydrocarbon fuels, burning methane produces
less carbon dioxide for each unit of heat released.
At about 891 kJ/mol, methane's combustion heat is lower than any other
hydrocarbon; but a ratio with the molecular mass (16.0 g/mol) divided
by the heat of combustion (891 kJ/mol) shows that methane, being the
simplest hydrocarbon, produces more heat per mass unit than other
complex hydrocarbons.
In many cities, methane is piped into homes for domestic heating and
cooking purposes. In this context it is usually known as natural gas,
and is considered to have an energy content of 39 megajoules per cubic
meter, or 1,000 BTU per standard cubic foot.
Methane in the form of compressed natural gas is used as a vehicle
fuel, and is claimed to be more environmentally friendly than fossil
fuels such as gasoline/petrol and diesel.
At high pressures, such as are found on the bottom of the ocean,
methane forms a solid clathrate with water, known as methane hydrate.
An unknown, but possibly very large quantity of methane is trapped in
this form in ocean sediments.
Theories suggest that should global warming cause them to heat up
sufficiently, all of this methane could again be suddenly released into
the atmosphere. Since methane is twenty-five times stronger (for a
given weight, averaged over 100 years) than CO2 as a greenhouse gas;
this would immensely magnify the greenhouse effect, heating Earth to
unprecedented levels
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Natural Industry
Methane is used in industrial chemical
processes and may be transported as a refrigerated liquid (liquefied
natural gas, or LNG). While leaks from a refrigerated liquid container
are initially heavier than air due to the increased density of the cold
gas, the gas at ambient temperature is lighter than air. Gas pipelines
distribute large amounts of natural gas, of which methane is the
principal component.
In the chemical industry, methane is the feedstock of choice for the
production of hydrogen, methanol, acetic acid, and acetic anhydride.
When used to produce any of these chemicals, methane is first converted
to synthesis gas, a mixture of carbon monoxide and hydrogen, by steam
reforming. In this process, methane and steam react on a nickel
catalyst at high temperatures (700–1100 °C).
The major source of methane is extraction from geological deposits
known as natural gas fields. The gas at shallow levels (low pressure)
is formed by anaerobic decay of organic matter and reworked methane
from deep under the Earth's surface. In general, sediments buried
deeper and at higher temperatures than those which give oil generate
natural gas.
Although less dramatic than release from clathrates, but already
happening, is an increase in the release of methane from bogs as
permafrost melts. Although records of permafrost are limited, recent
years (1999 to 2007) have seen record thawing of permafrost in Alaska
and Siberia.
Recent measurements in Siberia show that the methane released is five times greater than previously estimated
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