Environmental Engineering Reference
In-Depth Information
Gas
The greenest fossil
Gas has become the vital supporting element in our fossil-fuelled
energy system. It is used residentially for cooking and heating. It
meets 21 percent of overall energy demand, and is second only to
coal in generation of electricity - gas provides a fifth of the world's
power. To a small extent, as compressed gas, it is a transport fuel. It
also has non-energy uses. Like oil, it is a feedstock for petrochemicals,
and for agriculture it provides the ammonia used in fertilizer.
The basics
As a lighter version of oil, gas has a near-identical geological provenance
(see p.47). Gas is found alongside oil (when it is known as associated gas),
by itself in distinct gas fields, or sometimes seeping out of coal seams. It
is frequently burned off or flared - oil companies use spouts called gas
flares to discharge unexpected gas - particularly when gas comes up with
oil, but not in a large enough quantity to justify a separate pipeline for it.
But in some countries, notoriously Russia and Nigeria, gas flaring takes
place routinely and on a large scale. This wasteful practice is declining, but
around 150 billion cubic metres of gas, or five percent of world produc-
tion, are still flared off every year. This is damaging for the environment,
though it's not as damaging as leaks of the uncombusted gas would be
because methane, the main component of gas, is twenty times more pow-
erful a greenhouse gas than carbon dioxide.
The latecomer
Of the three main fossil fuels, natural gas is the latecomer. Natural gas was
known about in ancient times - agnostic scientists have conjectured that
the vision of the burning bush referred to in the Bible may have been an
incidence of a gas leak. And town gas was manufactured from coal from
