Environmental Engineering Reference
In-Depth Information
Energy and Greenhouse Emission from Fossil Fuels
Coal
s energy comes from turning carbon into carbon
dioxide, so all of the energy from coal comes with green-
house gas emissions. Oil is mainly a complex molecule with
roughly two hydrogen atoms for each carbon atom, and its
energy comes from turning one carbon atom into carbon
dioxide and two hydrogen atoms into water (H
'
O). Only
that part of the energy coming from turning carbon into
CO
produces greenhouse gas, and so oil produces about
emission of coal for the same primary
energy. Natural gas has four hydrogen atoms per carbon
atom and its energy comes from turning the carbon into
CO
% of the CO
and the hydrogen into two molecules of water. Of the
primary energy produced by burning gas, only about half
comes with CO
emissions and so natural gas emits
%of
the CO
of coal for the same primary energy.
Combustibles are largely the plant material gathered by
the world
s poor to supply heat; they are not the biofuels
so talked about today. Since plants get the carbon for
their growth from the CO
in the atmosphere and
release it on burning, they do not give any net increase
in greenhouse gas as long as they are grown without
fertilizer and other modern agricultural technology.
They are part of the photosynthesis component listed
in
Table
'
.
The category
.
includes all of what
are called Renewables: biofuels (which do have green-
house gas emissions), wind, solar, geothermal, etc. They
are a negligible component of the energy mix today, but
are expected to grow. Their problems and promises are
the subject of later chapters.
“
Other
”
in
Table
.
