Page 110 - The Green Building Bottom Line The Real Cost of Sustainable Building

GREEN FROM THE INSIDE OUT 89

36 ppm increase from 1760 to 1960). 15 What this means is that humans are releasing
a variety of greenhouse gases at much higher rates than has happened historically.
Additionally, all of these gases differ in their ability to trap heat. As Table 3.1 shows, the
six primary greenhouse gases have varying lives in the atmosphere, and vary in their
ability to trap heat. This makes comparing the gases difficult, so GHG emissions are
often reported by each gas’s global warming potential. For example, methane has a
global warming potential of 21, meaning that one molecule of methane has twenty-
one times more heat-trapping ability than one molecule of carbon dioxide. Thus, while
carbon dioxide is the gas we hear most about, even minor releases of other gases have
significant impacts. Some of the gases are over 20,000 times more potent than carbon
dioxide, though they are released in such small quantities that they are not likely to
trigger widespread warming on their own.
When reporting emissions for an organization’s carbon footprint, all the gases are
represented as carbon dioxide equivalents, or eCO , which translate the global warm-
2
ing potential for each gas into one common denominator so it is possible to compare
total emissions, regardless of which gas is emitted. For example, if a company is
responsible for one thousand units of carbon dioxide (with a global warming potential
of 1) and one hundred units of methane (with a global warming potential of 21) the
total GHG emissions would be expressed as 12,100 units of eCO . (1,000 CO × 1 +
2 2
100 methane × 21 = 12,100).
So Where Do All These Gases Come from?
Carbon dioxide is by far the most significant GHG, making up 77 percent of global
GHG emissions. Nearly all CO is released through our burning of fossil fuels for
2
energy generation (coal for electricity, natural gas for heating, or oil for transportation).
Methane is the result of decomposition of organic matter in landfills, but it is also asso-
ciated with leaking natural gas, as well as rice and livestock production. Nitrous oxide
is released through fossil fuels combustion (especially automotive) as well as fertilizer
production and use. Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are
complex compounds that are produced for industrial and manufacturing processes, as
refrigerants, and as replacements for ozone-depleting substances. Typically, service-
based organizations do not emit these gases unless they have a refrigerant leak. These
gases are associated with mining, refining, and electricity distribution.
Now that you know what the greenhouse gases are and how they are expressed,
your organization can get around to measuring its own carbon footprint. This will not
require the services of a dedicated climate scientist, greenhouse gas specialist, or envi-
ronmental engineer. This is a process that can be done in-house.

What Resources Can Help Me with Carbon Footprinting?
A challenge to implementing a successful sustainability strategy is the lack of avail-
able resources. While a Fortune 500 company may have the assets to hire a specialist
to focus on greenhouse gas emissions and other sustainability indicators, smaller service-
based organizations may not have such resources or expertise available. Fortunately,
there are a host of free resources available to help organizations large and small imple-