The Carbon Quandary: Essential and Detrimental - Sustainable Design: The Science of Sustainability and Green Engineering - page 258

Figure 7.1 Global carbon cycle,
1992 to 1997. Boxes represent
the carbon pool, expressed in
gigatons (Gt) of carbon. ( Note: 1Gt
C = 10 15 g C.) Annual increments
are expressed in Gt C per year
(shown in parentheses). All fluxes
indicated by the arrows are
expressed in Gt C per year. The
inferred net terrestrial uptake of
0.7 Gt C per year considers gross
primary production ( ∼ 101.5),
plant respiration ( ∼ 50),
decomposition ( ∼ 50), and
additional removal from the
atmosphere directly or indirectly,
through vegetation and soil and
eventual flow to the ocean
through the terrestrial processes
of weathering, erosion, and
runoff ( ∼ 0.8). Net ocean uptake
( ∼ 1.6) considers air-sea
exchange ( ∼ 92.4 gross uptake,
− 90.8 gross release). As the rate
of fossil-fuel burning increases
and CO 2 is released to the
atmosphere, it is expected that
the fraction of this C remaining in
the atmosphere will increase,
resulting in a doubling or tripling
of the atmospheric amount in the
coming century.
From M. Post, Oak Ridge National
Laboratory,
http://cdiac.ornl.gov/pns/graphics/
c cycle.htm, accessed July 25, 2007.

a decision, knowingly or otherwise, that this compound is more likely to end
up in the water than if the original nonhydrolyzed form were used. This does
not mean that the choice is a bad one. It could be good; since the process also
lowers the vapor pressure, the alcohol may be easier to keep from being released
from stacks and vents. The key is knowing ahead of time that the choice has
consequences, and to plan for them accordingly.
Organic compounds can be further classified into two basic groups: aliphatics
and aromatics. Hydrocarbons are the most fundamental type of organic com-
pound. They contain only the elements carbon and hydrogen. We hear a lot
about these compounds in air pollution discussions. As mentioned, the presence
of hydrocarbons is an important part of the formation of smog. For example,
places such as Los Angeles that have photochemical oxidant smog problems are
looking for ways to reduce the amount of hydrocarbons released to the air.
Aliphatic compounds are classified into a few chemical families. Each carbon
normally forms four covalent bonds. Alkanes are hydrocarbons that form chains,
with each link comprised of the carbon. A single link is CH 4 , methane. The
carbon chain length increases with the addition of carbon atoms. For example,