Energy and Electricity - Introduction to Carbon Capture and Sequestration - page 39

The relative ease and automation of transportation has made it easy
to forget the toll it takes on the environment. Whether it is a drive down
the street or a flight across an ocean, all modern transportation has a
carbon footprint. While it is possible to reduce carbon emissions through
various lifestyle changes, the relative tradeoffs between modes of trans-
portation make it difficult to judge the scale and net effectiveness of
these savings. For example, a dramatic environmental change at home
could be wholly negated by a single vacation flight.
Let's look more closely at the case of our Prius-driving, world-
traveling professor. His United Airlines 1k Frequent Flyer Status requires
a minimum of 100,000 km of yearly air travel, yet his Prius saves gas by
getting 50 mpg versus around 16 mpg with an SUV. According to the
Federal Highway Administration, American males of roughly professorial
age (35-54) drove an average of 15,859 miles per year in 2011. Females
in the same age bracket, on the other hand, drove an average of only
11,464 miles per year. We will use an average of these two estimates for
our current calculation, and assume our professor drives about 13,661
miles per year.
According to the EPA, one gallon of gasoline produces around
8.92 10 − 3 metric tonnes of CO 2 . We can use this information to con-

struct a simple calculation of CO 2 savings based on our professor's
choice of vehicle:

×

− 3

8.92 10 metric tons of CO

1 gallon gas ×

2

SUV: 13,661 miles

× ×

16 miles 1 gallon gas

= 7.61 metric tons of CO

2

− 3

8.92 × 10 metric tons of CO

1 gallon gas

2

Prius: 13,661 miles × ×

50 miles 1 gallon gas

= 2.43 metric tons of CO

2

By driving a hybrid vehicle, our professor reduces his car's carbon
emissions by a factor of 3 (see Table 1.5.5 ), saving approximately 5.18
tonnes of CO 2 per year. Yet how do his CO 2 savings on the road compare
with his emissions in the air? To find out how much carbon is released
on his behalf, we imagined the professor must make frequent trips
between San Francisco and Amsterdam (6,230 miles), with a layover in