Environmental Engineering Reference
In-Depth Information
Turning back the clock and reducing the number of cars, planes, trucks and ships
would be a hopeless undertaking. Modern economies and modern lifestyles have
become so fast-paced that they demand increased mobility. Holidays tend to be
short, so air trips are necessary not to eat into travel time. Weekend breaks by air
provide relaxation in hectic schedules. Our economic growth also is based on high
levels of exports and reasonably priced raw materials, both of which are associated
with long - distance transport.
Nevertheless, to reduce carbon dioxide emissions, we simply have to get from A to
B using less energy. In the medium term, carbon-free transport must be available
to cut out emissions completely.
Selecting the right means of transport is the best option for a quick reduction in
energy requirements and emissions in traffi c. For example, per passenger kilometre
the secondary energy requirement of a train is less than one-fi fth that of a car. To
compare the two modes of transport, the energy consumption of the train is divided
by the average number of passengers and the energy consumed recalculated into
petrol.
Although the secondary energy consumption of a train is still less than that of a car
by several orders of magnitude, the difference in carbon dioxide emission is not as
dramatic (Figure 3.9). This is because about one-half of a train's electricity comes
from coal - fi red power plants that in turn produce large amounts of waste heat in
generating the electricity. In Germany around 24% of a train's electricity comes
from nuclear power stations and more than 10% from renewable energies. In coun-
tries that use a higher proportion of renewable energies in electricity generation,
such as Norway, Austria and Switzerland, the carbon dioxide emissions of the trains
are considerably lower than in Germany.
passenger
car
passenger
car
43 2
1 person
43
2
1 n
aeroplane
aeroplane
maglev
train
maglev
train
city train
city train
coach
coach
Intercity-
Express
Intercity-
Express
intercity
train
intercity
train
012345678
0
50
100
150
200
250
energy demand in litres petrol per 100 km
CO
2
emissions in grammes per km
Figure 3.9
Secondary energy requirements and carbon dioxide emissions per person for different
means of transport with an average use load (
data for trains is estimated from the German electricity grid
).
The calculations shown here are based on average values. The average carbon
dioxide emissions of new cars in Europe are currently around 160 g of carbon
