Page 104 - Materials Chemistry, Second Edition

88 3 Life Cycle Inventory Analysis

3.2.5
Transports
Transportations occur in every LCA and are often not expressly referred to as
individual unit processes but added to other unit processes whereby double counting
must be avoided (the output of an ‘upper’ unit process can be the input of a ‘lower’
one). For reasons of transparency, the transportation processes must be modelled
just as carefully as all other unit processes.
Transportation data are nearly always taken from (external and/or internal)
generic data bases except when the transport itself is the system to be studied,
in which case relevant primary data is required. Many systems that have been
optimised by re-use and recycling (e.g. reusable packaging) are substantially affected
or even determined in the final result by transportation, in particular due to:

• Distance,
• Means of transport and
• Extent of utilisation/logistics.
The transportation of raw materials, energy sources, materials, products, and
waste is usually at the centre of attention, whereas the passenger transportation
plays a minor role. Things of course change if transportation is the topic of the
study. With regard to passenger transportation, the comparison between rail, car
and air plane may be under investigation; with respect to transportation of goods,
different transportation variants such as rail, truck, and ship may be compared.
Usually two key figures are employed for quantification in LCI:

• passenger kilometre (Pkm).
One person is transported over a distance of 1 km.
• tonne-kilometre (tkm).
A mass of 1 ton (Mg) is transported over a distance of 1 km.

For calculating passenger kilometres, the number of persons is multiplied with
the distance in (km). Relating environmental loads of the transport (e.g. CO 2
releases per 100 km) to passenger kilometres provides a meaningful measure
for comparing different transport types: If a person travels 100 km in a car,
the environmental loads per passenger kilometre are about four times as high
compared to a car occupied by four passengers. Likewise, the degree of utilisation
(actual number of passengers/maximum capacity) for transports by bus, train and
air plane plays an important part in the quantification of environmental load per
passenger kilometre which, however, is not always easy to obtain.
For the determination of ton kilometres, the transported mass (tons) is multiplied
with the distance covered (km) and the environmental load of the vehicle (e.g. its
fuel consumption) is related to the ton kilometres. In contrast to the calculation of
the environmental load per passenger kilometre, it is considered that the energy
consumption is split into a load-independent portion of the empty vehicle and
a load-dependent portion. As the energy consumption of the empty vehicle is