Environmental Engineering Reference
In-Depth Information
GHG emissions from steadily growing civil aviation, a technical fix that is relatively
easy to implement - such as that for ozone-depleting substances regulated by the
Montreal Protocol - does not exist. Even if hydrogen produced from renewable energy
sources were used for jet aircraft, this would not achieve zero GHG emissions due to
the climate impact of water vapour.
2
Taking into account these obstacles and the time that will most likely be required
to integrate the aviation sector into a binding global climate regime, the question
arises as to how the challenges ahead might be accommodated in the meantime. The
lack of effective policy for global environmental issues is an important aspect of the
contemporary critique of globalization. One might argue that some of the phenom-
ena embraced by the phrase 'globalization' are not new and are difficult to track
empirically, even for international trade and direct investment where economic inte-
gration is primarily taking place within and between the predominant economic
unions such as the European Union (EU) and the North American Free Trade Area
(NAFTA) (Kleinknecht and Wengel, 1998, p645). Nevertheless, civil aviation is a
global industry and is of key importance for globalization in that it allows for rapid
travel over the globe. Moreover, with the exception of contrails and cirrus clouds, its
climate impacts are global in character.
T
HE
POTENTIAL
FOR
REDUCING
THE
CLIMATE
IMPACT
OF
AVIATION
As today's transport operation normally involves various technologies, tackling emis-
sions from transport has often focused upon technology forcing. In principle, it is
imaginable that technology might be used for achieving zero GHG emissions from
aviation. This necessarily requires other fuels than kerosene to be considered. So far,
aircraft fuelled by hydrogen have only been taken into consideration with modified
jet engines that come with the disadvantage of radiative forcing from emissions of water
vapour at altitude, resulting in the formation of contrails and cirrus clouds (Lewis
and Niedzwiecki, 1999, pp257-258). Aircraft that would emit no GHG might use
hydrogen in a fuel cell, with the hydrogen produced from renewable primary energy
sources. The electricity generated might propel electric motors and the water result-
ing from the chemical reaction in the fuel cell would have to be disposed of into the
atmosphere in a way that safely prevents the formation of contrails and cirrus clouds.
Within the framework of a general conversion of human primary energy use to renew-
ables, and provided such aircraft are technically feasible, this would be the first, best
long-term technical option. It is actually unclear whether such aircraft will become
technically feasible and at what price. Taking into account the development of the
required new airframe and other aircraft components, the relatively long lead times
of aircraft development and the average economic lifetime of aircraft of around 30 years,
significant contributions to reducing radiative forcing cannot be expected within 50
years. Unfortunately, stabilizing the climate cannot wait that long and therefore
non-technical options need to be considered for the short and medium term.
Even though technology necessarily plays an important role, it cannot be expected
to provide the emission reductions needed for sectors that, in the long term, display
substantial growth in output. In such cases, policy-making needs to take a broader
