PDF: 9795 KB - Bureau of Infrastructure, Transport and Regional ...

BITRE | Working paper 73
pollutant control technology, or many other measures that promote the reduction
of noxious non-CO 2
engine emissions, could also then be counted as greenhouse
abatement measures).
In fact, care should be taken to not base the selection of the most effective abatement
measures solely on their impacts with regard to the usual current definition of ‘total’
greenhouse gas emissions (i.e. direct CO 2
equivalent), since even though this is a
comparatively sound indicator in many cases, it is capable of biasing assessments of
some measures, especially if they mostly concern the output of non-CO 2
emissions.
For example, three-way catalytic converters are very efficient at reducing noxious
emissions from road vehicles but their operation can lead to slight increases in N 2
O
emissions, a powerful direct greenhouse gas. So, despite their environmental and
community health benefits, any policy sponsoring the increased penetration of such
converters across the Australian vehicle fleet might receive a negative greenhouse
assessment, if just direct CO 2
equivalent emissions were considered. However, a
suitable quantification of the indirect greenhouse effects avoided by the converters’
reduction of ozone-precursors is likely to be significantly greater than the possible
slight increase in direct effects, probably making such a measure a particularly
effective one, if assessed using changes in total radiative forcing.
This is likely to be the case with a variety of technologies that target overall levels of
air pollution, as opposed to purely CO 2
emissions. Another example is suspended
particle emissions and the more reactive of the volatile organic compounds (VOCs)
released from transport fuel combustion. Most of the worst health effects due to
urban air pollution originate from ultra-fine (respirable) particulates (which are not
tightly controlled by current air quality or vehicle design standards, and are likely
to remain at significant levels in our cities into the foreseeable future) and from
carcinogenic VOCs such as benzene and poly-cyclic hydrocarbons (PAHs). Improved
emission control systems on vehicles (and fuel reformulation at the refining stage)
are typically capable of making major reductions in such pollutants—yet many of the
most promising technologies have slight fuel efficiency overheads. That is, their use
will tend to lead to a small increase in total fuel consumption, and thus a small increase
in CO 2
emissions. However, in addition to the obvious social benefits of decreasing
harmful air pollutant levels, this slight greenhouse ‘negative’ could possibly be
cancelled out if the total (i.e. direct plus indirect) greenhouse emission changes from
their use were considered, instead of solely changes to the direct gases.
Viewed in this light, even such current policy directions as pursuing the reduction
of fuel sulphur content could be regarded more positively from a greenhouse
abatement point-of-view (though this particular issue is complicated by the fact that
sulphates due to vehicle emissions, which are harmful urban pollutants, probably
cause a partial cooling effect). Not only does having ultra-low sulphur automotive
fuels allow the introduction of new emission control technologies (which would
otherwise have suffered rapid de-activation from sulphur-poisoning), but the lower
sulphur content leads to longer average operational life-times for existing catalytic
converters—serving to improve control of indirect greenhouse gas output from the
vehicle fleet, and probably also reducing emission levels of the direct greenhouse gas
N 2
O (since its rate of emission has been strongly linked to catalyst deterioration). In
fact, a number of international studies have shown that the reduction of fuel sulphur
72