Emissions Scenarios - IPCC

148 Scenario Driving Forces
emissions, wliicli coincidentally also converts about 99% of the
into nitrogen gas (N,). In other regions only about 20% of
emissions had been abated by the early 1990s.
Major adipic acid producers worldwide have agreed to
substantially reduce NjO emissions by 1996 to 1998. In July
1991 they formed an inter-industry group to share information
on old and new technologies developed for N^O abatement,
such as improved thermal destruction, conversion into nitric
oxide for recycling, and the promising low-temperature
catalytic decomposition into N2 currently being developed by
DuPont. The introduction of all three technologies could result
in a 99% reduction of N.,0 emissions from adipic acid
production (Storey, 1996). They are expected to be introduced
at plants owned by Asahi (Japan), BASF and Bayer (Germany),
DuPont (US), and Rhône-Poulenc (France) {Chemical Week,
1994). After the planned changes, US producers will have
abated over 90% of the N2O emissions from adipic acid
production. In recent years nylon-6.6 production dropped in the
US, Western Europe, and Japan, largely in response to capacity
and production in other Asian countries. By 2000 production is
expected to recover in these countries (Storey, 1996).
Another major source of N2O is the transport sector. Gasoline
vehicles without catalytic converters have very low, sometimes
immeasurably small, emissions of N2O. However, vehicles
equipped with three-way catalytic converters have N2O
emissions that range from 0.01 to 0.1 g/km in new catalysts,
and from 0.16 to 0.22 g/km in aging catalysts (IPCC, 1996).
Emission levels also depend on precise engine running
conditions. At the upper end of the emission range from aging
catalysts, N2O emissions contribute around 25% of the in-use
global warming impact of driving (Michaelis et al, 1996).
The introduction of catalytic converters as a pollution control
measure in the majority of industrialized countries is resulting
in a substantial increase in N,0 emissions from gasoline
vehicles. Several Annex I countries include projections of N^O
from this source in their national communications to the
UNFCCC, using a variety of projection methods (for example,
Environment Canada, 1997; UNFCCC, 1997; VROM, 1997).
The projections from these counties differ substantially in the
contribution that transport is expected to make to their national
N2O emissions in 2020, ranging from about 10% in France to
over 25% in Canada. They anticipate that mitigation measures
will be much more effective in reducing industrial and
agricultural emissions of N2O than mobile source emissions.
Indeed, little research has been cartied out to identify catalytic
converter technologies that result in lower NjO emissions.
However, emissions are likely to be lower in countries that
require regular emission inspections and replacement of faulty
pollution control equipment.
3.6.3. Methane
Agricultural and land-use change emission drivers are
discussed in Section 3.5.2. The other major sources are from
the use of fossil fuels and the disposal of waste, for which the
driving forces are briefly reviewed here. The earlier literature
is reviewed in В ames and Edmonds (1990). A more detailed
recent literature review is given in Gregory (1998).
Emissions from the extraction, processing, and use of fossil
fuels will be driven by future fossil fuel use. CH^ emissions
from venting during oil and gas production may decrease
because of efforts to reduce them (IGU, 1997b). Flaring and
venting volumes from oil and gas operations peaked in 1976 to
1978, but a gradual reduction in volumes of gas flared and
vented has occurred over the past 20 years (Boden et al., 1994,
Marland et ai, 1998; Stem and Kaufmann, 1998). Shell
Intemational Ltd. (1998) estimated a reduction in its own
emissions from venting by 1 MtCH^ per year to 0.367 MtCH^
in the ñve years to 1997. The lEA Greenhouse Gases R&D
Programme (1997) notes that emission reductions from the oil
and gas sector would yield a high economic return.
Additionally, new natural gas developments generally use the
latest technology and are almost leak free compared to older
systems. Taking all these factors into account, it seems plausible
that CH4 emissions from the oil and gas sector should fall as the
2U' century progresses. Nonetheless, the primary driver (oil and
gas production) is likely to expand significantly in the future,
depending on resource availability and technological change. A
representative range from the literature, for example the
scenarios described in Nakicenovic et al. (1998a), indicates
substantial uncertainty in which future levels of oil and gas
production could range between 130 and some 900 EJ.
Assuming a constant emission factor, future CH^ emissions
from oil and gas could range from a decline compared to
current levels to a fourfold increase. With the more likely
assumption of declining emission factors, future emission levels
would be somewhat lower than suggested by this range.
The concentrations of CH^ in coal seams are low close to the
surface, and hence emissions from surface mining are also low
(lEA CIAB, 1992). Concentrations at a few hundred meters or
deeper can be more significant; releases from these depths are
normally associated with underground mining. Emissions per
ton of coal mined can vary widely both from country to country
and at adjacent mines within a country (lEA Greenhouse Gases
R&D Programme, 1996a). CH^ mixed with air in the right
proportions is an explosive mixture and a danger to miners.
Measures to capture and drain the CH4 are common in many
countries - the captured CH^, if of adequate concentration, can
be a valuable energy source. The techniques currently used
reduce total emissions by about 10%. Many older, deeper coal
mines in Europe are being closed, which will reduce emissions.
Replacement coal mines tend to be in exporting countries with
low cost reserves near the surface, so the emissions will be low.
For the future, emissions will depend principally on the
proportion of coal production from deep mines and on total
coal production.
A representative range of future coal production scenarios
given in Nakicenovic et al. (1998a) indicates a very wide range
of uncertainty. Future coal production levels could range