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Central Eastern Europe GRIP 2017
5.4 Emissions Evaluation
5.4.1 GREENHOUSE GAS EMISSIONS
The two main approaches to greenhouse gas (GHG) evaluation of vehicles present-
ed in this chapter are:
\\
JEC (Joint Research Centre) Methodology Versions 2.c (March 2007) and 4.a
(January 2014) (Figure 5.6), which use the 5-seat C segment passenger car as
a reference vehicle
\\
DLR (Deutsches Zentrum für Luft und Raumfahrt) & Partners (July 2013)
(Figure 5.7), which use mid-size passenger car and city bus as reference vehi-
cles
Both methods work with an overall balance of “well to wheels” (WTW), which
accounts for production and transmission (well to tank – WTT) and consumption
(tank to wheel – TTW) of the fuel, closely described in Figure 5.5. It should be
mentioned that these studies comprise all emissions causing the greenhouse effect
including, but not limited to, CO ² , N ² O, and CH
4
. Methane (CH
4
) is an especially
potent greenhouse gas. Thus, any loss of unburned NG during exploitation,
transmission, and distribution must be strenuously avoided.
Figure 5.5:
Well to wheels lifecycle diagram
Well to tank
Natural Gas
Well to wheels
Tank to wheel
Feedstock
production
Transmission
Refining
Distribution
Consumption
As shown in Figures 5.6 and 5.7, GHG emissions per kilometre were in 2010 (JEC)
and 2012 (DLR) about the same for CNG and diesel vehicles, as resulted from both
evaluation methodologies. However, both evaluation methodologies predict a trend
that the GHG emissions of CNG vehicles in the future will undercut the GHG emis-
sions of diesel. While the JEC predicts a gap of 3.8% in favour of CNG vehicles in
the year 2020, the DLR predicts a gap of 9.8% in favour of CNG passenger vehicles
and even a gap of 14.3% in favour of CNG buses by the year 2030.
The specific CO ² emission per kWh given in Table 1 suggests a gap of 26%. This
theoretical value, however, is reduced, because the energy efficiency of a diesel-
fuelled compression ignition engine is actually higher than the efficiency of a NG- or
petrol-fuelled spark ignition engine, which is indicated in previous paragraph. For
the same reason, compared to petrol-fuelled engines, NGVs by contrast actually
demonstrate a positive advantage of 20% regarding GHG emissions.
The DLR result for CNG buses is especially encouraging, and it confirms ongoing
projects in Bulgaria and Germany for NG-fuelled buses and garbage collection
trucks in urban areas.