Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportations Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
equivalent leakage emissions by 99.7 percent when HFC-134a is completely phased out.
HFC-152 would reduce CO2 equivalent leakage emissions by 91.3 percent at full phaseout,
and R-744 would reduce equivalent leakage emissions by 99.9 percent. Currently, a
phaseout of HFC-134a is planned in the EU. This phaseout does not specify a replacement
refrigerant, but rather that no new vehicle may be sold after 2011 containing refrigerant
with a GWP over 150 (U.S. EPA, 2007d).
Little specific data exist comparing the engine load requirements of the alternative
refrigerants. The available data suggest that HFC-1234yf would increase required engine
load by 2.3 to 6 percent over HFC-134a. R-744, however, would increase engine load by
70 percent to 100 percent over HFC-134a (Atkinson, 2008). The move to alternative
refrigerants represents a long-term option for GHG reduction in the case of HFC-152a and
R-744, as inuse vehicles are not likely to be retrofitted with this refrigerant. HFC-1234yf
may be used with current vehicles with little to no modification, making it possible that
GHG benefits for this refrigerant could be realized in the short term, if research shows that
direct substitution into current R-134a systems is feasible.
In addition, according to a 2004 report, it was estimated that mechanical loads from LDV
MAC system use increases fleetwide gasoline consumption by 7 billion gallons per year
(U.S. EPA, 2009d), or approximately 5 percent of total LDV consumption in 2010.
Reduction of vehicle cooling loads can reduce these emissions. Solar reflective glazings
and paints can reduce MAC fuel use by up to 30 percent (Rugh et al., 2006). If new
vehicles adopted secondary loop systems, a reduction in fuel use also could be realized. It
is estimated that a small car operating with a secondary loop system with HFC-152a
refrigerant would have 21 percent lower MAC-related fuel usage than a similar vehicle
with a conventional MAC system. The implementation of improved compressor cycling
and control, coupled with more efficient compressors and heat exchangers, also could
result in fuel consumption reductions of up to 30 percent. 67
Cost-Effectiveness
It is expected that these
technologies could enter the market in the next few years but would likely only affect new
vehicles sold, resulting in these reductions only being realized in the medium term (U.S.
EPA, 2007e).
Cost estimates for DIY MAC service restrictions are taken from California ARB estimates.
The increased cost of a DIY “can ban” comes primarily from the increased cost of
professional vehicle servicing. It is estimated that the cost increase, borne primarily by
consumers that had previously performed DIY service on their own vehicles, would be
$135 per tonne CO2e. Implementing a deposit program also would create additional costs
for the consumer. It is estimated that this type of program to reduce heel emissions would
cost between $9 and $19 per tonne CO2e, largely paid for by consumers in the form of
more costly containers and shipping logistics. The cost-effectiveness of adding an
67 Personal communication with Dr. Stephen Andersen, U.S. EPA.
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