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

Transportations Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
environmental fee is highly dependent upon the fee level and whether the fees collected
are applied to other GHG mitigation strategies. High fee levels could obtain reductions at
similar cost-effectiveness to a can ban, but the cost-effectiveness of lower fees would
depend strongly on the cost-effectiveness of the mitigation strategy to which the fees
would be applied (CARB, 2008c).
Alternative refrigerant cost estimates are not frequently cited in the literature. Based on
current estimates, refrigerant costs for HFC-1234yf will likely be the highest of the three
alternatives discussed above, but the complete systems for this refrigerant will be very
similar or interchangeable with current designs, so the system costs will likely be the
lowest. HFC-1234yf systems may cost around $40 more per vehicle than current systems.
HFC-152a will have greater system costs than HFC-1234yf due to toxicity mitigation,
resulting in an estimated cost of around $50 more per vehicle. R-744 will have the highest
costs due to requiring larger components that are much different than those in current use,
resulting in systems that could cost $200 more than current systems. 68
Secondary loop systems will add cost and complexity to vehicles. While specific cost
estimates were not found in the literature, estimates imply that the cost increase would be
low enough to easily be paid back by fuel savings in climates where air conditioning is
used often (U.S. EPA, 2007d). Further cost and benefit analysis for secondary loop
systems and other methods of reducing MAC system load are not performed due to lack
of sufficient cost data in the literature.
3-122
R-744 systems may
be more feasible in heavy-duty applications where the physical size requirements and
system cost can be more easily managed.
Cobenefits
To the extent that engine loads are reduced, reductions in exhaust criteria pollutants may
result. It is estimated that MAC compressor use can increase emissions of NOx and carbon
monoxide by 70 to 80 percent, and increase hydrocarbon emissions by 30 percent
(Farrington and Rugh, 2007). In addition, as system integrity and leak prevention become
higher priorities, overall reliability increases, resulting in lower maintenance
requirements. After the change from CFC-12 to HFC-134a, reliability increased due to the
attention given to connections and leakage. The IMAC program is likely to result in
similar improvements.
Feasibility
Of the methods identified to reduce MAC system leakage from DIY servicing, a can ban
has the most significant barriers to implementation. Such a ban would completely
eliminate the small can refrigerant business. However, the economic impact would be
68 Andersen (2008); Personal communication with Dr. Stephen Andersen, U.S. EPA.