Sustainable automotive air conditioning

Sustainable automotive air conditioning is the subject of a debate – nicknamed the "Cool War" – about the next-generation refrigerant in car air conditioning. The Alliance for CO2 Solutions supports the uptake of carbon dioxide (CO2) as a refrigerant in passenger cars, and the chemical industry is developing new chemical blends.
The Alliance and its supporters – scientists, NGOs and business leaders – urge the car industry to replace high global warming chemical substances with the natural refrigerant carbon dioxide (CO2, R744/ R-744) in car cooling and heating. This, they argue, would lead to 10% less car emissions, and knock out 1% of total greenhouse gas emissions worldwide. If CO2 Technology is applied in other sectors, such as commercial and industrial refrigeration, heat pumps for water heating etc., it may even save up to 3% of the world's greenhouse gases.
Opponents of the Alliance claim that CO2 Technology is not cost-efficient and safe, hence seeking to postpone the global industry decision to be taken to develop new chemical blends instead.
Background.
A debate had emanated from the decision of the European Union to phase out the current high global warming refrigerant HFC-134a in car air conditioning from January 2011 onwards. To comply with the legislation, carmakers have to decide on new refrigerants as they typically need 3 to 4 years to develop and introduce a new car platform including the air conditioning system.
Arguments.
Arguments for CO2.
The Alliance for CO2 Solutions and its supporters agree that the refrigerant CO2 is:
Arguments against CO2.
CO2 Technology requires the design of completely new high-pressure systems whereas so-called "drop-in solutions" (the adaptation of current systems to new substances) are potentially more cost-efficient.
The Alliance for CO2 Solutions claims, however that the initial costs of CO2 systems will be around €5 higher than drop-in solutions and that over a car's life cycle, CO2 air conditioning systems will be more cost-efficient than any currently used or proposed new chemical blends. (see Arguments for CO2).
 has been classified as Safety Class A1 (low-toxic, non-flammable refrigerant) by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) – the highest safety class possible. As the charge of CO2 to the air conditioning systems is very small (200-400 g) there is no realistic danger for the passengers, even in case of accidental release.
Arguments against non-CO2 refrigerants.
Butane and propane are very flammable petroleum products; they are used as fuels for gas barbecue grills, disposable lighters, etc. Like gasoline, to which it chemically is closely related, propane has a tendency to explode if mixed with oxygen and ignited in an enclosed container.
The use of highly flammable hydrocarbon gases such as butane and propane as automotive refrigerants raises serious safety concerns. The EPA, in evaluating motor vehicle air conditioning substitutes for CFC-12 (Freon, or R-12) under its SNAP program, has classified as "Unacceptable Substitutes" other "Flammable blend[s] of hydrocarbons" by reason of "insufficient data to demonstrate safety." The EPA defines "Unacceptable" in this context as "illegal for use as a CFC-12 substitute in motor vehicle air conditioners". All of the refrigerants which EPA approved for motor vehicle use in place of CFC-12 (as of 28 September 2006) contain no more than 4% total flammable hydrocarbons (butane, isobutane, and/or isopentane). Therefore, it appears unlikely, for safety reasons, that EPA will approve 'Greenfreeze' or similar hydrocarbon-based refrigerants for automotive use.
Latest and next steps.
In September 2007, the German Association of the Automotive Industry (VDA) officially announced its decision to use CO2 as the refrigerant in next-generation air conditioning. Other carmakers from Europe and the rest of the world may follow the German lead.
A working group at ACEA, the European carmakers' association, was to be drafting a common position on the issue to be adopted across the whole industry by end-2007.
However, on 9 April 2009, German public television channel ARD aired a report claiming that VDA members would be using loopholes in the law to avoid complying with the EU directive.