Refrigerant CO2

Effective climate protection with the refrigerant CO2

Chemical refrigerants: drivers of the greenhouse effect

Chemical refrigerants are still the standard in many industries today. At the same time, they contribute significantly to climate change.

The problem: air conditioning agents permanently escape through leaks, maintenance or accidents.

Hazardous release of refrigerants:

The average leakage rate of R-134a in new buses is 13.3% refrigerant per year for overland buses and 13.7% for city buses (Schwarz, Establishment of Leakage Rates of Mobile Air Conditioners in Heavy Duty Vehicles, 2007). According to publications of “Deutsche Umwelthilfe e.V.”, buses across Germany emitted nearly 100 tons of R-134a refrigerant in 2008.

The amount of refrigerant released by buses corresponds to 140,000 tons of CO2 equivalents per year. That corresponds to the annual CO2 emissions of 90,000 fuel efficient compact cars with an average manner of driving.

Climate change

Climate change is causing numerous regions in Africa and south-east Asia to turn into steppe and deserts. As a result, the population already suffering from hunger in these areas will find it even more difficult to grow their food in the parched soil in the future.
Climate change is increasingly leading to severe storms and flooding as well, which will also affect harvests.

Europe is being flooded with refugees as a consequence of climate change.
The poorest from rural regions in Africa and south-east Asia will leave their homes and flee to the world’s wealthier regions as a result of climate change.

Current studies confirm that the consequences of climate change are causing high costs for us in Germany as well. The costs of storm and flood damage as well as harvest losses will have to be paid by our farmers and ultimately by us as consumers. Investments for higher dikes against rising sea levels as a result of climate change caused by us will have to be covered by us as taxpayers.

EU climate targets
New regulations such as the ban on refrigerants with a particularly severe climate impact are intended to help stop climate change. Europe is thereby setting new global standards for climate change.
With the climate and energy strategy, the “20-20-20 Targets”, the EU has passed a package of directives intended among other things to achieve a 20% reduction in greenhouse gas emissions by the year 2020. 
The European targets for the year 2020 are as follows:

  • 20% reduction in greenhouse gas emissions compared to 2005
  • 20% share of renewable energy
  • 20% improvement in energy efficiency

All member states contribute to the reduction in greenhouse gas emissions with differentiated national targets determined in the course of a “burden sharing” process.
This is an ambitious project encompassing various concrete measures. One of them relates to the use of partly fluorinated hydrocarbons – also known as F-gases.
In order to minimise their influence on global warming, the EU Council in April of 2014 passed Regulation (EU) No. 517/2014 on fluorinated greenhouse gases (F-Gas Regulation).

F-gases contribute approximately 1.4% to the greenhouse effect worldwide (2011).
The demand for F-gases or products involving F-gases is skyrocketing as the quality of life in industrialised nations and emerging markets improves. The global installed cooling capacity and therefore the demand for refrigerants is increasing in direct correlation with the improving quality of life. Discontinuing the use of HCFCs is leading to a massive increase in HFC and PFC emissions. F-gases are extremely persistent, breaking down very slowly and therefore steadily accumulating in the atmosphere. They also have a major impact on our climate, meaning that small increases have a pronounced and long-lasting negative effect. Substituting natural substances for F-gases has become technically possible in many fields so that ambitious targets can be set.
F-gases are not only emitted as refrigerants but also due to numerous other applications.

Examining the refrigerants that are available in the foreseeable future shows that, from today’s perspective, only natural refrigerants can be considered as an alternative to the climate-damaging refrigerants currently in widespread use. Environmental acceptability, nearly unlimited availability and low prices are typical for these substances.

The Global Warming Potential is the potential contribution of a substance to warming atmospheric layers close to the ground, meaning what is known as the greenhouse effect. The contribution of the substance is stated as a GWP value relative to the greenhouse potential of the substance carbon dioxide (CO2).
GWP100 values – meaning the contribution of a substance to the greenhouse effect averaged over a period of 100 years – are used for the classification.
The lower the value of the CO2 equivalent, the lower the potential effect on global warming and the related environmental impact.
(Source: BNB UN 1.1.1)

Time to act - climate protection

Since the World Conference on Environment and Development in Rio in 1992, there has been international agreement that climate change must be stopped.

With the climate and energy strategy - the "20-20-20 goals", the EU has adopted a pact of directives which, among other things, aims to reduce greenhouse gas emissions by 20% by 2020. New provisions, such as the ban on particularly climate-impacting refrigerants, are intended to help achieve the EU climate targets. Europe is thus setting new global standards for the reduction of CO2 emissions.

In vehicle air conditioning systems, the fluorinated greenhouse gas tetrafluoroethane (R134a) has so far been used as a refrigerant. Directive 2006/40/EC on emissions from air conditioning systems in motor vehicles bans the use of refrigerants with a global warming potential higher than 150 in new passenger cars and car-like commercial vehicles from 1 January 2017. In the first step this only affects the automotive industry, but in the long term a general ban of R-134a is expected.

The key points of the EU F-gas regulation

Phase Down:

  • Step-by-step reduction of F-Gases
  • Reduction of the quantity to 21% by 2030 in six stages Use restriction
  • Step-by-step ban on particularly climate-damaging F-gases
  • Quotas - F-gas quotas are allocated to manufacturers and importers
  • Stricter requirements for leakage checks of refrigeration and air-conditioning systems
  • Extended operator obligations: Installation, maintenance, servicing, repair, etc. may only be carried out by certified staff

Fluorinated greenhouse gases and CFCs

While the classic greenhouse gases are mostly released as undesirable by-products, for example during the combustion of fossil fuels, fluorinated greenhouse gases are for the most part produced and used in a targeted manner. They are used today in a similar way to chlorofluorocarbons (CFCs) and halons, which are responsible for the destruction of the stratospheric ozone layer.

The global contribution of F-gases to the greenhouse effect today is about 1.3 percent (2004). A 2010 study by the Federal Environment Agency predicted that by 2050 F-gas emissions would increase to 7.9 percent (excluding HFC phase down) of global direct CO2 emissions.

In direct connection with the increasing quality of life, the installed cooling capacity and thus the demand for refrigerants is increasing globally. The phasing out of the use of ozone-depleting HCFCs leads to a massive increase in HFC and PFC emissions. F-gases are extremely long-lived, are only broken down very slowly and therefore accumulate constantly in the atmosphere. Furthermore, they have an extremely high climatic impact, i.e. small increases have strong and long-lasting negative effects. Substitution of F-gases by natural substances has become technically possible in many areas, so that ambitious goals can be set.

The Global Warming Potential is the potential contribution of a substance to the warming of the air layers near the ground, i.e. to the so-called greenhouse effect. The contribution of a substance is expressed as a GWP value relative to the global warming potential of carbon dioxide (CO2).
The GWP100 values are used for the assessment, i.e. the contribution of a substance to the greenhouse effect averaged over a period of 100 years.
The lower the value of the CO2 equivalent, the lower is the potential effect on
global warming and the associated environmental impacts. (Source NBB UN 1.1.1)




R-744 (CO2)


atmospheric residence time




GWP (100 years)


1 (0)


lower explosion limit




Ignition temperature




Vapor pressure at 60°C




Vapor pressure at 30°C




Vapor pressure at 0°C




Evaporation enthalpy at 0°C




Gas density at 0°C




volumetric cooling capacity at 0°C




Directives and regulations are aimed at reaching the targets of the climate and energy strategy.

The 2005 United Nations Climate Change Conference took place between November 28 and December 9, 2005, in Montreal, Canada. The conference included the 11th Conference of the Parties.

The aim of the Climate Convention is "to prevent a dangerous, man-made disruption of the climate system and to slow down global warming and mitigate its consequences" (Article 2 - Framework Convention on Climate Change). The main commitment of the Climate Convention is that all contractors must periodically publish reports containing their current greenhouse gas emissions and the likely evolution of greenhouse gas emissions.

The Climate Change Conference in Montreal in 2005 was attended by the 189 States Parties to the Climate Convention. This conference was also the first meeting of the Parties to the Kyoto Protocol, which entered into force on ratification of Russia on 16 February 2005.
The aim of this conference was to discuss the implementation of the Kyoto Protocol and to enforce the Kyoto Protocol.

The new F-Gas Regulation is a contribution towards reducing the emissions of the industry sector by 70 percent until the year 2030 compared to 1990. Emissions of fluorinated greenhouse gases (F-gases) in the EU are to be reduced by 70 million tons of CO2 equivalents to 35 million tons of CO2 equivalents by the year 2030 through the new rules. Three main regulatory approaches are intended to reduce the emissions of fluorinated greenhouse gases:

  1. A phase-down of the volume of partly fluorinated hydrocarbons (HFCs) available in the market by the year 2030 to one-fifth of the current sales volume.
  2. Implementing bans on use and bringing to market when technically feasible, more climate-friendly alternatives are available.
  3. Maintaining and amending the regulations for tightness tests, certification, disposal and labelling.

In particular, the new F-Gas Regulation is intended to create an incentive for the use of alternatives to F-gases.

As a consequence of the new F-Gas Regulation coming into force, the federal government will revise the Chemicals Climate Protection Regulation (ChemKlimaschutzV) and implement sanctions by amending the Chemicals Sanctions Regulation (ChemSanktionsV).

Overview of the F-Gas Regulation
Gradual reduction of F-gases

  • Reduction of the volume to 21% in six stages by 2030
  • Restrictions on use – gradual ban on F-gases with a particularly severe climate impact
  • Quota system – assignment of F-gas quotas to the manufacturers and importers
  • Tightness testing – stricter regulations for the tightness testing of refrigeration and air conditioning systems
  • Expanded operator obligations – installation, upkeep, maintenance, repair etc. exclusively by certified staff

More than 150 countries meeting in the capital of Rwanda agreed to limit the use of climate-damaging fluorocarbons.
Industrialised nations such as the USA are to reduce the use of PFCs by ten percent starting in 2019. They intend to reduce their use by 85 over the years. This is slated to happen by 2036 at the latest.
Most of the countries that signed – including China – will begin reducing their use in 2024. Developing countries are given more time. Emerging markets and developing countries such as India had urged a later start and pointed out the high costs incurred for switching to other substances.
The agreement that has now been reached is considered a milestone in the fight against climate change.

Another legal aspect for the handling of refrigerants is established in the Chemicals Climate Protection Regulation (ChemKlimaschutzV). It states that only specialists with a personal certificate of competence may carry out work on systems with fluorinated refrigerants. The operation has to be certified as well. Starting in 1989, the chloric and ozone-depleting refrigerant R-12 (CFC, chlorofluorocarbon) in air conditioning systems was replaced by the chemical PFC refrigerant R-134a used until today (tetrafluoroethane – a fluorinated hydrocarbon). While this substance is far more environmentally friendly compared to CFC, it nevertheless has a factor 1430 global warming potential (GWP) and was declared a transition solution at the time.

The European Union has grasped that fact and, in its Mobile Air Conditioning Directive (MAC) – in the interest of protecting the environment – imposed strict requirements for refrigerants used in the air conditioning systems of motor vehicles (Directive 2006/40/EC).
Vehicle manufacturers were obligated starting on 1 January 2011 to use refrigerants with a global warming potential (GWP) less than 150 according to EC No. 842/2006 for air conditioning systems in vehicles approved as new models in the EU. This applies for all approved passenger vehicles and light commercial vehicles (less than 1.3 tons) effective on 1 January 2017. The bus sector is mentioned in this directive as well. A date for a ban on R-134a has not been set but is expected to be forthcoming.


GWP < 150

Affects passenger vehicles (M1) and light commercial vehicles N1 up to 1.3 t.

Banned (Art. 5) in new models effective 1 January 2011,

in all new vehicles effective 1 January 2017

Certain certifications/awards and also subsidies will only be available in conjunction with the use of environmentally friendly and non-toxic refrigerants in the future in order to create additional incentive for the environmentally friendly use of natural refrigerants.

German designations and ecolabels - Blue Angel environmental label

3.3 Air conditioning technology
A GWP value < 150 will be required under the “Blue Angel” environmental label going forward.

Furthermore, only halogen-free refrigerants can be used for 2-axle urban buses starting on 1 January 2018.

VDV Directive – VDV Requirement 236 “Air Conditioning of Line-Service Buses”
VDV Requirement 236 in the area of air conditioning under the general requirements, point 3.1 calls for the use of “environmentally friendly and non-toxic refrigerants”.


According to legal regulations, environmentally friendly and non-toxic state-of-the-art refrigerants have to be used. Here the filling capacity must be kept as small as possible while maintaining an adequately dimensioned reserve quantity for reliable operation.

German subsidy for hybrid buses, 12 December 2014
The new “Directives for Promoting the Acquisition of Diesel-Electric Hybrid Buses in Public Transit” officially came into force in January of 2015 and apply until the end of 2017. This subsidy is linked to meeting ambitious environmental standards that have been expanded to include air conditioning in the meantime: “Applications for projects to acquire vehicles with environmentally friendly CO2 air conditioning technology will be considered preferentially.” Interested transport companies can submit project outlines effective immediately.

Financial aid for climate-friendly refrigerants
Subsidies and grants for climate-friendly refrigerants already exist in the following EU countries:

  • Germany
  • Austria
  • Great Britain
  • Switzerland
  • Belgium
  • Netherlands

To complement the F-Gas Regulation, the price of PFCs is being purposely increased through additional taxes in some EU states. While the national regulations vary, taxation of approximately EUR 20 per ton of CO2 equivalents is the goal.

China, der weltweit größte Hersteller und Emittent von HFKW, hat angekündigt, dass durch die Kigali-Änderung des Montrealer Protokolls festgelegte globale HFC-Abbauabkommen anzuerkennen, so die staatliche chinesische Nachrichtenagentur Xinhua.

Der chinesische Präsident Xi Jinping gab dies auf einem virtuellen Gipfel am 16. April zusammen mit dem französischen Präsidenten Emmanuel Macron und der deutschen Bundeskanzlerin Angela Merkel bekannt.

Darüber hinaus gaben die USA und China am 17. April eine gemeinsame Erklärung ab, in der sie feststellten, dass beide Länder "jeweils die in der Kigali-Änderung des Montrealer Protokolls festgelegte Phase der Produktion und des Verbrauchs von Fluorkohlenwasserstoffen umsetzen werden".

Nach Schätzungen der Vereinten Nationen, würde die vollständig umgesetzte Kigali-Änderung bis zum Ende des Jahrhunderts einen Anstieg der globalen Temperatur um bis zu 0,4 ° C (0,7 ° F) vermeiden.

Die Kigali-Änderung des Montrealer Protokolls wurde im Oktober 2016 von 197 Ländern (plus der Europäischen Union) verabschiedet. Sie trat am 1. Januar 2019 in Kraft. Ziel ist es, den HFKW-Verbrauch bis 2047 um mindestens 80% zu senken.

Kambodscha war das letzte Land, das am 8. April 2021 einwilligte, und wurde das 117. Land sowie die Europäische Union (EU), die das globale Abkommen ratifizierte.

China, the largest producer and emitter of HFCs in the world, has announced that it will ratify the global HFC phase-down agreement established by the Kigali Amendment to the Montreal Protocol, according to China's state-run press outlet Xinhua News Agency.

Chinese President Xi Jinping made the announcement in a virtual summit held on April 16 together with French President Emmanuel Macron and German Chancellor Angela Merkel.

In addition, the U.S. and China issued a joint statement on April 17 stating that both countries will "each implement the phase down of hydrofluorocarbon production and consumption reflected in the Kigali Amendment to the Montreal Protocol".

Fully implemented, the Kigali Amendment would avoid up to 0.4°C (0.7°F) increase in the global temperature by the end of the century, according to United Nations estimates.

The Kigali Amendment to the Montreal Protocol was enacted by 197 countries (plus the European Union) in October 2016. It entered into force on January 1, 2019. Its goal is to achieve at least an 80% reduction in HFC consumption by 2047.

Cambodia was the latest country to ratify on April 8, 2021, becoming the 117th country, plus the European Union (EU), to ratify the global agreement .

The consequences: These commercially available refrigerants are currently becoming very expensive and will no longer be available in the future.

CO2 as refrigerant (R744)

The climate friendly alternative

CO2 as a natural refrigerant, also known as R744, is the climate-friendly alternative to today's common chemical refrigerants. It is environmentally friendly, has a high cooling capacity, is not flammable and does not form any decomposition products. Furthermore, it is inexpensive and permanently available.

CO2 is a natural component of air and has a global warming potential of only factor 1 - chemical refrigerants are 1000 times higher (R134a GWP 1340) or they are combustible and the decomposition products are dangerous for the environment.

CO2 can be used not only in air conditioning systems but also to operate heat pumps. These can cool as well as heat efficiently.

Economic benefits of R744/CO2

CO2 heat pumps: zero emissions, highest energy efficiency

With natural CO2 as a refrigerant, considerable energy savings can be achieved in cooling and heating operation. Because CO2 has an up to 20% higher efficiency than chemical refrigerants, accordingly, the target temperature is reached 20% faster.

CO2 is particularly suitable for use in heat pumps.

Field reports from public transit companies

BVG made itself available for a long-term test of this technology back in 2008 as one of the first transport companies. A standard city bus was equipped with a CO2 air conditioning system for this purpose.
To date this bus has covered more than 500,000 km. Thanks to positive experience with the first bus, 6 additional city buses with this technology have been operated daily by BVG since May of 2010. Burkhard Eberwein, Fleet Manager at BVG and member of the VDV Technical Committee, finds the innovative air conditioning technology convincing and speaks of a concept for the future.

Satisfaction at BVG: 122 buses have been delivered to the transport company by the end of 2020, with more to follow.

Raimund Loogen, Workshop Manager at NIAG, sums it up: “The R744 refrigerant not only pays off for the environment. Aside from the cost of the refrigerant, maintenance costs are significantly reduced as well since it can simply be discharged and a filter dryer is no longer needed either. It is also safe and easy to handle. We as a public transit company are visible to the public and a figurehead for the region. Due to this responsibility, we decided to equip the first buses with air conditioning systems using R744 five years ago. We are very proud of these R744 buses. They run flawlessly and only incur about one-fifth of the maintenance costs compared to a vehicle with a conventional R134a system.”

More Information

60 years of innovation: For the environment of tomorrow

Konvekta stands for environmental protection and sustainability. Therefore we have been taking our own paths in the development of efficient and climate-friendly cooling and heating technology for more than 20 years.

With natural CO2 as a refrigerant, we make a major contribution to active climate protection. Our "Made in Germany" technologies are used in the vehicle industry.

nach oben