Current Status and Future Prospects of Refrigerants for Refrigeration and Air Conditioning Systems: Environmental Impact and Regulatory Measures

INTRODUCTION

Global warming, driven by greenhouse gases like carbon dioxide, CO₂, hydrofluorocarbons and HFCs, has led to an increase in extreme weather events. Although fluorocarbons represent a minor fraction of greenhouse gas emissions, their high global warming potential, GWP, and widespread use in refrigeration and air conditioning significantly impact climate change. Initially, fluorocarbons of CFCs and HCFCs were adopted as safer alternatives to toxic and flammable natural refrigerants. However, due to their ozone-depleting properties, HFCs were introduced in the 1990s. Despite being less harmful to the ozone layer, HFCs have high GWPs, prompting international treaties to limit their use. To mitigate global warming and achieve sustainable development goals, it is crucial to regulate fluorocarbon use, develop low-GWP refrigerants, and enhance the efficiency of refrigeration and air conditioning systems. Additionally, establishing effective refrigerant management systems and exploring innovative refrigeration technologies are essential steps towards minimizing environmental impact.

CURRENT TRENDS AND CHALLENGES IN REFRIGERANT USAGE

Figure 1 shows the mass balance of HFCs in the EU, USA, and Japan, based on 2022 data from the Japan Society of Refrigerating and Air Conditioning Engineers. Despite efforts to meet target values (red rectangles), progress is only halfway even in developed countries, necessitating stronger measures to limit refrigerant production and consumption.

Additionally, HFC recovery, reclamation, and destruction are lagging. To globally reduce HFC emissions, increasing recovery and systematically reclaiming and destroying HFCs are essential, with the purpose of establishing an effective refrigerant management system.

TOWARDS A CIRCULAR ECONOMY: EFFECTIVE REFRIGERANT MANAGEMENT

To promote sustainable societal development, it is crucial to create circular systems with minimal environmental impact (Figure 2). This includes developing high-efficiency (high-COP) equipment using low-GWP refrigerants and generating minimal CO₂ emissions. Safety, minimal refrigerant charge, low leakage, and systems facilitating refrigerant recovery during disposal and maintenance are essential. Establishing robust refrigerant management systems is also vital.

Figure 3 shows the relationship between the recovery and reclamation rates called the K-plot of R 22 (HCFC) and R 410A (HFC) in Japan. Since 2020, the new production and import of R 22 as a refrigerant have been prohibited, and only reclaimed R 22 is supplied to the market for maintenance. According to the K-plot, there is a correlation between the recovery rate (calculated as the recovery amount divided by the averaged market supply from 12 to 14 years ago, assuming an averaged equipment disposal period of 13 years) and the reclamation rate (calculated as the reclamation amount divided by the recovery amount of each year) of these two refrigerants. For circular refrigerants, the plot shows an upward trend. Although it varies by refrigerant, R 32, in addition to R 410A, is considered to be a circular refrigerant. Moreover, comparing the energy required for reclamation and destruction of refrigerants shows that reclamation requires about 1/20 of the energy, making it superior from both environmental and resource utilization perspectives. Figure 4 depicts the relationship between the recovery and reclamation rates of refrigerants recovered during the disposal of home air conditioners, RACs using R 22, R410A, R 32 under the Home Appliance Recycling Law, car air conditioners, MAC using R 134a mainly under the Automobile Recycling Law, and commercial refrigeration equipment (PAC, VRF, etc.) using R 134a, R 404A, R 410A, R 32, and other HFCs under the Fluorocarbon Emission Control Act in Japan.

The recovery and reclamation rates are high for RACs and commercial refrigeration and air conditioning equipment, but low for MACs. Recovered RAC equipment is dismantled in specialized factories where refrigerants are recovered. Commercial equipment refrigerants are recovered on-site. Considering unrecovered RAC equipment that does not reach processing plants, the recovery rate is not much different from that of commercial equipment. On the other hand, MACs, due to their mobility, have an annual leakage of about 10 g during their use over about ten years, resulting in a lower recovery rate. Additionally, the law was initially enacted to address the destruction of R12 (CFC), so while R134a is currently being recovered, most of R134a is destroyed even though MAC aftermarket uses new products.

FUTURE PROSPECTS: INNOVATIONS AND ALTERNATIVES IN REFRIGERANT TECHNOLOGY

The rising global temperatures are driving the adoption of mid-to-small-sized air conditioning and heat pumps units, especially in the EU and the USA. The EU is developing small heat pumps and water-circulating heating units using R 410A and R 32 as replacements for fossil fuel-burning heaters. Propane-based alternatives to HFCs are also being explored for these systems, while Japan uses CO₂. Compact monoblock units like heat pumps and window-type air conditioners are increasingly using hydrocarbons such as propane, despite its flammability, due to easier safety management. These natural refrigerants are already in use in household refrigerators, replacing CFCs and HCFCs with isobutane and n-butane.