Mitigating environmental burden of the refrigerated transportation sector: Carbon footprint comparisons of commonly used refrigeration systems and alternative cold storage systems

Concerns about potential climate change stemming from refrigerated systems have increased because of the environmental burden of nonrenewable energy use and refrigerants' high global warming impacts. Currently, cold storage systems based on phase-change material (PCM) technology have emerged as an alternative solution to the commonly used vapor-compression refrigeration system (VCRS). This study compares the carbon footprint of a conventional VCRS with an alternative PCM-based cold storage system (PCCSS). As such, we first develop a comprehensive life cycle assessment approach, focused on climate change, to examine the carbon footprint of the two refrigeration systems. To validate this model, we conducted the comparison by addressing key factors-such as various ambient temperatures, refrigeration temperatures, national energy mix and different refrigerants-that influence the two systems' potential climate change impacts. Upon analysis of the key parameters, the results revealed that the PCSSS has a smaller carbon footprint. The PCCSS showed a reduction ranging from 22% to 56% when compared with the conventional VCRS. Our results show that the use-stage is the carbon footprint hot spot in both investigated cases, accounting for 84%-91% of the VCRS's total carbon footprint and around 68% for the PCCSS's. The PCCSS's potential carbon footprint reduction mainly depends on electric grids, which could achieve up to 56% reduction with a lower emission factor than the VCRS, which uses fossil fuels. Moreover, compared to the VCRS, the PCCSS presented a greater potential to reduce the carbon footprint in warmer climates. Additionally, reducing refrigerated temperatures from 0 degrees C to -18 degrees C increases the life-cycle carbon footprint of the VCRS by an average of 47% and that of the PCCSS by an average of 58%. Compared with R404A, the carbon footprint for the VCRS was reduced by 1.5-1.8% when using refrigerant R410A (over a 10-year lifespan), while the use of R744 in the same time frame, resulted in a reduction of 3.2%-3.9%. It can be concluded that the PCCSS has an advantage in reducing its carbon footprint during the use stage, but its carbon footprint increases with higher resource input for the production and recycling stage than conventional VCRS. In the future, engine efficiency, clean electricity grids, and refrigerants' global warming potential must be further prioritized for low-carbon refrigeration systems.