Carbon footprint model for evaluating the global warming impact of food transport refrigeration systems

This paper presents a model for assessing the carbon footprint of food transport refrigeration systems. The model considers all the impacts of the refrigerators and refrigerants in each process, including production, transport, use, repair and recycling, on greenhouse gas emissions expressed as the CO2 equivalent emissions in total. The carbon footprint can be divided into direct emissions which are the greenhouse effect caused by various greenhouse gas emissions and leakage in each process, and indirect emissions which are the CO2 equivalent emissions due to the energy consumption in each process. This model was used to evaluate the carbon footprint of food transport refrigeration systems with three refrigerants, R404A and the environmentally benign refrigerants R744 (CO2) and R410A for various ambient temperatures, refrigeration temperatures, lifetimes and refrigerator drive modes. The results show that the carbon footprint of food transport refrigeration systems with R404A is larger than for R744 and R410A. Although the Global Warming Potential (GWP) of R744 is the lowest, the carbon footprint of food transport refrigeration systems with R744 is not always the smallest, but may exceed that of R410A in high temperature areas. The CO2 emissions caused by the energy consumption are a large part of the total CO2 emissions, with the energy consumption to power the refrigerator and to carry the refrigeration unit weight resulting in the largest proportions; thus increasing the coefficient of performance (COP) of the refrigerator and the efficiencies of other equipments can significantly reduce the energy consumption and CO2 emissions. Higher ambient temperatures and lower refrigeration temperatures lead to more CO2 emissions. Refrigerators driven by auxiliary engines have higher CO2 emissions than refrigeration systems driven by the main vehicle engine or electricity. The carbon footprint evaluation model developed in this paper can also be used to evaluate the carbon footprint of mobile air conditioning and other systems.