# Efficient and Sustainable Cleaning: A Comparative Analysis of Cryogenic Technology
## 1 Introduction  
The use of dry ice blasting technology for surface cleaning has been investigated since 1945 by the US Navy as a degreasing system and was introduced into the market during the 1980s [1] for a variety of uses and applications [2]. The dry ice blasting system is based on three mechanisms that contribute to breaking the bond between the contaminant and the substrate from which it is to be removed: thermal shock by cooling the surface, kinetic energy from the use of compressed air, and sublimation of the pellets used [3]. The advantages of the system compared to other surface contaminant removal methods have been extensively analysed [4; 5; 6; 7; 8], with a focus on environmental and operational aspects. First is its eco-sustainability, as the CO2 used is recycled, which reduces the use of large quantities of water and avoids the use of environmentally polluting and health-hazardous solvents. Second, it ensures surface safety, as it is not an abrasive system; the pressure required is reduced compared to other projection systems, and the pellets used have a very low hardness. Third, its versatility allows for adjustments according to the parameters used. Fourth, it is highly adaptable to sensitive surfaces and complex geometries. Finally, the system is simple, as it is not necessary to remove any residues from the surface, which is completely dry at the end of the treatment. Cryo-cleaning is an established technology in many industries, and interest in its use continues to grow [6]. Leading dry ice blasting machine manufacturers promote the technology for its many benefits. Its characteristics make it ideal for the cleaning and maintenance of production lines and equipment in various industries, extending their useful life. In addition, it has applications in sectors such as plastics and rubber manufacturing, metal casting, energy companies, food processing plants, surgical instrument and equipment manufacturing, printing, paint and adhesive factories, and vehicle manufacturing. It is also effective for the periodic cleaning of air conditioning systems and public transport fleets, as well as for the conditioning of private vehicles. In addition, it is useful in the remediation of the effects of fires and floods, removing smoke, carbonaceous particles, moulds, and the odours derived from these situations (see Table 1). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  
The configuration of most commercially available dry ice blasting equipment focuses on fast, efficient, economical, and environmentally friendly cleaning [1]. This technology aims to remove hard concretions on large, regular and irregular substrates in short timeframes at a low cost and in compliance with the climate neutrality pact [43]. This approach translates into specific goals, such as ensuring worker safety or minimising the impact of the process on serial production by reducing waste and by-products derived from cleaning [6]. The management of the non-volatile residue deposited on the surface is addressed without the need for a second washing treatment or material replacement, thus eliminating associated challenges, such as those found in processes that use soaps and solvents, as well as sandblasting [44]. Several studies confirm the versatility of the system, which can be adjusted by varying the main parameters, including compressed air pressure, granule feed rate, granule size, and nozzle type [2; 5; 6; 11]. In this way, they can be adapted to very delicate surfaces, such as electronic systems [15], even with complex geometries [12]. The range of materials to be removed is very diverse [11], both organic, e.g., heavy oils in storage tanks [13], and inorganic, e.g., corrosion layers on metals [7; 36]. Furthermore, some applications demonstrate the possibility of very selective cleaning of extremely delicate materials [41].