### COVID-19 and Environmental Efficiency in the Hospital Sector  
Healthcare organisations and workers have proved themselves to be crucial in responding to the COVID-19 situation. They are indeed a crucial and strategic factor in the fight against the pandemic, which had to be adapted and focused on a surge in the responsiveness of the health care system to treat people infected by COVID-19. Internationally, the enormous demand to manage the COVID-19 pandemic has challenged hospitals in terms of staffing, supplies and equipment [22]. Since the beginning of the pandemic, the WHO has made several announcements with recommendations on the use of face masks and other PPE (personal protective equipment) as part of transmission precautions for health workers caring for COVID-19 cases [23]. Along with these recommendations, the WHO made an estimate of the expected consumption of this type of protective equipment by healthcare workers. Specifically, it fixed values of 1.6 million goggles, 2.9 million hydroalcoholic gels, 30 million gowns and 76 million gloves needed each month to protect health workers worldwide [23]. According to WHO reports, these figures will affect the global supply chain, leading to a 40% increase in the medical protective equipment supplies. Plastic material, found in a variety of personal protective equipment (PPE) (see Figure 1) and other disposable devices used in the medical industry, has been the main barrier to protect healthcare workers during the coronavirus crisis. The specific properties of plastic materials, such as good strength-to-weight ratio, as well as its versatility and durability, made it one of the most widely used materials in a variety of common healthcare equipment and systems [24]. The WHO recognises that it is essential to provide healthcare workers with the correct PPE, and in addition, it deems decisive to achieve this while paying attention to the  
Figure 1: Personal protective equipment (PPE). environment and the impact that the consumption of PPE can generate. In this regard, a WHO report [25] recommends the use of waste management best practices to combine safety and sustainability in the use of plastic materials, both for the duration of the pandemic and in the case of other future crises that may require the use of similar protective systems. A consequence of the use of PPE is that they are considered infectious waste and are managed as such, as provided for in the information published by the different competent authorities on health care waste. The medical waste generated has increased exponentially due to the coronavirus crisis. For example, in the case of Wuhan, China, there has been a 600% increase, from 40 to 240 tonnes of medical waste per day. This added an extra 190 tonnes to the maximum available incineration capacity of 50 tonnes per day [26]. Similarly, all the worldwide hospital activity resulting from the pandemic has led to the production of hazardous waste, which in many cases came from PPE, which could thus be infected. Therefore, managing this hazardous biomedical waste is a vital aspect of dealing with the coronavirus crisis. This should include not only the usual waste treatment chain, i.e., identification, collection, segregation, storage, transport, treatment, and waste disposal, but also more specific components associated with the pandemic, such as the training of healthcare personnel or the disinfection of equipment and facilities [27]. Oxygen, on the other hand, has been officially treated as a medicine, and has been the basis for the treatment of SARS-CoV-2 pneumonia. The use of oxygen in healthcare settings has been considered a key element in the treatment of patients with severe forms of coronavirus. According to the World Health Organisation (WHO), 15% of COVID-19 patients (one in five patients) require oxygen. The oxygen supply system in hospitals has been overwhelmed by the pandemic, experiencing an extraordinary growth in demand in the face of the unstoppable growth in COVID-19 infections.