Inventory analysis
Before computing the environmental effects, we first analyzed the inventory data and then input them into the software program to simulate them. For reusable masks, we measured the raw materials on site and calculated the energy requirements for processing (e.g. laying, cutting, sewing etc.).The Italian Social District provided information about packaging materials, reuse options, transport distances, cleaning activities, and packaging material configurations. Schmutz et al. adapted the requirements for washing the reusable mask.9In compliance with the producer’s information. Allison et al. also gathered waste disposal scenario information for both types from the preprint.23Finally, inventory data for single use masks were gathered from independent producers via certified labs. Supplementary Table 1 contains the final set data for background and foreground.
Three layers of nonwoven polypropylene are used in single-use masks. The inner and outer layers of fabric are Spunbond while the middle layer consists of 99% filtering Meltblown.24. Type IIR face masks that can be reused are also made of three layers: an interior layer of antibacterial cotton, a middle layer with Meltblown, as well as an external layer made of Spunbond. The quality of the components determines the quality of the mask and can be traced back to the suppliers. Supplementary Table S2 provides information on suppliers and product types (including certifications) and features. The central portion of reusable masks is made from Meltblown (suppliedby Ramina). This component, combined with the high-quality anti-drop C6 antibacterial Cotton (suppliedby Olmetex), guarantees a greater than 99% filtering performance. It can withstand up to 10 washes per immersion. These materials, which are forged using specialized machinery, improve Type IIR surgical masks over all others in respect to their superior performance in filtering quality, reusability and environmental sustainability. The masks’ cotton inner fabric is as effective in reducing transmission of respiratory virus than single-use masks.25.
No direct datasets are available for elastic bands, nose clips material (for single-use faces) and fabric layers in the ecoinvent database. For the present study, we assumed that non-allergenic latex-free elastic band produced using a flexible polyurethane process were used. The nose clip material, which is used only for single-use masks was assumed to have been modelled using a B-PVC process. For the TnT SPunbond and Meltblown layers, we assumed that a granulate polypropylene process was used. Reusable face masks are wrapped with biodegradable plastic bags while single-use masks come in plastic bags. Both types of masks come in sets of 10 and are delivered in recycled cardboard boxes. The following packaging materials were used to introduce the software: packaging film, low-density plasticethylene, polyester-complexed Starch biopolymer, packaging films, low-density Polyethylene, and corrugated box boxes: 16.6% primary fiber; 83.4% repurposed fiber. Transport, freight, lorry 1632 ton, EURO6 process was used. This included nationwide distribution by road using Euro 6D vans.
Based on statistics from Organisation for Economic Co-operation and Development, we calculated the number of face-masks that would be used in Italy in 2020.26. According to WHO recommendations, we were required to wear one mask per person and one per day for both types of masks.27. Reusable face masks can be washed as many times as 10 times without losing their virus filter performance (according the manufacturer’s specifications), so we assumed that the maximum number of washes was necessary for the use phase. The total number of face-masks used in Italy was 2.18 billion and 22.1 million for single-use and reusable masks, respectively. The total amount of waste was calculated by the number and packaging materials of used masks (e.g. plastic wrap and cardboard boxes). (Table 2). Comparatively to reusable masks, single-use face masks produced almost 10 times as much waste.
Our basic case scenario for mask use was based upon WHO recommendations27According to the, reusable face masks must be washed with soap/detergent and hot water (60C), at least once per day. The entire household (2.3 people in Italian) should wash the masks together with the other clothes in a 7kg washing machine. This is consistent with both the literature and our assumptions.9Instructions for producers. Schmutz et al.9According to the report, a half-full washer (a common situation in Europe) requires 84g detergent and 52.3 L of tap water. The load also requires 1.1 kWh of electricity. The average washing consumables for each mask can be calculated by normalizing the requirements with respect one mask (i.e. by multiplying a half full load requirement by 0.2%).
However, it is important to note that user behavior can be difficult to predict and washing machines might not always be the best option. We also investigated different user behavior in order to determine which sensitivity cases. Hand washing was first introduced as the main sensitivity scenario.9,23,28. In this example, we assumed that the whole household masks would be washed together daily after use in a bowl 5 L filled with water at 60C. After washing, rinse the bowl with water and soap-free detergent. Each manual washing session requires 6.24g liquid detergent and 6L of water.23. Similar to the machine washing case, the average amount of washing consumables needed for each mask can be calculated by normalizing one mask’s requirements (e.g., the required washing consumables per mask per wash is 2.609 L water, 2.713g detergent and 447.7kJ heat provided by the gas boiler).
We also considered other user behavior scenarios. For example, we assumed that reusable masks could be washed more often than the recommended 10 washes. We created a second sensitivity model for reusable masks that had been washed 15x before they were disposed. We also considered a longer wearing time when considering single-use masks. Even though the recommended daily use of a face mask is one per day (or 48 hours), many users wear single-use surgical masques for longer periods. In this case, we assumed that the mask would be worn for at least two days. However, the masks’ protection and human health might be compromised by the wearing of the masks for longer periods of time in the sensitivity cases.
Concerning packaging and waste disposal activities the Italian Social District provided data based on ongoing studies about the biodegradability packaging materials for reusable face masks (Type IIR). The lack of approved assessments meant that the current study could not include actual waste disposal activities (i.e. recycling and reuse). Therefore, waste disposal was based mainly in previous studies which indicated that landfilling and incineration are viable options.23,29. We assumed that contaminated materials and discarded packaging would go directly into waste disposal sites. 43% would be landfilled and 57% would be incinerated.23. Concerning alternative disposal activities, two scenarios were considered: one that assumed all masks of each type would be fully burned and the other that they could be used for a variety of purposes.9,30One that assumed all masks of each type would be fully filled with soil.31.
