During the coronavirus pandemic, we wear them constantly on our faces – disposable masks in white and blue or fabric masks, so-called community masks, in various designs. They are in use millions of times a day. Depending on the type, they end up directly in the waste bin or can be washed in the washing machine and reused. Besides their protective function, the masks' environmental compatibility is therefore also an issue. Are disposable masks a waste of material and a burden on the environment? Or do textile products also have harmful environmental aspects that need to be considered? Which factors show the strongest environmental impact, and how can masks be made more ecological? Working in an interdisciplinary team Empa researchers have investigated these questions and have now published their results (Sustainability).
13 masks per week
For an initial environmental assessment of masks, the researchers compared disposable surgical masks with two-layer fabric masks made of cotton. "This is a first, simple LCA, which enabled us to identify the relevant ecological factors," says Claudia Som from Empa's "Technology and Society" lab in St. Gallen, who coordinated the interdisciplinary study. "Our aim was to create a basis for optimizing sustainability right from the design stage", she says.
The CO2 balance, energy and water consumption as well as the overall environmental impact of the production, use and disposal of the masks (expressed in so-called environmental impact points, UBP) were calculated for a person who uses public transport to commute to work on a daily basis and who makes three purchases per week. Based on the recommendations of the "Swiss National COVID-19 Science Task Force" (www.ncs-tf.ch), this person uses either two (alternating) community masks per week, which are washed at 60°C after use and disposed of after five washing cycles, or 13 disposable polypropylene surgical masks.
Decisive: the useful life of textile masks
The calculations show that the energy consumption is lower with fabric masks than with surgical masks. In contrast, the surgical mask performs better than its cotton counterpart in terms of CO2 balance, water consumption and overall environmental impact. "The reason for this is the unsustainable, resource-intensive production of cotton," says Empa researcher Roland Hischier.
The data the researchers used were based on an assumed global average cotton production, whose water consumption is enormously high due to irrigation, fertilization and pesticide use for cotton. "If production were to be based on regions with a high proportion of rain irrigation and on organic cotton or even on recycled cotton, the so-called water footprint of cotton masks would probably look much better," says Hischier.
Washing the fabric masks, on the other hand, is hardly significant compared to their production. "This means that the strongest leverage is in the service life of the textile masks, since the greatest part of the environmental impact is caused by the production of these masks".
Improvements for design
In a second step, the researchers analyzed the effects of various options in the design of the masks that could reduce the environmental impact. This sensitivity analysis shows that lighter fabric masks with a weight of around ten grams – instead of twelve grams as in the initial analysis – already result in a significant reduction in pollution.
The frequency, with which the fabric masks are washed before they have to be disposed of, has an even greater impact. If a cotton mask can be washed seven or more times, the fabric mask performs better than the disposable mask not only in terms of energy consumption, but also in terms of CO2 balance. If a cotton mask is washed 14 times or more, the fabric mask even comes out ahead in terms of the overall environmental impact. "There are manufacturers who already allow 20 or even 30 washing cycles per mask," says Melanie Schmutz, lead author of the study.
The Empa team also investigated the influence of different washing temperatures on the environmental impact of a mask. They found that colder washing temperatures, for instance 40 or 30 degrees, hardly reduce the environmental impact. Some of the fabric masks certified in accordance with the requirements of the Swiss National COVID-19 Science Task Force are made of other materials, for example polyester, which will have a different impact on the environment compared to cotton. This first life cycle assessment study cannot yet make any statements about these masks.
Eco-littering and compostable disposable masks
As a next step, the researchers want to include additional factors in their LCAs, such as different materials for textile masks (e.g. polyester), antiviral and/or antibacterial coatings that could further reduce the number of washes required, or packaging, which has a different significance for individually sold surgical masks than for bulk packaging.
"Another often discussed issue is the environmental pollution caused by incorrectly disposed masks," says Empa researcher Som. The aim is to find out whether these entries into the environment are really relevant, and whether bio-compostable masks could help reduce environmental pollution. And all this must take into account the fact that the masks must be able to do one thing above all else: effectively stop the transmission of viruses.