Life cycle assessments of corona masks
Disposable or fabric? Here is what matters
Anyone who wants to protect themselves and others from a COVID-19 infection wears a mask these days. But what about the environmental impact of this mass product, which is used millions of times over? Which factors are relevant for sustainable design? Empa researchers have examined these questions by means of life cycle assessment analyses, using cotton masks and disposable masks as an example.
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? Which factors show the strongest environmental impact, and how can masks be made more eco-friendly? Working in an interdisciplinary team Empa researchers have investigated these questions and have now published their results.
13 masks per week
For an initial environmental assessment of masks, the researchers compared disposable surgical masks with 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 greenhouse gas balance, energy and water consumption as well as the overall environmental impact (expressed in so-called environmental impact points, UBP) of the production, use and disposal of the masks 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 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 analyses show that cotton fabric masks perform better than surgical masks in terms of energy consumption and greenhouse gas balance. In contrast, the surgical mask performs better than its cotton counterpart in terms of 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 carried out a sensitivity analysis to analyze the effects of various options in mask design that could reduce the environmental impact. It was found that the lifetime of the fabric masks has the greatest influence. Above a washing frequency of about 20 washes, cotton fabric masks not only lead in terms of energy consumption and greenhouse gas balance, but also in terms of overall environmental impact. "There are manufacturers that already allow 20 or more wash cycles per mask," says Melanie Schmutz, lead author of the study.
Other factors that were investigated were weight and wash temperature. In terms of weight, it was found that even a reduction to around nine grams - instead of twelve grams as in the original analysis - leads to a further significant reduction in environmental impact. On the other hand, a reduction in washing temperatures, for example from 60 to 40 or 30 degrees, hardly affects 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
In future, the Empa team also intends to investigate the environmental impact of masks through littering and whether compostable disposable masks would be a solution. Photo: Empa
As a next step, the researchers want to include additional factors in their LCAs, such as further materials for textile masks, antiviral and/or antibacterial coatings that could increase the wearing time between washes, which can greatly improve their environmental sustainability, 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.
M Schmutz, R Hischier, T Batt, P Wick, B Nowack, P Wäger and C Som; Cotton and Surgical Masks – What Ecological Factors Are Relevant for Their Sustainability? Sustainability (2020); doi: 10.3390/su122410245
Empa researchers Claudia Som and Roland Hischier report on the comparison of life cycle assessment of disposable and fabric masks. Radio program on Deutschlandfunk, Umwelt und Verbraucher of December 16, 2020 (in German)
Empa researcher Melanie Schmutz explains the life cycle analyses of polyester and cotton. Radio program on RTS 1, La Matinale, of February 4, 2021 (in French)