Fabric or disposable masks - what does the life cycle assessment say?

During the coronavirus pandemic, we are constantly wearing them on our faces - disposable masks in white and blue or fabric masks, so-called community masks, in various designs. Millions of them are in use every day. Depending on the type, they end up in the trash or can be cleaned in the washing machine and reused. In addition to the protective function of the masks, their environmental compatibility is therefore also an issue. Are disposable masks a waste of material and a burden on the environment? Which factors have the greatest impact on the environment, and how can masks be made more ecologically sustainable? Researchers at Empa, working in an interdisciplinary team, have investigated these questions and have now published their findings.

13 masks per week

For the life cycle assessment, the researchers compared disposable surgical masks with fabric masks made of cotton. "This is an initial, simple life cycle assessment that enabled us to identify the relevant ecological factors," says Empa researcher and study coordinator Claudia Som from the "Technology and Society" department in St. Gallen. "Our aim was to create an initial basis with which masks can be optimized in terms of sustainability as early as the design phase," says Som.

The greenhouse gas balance, energy consumption, water consumption and the total environmental impact (expressed in environmental impact points, EIP) of the production, use and disposal of the masks were calculated. The effects were considered for a person who travels to work by public transport every day for a week and goes shopping three times. Based on the recommendations of the Swiss National Covid-19 Science Task Force (www.ncs-tf.ch), this person uses either two cloth masks per week, which are washed at 60°C after use and discarded after five washes, or 13 disposable polypropylene surgical masks.

Decisive: useful life of a fabric mask

The calculations show that the cotton fabric masks perform better than the surgical masks in terms of energy consumption and greenhouse gas footprint. 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 less sustainable, resource-intensive cotton production," says Empa researcher Roland Hischier.

The data sets used represent the global average production. On a global average, water consumption is huge due to irrigation, fertilization and pesticide use for cotton. "If we were to focus production on regions with a high proportion of rain irrigation and on organic cotton or even 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 of little consequence compared to production. "This means that the strongest leverage is in the service life of the fabric masks, since most of the environmental impact occurs in the production of this mask."

Scope for sustainable design

In a second step, the researchers analysed the effects of various options in the design of the masks that could reduce the environmental impact as part of a sensitivity analysis. This showed that the service life of the fabric masks has the greatest influence. Starting at a level of about 20 washes, the fabric mask made of cotton comes out ahead not only in terms of energy consumption and greenhouse gas footprint, but also in terms of overall environmental impact. "There are manufacturers who already allow 20 or more washing cycles per mask," says Melanie Schmutz, lead author of the study.

Other factors that were examined were weight and washing temperature. With regard to weight, it was found that a reduction to around nine grams - instead of twelve grams as in the original analysis - leads to a further significant reduction in environmental impact. Lowering the washing temperatures, for example from 60 to 40 or 30 degrees, on the other hand, has hardly any effect on the environmental impact.

Some of the fabric masks certified according to 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 than cotton. This first life cycle assessment study cannot make any statements about these masks.

Eco-littering and compostable disposable masks

Next, the researchers plan to incorporate additional factors into the life cycle assessment, such as additional materials for fabric masks, antiviral and/or antibacterial coatings, which can also increase the wearing time between washes and thus further greatly improve their environmental sustainability, or packaging, which has a different significance for surgical masks sold individually than for bulk packs.

"Another point that is often discussed is the environmental pollution caused by masks that are not disposed of correctly," says Empa researcher Som. How relevant these inputs into the environment are, and whether, for example, bio-compostable masks help to reduce environmental pollution, needs to be clarified. And in all of this, it must be taken into account that the masks must be able to do one thing above all: effectively prevent virus transmission.

Source: Empa

Literature: 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