The University of Belgrade's Institute for Multidisciplinary Research has developed an urban photo-bioreactor called Liquid 3, which serves as a bench and cleans the air in Belgrade city centre. Serbia has one of the highest air pollution death rates in Europe, and Liquid 3 was created in response to an appeal from the Development Program of the United Nations to tackle air pollution. Image source: liquid3 The device uses microalgae to bind carbon dioxide while also serving as an urban design feature. It was installed in September 2021 in front of the Municipality of Stari Grad in Belgrade. Air pollution is a major problem in Serbia, with at least 75% of Serbian citizens breathing air polluted by particular airborne matter (PM) throughout the year. Belgrade was ranked as the world's fifth most polluted major city by Swiss air quality database IQ Air in early November 2021, and thousands of people protested against the massive air pollution in the city two weeks later. ...