March 4, 2024

Aliyan Nadeem

12th Grade

Beaconhouse Margalla

Pollution is an intractable issue that has been persisting for centuries. More specifically, air pollution is the deadliest type of pollution, with around 99% of the global population breathing air that exceeds the WHO guidelines. Consequently, the combined effect of environmental and household air pollution leads to seven million annual premature deaths. To tackle this pressing issue, a team of researchers in the Institute for Multidisciplinary Research of the University of Belgrade, Serbia, developed a photo-bioreactor that they call Liquid 3. Liquid 3 essentially mimics the photosynthesizing functions of a tree– that is, cleansing the environment’s air by absorbing carbon dioxide (CO2) and releasing oxygen (O2) into the atmosphere. As such, Liquid 3 has fittingly been referred to as a “liquid tree”, despite it not being a liquidized tree, but rather a photo-bioreactor containing water, nutrients, and microalgae. 

Serbia suffers from one of the harshest cases of air pollution in the world, being ranked 33 globally for the worst air quality in 2022, and ranked number one in Europe for the highest pollution-related deaths; according to the Global Alliance for Health and Pollution in 2019, 175 people per 100,000 succumb to a deadly fate caused by air pollution. Additionally, there is little to no space for trees to be planted in the urban cities of Serbia, especially in Belgrade, where statues and monuments take up most available space. Hence, these facts motivated Dr. Ivan and his colleagues in 2018 to create an appliance that cleans the environment’s air the same way a tree does but does not require much space to be placed in urban areas. In 2021, a prototype of the Liquid 3 was made and placed in Belgrade. The invention quickly garnered widespread media coverage, helping to publicize their work. The following year was an important one for the finalization of the Liquid 3 prototype, as more units were installed at various locations in Belgrade, and were continually tested and modified. Furthermore, partnerships and collaborations for its testing, construction, and placement also made significant strides, and in 2022, Liquid 3 managed to upgrade from its prototypical phase. From 2023 and onwards, more units are being placed and extensive research is being done to optimize performance. 

Liquid 3 is made up of a mixture of water, microalgae, and nutrients. As Microalgae are aquatic organisms, water provides them the medium necessary to thrive and carry out their biological processes. Moreover, water also dissolves nutrients and CO2, which the microalgae use for photosynthesis. The microalgae in each Liquid 3 unit can replace two 10-year-old trees or 200 m2 of lawn, and since both microalgae and trees photosynthesize, both achieve the same air-cleansing effect. Furthermore, an added advantage of microalgae is that they’re 10 to 50 times more efficient in photosynthesis than trees; as microalgae are single-celled organisms, they have simple cellular structures that allow them for a more efficient exchange of CO2 and O2, due to direct interaction with the environment which facilitates better gas diffusion. Another advantage of these single–celled freshwater algae is that they can grow in tap water and are resistant to high and low temperatures. Moreover, the system does not require special maintenance, meaning that the biomass can be removed by dividing the algae, which can then be used as a fertilizer, allowing the algae to continue growing for an indefinite amount of time. 

Currently, the units have only been established in Belgrade, but Dr. Ivan and his colleagues plan to install units in other urban areas of Serbia, and eventually the rest of the world. Liquid 3 has proven itself to be an innovative approach to making urban areas cleaner. However, the establishment of Liquid 3 as commercially feasible by other countries depends on how it will be optimized. This will require further research, hypothesis, and testing as well as support from governments and organizations to transform the innovation into a commercial success. Imagine, in the distant (or not-so-distant future), sitting on the bench side next to one of these units, admiring the view of the clean, urban environment to which Liquid 3 has contributed!