A deep dive into the technology that could be the future of urban air purification.
According to an article by CNN, a staggering 90% of countries worldwide had a level of average annual air pollution in 2022 that surpassed the World Health Organisation’s (WHO) air quality guidelines. While a few international agreements such as the Long-Range Transboundary Air Pollution (LRTAP Convention) have been successful in producing downward trends in greenhouse gas emissions, they are proving increasingly insufficient due to growing emissions from both industrial and household sectors. The release of such untreated, polluted gases has contributed to deteriorating air quality globally over the years. The detrimental effects of this are evidenced by it being the cause of 16% of lung cancer deaths, 25% of pulmonary disease deaths, and 26% of respiratory infection deaths, according to WHO.
Despite the evident health concerns, unregulated emissions have continued often due to a lack of social awareness or limited financial resources. This administrative failure, paired with rapid urbanisation that leaves no space for trees to grow, has left big cities across the world struggling to ascertain a feasible solution that ensures healthy air. One such city, Belgrade, the capital of Serbia, has found itself to be the home of an innovative solution to the problem – Liquid Trees. A ‘Liquid Tree’ is a biotechnological device that employs resistant microalgae to purify air at a much faster, more efficient rate to fill urban pockets where planting trees is impractical.
Mimicking Natural Microalgae
Liquid Tree, also dubbed LIQUID3, works to purify the air of pollutants and harmful particulate matter. Designed by Serbian scientist Dr Ivan Spasojevic of the Institute for Multidisciplinary Research, Liquid Tree is Serbia’s first urban photo-bioreactor. Although first installed in Belgrade in September 2021, news of the invention has picked up traction only recently worldwide in March 2023 when Yup That Exists made a post about it on its Twitter (now, X) @yupthatexists.
A ‘Liquid Tree’ is a biotechnological device that employs resistant microalgae to purify air at a much faster, more efficient rate to fill urban pockets where planting trees is impractical.
The picture used by Yup That Exists displays the Liquid Tree in its compact, glass tank form. It holds 600 litres of water filled with microalgae, which gives it an almost neon-green hue often seen in sci-fi movies. Electricity supplied by the device’s solar panels powers a small pump in the structure that provides air into the tank through holes. Once carbon dioxide is retrieved from the supplied air, the powerful microalgae utilises it alongside water and available sunlight to photosynthesise in a manner that mimics the functions of naturally found algae. This process of photosynthesis then produces oxygen and biomass (caused by the division of microalgae). In addition, the Liquid Tree also features benches for seating, and charging ports for mobile phones in a nod to its civic duty. Furthermore, Liquid Tree’s qualities of sourcing most of its energy from its solar panels and requiring very little maintenance make it an almost self-sufficient solution to the problem of poor air quality.
Calculated Features Translating Into Advanced Efficiency
Such a promising quality of the Liquid Tree is largely due to the nature of microalgae employed, alongside a multitude of features thoughtfully prepared to tackle air pollution in cramped urban spaces. Dr Spasojevic’s particular choice of single-celled freshwater algae, for instance, is largely due to its efficiency over trees. “Through analysis of biomass,” he says, “we found that they clean 300 to 3,000 cubic metres of air from heavy metals.” To reward such a creative solution, Liquid Tree has been awarded one of the 11 best innovative and climate-smart solutions by the Climate Smart Urban Development project, created by the United Nations Development Program (UNDP). It has been claimed that one Liquid Tree is capable of functioning as a 10-year-old tree or 200 square metres of lawn, thus proving its superiority over actual trees.
In addition to the utilisation of highly capable microalgae, what sets Liquid Tree apart are its attributes of durability and functionality, and a context-appropriate design fit for Belgrade’s cramped urban scene. The microalgae, described to be a ‘robust type’ by Dr Spasojevic, can withstand a wide range of temperatures from 5 to 35 degrees Celsius and are resistant to pests. Even poor air quality admits defeat in the face of this algae as they are capable of enduring extreme levels of pollution. Furthermore, Liquid Tree’s compact design and speedy installation allow for it to be placed across the city in cramped spaces or ‘urban pockets’ where it is impractical to plant trees. Such a wide array of features makes Liquid Tree an eco-friendly, efficient, and sustainable solution to battle air pollution.
An Alternative Rather Than a Replacement
In parallel to its many upsides, the Liquid Tree entails several disadvantages that make it cumbersome and difficult overall to be utilised widely. One such disadvantage is its lack of tree-like qualities. Unlike trees, “Liquid Trees don’t reduce erosion, enrich the soil, prevent flooding, or improve the quality of the groundwater,” the Atlanta Community Press Collective noted disappointedly on X. Moreover, Liquid Trees are more costly than regular trees, thus raising the question of whether widespread installations of it will even be feasible in lesser developed countries. It is equally important to note that while the Liquid Tree functions in an eco-friendly manner, its construction, which entails the production of steel, glass, and solar modules, involves emitting carbon dioxide.
Nevertheless, such drawbacks have not proven enough to deter the world from applauding this groundbreaking invention. While some have complained about its eerie green appearance and bold modern design, others have described its unique design as ‘futuristic’ and ‘cyberpunk’. Some have argued that Liquid Tree is not a replacement for actual trees, to which Dr Spasojevic reiterated by pointing out that Liquid Tree is not intended to be a replacement for trees, rather an air purifying tool to “fill urban pockets where planting trees is not feasible.” Parallelly, Liquid Tree has amassed many humorous comments online by users expressing that they would be tempted to drink the green liquid at night when no one is watching. Overall, the Liquid Tree has garnered incredible attention from across the globe, with most of it being humorous and supportive.
Right for Dhaka?
The global attention amassed by Liquid Tree calls for consideration of such inventions more locally in the Bangladeshi context. Dhaka has been witnessing rapid urbanisation for the last few decades, with its population density now standing at a staggering 23,234 people per square kilometre. This figure is only forecasted to rise in the coming years, with a 3.39% increase in population already observed between 2021 and 2022. In this second-most densely populated city of the world, there is little space as it is to accommodate incoming rural-urban migrants searching for better opportunities in Dhaka. In the backdrop of a developing city where finite financial resources are directed towards creating better infrastructure and housing, investment in the likes of Liquid Trees can appear to be a luxury. Such lack of financial resources, paired with insufficient attention paid to the deteriorating air quality of Dhaka, stand as roadblocks in the path of attaining environmental sustainability and health overall. Nevertheless, the city’s poor air quality is still a threat to its dwellers, hence innovations like Liquid Trees can be explored to hinder further deterioration of Dhaka’s air quality.
The Liquid Tree may not be a complete replacement for trees, however, this does not take away from the fact that it is one step forward in tackling air pollution and consequently climate change overall. As traditional ideas of reversing climate change continue to become more and more ineffective, inventions like Liquid Trees indicate hope for a more technocentric approach to resolving the global issue of air pollution and consequently climate change.