Governments and companies have commonly used tree planting to reduce carbon dioxide in the atmosphere. However, this method may not be feasible in densely populated urban areas that are also hotspots for air pollution.
Luckily, a group of scientists from the University of Belgrade, Serbia has come up with ground-breaking solution- a Liquid Tree also named LIQUID 3- a kind of photobioreactor that will tackle greenhouse gas emissions and improve air quality. Interesting isn’t it? What is it, how is it designed and how does it work?
To overcome the increasing problem of air pollution in Belgrade, which is also the most populated city in Serbia- the bioreactor has been designed.
The city accumulates maximum pollution due to the two large coal power plants in its vicinity. As per the European NGO Health and Environment Alliance (HEAL), these two plants are among the top 10 dirtiest plants in Europe.
According to some activists in the country, the pollution in Serbia and in other parts of the
Balkan peninsula is so bad that it can be smelt, seen and even tasted during winter and
autumn.
LIQUID 3 won the position as one of the 11 best innovative and climate-smart solutions by the Climate Smart Urban Development project, created by the UNDP, the Ministry of Environmental Protection, and sponsored by the Global Environment Facility (GEF) owing to its functional and innovative design.
What is Liquid Tree?
The “liquid trees” actually emerged in late 2021, having been developed by scientists from the University of Belgrade in Serbia. Named “LIQUID 3,” the tanks were said to be the first urban photo-bioreactor in Serbia, designed to remove carbon dioxide (CO2) from city air.
The 600-liter (around 158-gallon) tank is filled with microalgae, which use photosynthesis to convert CO2 to oxygen in the same process as trees and other plants do, harvesting energy from sunlight using chlorophyll.
Liquid Tree is a new ingenious solution provided by scientists in Serbia which helps to convert carbon dioxide into oxygen just like the plants do. It is Serbia’s first urban photo-bioreactor- a tool to combat air pollution.
“The microalgae replaces two 10-year-old trees or 200 square metres of lawn,” Ivan Spasojevic, one of the scientists working on the project from the Institute for Multidisciplinary Research at the University of Belgrade, said in a statement from the United Nations Development Programme in 2021.
“The system is the same because both trees and grass perform photosynthesis and bind carbon dioxide.”
The algae is also more efficient than trees at removing CO2 from the atmosphere, acting between 10 to 50 times faster. One species of algae, Chlorella vulgaris, is up to 400 times more effective at harvesting CO2 than trees, according to biotechnology company Hypergiant Industries.
The Problem
Ms. Francine Pickup, Resident Representative of the United Nations Development Program (UNDP) in Serbia, explained that: “It is estimated that cities are the source of as much as 75% of total CO2 emissions in the world, of which the largest percentage comes from traffic and cooling and heating in buildings”. She later continued to explain that 59% of the Serbian population lives in urban areas and that the number is constantly increasing. Because the population density is so high, creating green areas and planting trees – which represent natural air purification in urban areas– is a complex goal to achieve, as there is a lack of free areas for landscaping.
What is being done about it?
Dr. Ivan Spasojevic, Ph.D. in Biophysical sciences, and one of the authors on the project from the Institute for Multidisciplinary Research at the University of Belgrade, developed an innovative tool for reducing greenhouse gas emissions and improving air quality: the liquid tree. Also dubbed LIQUID 3, the novel creation is Serbia’s first urban photo-bioreactor, a solution in the fight for clean air. It contains six hundred litres of water and works by using microalgae to bind carbon dioxide and produce pure oxygen through photosynthesis.
The microalgae replace two 10-year-old trees or 200 square meters of lawn. The function of the LIQUID 3 is practically an imitation of it. Both trees and grass perform photosynthesis and bind carbon dioxide. However, the advantage of microalgae is that it is 10 to 50 times more efficient than trees. The team behind LIQUID 3 has stated that their goal is not to replace forests or tree planting plans but to use this system to fill those urban pockets where there is no space for planting trees. In conditions of intense pollution, such as Belgrade, many trees cannot survive, while algae do not have a problem with the great levels of pollution.
GREEN GOOP
It’s perhaps understandable why the so-called “Liquid Trees” have caused so much consternation. Much of that may be down to their futuristic, cyberpunk aesthetic. The devices consist of eerie green fluid in a transparent tank, lit from inside. They looks like something straight out of science-fiction, which naturally leads people to connect with the scary tropes of such media.
In reality, though, the devices serve a real and positive purpose. The photo-bioreactors, as they are technically known, are air quality control devices built specifically to suit the urban environment. Inside the tank, microalgae is grown in 600 liters of water, using CO2 from the atmosphere combined with photosynthesis to produce oxygen and biomass. One LIQUID3 bioreactor is capable of replacing one 10-year-old adult tree, or a full 200 m2 of lawn. This is of huge benefit, as the bioreactors can be built and installed far more quickly, and start processing polluted air immediately.
Like trees, the devices are solar-powered, with panels on top to capture light and turn it into electricity. Built-in lighting allows the microalgae to photosynthesize year round, even in the dimmer winter months. There’s also a pump which captures polluted air and bubbles it up through the water to feed the algae. The LIQUID3 bioreactors are built with an eye to civic duty, as well. They’re constructed to also serve as city benches, while also providing a power outlet for charging mobile phones.
The bioreactors are well-suited to the built environment of Belgrade, Serbia. The city is subject to significant air quality issues, with high PM2.5 counts by virtue of two neighbouring coal power stations. Serbia as a whole records 175 pollution related deaths per 100,000 people, making it Europe’s worst performer by this metric. It’s also 33rd in the world for having the worst air quality. Anecdotally, activists complain of pollution so bad that it can be readily detected by sight, smell, or taste during the worst periods. If you were in Beijing in the winter of 2015/2016, you’d be familiar with the flavor.
Much of the uproar towards the devices is misguided. The bioreactors aren’t intended to replace urban trees with scary-looking machines. Instead, they’re designed to slot into spaces where growing a tree is impractical. Plus, the microalgae bioreactors offer efficiencies that trees and grasses simply can’t match. Microalgae can be capable of removing CO2 at a rate 10 to 50 times faster than even mature trees, to boot. Once grown, the microalgae can be harvested and used as a potent fertilizer, as well.
Twitter reactions
Twitter users haven’t taken well to the suggestion that these tanks are an alternative to trees, however.
“Before Atlanta gets any ideas, liquid trees don’t reduce erosion, enrich soil, prevent flooding, and improve the quality of groundwater,” tweeted Atlanta Community Press Collective, @atlanta_press.
“”Liquid trees” THERES ALREADY FREE AIR!!!! FROM REAL TREES!!!!” tweeted @nightmeir_1.
As valuable as efforts like the Trillion Trees project may be, there’s something to be said for the sheer practicality of building compact bioreactors. The fact that they start capturing useful amounts of carbon dioxide from day one is just a further mark in their favour. As the world struggles against rising carbon levels in the atmosphere, expect to see bioreactors like these proliferate in cities around the world. They may just be a key weapon in the fight against climate change, while also transforming our urban spaces into the futuristic cityscapes science-fiction had promised us.
4 Comments
When will this come to India?
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I couldn’t refrain from commenting. Well written!