15 Dec 2023

Liquid trees cleaning Serbia's air pollution

From First Up, 5:11 am on 15 December 2023

Photo: LIQUID 3

As the air fills with man made pollutants, trees are working harder to break down carbon dioxide and produce energy and oxygen. 

A scientist in Serbia, Dr Ivan Spasojevic has created a new "liquid" tree to help clean the air.

The liquid tree comes in the form of a large glass structure containing water and microalgae. Several of the bright green liquid trees are now lining the streets of Serbia's capital Belgrade.

Belgrade, with two large coal power plants on its horizon, is one of the most polluted cities in Serbia.

Spasojevic told First Up the liquid tree, also dubbed LIQUID 3, uses microbiology to capture carbon.

It also removes particles like heavy metals from the air and serves as a bench, a USB solar-powered charger and a night-light, he said.

"What we did is put the photo-bioreactor into the street, into the organic environment. This required an additional structural solution and functions.

"It removes carbon dioxide in an equivalent amount to one adult tree... We calculated the system cleans between 300 and 3000 cubic metres of polluted air per month."

Microalgae is 10 to 50 times more efficient at photosynthesis than trees. 

Dr Spasojevic said his invention is the first of its kind.

"Basically you can buy photo-bioreactors to grow microbiology, for example to produce food pigments, but these systems are very fragile and are not designed for the urban environment and they're very expensive."

"So we combined two types of these systems to make a new type of a photo-bioreactor that can be used in the streets."

His team made a simple shape of the photo-bioreactor that is easy to maintain and strong to ensure no mechanical damage.

They then incorporated it into "street furniture," to encourage the public to "accept" the new conspicuous infrastructure.

"It's not only a type of greenery but it's a place to sit, relax and charge their phone or chat with friends."

"It's the colour of spring."

The by-products of the liquid trees - water and biomass - can be used to water and fertilise plants.

The trees are maintained once a month where 95 percent of the water is replaced with new water and minerals.

"It's very simple and anyone can be trained to do it and it only takes about two working hours."

Dr Spasojevic is proud of the project and its contribution to the global fight for better air quality in urban areas, as well as fighting climate change. The goal is not to replace forests, but rather to fill the urban pockets where there is no space for planting more trees.

He has already received interest from about 500 companies and entrepreneurs about expanding the project.

"The main interest has come from a couple of European countries, Brazil, the US and the Middle East. We also received a lot of interest from Australia and we have been contacted by one or two companies in New Zealand."

"The idea is to find someone from your region who would like to build these on site ... and that way we wouldn't have that carbon footprint of importing the system."