'Liquid tree’ bioreactors appear in cities and Swansea primary schools, why and what are they?
What are these 'liquid trees' springing up in schools and cities in recent years and why are they called natural bioreactors?
Air pollution is one of the biggest concerns of the World Health Organisation today, being one of the main causes of cardiovascular and respiratory diseases. The concept of the “liquid tree” to mitigate this has been sprouting in recent years all over the world. We take a look at what these are and some recent developments.
The liquid Tree Initiative was launched by the Swansea Building Society as the Finance Director of the organisation donated a liquid tree every Primary School in Swansea, Wales. This was not only educational, but to promote innovative thinking towards climate solutions.
What are they?
These ‘bioreactors’ are said to capture CO2 up to 400 times faster than natural trees, but to see how they work we take a look at the full-scale liquid tree concept which was introduced to the city of Belgrade in Serbia as a solution to tackle greenhouse gas emissions.
Some might see it as a space saving solution where dedicated green spaces are not possible. It was the project Liquid 3 which brought forward Serbia’s first “liquid tree” which has the ability to absorb carbon while improving air quality.
Water is the main ingredient, with a 600 litre capacity tank installed in busy parts of the city. Microalgae are added to the water, which blooms and absorbs carbon, converting it to oxygen through the process of photosynthesis thanks to light. This is why it is called an “urban photo-bioreactor.” One of these tanks can absorb as much carbon as two 10-year-old-trees or the equivalent of 200 square metres of lawn space of grass.
According to a Global Alliance on Health and Pollution report published in 2019, Serbia ranked worst in Europe for per capita premature deaths attributed to urban pollution, which may be exacerbated by its geographical landscape and degree of deforestation around, Reset pointed out.
While this is a positive innovation, many Serbian cities are still affected with pollution with much of the country still relying on fossil fuels, and this is a similar case for most cities of the world.
Why algae?
Microalgae are much more effective at holding carbon dioxide compared to trees, and obviously, having a tank of microalgae saves space. However, there may also not be the nutrients, moisture and soils available for trees to thrive in some city streets. Roots can be prone to be inhibited by concrete pavements, or they may do damage to the pavements themselves.
However, trees still have major value and cannot be replaced. Trees not only store carbon but protect biodiversity, provide shelter, promote a cooling, and improve the atmosphere and mental wellbeing of an urban population.
Therefore, both trees and microalgae could work together to boost carbon pollution mitigation and city greenification in busy urban environments.
Sustainable development
A similar innovation is also seen with the MicroAlgaex Innovative Biorefinery, based in Istanbul, where it is said each of their Liquid Trees are able to absorb as much CO2 as fifty tall trees, providing environmental benefits of a green space.
This is also based on the biology of microalgae. Being composed of chloroplasts, algae can utilise light as an energy source and make CO2 into oxygen, and by feeding on light, organic matter can be absorbed. Through the company's “Algae library” they manage a large collection of algal strains from nature and research experiments at Bosphorus University and in-house.
There are also other innovations springing up, such as through the use of diatoms (a type of silicious algae) shared by LiquidTrees.org who are a member of Google Startups for Sustainable Development. This project claims to support the following Sustainable Development Goals:
- 6: Clean water and Sanitation.
- 8: Decement work and Economic Growth.
- 12: Responsible Consumption and Production.
- 13: Climate Action.
Positive steps can be taken with "liquid tree" technology by multiple companies, but sustainable development involves diverse approaches, not just one. Currently, there does not appear to be a strong motivation for governments to pledge to major greenification of cities, whether it be through grass, plants, trees or microalgae.