Scientists at the CSIR-Central Institute of Mining and Fuel Research (CSIR-CIMFR) have developed India’s first mobile Smart Algal Liquid Tree (SALT), a compact air purification system that uses microalgae to absorb carbon dioxide and release oxygen. The patented device is designed for densely populated urban areas where planting conventional trees is difficult due to space constraints. It is currently deployed at the CSIR-CIMFR campus in Dhanbad, Jharkhand, and at Northern Coalfields Limited (NCL) in Singrauli, Madhya Pradesh.
What Is the Smart Algal Liquid Tree?
A liquid tree is a sealed container filled with water and microalgae, which are microscopic single celled photosynthetic organisms found in water bodies. Unlike a real tree with leaves, trunk, and roots, SALT houses microalgae in an enclosed unit where they continuously absorb carbon dioxide from the surrounding air and release oxygen through photosynthesis. Microalgae are among the most efficient carbon capture organisms on the planet, responsible for generating approximately 50% of the global oxygen supply. They can capture carbon dioxide 10 to 50 times more efficiently than terrestrial plants.
The Council of Scientific and Industrial Research (CSIR) , under which CIMFR operates, was established in 1942 as an autonomous body under the Ministry of Science and Technology. Headquartered in New Delhi, CSIR is one of the largest publicly funded research and development organisations in the world, with 37 national laboratories. CSIR-CIMFR itself was formed in 2007 through the merger of the Central Fuel Research Institute (CFRI) , founded in 1946, and the Central Mining Research Institute (CMRI) , founded in 1956. Located in Dhanbad, known as the coal capital of India, CIMFR focuses on research across the entire coal energy chain from exploration to utilisation.
How Does SALT Work?
SALT functions as a photobioreactor, a closed system designed to cultivate photosynthetic microorganisms using light. Ambient air is drawn into the unit, where microalgae absorb carbon dioxide through photosynthesis and release oxygen as a byproduct. The system also helps reduce dust and particulate matter from the air, providing a multi-pronged air cleaning effect.
The device can operate round the clock using either natural sunlight or artificial light, ensuring continuous air purification regardless of weather conditions. It is powered by solar energy as well as electricity, making it energy efficient and suitable for deployment in locations with varying power availability.
Key Features and Public Utility
SALT is designed as a mobile unit that can be relocated as needed, setting it apart from fixed infrastructure like trees. It is equipped with sensors that display real time air quality data, including carbon dioxide levels, temperature, humidity, and particulate matter concentration. This allows the public to see the immediate impact of the device on local air quality.
Beyond air purification, the unit doubles as a public amenity. It provides shaded seating for four to eight people and includes charging points for mobile phones and laptops. This multifunctional design makes it suitable for high footfall areas where utility and comfort are as important as environmental benefit.
The enclosed algae based system requires no soil, is largely unaffected by urban pollutants and pests, and needs minimal maintenance compared to conventional trees. The technology is patented by CSIR-CIMFR, with the project led by Vetrivel Anguselvi, Senior Principal Scientist at the institute.
Deployment and Significance
The choice of deployment sites is notable. Northern Coalfields Limited (NCL) , where one unit is installed, is a wholly owned subsidiary of Coal India Limited and was established in 1985. Headquartered in Singrauli, Madhya Pradesh, NCL operates ten mechanised opencast coal mines and is one of the country’s largest coal producers. Installing an air purifying technology at a major coal production hub underscores the potential of SALT to function in highly polluted industrial environments where conventional trees struggle to survive.
The other installation at the CIMFR campus in Dhanbad demonstrates the technology within the institute’s own premises. Dhanbad, situated in the Damodar basin, is surrounded by extensive coal mining operations and faces significant air quality challenges, making it an ideal testing ground for the device.
Potential Applications and Commercialisation
CSIR-CIMFR envisions SALT being deployed across a wide range of public and industrial spaces, including schools, airports, railway stations, bus terminals, shopping malls, parks, theatres, and industrial zones. The institute is actively exploring commercial production of the device, with efforts focused on making it affordable enough for use in residential areas and localities facing severe air pollution.
The liquid tree concept is not entirely new globally. Serbia’s LIQUID 3, developed by the University of Belgrade, was an earlier photobioreactor installation that inspired similar innovations worldwide. India itself has seen other liquid tree projects, including an outdoor installation by the DS Group in Noida in 2024 and a prototype developed by LO Carbon Solutions in Kerala. However, SALT is India’s first mobile liquid tree, offering flexibility that fixed installations cannot match.
Key Takeaways
- CSIR-CIMFR has developed India’s first mobile Smart Algal Liquid Tree (SALT) , a photobioreactor that uses microalgae to absorb carbon dioxide and release oxygen.
- Microalgae are responsible for approximately 50% of the global oxygen supply and can capture CO2 10 to 50 times more efficiently than terrestrial plants.
- SALT is currently deployed at two locations: the CSIR-CIMFR campus in Dhanbad (Jharkhand) and Northern Coalfields Limited in Singrauli (Madhya Pradesh).
- The device runs on solar or electric power, operates round the clock using natural or artificial light, and provides shaded seating with device charging points.
- CSIR was established in 1942 and is headquartered in New Delhi, while CSIR-CIMFR was formed in 2007 through the merger of CFRI (1946) and CMRI (1956).
- The project is led by Vetrivel Anguselvi, Senior Principal Scientist at CSIR-CIMFR, and commercial production is being explored for wider deployment.
