Backdrop: A Growing Carbon Dioxide Challenge
Across the world, air pollution has become a pressing environmental crisis. While discussions on urban pollution often emphasize particulate matter, nitrogen oxides, and industrial smog, the silent and persistent rise of carbon dioxide (CO₂) pollution is equally alarming. In both outdoor and indoor environments, CO₂ levels are steadily climbing to unhealthy concentrations, threatening public health, productivity, and climate stability.
Globally, the combustion of fossil fuels, deforestation, unregulated industrial discharges, and high-density urban lifestyles have fueled the rise of atmospheric CO₂ to levels unprecedented in human history. According to recent climate data, global CO₂ concentrations exceeded 420 parts per million in 2024, far above the safe threshold identified by scientists. This invisible pollutant not only accelerates climate change but also directly affects human well-being, particularly in closed indoor spaces where fresh air circulation is limited.
Indoor CO₂: A Hidden Crisis
While outdoor pollution is visible in the form of smog, dust, and haze, indoor CO₂ accumulation is often ignored despite its significant health impact. Modern urban lifestyles have led to the proliferation of enclosed, temperature-controlled environments — classrooms, meeting rooms, conference halls, lecture theaters, and corporate offices. In these environments, high occupancy combined with insufficient ventilation causes CO₂ concentrations to rise rapidly.
Scientific studies have shown that indoor CO₂ levels often exceed 1000 parts per million during crowded sessions, far above the recommended safe limit of 600–800 ppm. Elevated CO₂ inside such environments has been linked with headaches, fatigue, reduced cognitive performance, poor concentration, drowsiness, and long-term health risks. For students in classrooms and professionals in meetings, high indoor CO₂ directly translates into reduced productivity and impaired decision-making.
In Bangladesh, this issue is especially pronounced because of the rapid expansion of educational institutions, corporate offices, and conference facilities that are air-conditioned but not adequately ventilated. The invisible buildup of CO₂ inside these enclosed environments is a silent health threat.
Outdoor CO₂: The Urban Burden
Dhaka and other major Bangladeshi cities face a dual challenge. Alongside particulate matter pollution and heat island effects, outdoor CO₂ emissions have increased drastically due to high vehicular density, brick kilns, cement factories, tanneries, chemical industries, and rapid deforestation. A study by BUET revealed that Dhaka lost nearly 88% of its healthy green space between 1989 and 2020. With only 2% tree cover remaining in 2022, the city’s natural capacity to absorb CO₂ has been drastically reduced.
This unchecked rise in CO₂ intensifies the impacts of climate change, raises urban temperatures, worsens respiratory conditions, and contributes to long-term health risks. Moreover, Bangladesh is one of the most climate-vulnerable countries in the world. Rising CO₂ is not just an environmental issue but a matter of national survival.
Liquid Tree: A Nature-Inspired Biotechnology Innovation
In response to this urgent challenge, using our own algae, research team at Bioresources Technology and industrial Biotechnology Lab of BGE department of Jahangirnagar University has developed the Liquid Tree — an innovative biotech solution designed to combat CO₂ pollution in both indoor and outdoor environments under the RIC-JU umbrella of EDGE project of Bangladesh Govt. Unlike conventional approaches, the Liquid Tree harnesses the power of microalgae to capture CO₂ and release oxygen through photosynthesis. This technology mimics the natural function of terrestrial trees but in a controlled and highly efficient system. Liquid Trees are transparent photobioreactors that cultivate microalgae. When exposed to sunlight (outdoor models) or artificial light (indoor models), the microalgae perform photosynthesis, absorbing CO₂ and releasing oxygen as a natural byproduct in a similar manner like trees. The system is designed for autonomous, low-maintenance operation, making it suitable for dense urban areas and enclosed indoor spaces.
Dual Model Design: Indoor and Outdoor
What sets our innovation apart is the deliberate design of two complementary models:
- Outdoor Liquid Tree – Engineered for space-constrained urban footprints such as sidewalks, road dividers, rooftops, parking areas, and industrial zones. These units capture CO₂ from vehicle emissions and industrial activity while providing localized oxygenation in polluted neighborhoods.
- Indoor Liquid Tree – Specifically developed to address the growing concern of CO₂ accumulation in enclosed environments. These compact bioreactors are ideal for classrooms, conference halls, meeting rooms, and offices. By actively absorbing CO₂ exhaled by occupants and releasing oxygen, they ensure healthier air quality, improved focus, and enhanced productivity.
Proven Global Inspiration, Local Innovation
The first prototype of a Liquid Tree was installed in Belgrade, Serbia in 2021, where it demonstrated the ability to absorb the equivalent CO₂ of two mature trees daily. Building on this inspiration, our Bangladeshi innovation refines the concept further by adapting it to tropical conditions using our own algae and specifically designing indoor models, an area that has remained largely unexplored globally.
Efficiency and Advantages
Experiments and modeling suggest that a single Liquid Tree bioreactor can perform CO₂ capture and oxygen release with excellent efficiency compared to traditional trees. Unlike natural trees, which take years to mature, Liquid Trees can be fabricated and deployed within weeks.
Additional features include:
- Biomass harvesting: The microalgal biomass produced can be repurposed as organic fertilizer or biofuel.
- Low space requirement: Compact footprint allows installation in dense urban
- Year-round functionality: With artificial lighting support, indoor models can function 24/7.
- Educational and awareness value: The futuristic design attracts public interest and raises awareness about sustainability.
Challenges and Opportunities
Like all pioneering technologies, Liquid Trees face hurdles. High initial investment, need for consistent light and water supply, and routine maintenance are practical challenges. Additionally, large-scale deployment may required to achieve city-wide impact.
Yet the opportunities are far greater:
- Scientific advancement: Optimizing native algal strains for Bangladesh’s
- Circular economy: Utilizing byproducts such as organic fertilizer, bioenergy
- Integration with urban design: Rooftops, building facades, and public spaces can host Liquid Trees.
- Economic potential: Development and deployment will create new jobs in biotechnology, green manufacturing, and maintenance.
Bangladesh at the Forefront
For a country like Bangladesh, where rapid urbanization has strained both environmental and public health systems, the Liquid Tree is more than just a symbolic innovation. It is a practical solution for mitigating CO₂ pollution in environments where traditional greening is not possible. It aligns with the national agenda for climate resilience, sustainable urban planning, and green technology development.
By pioneering indoor Liquid Tree models, Bangladesh can take global leadership in addressing the often-ignored crisis of indoor CO₂ accumulation. This innovation not only protects public health but also enhances learning environments, workplaces, and community well-being.
Conclusion and Call to Action
The Liquid Tree is not a replacement for natural greenery but a complementary solution. Trees, parks, and forests remain irreplaceable for biodiversity and ecological balance. However, in space-cramped urban areas and sealed indoor environments, Liquid Trees provide a scalable, rapid-deployment alternative for ensuring breathable, healthier air.
We call upon policymakers, urban planners, academic institutions, and industries to support the deployment and further research of Liquid Trees in Bangladesh. With collective effort, this biotechnology can evolve from a promising prototype into a transformative tool for sustainable living.
Team info:
- Golam Moinuddin, Professor, Dept. of Urban and Regional Planning, Jahangirnagar University
- Mohammad Shahedur Rahman, Professor, Bioresources Technology and Industrial Biotechnology Lab, Biotechnology and Genetic Engineering, Jahangirnagar University
- M G Sorwar Hossain, Professor, EEE Department, BRAC University
- M Shakilur Rahman, EPL solutions, USA
Support team:
The researchers of Bioresources Technology and Industrial Biotechnology Laboratory