Biosynthetic Trees

At a time when acceleration in climate change coincides with increasing densification in urban areas, biotechnology has emerged as a strong tool that enables cities to reimagine carbon emission management. Perhaps one of the most innovative concepts in the field is that of the biosynthetic tree, a system engineered through synthetic biology and bio-based materials, either mimicking, enhancing, or surpassing the carbon-absorbing functions of natural vegetation. Biosynthetic trees do not depend on purely mechanical filters or artificially created structures but use living, engineered organisms that will perform specific ecological functions in places where the growth of natural trees is impossible.

The central theme of research in the area of biosynthetic trees is to improve photosynthesis by biotechnological means. While natural trees are very efficient converters of CO₂ to biomass, they suffer from slow growth rates, seasonal dormancy, and environmental stress. Engineered organisms-most often can transcend these limitations. It is possible for scientists, through changes in metabolic pathways, addition of high-efficiency light-harvesting proteins, or enhancement of carbon fixation enzymes like rubisco, to construct organisms that capture carbon faster than typical plant cells.

These value-added organisms often reside within bioreactor "tree trunks" constructed from translucent, UV-resistant bioplastic. The algae swirl internally through nutrient-rich solutions, continuously executing improved photosynthesis. Other designs embed synthetic scaffolds like bacterial cellulose provide for microbial growth while maintaining biodegradability and low cost. The outcome is a living, modular tree-like unit that can be installed on the plaza, sidewalk, or mall-even where soil, space, or water limitations would prevent traditional planting.

Some research teams have also explored symbiotic systems in which the engineered algae coexist with beneficial bacteria that recycle nutrients or produce protective compounds. This is an attempt to achieve ecological resilience in ways that natural forests do, while remaining within a controlled biotech environment.

Biosynthetic trees have a number of advantages from an environmental biotechnology perspective. They can be calibrated to absorb specific pollutants-nitrogen oxides or particulate matter, for example-and they maintain productivity year-round. Unlike mechanical carbon capture devices, biosynthetic systems grow their own biomass, which may later be harvested for use in biofuel or bioplastic production, or in compost. Their modular design also allows for scaling, enabling deployments in both dense urban districts and remote industrial sites.

However, the biotechnology underlying these systems does have its limitations: engineered organisms are kept in closed bioreactors to avoid environmental release and therefore require maintenance and monitoring; regulatory frameworks for deployment of synthetic biology applications in public spaces are still under development; and energy inputs for pumps, sensors, and temperature control are occasionally required, although passive circulation and solar-powered systems are reducing these costs at a rapid pace. Nevertheless, the biosynthetic trees now represent some of the most promising crossroads between biotechnology and climate engineering. Through the use of synthetic biology, cellular engineering, and sustainable material science, they are pushing the boundaries of what a "tree" is or can be, shaping it from an organismal, biological staple to a dynamic, programmable, highly efficient carbon-capturing system. And as innovation in biotech continues to accelerate, biosynthetic trees might sooner rather than later complement natural ecosystems everywhere, forming hybrid landscapes that are at once alive and engineered in service of a resilient planet.

References:

Barbier, Marjolaine, et al. “Enhanced Carbon Fixation in Engineered Cyanobacteria.” Nature Communications, 2021. www.nature.com/articles/s41467-021-21440-x. 

BiomiTech. “BioUrban: The Artificial Tree That Cleans the Air with Microalgae.” BiomiTech, 2020. www.biomitech.com/en/biourban. 

Khalil, Ahmad S., and James J. Collins. “Synthetic Biology: Applications Come of Age.” Nature Reviews Genetics, 2010. www.nature.com/articles/nrg2775. 

NowBioWorks. “Living Trees: Synthetic Biology for Urban Air Purification.” NowBioWorks Research Blog, 2023. www.nowbioworks.org/blog/living-trees-synthetic-biology. 

Pawar, Abhijeet A., et al. “Bacterial Cellulose: A Sustainable Scaffold for Bioreactors.” Frontiers in Bioengineering and Biotechnology, 2021. www.frontiersin.org/articles/10.3389/fbioe.2021.628709/full. 

Silva, Luis Miguel, et al. “Genetic Circuits for Enhanced Photosynthesis and CO₂ Fixation.” ACS Synthetic Biology, 2022. pubs.acs.org/doi/10.1021/acssynbio.1c00562. 

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