In the effort to combat climate change, the role of carbon fixation has never been more urgent.
Quick recap: through the process of photosynthesis, trees and other plants absorb carbon dioxide (CO2) from the atmosphere, converting it into oxygen and biomass. This therefore not only sustains the tree's growth, but also plays a key role in lessening the accumulation of the greenhouse gas CO2.
However, as the climate crisis continues to escalate, whilst landmass becomes more and more expensive, there's an ever-more pressing need to enhance the efficiency of the natural carbon fixation process. Advances in synthetic biology and biotechnology offer promising avenues to augment the capability of trees to absorb carbon more efficiently, potentially turning forests into even more powerful carbon sinks than they already are.
Through harnessing the power of both nature and technology, we stand on the brink of transforming our forests once more into some of our strongest allies against climate change.
Understanding Carbon Fixation
Carbon fixation is a fundamental biochemical process; integral to the photosynthesis pathway - allowing plants, algae, and certain bacteria to convert CO2 from the atmosphere into energy-rich organic compounds. Since plants are at the bottom of the food-chain, this process is central to sustaining life on Earth - providing the primary means through which CO2 is removed from the atmosphere and stored in biomass.
Unfortunately, though, the process is notoriously inefficient: the photosynthetic efficiency of terrestrial plants is around 1~2%. For reference, microalgae sit around 4~8% - and trumping even that are solar panels with an efficiency of ~20%.
If we want to improve carbon fixation in photosynthesis, perhaps the best way would be to improve the slowest part, RuBisCo, which is bottlenecking the system - as despite its crucial role in carbon fixation, RuBisCO is actually wasteful because of a process called photorespiration, in which it often binds to oxygen (O2) instead of CO2, catalyzing a reaction in the precise opposite direction of what it’s meant to be doing. This inefficiency limits the overall rate at which plants can fixate carbon, slowing their growth and thereby diminishing the capacity of forests to act as effective carbon sinks.
Addressing RuBisCO and other limitations through genetic engineering and other biotechnological approaches, therefore, could enhance carbon fixation efficiency - again making plants more potent allies in the fight against climate change.
Genetic Modification Approaches
Our quest to investigate and ultimately boost the natural carbon fixation capabilities of trees has led scientists to explore a few different genetic modification strategies. There are countless avenues to explore, but a few of them appear to be exceptionally promising for enabling plants to capture and store more CO2.
RuBisCo Optimization: As mentioned, central to enhancing photosynthesis could be the optimization of RuBisCo, the enzyme responsible for carbon fixation. However, as we hinted at earlier, RuBisCo has a slow turnover rate and can mistakenly bind to oxygen, leading to inefficient carbon fixation. By employing gene-editing techniques like CRISPR/Cas9, researchers aim to engineer a version of RuBisCo with a higher affinity for CO2 and reduced photorespiration rates. This could enhance photosynthesis efficiency and ultimately boost tree growth and carbon capture capabilities. Unfortunately, if it were this simple, it’d be solved already. There’s a big tug of war too complicated to explain here between improved CO2 versus O2 binding and reduced efficiency. Currently, RuBisCo appears to be in what’s called a local maximum in terms of performance. To make big gains here, we may need to re-engineer RuBisCo ourselves from the ground up, potentially using AI.
C4 Photosynthesis Engineering: Trees and most plants use a process of C3 photosynthesis - whereas some others, like maize and sugarcane, use C4 photosynthesis, the latter of which effectively concentrates CO2 around RuBisCo (and also minimizes oxygen getting accidentally attached). This mechanism allows C4 plants to photosynthesize more efficiently, especially in high-light and high-temperature environments. There is currently research being done exploring ways to introduce C4 pathways into C3 plants (such as trees), therefore to improve their growth rates and carbon sequestration potential. This approach would include modifying the plant’s leaf anatomy, metabolic pathways, and regulatory processes to imitate C4 photosynthesis, so it wouldn’t be simple - but given the state of the research, it is extremely promising nonetheless.
Increasing Light Absorption Efficiency: Another approach involves adjusting the light-harvesting complexes in plants to enhance their ability to absorb and use light energy, especially under lower-light conditions. This adjustment could lead to more efficient photosynthesis and faster growth, allowing trees to capture more CO2. By tweaking the absorption spectra of these complexes (such as through using cyanobacterial photosynthetic pigments such as chlorophyll F and D), scientists aim to maximize light use across a broader range of wavelengths, increasing overall photosynthetic efficiency.
Enhancing Carbon Concentration Mechanisms (CCMs): Some algae and cyanobacteria have evolved mechanisms separate from C4 photosynthesis to increase the concentration of CO2 around RuBisCo, thereby boosting its photosynthetic efficiency. Researchers are investigating how these mechanisms could be transferred to other plants. This involves introducing genes that code for specific structures and enzymes, allowing plants to better concentrate CO2, improving carbon capture as a whole.
By implementing these genetic modifications, the aim is to develop trees that not only grow faster but also fixate carbon more efficiently. Companies like Living Carbon are pioneering this field, having developed genetically modified trees that demonstrate significantly enhanced growth and carbon capture capabilities. We should note however, these advancements are still in the early stages, and further research is needed to assess their real-world applicability and ecological impacts.
Challenges/Considerations
While the genetic modification of trees presents some potential for enhancing carbon fixation, there are definite concerns we need to address. One of the primary challenges is the impact of introducing genetically modified organisms (GMOs) into natural environments. Given these hypothetical trees would fixate CO2 into biomass faster than their wildtype cousins, there is a risk that these trees could outcompete native species, alter habitats, or affect biodiversity in unforeseen ways.
Additionally, the long-term effects of these modifications on ecosystems remain pretty much entirely unresearched and hence would necessitate extensive field testing and monitoring. The standard ethical considerations around biotech also come into play, particularly about our right to modify living things and the potential consequences of such actions on natural balance and biodiversity, as well as manipulating natural organisms and ecosystems for potential human benefit.
The main thing however is that it's important to consider this sort of genetic modification alone cannot address the root causes of climate change.
While enhancing the carbon-capturing capabilities of trees is and will be a valuable tool in mitigating global warming, it should complement - rather than seek to replace - efforts to reduce greenhouse gas emissions and transition to sustainable energy sources. At ValleyDAO we understand this, and our focus is on addressing climate challenges from every angle imaginable, whilst keeping our focus on restoring the balance between humanity and nature; moving toward a carbon-negative future built on living technologies.
We’ve recently launched a new initiative called the Carbon Arc, which aims to bridge the "Valley of Death," i.e. the gap between research and real-world implementation. The Arc itself focuses on innovative solutions for carbon capture.
As we continually make significant advancements in enhancing the natural carbon-fixing capabilities of the world, our role in uniting technology with nature's resilience offers a hopeful path forward in our collective effort to combat climate change.
If you want to contribute to these efforts, join the Discord, or apply to join one of the working groups pushing ValleyDAO’s community forward.
