Crop Based Carbon Capture: A Future to Behold

An Immediate and Efficient Solution to Carbon Emissions and Global Climate Change

Lets face it. The world is warming at an alarming rate. The human induced carbon emissions have skyrocketed since our industrial revolution in the 1760s. Prior to this time, carbon dioxide in the atmosphere fluctuated between 180 ppp and 280 ppp as Earth was going through warmer and cooler cycles. Since acceleration of human emissions, carbon dioxide levels in the atmosphere have since increased to a alarming 400ppp. As a result, the earth’s average surface temperature has since risen of 1.18 degrees, causing us to loose more than 400 billion tons of ice per year and giving a 8 inches rise in sea level over the past century.

Changing climate and temperature have also led to a sharp increase in extreme natural phenomena. Every year, climate change results in displacement of 20 million people, not to mention the $140–300 billion damage inflicted upon properties and infrastructures. We are not immune.

More and more voices in the scientific community now recognize that merely halting our emissions of carbon is no longer enough, whereas carbon capturing would be necessary to maintain earth in a livable state. However, the main hurdle to any existing efforts in carbon capturing is the enormous cost. Infrastructures need to be built, technology needs to be developed. Most current technologies requires upwards of hundreds of dollar per each tonne of carbon dioxide captured. This is a cost that many are simply not prepared to pay.

It does not have to be that way. Why build new and expensive infrastructure when we could have utilised existing ones? Recent breakthrough in the research of plants reveals another game changing option for low cost carbon capturing — GMOs.

Yes, but why plants?

Well, why not? Plants makes for a fabulous candidate for a carbon capturing technology. Most plants are autotrophs. This means that they have evolved to capture and convert carbon from the atmosphere into energy and building blocks through a process called photosynthesis. In fact, carbon makes up a significant portion of any plant’s biomass, between 45–55%, as compared to the less than 25% in most mammal. Through this process, plants already store 450 gigatons of carbon around the world, roughly 80% of all the biological carbon stored within organisms. All this means plants are naturally equipped to capture carbon as an integral part of their metabolic process, and all engineers have to do is to augment the capability.

Crops are even better. To begin with, human civilisations are literately founded upon the growing and harvesting of crops. The word civilisation derives from the latin word “civitas”, or “city”. Gathering of people is only made possible with concentration of food from “culture” originally meaning “place tilled (tillage)” and thus growing crops. We have to grow crops anyway, why not utilise it to capture some carbon? Beside, crops are notoriously terrible in storing carbon. Crops makes up more than 25% of all landmass covered by plants, yet they only store 10 gigatons of carbon in total. That is less than 2.3% of the total 450 gigatons of carbon stored in plants, a Whopping 92% less than the optimal level.

This seems to point toward a evidently obvious solution, to make crops capture and store more carbon. But we have to ask: how can that be done?

Its all about the genes

There are three crucial factor to how much carbon the crops can store: root biomass, photosynthesis efficiency and recalcitrance. Let me break it down for each of the factor and what can be done to optimise it.

Root biomass: Capacity

Carbon is relatively equally distributed throughout the plant. In case of crops, carbon accounts for an average of 45%-47% of the biomass depending on the organs. In most crops, the majority of biomass concentrates in the root section; with the root shoot ratio (below ground to above ground ratio) averaging between 2.5 to 1.5. This means the majority of the carbon fixated by the plant is stored in its roots, thus making the root bigger will allow the plants to store more carbon.

The size of the root of a plant is largely determined by a combination of external factors and genetic factors. The most relevant gene factors to root biomass are EXO70A3 gene, TOB1 inhibition pathway and NAC transcription factor. EXO70A3 and TOB1 are responsible for the regulation of a plant growth hormone, called Auxin, which induces growth in both root and stem. The NAC transcription factor is related to the biomass of the plants roots through a currently unidentified pathway, but is nevertheless strongly correlated. All three genes and factors are evolutionarily conserved, meaning they are similarly found in most plant species. The editing of all three is currently done with a CRISPR-Cas9 system.

Basing on science literature, if all three of the genes are optimised, the root biomass can be more than 135% larger than the base level. This means a significant increase in the amount of carbon the crop can store.

Photosynthesis efficiency: Capturing Carbon

For the past twenty years, scientists around the world have been experimenting to produce crops with more efficient photosynthesis. What this entails is a switch from the common C3 photosynthesis to the C4 photosynthesis. Let me explain.

The common C3 photosynthesis is the simple photosynthesis we all learn in school. Carbon dioxide enters a plant cell and is fixated by the enzyme rubisco through the Calvin Benson cycle into sugar. This chemical reaction occurs in a cell organ called chloroplast, exclusively in cells of autotrophs (mostly plants). This however is very inefficient. The rubisco want to fixate carbon, but there are also oxygen molecule in the chloroplast that they sometimes “accidentally” fixate. This reduces the rate of carbon fixation.

The C4 photosynthesis have an additional step. Carbon dioxide is first concentrated around the cell before it is delivered straight into the rubisco. This removes the contact between carbon and molecular oxygen, significantly increasing the efficiency of the C4 photosynthesis.

Scientists believe the key to generating crops with C4 photosynthesis lies with altering the plants tissue anatomy, allowing the carbon dioxide to bundle up. There are several genes identified to regulate the Calvin-Benson cycle and chloroplast morphology that is very promising in generating the C4 photosynthesis we desire. The effect is likely going to be a 50% or more increase in photosynthesis efficiency, significantly increasing the carbon capturing ability and the growth capacity of the plant.

Recalcitrance: How Long Carbon Remain Fixated

Recalcitrance is the scientific jargon for the plant’s ability to resist decomposition after it dies. We want to maximise recalcitrance because decomposition essentially releases the carbon fixated by the plant back into the atmosphere. The most promising path to increasing the recalcitrance of plants is in a chemical named suberin.

Suberin is a carbon polymer, of which the chemical structure somewhat resembles that of plastic. Plant naturally secrete suberin in their structure, which has been identified to help the plant become more resilient against decomposition. Thus, to achieve higher recalcitrance, we want to maximise the Suberin synthesis in the GMO crop. As Suberin is quite a new field of research, there are multiple genes that are identified to be associated with its biosynthesis.

The most promising genes involved in the synthesis of suberin are AtMYB41 of the MYB factors, the ABCG2, ABCG6 and ABCG20 of the ATP Binding Cassete G transporters, and the KCS genes. Experimental progress is still on the way to determine the quantified impact of modification on these genes, and the specific method of modification. From the most recent studies, it seems the modification will most likely be carried out with viral vectors.

What Does This All Mean?

This means a lot. Basing on our best knowledge and estimation; by performing these modification, we are capable of making the crop store 73% more carbon compared to the base level. At this rate, if similar approach is applied on only 10% of the worlds agricultural output, it will sequester more than 4% of the entire global emission. Further, if 50% of the worlds crop is modified under this framework, it will be able to fixate around 25% of the worlds carbon emission.

And the most mind boggling thing is that this comes at virtually no cost. The initial development of the GMO seed may cost a total of 1.3 to 1.5 Million dollar USD, taking a period of between 6 to 7 years before it reaches the market. But after that, there is very little that still need to be done. The GMO grows in much the same way as other plants, its seed is also produced in a similar fashion. A seed of this projected GMO will cost roughly equivalent to a similar seed product on the market, with some potentially sold at an even lower price than average.

But Whats In It For The Farmer To Adopt It?

Well, because it is highly profitable for them. The EXO70A3 gene modification will increase the vertical root extension and alter the root architecture. Deeper roots make the crops far more resistant against drought, and ironically enough climate change itself. The increased photosynthesis efficiency also leads to larger growth potential and thus larger yield per acreage by up to 50%. This is not to mention the C4 photosynthesis also enhance the plant’s heat and drought resistance. In fact, most naturally evolved C4 plants exist in environment with extreme heat and lack of humidity.

Taking an example; my team and I are currently working on a pioneering potato crop with these listed gene editing procedure. We project the crop will reach the market at earliest 2027 with a development cost of roughly 1.4 million USD. If the expectation is fully achieved, it could increase the asset return from the average of 1.609% to 53.54% for the farmer, while also storing 73% more carbon. This represents a 50 times increase in the economic prospect of the farmer, while also capturing more carbon than any crop ever planted. A typical win-win situation.

In Conclusion

We tend to think of future technology to be a mixture of grandiose sci-fi-like spaceships and super computers that can simulate the universe. However, solutions to some of our most prominent questions may lie within some of the most common, humble subjects. Crops, ones that have been cultivated by human for thousand of years may hold within themselves one of the keys to climate change. It is truly is a future worth a look.

Thanks for reading! I’m Henry, a 17 year old tech and longevity enthusiast on a mission to help extend human health span.

This article is written in collaboration with Flavie Prévost. If you like the content please remember to follow both of us on Medium. You can also find me on LinkedIn or join my monthly newsletter.