Artificial Photosynthesis

Over the past two years of reading about the field of artificial photosynthesis, I have become convinced that the field is now at the point where an influx of funding could give rise to a fast tech transfer.

For background, artificial photosynthesis is any chemical process that mimics how plants absorb the sun’s energy. Classically, this takes place in two steps; first through water splitting, which converts light energy into chemical energy, and then through carbon fixation, which makes the chemical energy storable by attaching carbon to the hydrogen from the split water.

While artificial photosynthesis may never store energy quite as well as solar panels, moving energy directly into a hydrocarbon form should prove useful in supporting the legacy hydrocarbon-consuming transportation infrastructure we see around us.

In the USA, there is almost the same number of cars as there are people, with gas car sales remaining constant, and gas car lifespan increasing. Phasing out these cars early almost necessarily involves wasting precious resources and filling up our dumps further.

Artificial photosynthesis presents a major opportunity to make these existent vehicles carbon-neutral. This technology has been fairly well funded, with work in the US being spearheaded by Harvard’s Nocera Lab and CalTech’s JCAP program.

The work that has been done has resulted in new processes that are 10% efficient at converting sunlight energy into fossil fuels in a lab setting. For reference, commercial solar panels currently operate at 20% efficiency, and the best research panels can almost hit 40% efficiency. Relevant solar panel numbers can be found in NREL’s PV Efficiency Chart. Due to such promise lab settings, a recent collaborative paper across relevant research groups has called for work to be done to create a governing body to measure these processes, and for groups to start working on increasing the scale of the processes.

Luckily, operationalizing similar tech has already started. Currently, the company that seems to be at the forefront of related research is Viridos. Their method is to grow photosynthetic algae, and then process the bodies of the algae using techniques similar to biofuel. Viridos’ technology is live right now, and the company has achieved an energy footprint of a third the quantity of classical fuel. [source]

Viridos has a commonality with the work done by Nocera’s lab. Both groups found that the carbon fixation process was prohibitively complex to engineer using inorganic methods. However, Nocera’s lab improves on the Viridos model in two ways. Firstly, Nocera et. al. found that substituting the light reactions with an inorganic hydrolysis method boosted efficiency by multiples, and they also seem to be able to directly create fuel, instead of needing to process the lipid bodies of the algae cells. However, Viridos’ technology is much further along, due to the comparative ease of “just” breeding special algae, instead of a more intensive hybrid approach.

Synhelion is the other company with an active plant. This company comes out of ETH Zurich and seems to be using concentrated solar power to heat classical CO2 splitting reactions, circumventing the need for exotic chemistry, with more exotic mechanical engineering challenges instead. Synhelion’s technique does not extract CO2 from the atmosphere itself. The group of scientists who published the new study claim that their technology is being used by Synhelion to create fuels, and by a separate company, named Climeworks, which will be solely concerned with Direct Air Capture.

In California, the startup named Twelve is also working in this space. However, they have not released any statistics on how well their tech works, and seem to be at the prototype stage, so I will just mention them in passing.

The burden of operationalizing artificial photosynthesis will be huge. The legacy infrastructure responsible for digging hydrocarbons out of the ground represents an inescapable barrier for any company in this space to overcome, but given the favorable investment climate we find ourselves in right now, a fund created to focus on bridging the gap between the pure science and real facilities seems to be imminent.

Written on December 2, 2021