Artificial Photosynthesis – A Case of Biomimicry

Humans have long sought solutions to their problems by observing nature and trying to mimic it. These endeavors have lead to improvements in the designs and production processes of countless things. In recent decades there has been a growing movement composed of scientists, engineers, and innovators of all types to expressly seek for answers to today’s most pressing problems by deeply observing and analyzing the natural world. These efforts are coupled with a desire to learn how to work with nature rather than against it in an attempt to secure a more sustainable future for life on Earth. This is the essence of biomimicry.

To this end, plants have much to teach us. Everything from their basic forms and functions to the way they fight off pests and diseases to the way they communicate with each other is worth exploring for biomimicry purposes. A plant-based phenomenon that has probably received the most attention – and for good reason – is photosynthesis, the process that enables plants to use the sun to make food.

Put another way, photosynthesis is the process of converting light energy into chemical energy. Specialized proteins in plant cells absorb particles of light which initiates the passing of electrons across a series of molecules. Subsequently, water is split by a protein complex into oxygen and hydrogen protons. The oxygen is released from the plant, while the electrons and hydrogen protons go on to help generate two compounds – NADPH and ATP – which are later used to power the reaction that transforms atmospheric carbon dioxide into sugars. The concept of photosynthesis, while fairly simple to grasp from a high level (i.e. light + water + carbon dioxide = sugars + oxygen), is actually quite complex, and there is still much too discover concerning it.

photo credit: wikimedia commons

photo credit: wikimedia commons

One thing is certain, photosynthesis is ubiquitous. As long as the sun is overhead, most plants, algae, and cyanobacteria are photosynthesizing at a steady clip and are thereby helping to power just about every other living organism on the planet. Without plants, most of the rest of us could not survive. Janine M. Benyus offers this human-centric view in her book Biomimicry:

Consider that everything we consume, from a carrot stick to a peppercorn filet, is the product of plants turning sunlight into chemical energy. Our cars, our computers, our Christmas tree lights all feed on photosynthesis as well, because the fossil fuels they use are merely the compressed remains of 600 million years worth of plants and animals that grew their bodies with sunlight. All of our petroleum-born plastics, pharmaceuticals and chemicals also spring from the loins of ancient photosynthesis. … Plants gather our solar energy for us and store it as fuel. To release that energy, we burn the plants or plant products, either internally, inside our cells, or externally, with fire.

Since plants are so well-versed in using sunlight to create food and energy, it only makes sense that we would look to them to learn how we might improve and expand upon our quest for renewable energy production. We already use the sun to produce electricity by way of photovoltaic systems; however, these systems are limited in that they can only produce electricity when the sun is shining, and electricity is difficult to store. Artificial photosynthesis involves using that electricity to power catalysts that can split water into hydrogen and oxygen. The hydrogen can be used as a fuel or can be fed into reactions involving carbon dioxide, ultimately resulting in a carbon-based fuel source. Fuels produced this way – referred to as solar fuels – could be stored and used regardless of whether or not the sun is out.

Artificial photosynthesis has largely moved beyond the theoretical stage. Multiple efforts have demonstrated ways in which water can be split using the light of the sun and solar fuels can thereby be produced. Mass production is the next step, and that is where the real limitations lie. The production of solar fuels has to be done cheaply enough to compete with other available fuels, and the infrastructure to use such fuels has to be available. These hurdles may very well be overcome, but it will take time. Meanwhile, research continues, adding to the mountains of studies already published.

photo credit: wikimedia commons

photo credit: wikimedia commons

On such study published in 2011 describes an “artificial leaf” that was developed at the Massachusetts Institute of Technology by Daniel Nocera and a team of researchers. Listen to an interview with Nocera on Science Friday and watch this BBC Worldwide video to learn more about this discovery. This Nature article explains why the artificial leaf is not yet commercially available, and why we are not likely to see it any time soon.

Another development in artificial photosynthesis was published earlier this year in Nano Letters. It is the product of Peidong Yang and the Kavli Energy NanoSciences Institute. While Nocera and his team stopped at the production of hydrogen gas, Yang’s lab added bacteria to the mix and were able to use the sun’s energy to transform carbon dioxide into acetate. If passed along to another species of bacteria, the acetate could be used to produce various synthetic fuels. Learn more about this by reading this livescience article and watching this FW: Thinking video. As with other artificial photosynthesis developments, limitations abound, but the research is promising.

Artificial photosynthesis is a compelling subject and one worth keeping an eye on. Follow the links below to learn more:

Biomimicry is an equally compelling subject and one I hope to explore further in future Awkward Botany posts. Meanwhile, check out these links:

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