Powering the World with Artificial Photosynthesis

Subject(s):
portrait of Thomas Faunce
Thomas Faunce
illustration
GREG STEWART / NATIONAL ACCELERATOR LABORATORY, STANFORD UNIVERSITY
Artist’s concept of ultra-short X-ray pulse striking molecules containing manganese, a metal that, with calcium and oxygen, forms the water-splitting catalyst in photosystem II. Researchers believe that a better understanding of this process will contribute to developing artificial ­photosynthesis.

By Thomas Faunce

Humans are learning to mimic plant processes for producing sustainable energy.

Imagine all built structures—buildings, roads, bridges—capable of making their own hydrogen fuel by using sunlight to split water. Imagine further that they can all absorb atmospheric carbon dioxide and nitrogen, turning it into food or fertilizer.

Such an engineering feat would be the very blueprint for a sustainable world. Human structures at last would pay their own way in an ecosystem sense.

More solar energy strikes the Earth’s surface in one hour of each day than the energy used by all human activities in one year. World energy consumption is currently about 450 exajules per year (EJ/yr), or 125,000 terawatt hours. Photosynthesis, the ultimate source of our oxygen, food, and fossil fuels, is a great invention of nature that has been deployed on Earth for about 2 billion years. In its present technologically unenhanced form, photosynthesis globally already traps around 4,000 EJ/yr of solar energy in the form of biomass.

Photosynthesis can be viewed as the planet breathing: taking in carbon dioxide and releasing oxygen. But it can also be considered as the planet’s nervous system: generating a basic voltage that powers the world’s life. This is because photosynthesis takes light energy from the Sun and stores it in chemical bonds.

In the 1800s, most people believed that only birds would ever fly. Likewise, most people today still believe that only plants can “do” photosynthesis. But we are on the verge of not only fully replicating photosynthesis, but actually improving it through nanotechnology work under way by large national projects such as Caltech and Berkeley’s Joint Center on Artificial Photosynthesis, the Solar H2 network based at Uppsala University, the Solar Fuels Initiative (SOFI) based at Northwestern University, and Dan Nocera’s work at MIT and Harvard.

Public policy and investment interest in developing the so-called Hydrogen Economy is critically dependent on a cheap, abundant non-carbon-based source of hydrogen (H2). This would either serve as a source of electricity via fuel cells or a liquid solar fuel itself, or be combined with carbon dioxide to form fuels such as methanol.

In many developed nations, major energy policy documents have outlined the case for such a H2 fuel economy, particularly because of the need to reduce atmospheric greenhouse gases. But they have then faced problems associated with the high cost of generating H2, as well as the problem of intermittency in renewable energy electricity supplies.

The short-term benefits of recent bonanzas in coal seam natural gas and shale oil will also prolong humanity’s damaging dependence on “archived” photosynthesis fuels (fossil fuels such as natural gas, coal, and oil), as will the subsidies that keep the prices of such fuels down and so make it harder for renewable energy technologies to compete.

These problems would vanish if artificial photosynthesis could be routinely incorporated in all engineered structures on Earth, thus providing a cheap source of hydrogen fuel, oxygen, carbon-dioxide absorption, and soil nutrients.

The major scientific challenges in artificial photosynthesis fall into three areas: light capture, water splitting (or catalysis), and carbon-dioxide reduction. In each of these areas, nanotechnology and synthetic biology present opportunities for significant improvements.

Light capture. Nanostructured materials or synthetic organisms are being developed to absorb photons from a much wider region of the solar spectrum. The advantage is that nanoparticles used on any surface drastically increase its surface area compared with standard materials.

Catalysis. A crucial component of photosynthesis is the protein known as photosystem II, which splits water into hydrogen and oxygen. As well as the centers mentioned earlier, new research at the Dutch and South Korean artificial photosynthesis projects, the Max Planck Institute for Chemical Energy Conversion, and the Energy Futures Lab at Imperial College London now focuses on developing artificial water-splitting catalysts (currently focused on manganese, nickel, cobalt, and doped iron oxide) that stay active for extended periods of time or that can be easily regenerated and be made from readily available and inexpensive materials.

Carbon-dioxide reduction. Replicating how photosynthesis reduces atmospheric carbon dioxide may be the hardest challenge, yet perhaps the most significant for humanity. CO2 reduction is a major focus of the artificial photosynthesis groups working in Japan (for example, at Osaka University).

Governance Challenges for Artificial Photosynthesis

Nanotechnology deployed for the development of global artificial photosynthesis (GAP) offers both energy security and a climate-change solution. Yet, major challenges to the rapid global deployment of artificial photosynthetic technology may arise from the oil, coal, and natural-gas industries via international trade and investment law.

GAP as a combined off-grid energy and climate-change solution is a potential disruptor to corporations relying on abundant natural resources or cheap labor. An open-access model for research and marketing of GAP for solar food and fuel products, for example, could involve funding rules requiring public good licensing, technology transfer, ethical and social implications research, as well as rapid and free access to data.

Photosynthesis, like the human genome, deserves the status of “common heritage of humanity” under international law so it can be kept as a legacy for future generations and not completely enclosed by patents.

A GAP Project governance structure emphasizing international law might protect photosynthesis from excessive patents that promote inequitable or unsustainable use of the global commons. One mechanism for this could be a UNESCO Universal Declaration on Natural and Artificial Photosynthesis. Such a Declaration could place reasonable limits on private appropriation, encourage the management of the research on behalf of all, encourage active sharing of the benefits, prohibit weaponry developed using artificial photosynthesis, and preserve natural and artificial photosynthesis for research by future generations.

Globalizing artificial photosynthesis technology will assist humanity to move into a “Sustainocene” epoch, where humanity is an environmental steward. We would have an ethical obligation to ensure that this epoch will last as long as the legacy that life has given us: some 2.3 billion years. It is a task that cannot wait and should be made the subject of a macroscience project, with attendant increase in resources and public-policy profile.

Thomas Faunce holds a joint position in the College of Law and the College of Medicine, Biology, and the Environment at the Australian National University (ANU), http://law.anu.edu.au/staff/thomas-faunce. He is on the Board of Directors of the Energy Change Institute at the ANU. He is an Australian Research Council (ARC) Future Fellow. His papers are accessible at http://law.anu.edu.au/staff/thomas-faunce?tb=5, and his latest book is Nanotechnology for a Sustainable World: Global Artificial Photosynthesis as Nanotechnology’s Moral Culmination (Edward Elgar, 2012).