Keynote: Solar Hydrocarbons from Air Captured Carbon Dioxide and Water

The value of liquid hydrocarbons is hard to overestimate. If they did not already exist, they would need to be invented. Today, mining fossil carbon provides access to hydrocarbons for fuels and chemicals. However, there are other ways to produce liquid hydrocarbons. For steel, aluminum and many other metal resources, societies have long accepted the energy cost of reducing metal oxides or sulfides to metal. The energy requirements are often large. The oxygen in aluminum oxide is far more tightly bound than the oxygen in carbon dioxide. Electricity – often from renewable hydropower – is used to reduce aluminum oxide to aluminum. Renewable energy could also be used to reduce H₂O and CO₂. The resulting syngas would serve as the starting point for hydrocarbon synthesis. The cost of solar energy is now so low that raw photovoltaic energy is comparable in price to natural gas. Water is cheap, and the promise of direct air capture technologies is that the cost of CO₂ from air is not dominating the cost of fuel. Once it is affordable to capture CO₂ from the air for sequestration, it is equally affordable to capture it for new fuels. The biggest remaining challenge is intermittency. The high capital cost of energy conversion systems makes it impossible to use them only for short times in the day. Overcoming this problem will require a different approach to deploying capital. Small mass-produced systems come down learning curves with the promise of dramatic cost reductions. Solar photovoltaic energy is not the only example, but it is the posterchild for the energy transition. As air capture and electrolyzers or other energy conversion equipment comes down the learning curve, it becomes possible to operate a fuel synthesis infrastructure on low-cost power that is only available for hours in the day. On a power basis, the capital cost of mass-produced car engines is two orders of magnitude lower than that of a power plant. As a result, car owners won’t fret because the car stands idle most of the day.