In the drive to create a zero-carbon economy by the middle of the century, multiple engineering solutions for replacing fossil fuels are in development. Power generation through wind, solar, nuclear, geothermal and other carbon-free technologies are on the rise. But transportation, particularly air transportation, is a much more difficult problem to solve with alternates. Aviation is driven primarily by jet fuel, essentially kerosene, a simple fossil fuel easily made from crude oil by vacuum distillation and catalytic cracking. When burned at high temperatures in efficient engines, it has all the hallmarks of a great fuel: easy to handle, energy dense, cheap and safe. The production of CO2, however, is inevitable in any combustion process. In jet engines, there is no way to sequester that carbon dioxide stream, as there can be in ground-based power systems. Sustainable aviation fuel promises to remove 80 percent of fossil-fuel-created greenhouse gases by formulating jet fuel from non-petroleum base stocks.Want to watch this podcast as a video? This Week in Engineering is available on engineering.com TV along with all of our other shows such as End of the Line, Designing the Future, and, Manufacturing the Future.