3 ms·

Synthetic biology can do it better. Fix CO2 by growing sugar cane, turn sugar into jet fuel with genetically engineered yeast. https://www.total.com/media/news

Synthetic biology can do it better. Fix CO2 by growing sugar cane, turn sugar into jet fuel with genetically engineered yeast. https://www.total.com/media/news/press-releases/total-and-amyris-renewable-jet-fuel-ready-use-commercial-aviation https://www.total.com/media/news/press-releases/total-and-am... Still not commercially viable, but much closer to it than the linked process.

tonyedgecombe 6y ago
Can we scale that up enough to cover all our air travel?
- freemint 6y ago
  Yeah but only using lots of land (more than it would require to run a solar powered electrified transport system) or using lots of energy and money (conservative guesstimate 50% of world GDP where air travel account for ~2% of CO2e emissions).
dreamcompiler 6y ago
That approach requires lots of land, water, and time. Nothing wrong with that, but much of the funding for CO2->jet fuel research comes from the military, which wants to be able to create liquid fuel quickly from CO2 in the atmosphere and they don't care how inefficient it is. Military customers are typically not very interested in processes that require running a farm.
- iguy 6y ago
  The military also spends a lot of time turning jet fuel into electricity, because the former is energy-dense, easy to store, easy to transport. And they need electricity in lots of places without a grid. Where would the reverse be useful? Somehow you have unlimited electricity but no fuel, and you have time and space to run a chemical refinery? (And isn't carbon capture from the atmosphere likely to require farm-scale infrastructure anyway?)
  - dreamcompiler 6y ago
    You cannot run aircraft on electricity; liquid fuel is the only option. The military is keenly interested in being able to refuel aircraft in situations where liquid fuel shipments might be denied or unavailable for some reason.
    - westurner 6y ago
      You can run aircraft on electricity. Locomotives run on electrical energy produced by diesel generators (because electric motors are more energy efficient), for example. The limits are the cost and weight of the batteries and the charge time.
      - dreamcompiler 6y ago
        You can't in any practical sense. Locomotives don't have a problem carrying the weight of a diesel engine plus a generator; in fact the extra weight works in their favor. If you tried that trick with an airplane it would never get off the ground. Locomotives use this system not for efficiency but because they need the low-end torque electric motors provide. (If they only needed efficiency they'd just drive the wheels with the diesel engine directly.) Airplanes don't need torque; they need power. You can run an airplane on batteries but only for a few minutes with modern battery technology. Practical battery-powered aircraft for military applications are not going to happen any time soon. We might see battery-powered air taxis soon but those are not even close to meeting military requirements for fighters, transports, etc.
        westurner 6y ago
        From https://en.wikipedia.org/wiki/Electric_aircraft https://en.wikipedia.org/wiki/Electric_aircraft : > [For] large passenger aircraft, an improvement of the energy density by a factor 20 compared to li-ion batteries would be required The time it takes to surpass this energy density threshold is affected by battery tech investments; which had been comparatively paltry in terms of defense spending. Trillions on batteries would've been a much better investment; with ROI. Sadly, some folks in defense still can't understand why non-oil investments in battery tech are best for all. There are multiple electric trainer aircraft with flight times over an hour and quite a few more in development. Jet engines are terribly inefficient (30-50% efficient) compared to electric motors.

tonyedgecombe 6y ago

Can we scale that up enough to cover all our air travel?

freemint 6y ago
Yeah but only using lots of land (more than it would require to run a solar powered electrified transport system) or using lots of energy and money (conservative guesstimate 50% of world GDP where air travel account for ~2% of CO2e emissions).

dreamcompiler 6y ago

That approach requires lots of land, water, and time. Nothing wrong with that, but much of the funding for CO2->jet fuel research comes from the military, which wants to be able to create liquid fuel quickly from CO2 in the atmosphere and they don't care how inefficient it is. Military customers are typically not very interested in processes that require running a farm.

iguy 6y ago
The military also spends a lot of time turning jet fuel into electricity, because the former is energy-dense, easy to store, easy to transport. And they need electricity in lots of places without a grid. Where would the reverse be useful? Somehow you have unlimited electricity but no fuel, and you have time and space to run a chemical refinery? (And isn't carbon capture from the atmosphere likely to require farm-scale infrastructure anyway?)
- dreamcompiler 6y ago
  You cannot run aircraft on electricity; liquid fuel is the only option. The military is keenly interested in being able to refuel aircraft in situations where liquid fuel shipments might be denied or unavailable for some reason.
  - westurner 6y ago
    You can run aircraft on electricity. Locomotives run on electrical energy produced by diesel generators (because electric motors are more energy efficient), for example. The limits are the cost and weight of the batteries and the charge time.
    - dreamcompiler 6y ago
      You can't in any practical sense. Locomotives don't have a problem carrying the weight of a diesel engine plus a generator; in fact the extra weight works in their favor. If you tried that trick with an airplane it would never get off the ground. Locomotives use this system not for efficiency but because they need the low-end torque electric motors provide. (If they only needed efficiency they'd just drive the wheels with the diesel engine directly.) Airplanes don't need torque; they need power. You can run an airplane on batteries but only for a few minutes with modern battery technology. Practical battery-powered aircraft for military applications are not going to happen any time soon. We might see battery-powered air taxis soon but those are not even close to meeting military requirements for fighters, transports, etc.
      - westurner 6y ago
        From https://en.wikipedia.org/wiki/Electric_aircraft https://en.wikipedia.org/wiki/Electric_aircraft : > [For] large passenger aircraft, an improvement of the energy density by a factor 20 compared to li-ion batteries would be required The time it takes to surpass this energy density threshold is affected by battery tech investments; which had been comparatively paltry in terms of defense spending. Trillions on batteries would've been a much better investment; with ROI. Sadly, some folks in defense still can't understand why non-oil investments in battery tech are best for all. There are multiple electric trainer aircraft with flight times over an hour and quite a few more in development. Jet engines are terribly inefficient (30-50% efficient) compared to electric motors.