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Fueling ground transport with bio-fuels probably doesn't make long-term sense -- the economics for battery electric already look like they're better. Bio-fuels

by curtis 9y ago

Fueling ground transport with bio-fuels probably doesn't make long-term sense -- the economics for battery electric already look like they're better. Bio-fuels for jet aircraft may make long-term sense though, because aircraft are vastly more weight sensitive than ground transport. Even though jet aircraft individually consume a lot of fuel, the entire air transportation sector is only responsible for a relatively small fraction of overall petroleum usage (on the order of 5%, I think). Fueling the worlds entire transportation sector with bio-fuels just isn't practical. Fueling 5% of it with bio-fuels might well be, though -- in particular the 5% where battery-electric is just not going to be feasible. That doesn't mean the current soybean to diesel programs make sense, but instead of canceling them, maybe we should be modifying them to produce jet-compatible fuel instead.

stcredzero 9y ago
I was also once an advocate of bio-fuel for mobile size/weight restricted transportation applications. For a 5% minority, it seems to make sense. Soybeans to fuel doesn't make sense, however. For awhile, the cheapest biodiesel in Houston was made from animal slaughter byproducts. You had to watch out for the winter, however, as that stuff had a rather high gelling and solidification temperature. It also has very high hysteresis, so the melting temperature of the resulting wax-like substance can be much higher than the freezing temp, as high as 60 degrees F. I know, because it temporarily bricked my car, and ruined my relationship with my Mercedes mechanic. I don't think that stuff would be good for aviation. Maybe palm or algae derived?
- curtis 9y ago
  I know jet aircraft have been tested with bio-fuel of some sort, but I don't know how they handle the gelling problem. I'm kind of assuming that the fuel tanks would need to be heated to make it work. On the flip side, if you wanted to use ethanol then the low temperatures wouldn't be a problem, but the big trade-off there is ethanol has a much lower energy density per unit weight.
  - xyzzyz 9y ago
    Heated tanks are already a thing on ships, which burn fuel that is pretty much solid at room temperature, and need to be heated to even pump to the ship.
  - scythe 9y ago
    There are two ways to convert a fatty acid to a volatile fuel: you can convert it to an ester or an alkane. Biodiesel is comprised of esters; biokerosene is made of alkanes. Converting fats to biodiesel is a much simpler process, which is why biodiesel is common and biokerosene has yet to take off -- currently, biokerosene is made by hydrogenation, and hydrogen usually comes from fossil fuels. This is described here: https://www.researchgate.net/profile/Ulf_Neuling/publication/269290472_Conversion_routes_for_production_of_biokerosene-status_and_assessment/links/57ecd5b908ae92eb4d266cfc.pdf https://www.researchgate.net/profile/Ulf_Neuling/publication... The most land-efficient way to produce fats from crops is by far the palm oil fruit ( http://journeytoforever.org/biodiesel_yield.html http://journeytoforever.org/biodiesel_yield.html ), but because most cropland is already used for growing food, most palm oil plantations are on recently cleared forest, which gives palm oil an undeservedly bad reputation (farmers in Southeast Asia would simply grow something else on cleared forest if not for oil palms).

by curtis 9y ago

stcredzero 9y ago

I was also once an advocate of bio-fuel for mobile size/weight restricted transportation applications. For a 5% minority, it seems to make sense. Soybeans to fuel doesn't make sense, however. For awhile, the cheapest biodiesel in Houston was made from animal slaughter byproducts. You had to watch out for the winter, however, as that stuff had a rather high gelling and solidification temperature. It also has very high hysteresis, so the melting temperature of the resulting wax-like substance can be much higher than the freezing temp, as high as 60 degrees F. I know, because it temporarily bricked my car, and ruined my relationship with my Mercedes mechanic. I don't think that stuff would be good for aviation. Maybe palm or algae derived?

curtis 9y ago
I know jet aircraft have been tested with bio-fuel of some sort, but I don't know how they handle the gelling problem. I'm kind of assuming that the fuel tanks would need to be heated to make it work. On the flip side, if you wanted to use ethanol then the low temperatures wouldn't be a problem, but the big trade-off there is ethanol has a much lower energy density per unit weight.
- xyzzyz 9y ago
  Heated tanks are already a thing on ships, which burn fuel that is pretty much solid at room temperature, and need to be heated to even pump to the ship.
- scythe 9y ago
  There are two ways to convert a fatty acid to a volatile fuel: you can convert it to an ester or an alkane. Biodiesel is comprised of esters; biokerosene is made of alkanes. Converting fats to biodiesel is a much simpler process, which is why biodiesel is common and biokerosene has yet to take off -- currently, biokerosene is made by hydrogenation, and hydrogen usually comes from fossil fuels. This is described here: https://www.researchgate.net/profile/Ulf_Neuling/publication/269290472_Conversion_routes_for_production_of_biokerosene-status_and_assessment/links/57ecd5b908ae92eb4d266cfc.pdf https://www.researchgate.net/profile/Ulf_Neuling/publication... The most land-efficient way to produce fats from crops is by far the palm oil fruit ( http://journeytoforever.org/biodiesel_yield.html http://journeytoforever.org/biodiesel_yield.html ), but because most cropland is already used for growing food, most palm oil plantations are on recently cleared forest, which gives palm oil an undeservedly bad reputation (farmers in Southeast Asia would simply grow something else on cleared forest if not for oil palms).