Originally Posted by
Mesabah
I highly doubt that biofuel catches on, the international market for these fuels will ultimately lead to bulldozing the rain forest, as that is the lowest cost "farm" on Earth.
All of the current biofuel projects (aviation and otherwise) have dropped all feed sources which might have other environmental or social impacts. Not only do they not use foodstock, they are also avoiding plants which would utilize land which would normally (or could be) used for food.
They are focusing on plants which would grow in environments normally unsuitable for agriculture and currently not cultivated... deserts for the most part.
Another feedstock concept is algea grown in a liquid... greatly simplifies harvesting/handling of the feedstock, as the liquid can be pumped around as needed and the outside environment/soil doesn't matter as long as it's sunny.
Also waste mass (ag, industrial, garbage) is going to be a feedstock source as well.
Most of the technical challenges are resolved, I'm actually quite impressed with the progress, ten years ago I didn't think they could develop a cost effective Jet A replacement. The only thing really missing now is economy of scale. There is a big gap to bridge there, but regulatory/social pressure might dictate the use of (initially) more expensive bio fuel even if Jet A is somewhat cheaper.
Originally Posted by
Mesabah
Liquefied natural gas is the biggest cost saver of the bunch, but the tanks become gigantic bombs, that I personally would not go near. If a ramper ran a cart into an external tank, the entire airport would likely be destroyed.
It's not about cost anymore. LNG is not carbon neutral or even close to it.
It's energy density is significantly lower than Jet A, so it would require about 50% more fuel volume, and associated structural weight, which you then have to haul up to the flight levels every leg... net result even more fuel burn and carbon.
You'd need clean-sheet designs, for larger tanks and different fuel systems (turbine engines can burn anything with minor tweaks, peanut butter has been demonstrated as turbine fuel, with powerful fuel pumps of course).
But I do agree LNG is far too flammable as well, while kerosene is actually hard to light on fire unless it's atomized or vaporized.
Originally Posted by
Mesabah
However, and here is the big issue, the price of Jet A will crater once any alternative technology takes hold, resulting in sticking with Jet A. We will see fully autonomous aircraft before any of those replace Kerosene.
Regulatory or social mandates/pressure will drive the need to lower carbon emissions (other emissions will still be a factor too). Bio fuel is about the only way to do that, since it's zero net carbon except for production and distribution overhead (which could also be near zero carbon if the grid is nuclear, solar, hydro).
Also huge advantage that it's a drop in replacement (at least up to 50%, probably good to 80%) for Jet A. Any other fuel/power scheme will require clean-sheet designs.