[alkonaut]

Using foodstock, or land that even competes with foodstock, or land that is important for sensitive ecosystems or CO2 balance is obviously all out of the question if this technology is to be viable.

It's possible to make sustainable jet fuel using trees from forests that aren't competing with food supply. Without that, yes, it's a bad idea. Anything involving soy or palm is usually also a bad sign. But in principle, nothing says you can't use "good" raw materials to produce fuel.

[ya_throw]

Arguably the Amazon rainforest isn't competing with food supply, at least on a global scale.

The UK has only just started reversing the almost complete deforestation it experienced due to human demand for fuel and materials. Once you start adding in calculations for "how sustainable is my product, once I've cut the trees down and have to wait for the forest to re-grow", you find that not much is sustainable at all.