Why are they focusing on making bio-oil to throw away instead of biochar that has many known non-fuel uses? https://en.wikipedia.org/wiki/Biochar#Applications

Nice!

There's been a proposal to bury them not-so-deep, but saturated with salt to prevent decomposition. It's not necessary to sequester the carbon forever, just on a time scale for natural absorption of the CO2 into oceans and then into carbonates (which is something like 100,000 years, IIRC).

So that someone in the future can discover these reserves and use it as fuel?!?!!?!

No, by then it's at least conceivable that cold fusion will by then be a reality. If an individual cracks this problem maybe they'll offer a paper ending with a comment akin to Watson & Cricks 1953 paper on DNA. "It has not escaped our attention that ..." Or words to that effect.

https://www.youtube.com/watch?v=PGgovWTBoWY (Hossenfelder) https://lenr-canr.org/ (Library)

It's wonderful how pseudoscience is a renewable resource. Ghosts, then ESP, then pyramid power, and now cold fusion.

https://www.livingcarbon.com - they actually genetically engineered trees to grow faster.

Biochar is exactly doing that and is an active area of research in many places. There is several ongoing projects also showing that biochar can improve soil quality and crop yields.