Creating Carbon-Negative Power

I read over the FAQ, seems interesting but kind of overcomplicated. The key principles (as I understand) are:

1. Source biomass that would have burned or decayed to atmosphere in a relatively short time without intervention, such as forestry or farming residues. This lets you say that any Carbon you don't release to the atmosphere is Carbon removal, but these materials tend to be difficult to consistently source and are energy-intensive to transport due to low density.

2. Use gasification to turn the hydrocarbon content into syngas, Hydrogen and Carbon Monoxide. Gasification is nice because you don't release pollutants like heavy metals as readily as regular combustion, and you can easily clean the gas of any pollutants that were released before burning it.

3. Combust the syngas with pure Oxygen in something that sounds like a rocket engine. Burning pure fuel and Oxygen creates much higher temperatures and efficiencies than when the Oxygen is diluted with "inert" gases, and you don't have to worry about NOx production.

4. Separate the water and CO2, leaving a pure supercritical CO2 exhaust stream. This is the part they seem most vague about, maybe centrifugal separation based on density?

5. Use a high-efficiency turbine to extract energy from the post-combustion supercritical CO2. They say this can power all of the other steps including the pure Oxygen production and still be energy-positive.

6. After extracting all possible energy, inject the resulting CO2 underground in rock formations of minerals rich in oxides that can both contain the CO2 and react with it to form carbonates, permanently storing it.

The biggest question marks for me are the process to burn the syngas and remove the water, whether the CO2 turbine will actually be energy-positive given all the energy costs, the energy costs of sourcing and transporting the biomass, and how well geological CO2 sequestration actually works (does the CO2 react with rock before leaking out into the air?).

My favorite CO2 removal concept is pyrolysis, which bakes material to release hydrocarbon gases and vapors which can be refined to replace petroleum or burned for energy, leaving behind Carbon-rich charcoal which doesn't easily break down. When sourced from biomass this charcoal can be a useful soil amendment for farms, or when sourced from waste that may have heavy metals or other toxic ingredients it can be landfilled with much higher density than the source material. It seems like the carbon sequestration of charcoal is much more proven than burying CO2 underground, and its a lot easier to site a waste-to-energy plant near a landfill than an appropriate rock deposit.