A couple of data charts I like sharing on what is happening with the peak temperature used in forming biochar:
Both charts indicate that 500C (plus or minus) may be optimal for use in the soil. As a reference to how hot that is, that is the temperature where you'll first start to see objects begin to glow red.
The electron donor and receiver groups are both important for aiding soil bacteria to carry out their metabolism at a lower energy cost, helping them aid plants in putting on more growth and yield.