Well, from the article you provided, spiritof1976:
"Biochar is different from the dry charcoal that you'd burn in a grill: It is produced by heating plant waste to 400 to 500 degrees C in the absence of oxygen—a process known as low-temperature pyrolysis—which makes a substance that has a greater number of smaller pores than charcoal. (The better to trap carbon dioxide with.) The process used to make biochar is a closed, sustainable one: Biomass is fed into the oxygen-free burners and turned into the char. The gases that are released during the reaction is then captured and converted into electricity (from combustible gases) or biofuel, while the remaining char is safe to throw directly into the soil. Biochar does the rest of the work underground. The substance improves the ground's composition and fertility by locking in water and nutrients, thereby reducing the need for fertilizers while boosting crop yields. It also stores the carbon from the plant materials that made it— around 50 percent of the carbon produced from converting biomass into biochar can be trapped—and traps even more carbon from decomposing plants in the soil."
It sounds like each step in the process of making biochar (which I only learned about just now, thanks!) is efficient. No oxygen used in burning means less C02 produced, correct? The gases released during the process are used, and the rest of the char then goes into the soil, where it helps hold water and nutrients. Then it works toward carbon sequestration, as it has a "greater number of smaller pores" than charcoal.
Sounds pretty good to me, but I'm no scientist
. I suppose the process where the gases are converted to electricity could be a little expensive, but Tanada or someone with expertise in this area could give an opinion about this.