By definition it isn’t carbon sequestration if the grams CO2 equivalent (gCO2e) isn’t negative after a full lifecycle study. Lifecycle studies are somewhat contentious as you might imagine since they try to encompass so much in one number, but generally studies agree that the major proposals are strongly negative.

You can read more about that here for a few of the more likely candidates. https://en.m.wikipedia.org/wiki/Carbon_sequestration#Geologic_carbon_sequestration