Sequestration remains an open problem. There are no large scale biomass capture projects in operation. But the science isn't hard: you bury it, basically. Or if you want to be fancy you burn it for biomass energy and capture the resulting CO2 for fancier sequestration techniques. Both are expensive, and no one is willing to foot the bill.

Right now the only realistic way to use photosynthesis to capture CO2 in a long term way is to plant a forest. There's some amount of this going on, though not enough to even cover deforestation elsewhere.