Here's a few biochar companies you might find interesting:

http://www.biocharsolutions.com/

https://www.biocarbontech.com/

http://blackcarbon.dk/

https://www.carboculture.com/

http://fullcirclebiochar.com/

(list is from AirMiners, index of companies mining carbon from the air, plus lots of other sequestration tech: http://airminers.org)