Long time since I've wielded a chainsaw...now I'm a CAD engineer,who Freeps too much ;-)
It has to be a very large operation to be economically viable. Any operation making wood biofuel would likely be large enough.
I've never been in large scale timber harvesting, i just think it's real cool. If I hit Powerball, I would probably start my own timber harvesting/land clearing business for fun and profit.