Are you out west? Some of the best wood to burn in the northeast is white ash and red oak, red oak needs two seasons to dry correctly, white ash has the lowest moisture content of good burning woods when green and will be ready after one season, the most readily avaiable wood here in Maine is red maple and that works pretty well. If your OWB is a gasification type(like mine) then you must burn dry wood, 6" round logs are perfect. If it is the old style single burn type, people do burn larger wood with more moisture in them, you will get much more smoke.But it is silly to burn green wood because you will burn a lot more of it because the heat is first used to boil off water from the wood then you get the extra heat.