Going off grid

Short answer is wood is made from mostly two major components cellulose and lignin with some compounds that are given off while heating..Cellulose are the fibers that give wood its tensile strength and lignin is the glue that makes the fibers stiff. RFO is basically the lignin portion of the wood which has a higher Btu content than the cellulose. The lignin is then further processed to get RFO and the cellulose is burned to supply heat to drive the process. Its the opposite of a pulp mill. In a pulp mill they keep the cellulose and burn the lignin in a recovery boiler. Raw lignin is hard stuff to deal with, it turns into something that looks like taffy and eventually glass at high concentrations unless kept hot. If you have heard or seen glazed creosote you have seen crude lignin with the volatiles driven off. The problem is when its heated high enough it turns into a liquid and burns hot. My guess is its easier to deal with a liquid than a solid plus there is tax incentive called a RIN that can be sold for qualified liquid fuels.It replaces #4 fuel oil and requires special materials so I dont see it even being used for home use.