The energy return on investment for firewood includes what you spend cutting and splitting it. However, after some rest and a good meal it's 100 percent renewable!
These bars represent the estimated maximum energy return on investment of both renewables and fossil fuels. Oil's ratio has declined over time with the increased difficulty of bringing it to consumers. Note its EROI value in 1930, 1970, 2000, and 2005.
SOURCE: CHARLES A. S. HALL AND JOHN W. DAY JR./AMERICAN SCIENTIST, GRAPH: MATTHEW T. STALLBAUMER