A comparative analysis of net energy from woody biomass

Energy inputs are compared with biomass energy output for several sawtimber and woody biomass programs covering rotation ages from 2 to 120 yr. A consistent comparision with several published studies supports the hypothesis that the energy ratio ER (i.e. the ratio of energy out to energy in) increases with increasing rotation age. For example, ER without fertilization and artificial drying increases from about 10–23 at rotation ages 30 yr. Furthermore, it is shown that large changes in ER often produce negligible changes in the ratio of net-to-gross energy NG. Without fertilization and artificial drying, NG is always >0.87. However, if fertilization and artificial drying are used, NG may be as low as 0.60.