Wood-based bioenergy products — land or energy efficient?

Woody feedstocks will play an important role in meeting the total demand for biomass to generate electricity and produce ethanol in the United States. We analyzed 186 different scenarios (31 rotation ages (10 to 40 years in annual time steps); two types of forest management (intensive and nonintensive); and three feedstocks (logging residues only, pulpwood only, logging residues and pulpwood combined)) for ascertaining relative savings in greenhouse gas (GHG) emissions of two wood-based energy products (electricity and ethanol) on per unit land and per unit energy bases with respect to equivalent fossil fuel based energy products. Relative savings in GHG emissions were higher under intensive forest management compared with nonintensive forest management on a per unit land basis, whereas this situation reverses on a per unit energy basis. Combined use of pulpwood and logging residues saved the highest amount of GHG emissions on a per unit land basis, but on a per unit energy basis, relative GHG savings were similar to when only logging residues were used as a feedstock. Existing policies promoting bioenergy development in the United States only consider GHG savings on a per unit energy basis. A need exists to consider GHG savings on a per unit land basis as well to ensure efficient utilization of existing land resources to mitigate GHG emissions.