Reply #2: offhand, I'm sceptical of that claim...

[mike_c]

...but I should hasten to add that I haven't read the ORNL report so I can't comment on their estimate or their assumptions. My skepticism stems from Jeffrey Dukes 2003 paper estimating that the annual global fossil fuel energy budget is "more than 400 times the net primary productivity of the planet’s current biota.” Assuming that ratio holds for the U.S. (which is a conservative assumption, IMO) suggests off the cuff that if the ORNL estimate is true, that means that 1/3 of our "fuel requirement" is still greater than 100 percent of the energy captured by ALL of the biomass in the U.S.

Dukes, J. S. 2003. Burning Buried Sunshine: Human Consumption Of Ancient Solar Energy. Climatic Change 61: 31-44