Actually, the key line is:
“In this study, switchgrass managed as a bioenergy crop produced estimated ethanol yields per acre similar to those from corn grown in the same states and years based on statewide average grain yields.”
In other words: it is currently no better than corn PER ACRE. Which - when you look at the amount of acreage required to fill our energy needs... well...
Yes, it is, because per acre a lot less energy was used to produce the same amount of ethanol.