Yes, this is the problem with cellulosic ethanol as well. Right now, when we just discard corn husks and such, it seems like a no-brainer to use them as a free

Yes, this is the problem with cellulosic ethanol as well. Right now, when we just discard corn husks and such, it seems like a no-brainer to use them as a free input to an ethanol process. But if you actually scale it up you'll run out of source material pretty quickly.