Cellulosic Ethanol: Are enzyme costs the last hurdle to cheap ethanol from switchgr, cattails,...?

It might be, but there are other concern. In California, the EPA was going after wineries for CO2 production. Fermentation of alcohol does produce CO2. That is why we have Champagne, Beer has head and bread rises. There is distribution concerns as well. Oil companies want to keep things as it is.