The International Energy Agency (IEA) admonishes that the only scenarios in their modelling software which avert catastrophic global temperature rise are those that include gasoline replacements made from biomass.
The cause of cellulosic ethanol has seen more defeats than victories over the past two decades. Ultimately it must prevail against vanishing fossil fuels, but at its present rate of implementation it will be too late for planet Earth. There is urgency in the need to get cellulosic ethanol back on the rails, but this is unlikely to happen without a quantum shift in economics.
While first generation ethanol has capital and operating costs on the order of $1.80/gal and $1.60/gal respectively, the corresponding numbers for cellulosic ethanol are in the order of $16.00/gal and $2.35/gal. Mere tweaking of existing processes is unlikely to bring the second generation costs in line with first generation and so win the confidence of financiers. It will require a new process.
A contender worthy of consideration is CARAF, an acronym for Concurrent Alcohol Removal And Fermentation. CARAF has been known since the 1970′s but never implemented at industrial scale for want of a separation technique. Pass-through Distillation (PTD) is a new separation technique that can fill that gap.