Robert Rapier writes: Despite optimistic federal mandates that required the addition of advanced biofuels to the fuel supply, commercialization has been slow to develop. Ethanol produced from cellulose was initially envisioned as a likely candidate for making a major contribution to the mandates, but project delays, overruns, and bankruptcy in the case of the first company to produce a qualifying batch of cellulosic ethanol have all tempered the initial enthusiasm. A different pathway called fast pyrolysis that results in drop-in fuels as the final product after upgrading has emerged as a contender, but this pathway has also struggled to gain a foothold.  The Future of Biofuels