Solazyme vs OriginOil
Gevo vs Terrabon
Joule Unlimited vs Qteros
LS9 vs Novozymes
Separately, a post in the MIT Technology Review ends with the text:
However, in the end, cautions Mielenz, all biobutanol processes face the crucial challenge of requiring a switch from food sources such as corn, sugarcane or beets for their sugar feedstock to cellulosic biomass, which is more expensive to convert to fuels.