Veridium Corp has announced its patent-pending technology for the conversion of exhaust carbon dioxide from the fermentation stage of ethanol production facilities back into new ethanol and biodiesel. Veridium's bioreactor uses an iron-loving blue-green algae species discovered thriving in a hot stream at Yellowstone National Park. The Viridium BioStarch Recirculation System routes exhaust carbon dioxide from the fermentation stage of the ethanol production process through the bioreactor, where it is consumed by algae that are comprised of about 94% starch and about 6% oil. Presumably, the starch byproduct can be reclaimed for ethanol fermentation and the oil for biodiesel production. Veridium Corp is a subsidiary of GreenShift, which we've written about before.
For perspective and a bit of controversy on the broader ethanol plant CO2 emissions topic, we suggest you have a look at this blast from TreeHugger's recent past.