So now we've got news of a bacterium that can digest seaweed and turn it directly into ethanol. That is a potential gamebreaker.
Seaweed study fuels bioenergy enthusiasm
"When the team fed alginate to their engineered E. coli, the microbes pumped out ethanol, the researchers report in the Jan. 20 Science. The system yields 80 percent of the theoretical maximum amount of ethanol for a given amount of biomass, the scientists noted, and with further tweaking will probably be even more efficient."Stunner.
Add more widespread deployment of nuclear power for domestic and industrial energy use, and then we might have something workable.