From their best case scenario, they can produce 25000 gallons per acre per year, which is 800 barrels a year.
Current world oil consumption ~80,000,000 bbl/day * 365 = 29.2 billion barrels per year.
29.2 billion bbl per year / 800 bbl per acre per year = 36.5 million acres of this biofuel to fulfill the world's needs.
36.5 million acres / 640 acres per square mile = 57031 square miles.
57031 square miles is roughly the size of Iowa.
US oil consumption is roughly 20,000,000 bbl/day, so that would be 14257 square miles set aside. Much more realistic - this is close to the area of Maryland.
If oil gets super expensive again (>$120/bbl) and stays there, this could definitely become a reality.