By way of comparison, Cornell University’s David Pimentel, an authority on ethanol, says that one acre of corn produces less than half as much energy, equivalent to only 328 barrels. If a few hundred barrels of crude sounds modest, recall that millions of acres of prime U.S. farmland are now used to make corn ethanol.
A remarkable number, but as far as I can find Pimentel claims no such thing about BARRELS per acre, but I can find that number in GALLONS per acre per year, e.g., see http://healthandenergy.com/ethanol.htm. So 328 gallons of ethanol per acre = 7.8 barrels of ethanol per acre per year
Among his [Pimentel's] findings are:
An acre of U.S. corn yields about 7,110 pounds of corn for processing into 328 gallons of ethanol. But planting, growing and harvesting that much corn requires about 140 gallons of fossil fuels and costs $347 per acre, according to Pimentel’s analysis. Thus, even before corn is converted to ethanol, the feedstock costs $1.05 per gallon of ethanol.
Joule Unlimited's website does says "20,000 gallons of renewable ethanol or hydrocarbons per acre annually" ( http://www.jouleunlimited.com/news/2009/joule-biotechnologies-introduces-revolutionary-process-producing-renewable-transportation- )
So one thought has occurred to me. If this technology involves growing green gunk in vertical clear walled tanks, then perhaps they have chosen to talk about the yield per tank in terms of tank horizontal footprint, i.e the amount of light input coming in the side of 1 square foot of tank horizontal footprint could be many times the amount hitting just the top... I can imagine a tank fourteen feet tall, 3 feet wide, but only 4 inches deep. So its footprint is only 1 square foot, but it catches 30 square feet of light if at Boston's 42 degrees latitude (or heck, 60 feet if one reflects light in on the back side.)