New Scientist has an article on biotech firm Joule’s upcoming ethanol production biofuel plant.
Joule already has a pilot plant covering 0.8 hectares in Leander, Texas. On 5 May, the firm announced that it had secured 486 hectares in Lea County, New Mexico, for a plant to produce ethanol and diesel. The project may be scaled up to 2000 hectares.
With its engineered microbes, Joule claims to be able to produce ethanol at a rate of 93,000 litres per hectare per year, suggesting its New Mexico site will generate 45 million litres per year, rising to nearly 200 million litres if the site is expanded to 2000 hectares.
Some quick math reveals that 93,000 litres per hectare per year is about 6.1 Watts / square meter of energy capture. That is well beyond the < 1 Watt / m^2 of most conventional biofuels, and above even the 5 W / m^2 that is claimed for genetically engineered algae.
While that is far less than the 40 Watts / m^2 that a solar PV installation should be able to capture in New Mexico, it is not at all bad. At 6 W/m^2, it would take on the order of 1 million square kilometers to produce as much liquid fuels to replace all of the world’s current oil production.
1 million square kilometers sounds like a large area, but it is about 0.6% of the world’s land area (148 million square kilometers), or around 2% of the land currently used for farming around the world (around 50 million square kilometers). Nor would biofuel production necessarily compete with agricultural land – deserts are perfect places for biofuels.
If biofuel techniques can actually produce 5-6 W / m^2 and can be scaled to large areas, then it is certainly viable on a planetary scale to gather enough energy via biofuels to replace oil.