I've stated before that for aquaculture to really become useful the mind set needs to change from raising fish to raising fish food, similar to graziers who call themselves grass farmers though their product is meat and milk. But that may not be the real end product.

“Shrimp farmers don’t raise shrimp, they raise algae,” Gary Wood, owner of Desert Sweet Shrimp, explained to Red Orbit. But there’s more to making biodiesel than simply growing algae. Wood is still experimenting to see what strain of algae will work best. While over a dozen startups have raised millions of dollars to perfect their algae production and squeezing methods, Desert Sweet doesn’t appear to have raised a lot of venture capital. The company is just using its shrimp husbandry know-how to help grow its feedstock for its new line of business.

Desert Sweet hopes to be able to produce biodiesel for $3 a gallon from its 50 aquaculture ponds. Located in Gila Bend, Ariz., warm nights and plentiful sunshine should allow rapid algae growth, enough to produce 5,000 gallons of biofuel per acre in two years, the company hopes.

Similarly, good grass farmers may at some point be motivated to sell their grasses to fuel producers. It isn't a straight forward swap though since grass production volume is intimately related to grazing pressure, and the costs of harvesting and fertilization would decrease the net benefit of grass growth. If the price is right . . .