I should have pointed out that yours was a good idea to solve this problem. I was wondering though if that method would be enough to meet all of the demand. Thats why I posted what I did.
I doubt it, since you are limited to nutrient-rich places like sewage plants and farm runoff unless you want to either destroy a natural lake's ecosystem or have the wildlife eat most of the crop. But because of the fast growth it should produce more per acre than any other crop. Plant one acre and you get 1024 acres back in a month, minus one acre for re-planting. The stuff's a pretty thin layer on top of the pond, but that should still produce over 150,000 cubic feet of biomass per month (assuming less than a 1/20-inch layer).
Every little bit helps.