The point of it is, this is a really cheap scrubber for stack emissions from power plants. And biodiesel is a byproduct.
First of all, you need to pre-scrub the emissions from such "beauties" as SO2, GeO2, As2O3 and particulates, or they will poison your pond faster than you could sneeze. [They called it "filtration"]. Secondly, a coal-fired plant of medium size exhausts something like 3000 tons CO2 a day. To absorb that much you would need the biopond of half a square mile size or bigger[doable] plus quite a system for pumping and sparging the exhaust gases through that pond [also doable, but $$$]. Plus, bioponds STINK. Harvesting kudzu vines would be cheaper - you don't need to filter them out of the pond, they already are concentrated nuisance. Now, if we could convert kudzu into moonshine fuel...