The article claims that they're making ethanol, not biodiesel (they compare their process to algae-generated biodiesel as the closest in terms of efficiency).

Given that, 20,000 gallons of ethanol x 76,100 BTU/gallon x .000293 kwh/BTU = 446,000 kwh, or about 6% efficiency. Could still be a scam, but more plausible.

All isotopes of plutonium are fissile, it's just that some of them are such strong neutron emitters that it's hard to make much of a bomb from them without predetonation sapping the yield, unless you've got a really good fusion boosted design. Some isotopes also give out a huge amount of heat due to spontaneous fission, making them unsuitable for bomb designs but great for RTGs, which is the real reason why NASA uses it: According to the Nuclear Weapons FAQ (http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2), Pu-238 generates 567 W/kg due to radioactive heating. The NWFAQ mentions that for RTG purposes Pu-238 is normally generated by neutron bombardment of Neptunium-237, not by buying it from the Russians. Weapons-grade plutonium has only a miniscule amount of the stuff, and even reactor-grade isn't very rich in it. It's also hard to separate out since the mass difference compared to Pu-239, which is the main isotope, is so small.