It sounds good, but what's the waste? obviously you don't take co2 and h2 out of seawater and get nothing left over.
Then, there's the question of input costs. if the $3-$6/gallon number works for all input costs, then that's pretty fun.
Then there's the question of time. If it's cheap and clean but still takes ages to make a single gallon, it'll not be utilized.
Now, show me a p51-mustang with an onboard cation system that can pick up seawater via ocean spray and maintain continuous flight, then I'll show you my geek O-face.