The Obama version involves a huge tax grab; because the government would charge for the emission credits. It doesn't have to be that way — but, the tax grab is obviously what Obama really wants.
Meaning, they would be bought and sold among producers.
Thats a cost that gets passed to the rate payer, and its an opportunity for financial mischief that will make Oil for Food look like a kid's piggy bank, just like Oil for Food made Enron look like a kid's piggy bank.
Regardless it will have a huge economic impact because companies have to comply with the number of credits they are given and doing so will be VERY expensive even if the government gives them away. It is just a shell game.