my comment referred to a choice between carbon tax vs. cap-and-trade for reducing emissions, which seems unrelated to ethanol credits.

I just think taxing coal/oil/natural gas as it's produced and sold, based on how much carbon it contains, is easy and effective, enforcing a carbon credit system is hard and prone to shenanigans, fraud, corruption.

Economically they're essentially the same and the shenanigans are a massive bug. But politically, shenanigans are a feature.