Your main point still stands, but aren't both of them renewable? Corn is a renewable resource, thus ethanol derived from it is too. It's just seemingly a much less efficient renewable fuel for powering a car compared to solar.
You're right. Perhaps clean would better capture the distinction in favor of solar in this context? Both corn and solar convert insolation to usable power with a short time between capture and use. Solar, on the other hand, is net negative when it comes to emissions, while the corn harvest is just burnt with the CO2 escaping back to the atmosphere. (And potentially, the solar panels can just be recycled back to new solar panels when they reach the end of their lifetimes. They're mostly aluminum and glass after all.)