CO2 is produced by fermentation.
In ethanol plants, it is compressed and sold. When I played in that sphere, it was a very valuable side product.
We did NOT vent it. It was pure stuff as long as the fermenters worked well
Most modern ethanol plants do indeed vent CO2. Not many are located where CO2 is in demand
That’s why there’s a big scam on for CO2 pipelines, where CO2 will be ‘stored’ or ‘sequestered’.
For those who are unaware, corn fermentation yields roughly equal weight of ethanol, distiller grains animal feed, and CO2.