Grayling Willer from Akron, Iowa has questions about proposed CO2 pipelines from ethanol plants:
“There have been CO2 pipeline projects proposed to go through our area, carrying CO2 from ethanol plants to underground storage- somewhere.
I thought the by-products of ethanol production were DDG, MWDG, and Syrup- all good, usable feed ingredients. I feel a little foolish to find there is one I didn’t know about, and they want to pump it far away for “storage”.
- Could this process be improving air quality but putting groundwater quality at risk?
- Why transport CO2 to “storage”? Can’t it be used or stored locally?
- Where is this CO2 going now without the pipeline?”
Great questions, but as I started working on the answers, I realized it couldn’t be done in three minutes. I’ll finish next week, maybe. Let’s look at how ethanol plants make carbon dioxide.
Here’s the big picture. Grind corn up, mix with water, cook it, add enzymes to turn the starches to simpler sugars, ferment the product, and distill it.
The carbon dioxide is produced during fermentation. Yeast, single celled organisms more like a fungus than animal or plant, consume the sugars and release CO2. It is this natural process that puts the bubbles in champagne and beer, and the holes in baked bread.
Using round numbers, the average ethanol plant generates about 150,000 metric tons per year. This is the stuff coming from fermentation and doesn’t include the CO2 from whatever fuel heats the mash. For comparison, a typical 500-Megawatt coal power plant emits 3.5 million tonnes, about 20 times more. Only 43 ethanol plants out of about 200 in the U.S. capture any CO2, so the rest vent to the atmosphere.
The industrial market for CO2 is about 30 mmt. The biggest use is for carbonation in beverages, but ethanol CO2 is not as pure as competing sources like ammonia plants for that market. The fastest growing use is Enhanced Oil Recovery (EOR) which helps squeeze out oil in wells with declining production. Ethanol is the largest supplier of the carbon dioxide market, but it’s not being produced where it’s needed in order to expand.
Next week, I’ll tackle CO2 storage, transportation, and economics.
