Residue or Residon’t: Untapped Fuel Yields from the US Corn Production System

by Jim Lane (Biofuels Digest) Why not use the materials we don’t need, to produce the fuels we do need? ... (R)educe, re-use, recycle. Use what’s already there. And there’s nothing more powerful in the Imperial Department of Re-Use than sustainable agricultural residues.

In the US corn production system — which will produce some 14 billion bushels this year for feed, fuel and food products — there are two primary residues that are available and just starting to be utilized. There’s corn stover (including stalks and cobs — the residue left in the field after harvest), and there’s CO2 (produced by yeast fermentation of corn starch, in the same yeast-starch reaction that makes bread rise when it is baked).

“Our research and experience tells us at least 75 – 100 million sustainably harvestable tons across the 9 states,” said Pacific Ag Vice President Harrison Pettit.

Though bullish, Pettit cautions against thinking about corn stover as a no-brainer. “In many areas of the corn belt harvesting corn stover is a new practice that requires a sophisticated and relentless outreach program coupled with a very strong harvest service ethic and performance. Growers have to be shown the benefits and the perceived risks addressed.”

Back to the numbers: this translates to 6.75-9.00 billion gallons of ethanol-equivalent fuel at 90/gallons per ton.

According to this infographic from DuPont, the numbers could go even higher — they see as much as 375,000 tons per year in the “feasible” belt.

The yields of CO2 liquefaction projects at ethanol plants bring in around 3.67 pounds of CO2 per ethanol gallon produced. Another calculator run shows:

(We’ve taken the yields from Algenol’s system, which yields 144 gallons per ton of CO2 in the following ratio: 87% ethanol, 6% diesel, 4% gasoline, 3% jet fuel).

We’ve found 10.6-12.8 billion gallons of fuel. For Renewable Fuel Standard purposes, we need to convert the gasoline, diesel and jet gallonages (they have higher energy densities). That’s 10.9-13.2 billion gallons of ethanol-equivalent fuel.

Think about the organic fraction of muncipal solid waste (around 61 percent, according to the EPA, of the 164 million tons in landfills) — enough to produce another 7.5 billion gallons of ethanol-equivalent fuel at 75 gallons/ton. READ MORE