WARF: P170271US04

  • Patent applied for.

Production of Medium-Chain Fatty Acids from Biorefinery Residue


Timothy Donohue, Matthew Scarborough, Daniel Noguera

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing a method for converting the residue from lignocellulosic fuel (e.g., ethanol, isobutanol) production to valuable medium-chain fatty acids using an anaerobic microbiome.

The new method can be used to generate a product stream approximately 10 times more valuable than anaerobic digestion alone, and could reduce the minimum selling price of ethanol by 18 percent.
OVERVIEWWhen lignocellulosic biomass is used for ethanol or biofuel production, the resulting liquid residue (known as stillage) contains large amounts of organic material that may be further transformed into recoverable bioproducts. Lignocellulosic residue contains a high amount of chemical energy, approximately 100,000 mg/L as soluble chemical oxygen demand (sCOD). This amount of chemical energy, comparable to the amount recovered as ethanol or other fuel compounds, is in the form of unreacted polysaccharides and sugars, proteins and other complex plant materials not used by the alcohol-producing microorganisms.

In existing processes, lignocellulosic residue is often digested to produce biogas. Biogas is combusted in a combined heat and power generation process. A portion of the generated heat and power is used for operating facilities, and excess electricity can be sold. Alternatively, biogas can be converted to natural gas and injected into a natural gas pipeline. Given the high sCOD content of stillage, however, alternative uses are possible.

One route to potentially improve the economics of biorefining is to produce valuable co-products, such as medium-chain fatty acids (MCFA), from stillage. MCFAs are used in the production of rubbers, dyes, pharmaceuticals and antimicrobials. They also can be used as precursors for chemicals currently derived from fossil fuels.
THE INVENTIONUW–Madison researchers led by Profs. Daniel Noguera and Timothy Donohue have developed a method for converting unreacted chemical components in stillage to valuable medium-chain fatty acids, such as hexanoic and octanoic acids, using a mixture of microbes (e.g., anaerobic microbiome).

Operationally, a portion of the stillage stream is separated and fed to a bioreactor containing the mixture of microbes, which transforms a fraction of the stillage to MCFAs. The other fraction of the stillage can be sent on to the anaerobic digester to generate electricity (similar to existing biorefineries).
  • Production of value-added chemicals from stillage
  • Enables additional product stream
  • Improves operational economics
  • Does not detract from biogas production
STAGE OF DEVELOPMENTA technoeconomic analysis indicates that, based on MCFA production experimentally observed, if 16 percent of the sCOD remaining in stillage is converted to hexanoic acid and 1.7 percent is converted to octanoic acid, the minimal ethanol selling price could be reduced by 18 percent, from $2.15 gal to $1.76 gal.

Optimizations to microbiome MCFA productivities, MCFA extraction, solvent recovery and selection of ethanologenic organisms, or the modification of the microbes to produce other products may contribute to further improving the economics of biorefining.
Contact Information
For current licensing status, please contact Joshua Carson at or 608-960-9844.
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