Piedmont Proves Out Liquid Enzyme Catalysis

Small North Carolina producer continues to innovate
By Ron Kotrba | February 28, 2012

The founder of Pittsboro, N.C.-based Piedmont Biofuels, Rachel Burton, gave details at the 2012 National Biodiesel Conference & Expo in Orlando on the company’s new commercially proven enzymatic transesterification process.

Last year at this time, Burton introduced Piedmont Biofuels’ FAeSTER process, an enzymatic pretreatment developed in collaboration with global enzyme maker Novozymes, to replace acid esterification. The FAeSTER process used immobilized enzymes, or enzymes fixed to a medium to esterify free fatty acids into biodiesel.

Now, the innovative team at Piedmont Biofuels has “switched gears,” as she said, and developed the first commercial-scale transesterification process using liquid, rather than immobilized, enzymes. The FAeSTER process still has its uses in Piedmont Biofuels’ new approach, however, but instead of it being used as a pretreatment step, it is now used as a fuel polishing procedure to convert FFAs in the biodiesel on the backend of the production cycle. Also, the feedstock can contain water with no issues, unlike when using chemical catalysts, which would cause soaps to form and loss of product yield.
During the same panel, Novozymes’ P.M. Nielsen discussed the same process, but instead of using enzymatic polishing, the company’s patent-pending BioFAME process uses a caustic wash to clean the fuel.

The liquid enzymes can be reused up to 10 times with 90 to 95 percent conversion rate. “The breakeven point is five or six uses,” Burton said. The liquid enzymes in the water/glycerin phase can be re-circulated back to the reactor, or they can be recovered through membrane filtration. The resulting glycerin is 97 percent pure, giving added value to the coproduct.

Burton said just a couple of weeks ago, Piedmont Biofuels scaled up to commercial volumes, 2,700 gallons in a coil-heated cone-bottom reactor. The feedstock was soy oil. After only six to eight hours of residence time, she said the results were “amazing”—less than 2 percent FFAs and the reaction was complete.

This, she said, proves that a 100 percent enzyme-converted fuel can meet ASTM quality specifications.

—Ron Kotrba

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