Milling Energycane and Sweet Sorghum for Biofuels

7/3/2014 6:05:33 PM

Energycane going through mill at pilot plant.

ST. GABRIEL, La. -- LSU AgCenter scientists are researching efficient means for processing energycane and sweet sorghum for use in biofuels.

Milling tests were conducted on both energycane and sweet sorghum at the LSU AgCenter's pilot plant, located in the Audubon Sugar Institute. Dr. Donal Day, professor and project director for the Sustainable Bioproducts Initiative (SUBI), said tests such as these are being done to help benefit Louisiana agricultural producers who plan on growing crops for the biofuel industry.

"We're looking at how we can extract the most fermentable sugars and the most fiber from energycane and sweet sorghum for use in creating biofuels," Day said.

As the biofuel industry develops, Day said, "this will benefit Louisiana producers because they will, in turn, get more money for their crops."

Three 5-ton lots of sweet sorghum were milled in the tests. According to Day, both leaves and stalks were processed in two of the runs. The seed heads and leaves were removed from the plants for the third run. The researchers found the feed rate through the mill was low as there was not enough fiber in the plants, which resulted in the mill "choking."

Milling energycane produced the opposite results. Because of the high fiber content of energycane, increased power to the mill was required. The researchers also found the feed rate of energycane through the mill was also dependent on the variety of cane. Leaf removal was necessary to improve efficiency.

This initial process runs highlighted problems in the milling train that included a large loss of fiber, plugging of juice pumps over-preparation of sweet sorghum and poor juice extraction.

Actions that are being taken to overcome these issues include redesigning turn plates, changing carriers and adding protective screens, installing higher-power motors, installing metal belts to replace the rubber belts, and changing the design so that the knives are removable. The pilot plant will be operational for this processing season, which is August for sweet sorghum and September for energycane.

The pilot plant was constructed as part of a larger project funded by a five-year, $17.2 million grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture. Its focus is on processing sweet sorghum, energycane and other grassy feedstocks into convertible sugars, fiber and bioproducts for further refining into butanol, gasoline, isoprene and biochemicals.

"This is a research project," Day said. "It is a work in progress. We are learning as we go. We are constantly gaining new knowledge that will benefit Louisiana producers who grow or who will grow crops for use in the biofuel industry."

The SUBI project is a multidisciplinary regional consortium of agricultural scientists, biotechnologists, technology and engineering companies, economists and educators who are studying different aspects associated with conversion of energycane and sweet sorghum into a portfolio of biobased fuels and chemicals. Researchers in the project are studying how energycane and sweet sorghum can help reinvigorate the Louisiana sugar and chemical industries through new and existing industrial partnerships. Because the crops currently being studied grow in warmer climates, such as those found in south Louisiana, the researchers also are studying how to improve cold tolerance and production characteristics so that the crops can be grown in north Louisiana as well, which will produce a steady stream of biomass (fiber) to be converted to economically viable sugars using existing Louisiana refinery infrastructure.

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