|Liquid fuel and chemical production from sweet sorghum. Source: Amyris. Click to enlarge.|
Amyris, Inc. has successfully processed sweet sorghum hybrids from energy crop company Ceres, Inc. into renewable diesel in a US Department of Energy (DOE) funded biorefinery project. Amyris is presenting a summary of the results at the 34th Symposium on Biotechnology for Fuels and Chemicals in New Orleans, Louisiana.
The pilot-scale project use both free (soluble) sugars and biomass (cellulosic) sugars from Ceres’ sweet sorghum hybrids grown in Alabama, Florida, Hawaii, Louisiana and Tennessee. To process the soluble sugars that accumulate in the plants, the sorghum juice was first extracted from the stems and concentrated into sugar syrup by Ceres. The syrup was then processed by Amyris at its California pilot facility using its proprietary yeast fermentation system that converts plant sugars into its trademarked product, Biofene, a renewable hydrocarbon commonly known as farnesene. (Earlier post.)
The inedible plant fibers of the sweet sorghum provided an additional source of cellulosic sugars. The DOE’s National Renewable Energy Laboratory (NREL), at its Colorado pilot-scale biochemical conversion facility, converted the biomass from Ceres’ hybrids into cellulosic sugars, which Amyris subsequently fermented into renewable farnesene.
Farnesene is a 15-carbon isoprenoid hydrocarbon molecule that forms the basis for a wide range of products varying from specialty chemical applications to transportation fuels such as diesel. When used as a fuel precursor, farnesene can be hydrogenated to farnesane, which has a high cetane number (58). Amyris modifies farnesene to become renewable diesel.
Life-cycle analysis of Amyris Diesel production from sweet sorghum indicates Greenhouse Gas (GHG) emission reductions of greater than 80%.
Secondary products from the biorefinery project include lubricants, polymers and other petrochemical substitutes. These secondary products are derived from the same C15 fermentation intermediate (farnesene) as Amyris Renewable Diesel, providing opportunities to de-risk commercial production.
The joint evaluation project was funded in part by a US Department of Energy Integrated Biorefinery grant awarded to Amyris. The grant included a sub-contract award to Ceres.
We believe that sweet sorghum could be an important and complementary source of fermentable sugars as the U.S. expands the production of renewable biofuels and biochemicals through the use of non-food crops outside of prime cropland. As an energy crop, sweet sorghum is an impressive producer of low-cost, fermentable sugars. A second stream of sugars from the biomass would be highly compelling.—Spencer Swayze, Ceres director of business development
The results from these evaluations confirmed that the Amyris No Compromise renewable diesel production process performs well across different sugar sources. Ceres’ sweet sorghum hybrids produced sugars that yielded comparable levels of farnesene as sugarcane and other sugar sources Amyris has utilized. Sweet sorghum can provide timely feedstock flexibility with environmental benefits. We look forward to utilizing Ceres’ sweet sorghum in our commercial-scale production facilities.—Todd Pray, Amyris director of product management
As a dedicated energy crop, sweet sorghum has a number of advantages. It is fast-growing and can efficiently produce both large amounts of fermentable sugars and biomass. The plants require substantially less fertilizer than sugarcane, and can be grown in drier areas since they utilize water more efficiently.
Ceres first commercialized its improved hybrids in Brazil this season. This spring, Ceres also introduced its first two hybrids to supply larger-scale evaluations in the United States. Ceres anticipates Florida and the Gulf Coast as well as California’s Imperial Valley, Arizona and Hawaii could be markets for sweet sorghum production.