Energy crop company Ceres, Inc. is working with CHOREN, a Biomass-to-Liquids (BTL) technology company, to optimize energy crops for thermochemical conversion to advanced low-carbon biofuels. The two-year bioenergy project is funded in part by a grant from the US Department of Energy. The thermochemical process does not require enzymes or microorganisms; instead, the biomass is gasified under certain heat and pressure conditions producing synthesis gas, a carbon monoxide and hydrogen-rich gas that can be converted into high quality synthetic fuels, intermediate chemicals or electricity.
In its role, Ceres will evaluate the composition of a broad range of switchgrass and willow plants, and provide biomass samples to CHOREN for thermochemical processing. The results will be used to identify the most relevant compositional traits, and later, to select the plants and traits that improve conversion and maximize fuel yields. Results of the study will also assist CHOREN in determining the location of its first commercial-scale BTL facility in the United States.
Chemical composition of grasses and woody crops varies considerably, even among different seed varieties of the same species. Through selective plant breeding and modern biology, therefore, the composition of energy crops can be optimized for greater thermochemical and economic efficiency. For instance, switchgrass biomass with lower amounts of sulfur or ash would be considerably less costly to convert into fuel.
Our goal here is to develop energy crop varieties specifically tailored to thermochemical processing. As with other conversion processes, improvements to the biomass itself—through higher tons per acre and higher convertibility—can have a tremendous impact on reducing costs.—Anna Rath, Ceres vice president of commercial development
Feedstocks could represent up to 50% of the cost of producing transportation fuels.
Fine-tuning feedstocks will contribute greatly to process economics, enhancing the quality of the synthesis gas mixture and reducing the capital costs associated with the downstream gas-cleaning operations. This type of lock-and-key approach between feedstocks and processing technology will be critical in the commercial scale-up of the advanced renewable fuel industry.—Christopher Peters, vice president of finance at CHOREN USA
In addition, Ceres and CHOREN plan to test commercial quantities of dedicated energy crops in a future collaboration effort at the world's first commercially operating Biomass to Liquids facility in Freiberg, Germany.
CHOREN’s Carbo-V process. The Carbo-V Process is a three-stage gasification process involving low temperature gasification; high temperature gasification; and endothermic entrained bed gasification. During the first stage of the process, the biomass (with a water content of 15 – 20%) is continually carbonized through partial oxidation (low temperature pyrolysis) with air or oxygen at temperatures between 400 and 500 °C, i.e. it is broken down into a gas containing tar (volatile parts) and solid carbon (char).
During the second stage of the process, the gas containing tar is post-oxidized hypostoichiometrically using air and/or oxygen in a combustion chamber operating above the melting point of the fuel’s ash to turn it into a hot gasification medium.
During the third stage of the process, the char is ground down into pulverized fuel and is blown into the hot gasification medium. The pulverized fuel and the gasification medium react endothermically in the gasification reactor and are converted into a raw synthesis gas for subsequent use as a combustible gas for generating electricity, steam and heat or as a synthesis gas for producing BTL fuels via Fischer-Tropsch (FT) synthesis.
Ceres ARPA-E Award. The US Department of Energy’s ARPA-E earlier awarded a $5-million research grant to Ceres to expand an advanced trait development project to increase biomass yields of several energy grasses by as much as 40% in coming years, while simultaneously decreasing the use of inputs such as nitrogen fertilizers. (Earlier post.)
Projections indicate that the Ceres traits alone could displace 1.3 billion barrels of oil and 58 million tons of coal over a ten year period. Depending on cropping practices, 1.2 million tons of nitrogen fertilizer could be eliminated (about the amount of nitrogen needed for 24 million acres of cotton), among other benefits.
The three-year project is expected to begin next month. Ceres researchers will test its advanced traits in a variety of energy grasses such as switchgrass, sorghum and miscanthus. Productivity and inputs requirements, such as fertilizer, will be evaluated as well as expected improvements to carbon and nitrogen cycles. Upon successful completion, the Ceres traits would undergo a customary evaluation by USDA prior to full commercialization.