Optimization, Upscaling, and Economic Feasibility of GBTL Technology

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Fast pyrolysis is a promising technology for the production of liquid fuels or bio-oil through thermal decomposition of biomass or municipal solid waste in the absence of oxygen. Bio-oil can be converted into hydrocarbons and has potential application in the transportation sector. However, converting bio-oil into usable fuels and chemicals remains a challenge. Bio-oil cannot be used directly without being upgraded because of its unwanted properties (e.g. high oxygen, acidic, and low energy). Traditional bio-oil upgrading usually involves extensive hydrotreating, which is energy intensive and costly.

ajay kumarDr. Ajay Kumar, Associate Professor of Biosystems and Agricultural Engineering at Oklahoma State University (OSU), together with two other OSU professors, Drs. Allen Apblett (Chemistry) and Francis Epplin (Agricultural Economics) demonstrated that natural Gas and Biomass to Liquids (GBTL) technology that utilized co-conversion of biomass and methane with metal-loaded HZSM-5 catalysts significantly improved aromatic hydrocarbon yield in the bio-oil.

Kumar’s team then leveraged results from their earlier GBTL study to make this novel technology ready for scale-up. The research team aimed to optimize key co-pyrolysis reaction conditions to maximize yield and selectivity of hydrocarbons and to determine production costs of liquid biofuel.

Kumar and co-workers used fixed bed and pyroprobe reactors to investigate the effects of methane, temperature, and catalyst in weight yield, energy recovery, chemical composition, and aromatic hydrocarbon yield of bio-oil from eastern red cedar and municipal solid waste.

“We achieved a maximum bio-oil yield of 53 wt% with an energy contact of 10 MJ/Kg and

56 wt% when we used methane over MoZn/HZSM-5 catalyst at 650oC and 750oC, respectively,” Kumar said. “This indicated that introduction of methane in catalytic pyrolysis of biomass improved the quality of bio-oil.”

“We also found that biochar yield increased when temperature was increased from 650oC to 750oC during pyrolysis,” Kumar added.

The research team also conducted an economic analysis that focused primarily on the availability and cost of eastern redcedar biomass that can be delivered to a biorefinery. A mixed integer programming was used to determine the optimal location for an eastern red cedar processing plant. The model produced solutions for several combinations of annual feedstock requirements, proportion of existing redcedar biomass in a county available for harvest, growth rate of unharvested trees, harvest cost transportation cost, and discount rate.

“In order to support a biomass processing facility with a capacity of 500 Mg/day of eastern red cedar, between 18% and 24% of the available eastern redcedar would need to be contracted for harvest over a 20-year period, with the difference in contracted percentage depending on the annual growth of redcedar,” Epplin said.

“The estimated cost to deliver eastern red cedar to the factory ranged from $44/Mg to $58/Mg depending on the proposition of eastern red cedar biomass under contract as well as the quantity of biomass required per day,” Epplin said.

Funding of this project was provided by the U.S. Department of Agriculture-National Institute of Food and Agriculture (USDA-NIFA) through the South Central Sun Grant Program.