(235b) Economic and Environmental Potentials for Natural Gas to Enhance Biomass to Liquids Technologies

With the increased availability of low cost natural gas, co-conversion of natural gas with biomass (GBTL) is one of the promising routes  being investigated by the U.S. Department of Energy (DOE) [1], in order to increase liquid fuel yields while lowering greenhouse gas emission relative to petroleum. For example, Praxair has developed a natural gas enhanced biomass to liquids process that increases liquid fuel yield by 2.5 times versus the base case of straight biomass to liquids [2]. It is necessary to fully understand how the use of natural gas and biomass may be optimized and integrated into a hydrocarbon liquid fuel conversion process.  

The conceptual process design and cost comparison of liquid biofuel using both biomass derived biogas intermediate and natural gas have been studied in this work. This GBTL techno-economic analysis (TEA) provides baseline cost results comparable produce hydrocarbon liquid fuels as well as can be viewed as a near term deployment opportunity for renewable jet fuel production. This paper offers insights on the current understanding of techno-economic performance analysis associated with the GBTL conversion process. The GBTL process consists of the key process steps of gasification, gas conditioning, reforming, Fischer-Tropsch, separation processes and energy integration.  The associated Life Cycle Assessment is included to provide the insights of on the sustainability metrics for the liquid fuels production from GBTL technology. The quantification and assessment of the sustainable metrics associated with the GBTL conversion process will be discussed including life-cycle greenhouse gas (GHG) emissions and fossil energy consumption. Sensitivity analysis and uncertainty analysis will be analyzed and discussed to understand the uncertainties of process variations, as well as impact from the variations of biomass to natural gas ratios, design assumptions and natural gas prices on the economics. Technologies based on the GBTL concept offer opportunities in optimizing the usage of natural gas along with biomass. Therefore, different blending ratios of natural gas/biomass could have a large effect on the economic and environmental performance, which would be investigated though scenario analysis. In addition, different operating parameters could also have a significant impact on equipment design, raw materials, utilities consumption, and overall process economic performance for GBTL system. Monte Carlo analysis is performed to assess the probability distribution of the minimum fuel selling price (MFSP) in order to investigate potential interactions among parameters studied. The goal of the sensitivity analysis is to provide an understanding of key cost drivers with significant environmental impacts.

 Reference:

[1]          Bioenergy Technolgies Office, "The Potential for Natural Gas to Enhance Biomass Technologies," 2014. Available at:

http://energy.gov/sites/prod/files/2014/04/f14/february2014_gbtl_webinar...

[2]          S. Chakravarti, D. P. Bonaquist, R. F. Drnevich, and M. M. Shah, "Natural gas enhanced biomass to liquids: Project development and modeling," Computers & Chemical Engineering, vol. 47, pp. 67-75, 12/20/ 2012.