(587a) A Comparison of Two Bioconversion Processes for the Production of Commercially Important C4 Streams

Four carbon compounds like 1,4-butanediol (1,4-BDO), succinic acid (SA) have been identified as platform chemicals for producing polymers from renewable resources. The successful commercialization of 1,3-propanediol by Dupont Tate & Lyle Bioproducts and 1,4-BDO by Genomatica Inc. has established the commercial viability of green chemicals. In this talk we present the techno-economic analyses to produce four-carbon compounds (C₄s) like 1,4-BDO, gamma butyrolactone (GBL), and tetrahydrofuran (THF) from dextrose through two separate routes - (i) single step bioconversion and (ii) hydrogenation of bio-based succinic acid (SA). In the single step bioconversion process for production of 1,4-BDO, capital cost of the bioconversion section was found to contribute to around 58 % of the installed equipment cost. Hydraulic load from bioconversion section and membrane filtration was found to contribute the most to operating cost. The process was found to be economically feasible with the minimum sales price (MSP) of 1,4-BDO of $1.82/kg as compared to a market price of $2.5/kg. A mechanical vapor recompression scheme used in the evaporator section was found to benefit the process, increasing energy efficiency and cost effectiveness. In comparison, the SA hydrogenation process, called the C₄s refinery, was not economically competitive given the current state of technological progress. The C₄s refinery produces 1,4-BDO, GBL, THF and ammonium sulfate (AS) fertilizer. The capital costs of the C₄s refinery were found to be 1.8 times higher while the operating costs were found to be 2.5 times higher. An important parameter is the SA fermentation titer. Increase in SA titer values to the maximum values reported in literature were not able to reduce the price of C₄s to below the market price, demonstrating the need for progress in this area. It was concluded that for an extended process involving hydrogenation of SA, additional increases in SA titer values and productivity by genetically modifying the relevant organisms will be required to achieve viability especially in comparison to the single step fermentation process for 1,4-BDO. A secondary reason for unfavorable economics was found to be the dependence of the C₄s refinery on thermal separations which contribute to significant operating and capital costs, technological progress in separation processes such as membranes for organic water separations is therefore necessary. Overall, given the published state of technology, the direct fermentation route produces C₄s (1,4-BDO) at $ 1.82/Kg and is economically viable while the C₄s refinery produces C₄s at $ 3.67/Kg and is not competitive with current production routes.