Development, validation, and use of a spreadsheet-based tool for early-stage technoeconomic evaluation of industrial biotechnologies
This thesis begins with a technoeconomic analysis (TEA) of bio-based sorbic acid (SA). The initial TEA focused only on SA, and did not attempt generalizations. However the experience of building the SA TEA inspired development of a more general tool designed for early-stage TEA's of hybrid biological/chemical systems for producing bio-based chemicals, as proposed by the founders of the NSF Engineering Research Center for Biorenewable Chemicals (CBiRC). This early-stage TEA tool, named BioPET (Biorenewables Process Evaluation Tool), was designed for the purpose of conducting rapid early-stage economic analyses of these hybrid systems. BioPET was validated against a commercial economic analysis tool, SuperPro Designer®, and against published literature. BioPET was subsequently used to evaluate a recently developed pathway for bio-based styrene. BioPET fills a critical niche in the evolving bio-based chemicals industry. This is because there is a need for low-cost tools capable of early-stage estimations of the economics for novel bioprocess systems. Such a tool can provide valuable insight into nascent projects.
This thesis is prepared in paper format, and is comprised of three manuscripts, as follow: The first paper was an evaluation of the economics of bio-based sorbic acid production. Sorbic acid has a growing market in food preservatives mainly due to health concerns about benzoic acid, currently-used food and cosmetic preservative. While bio-based sorbic acid has reached proof-of-concept stage, little has been done to understand the costs of a commercial-scale process and the economic feasibility of such a venture. A spreadsheet model was created for the purpose of conducting this evaluation and understanding how critical biokinetic parameters influence the final estimated selling price. Based on current values of these parameters, we appear far from producing a product that can be sold at commercial scale. However, by assuming improvements in key parameters that reflect experience with other fermentative systems, bio-based sorbic acid becomes cost competitive with current petroleum-based sorbic acid. Production costs were most sensitive to those parameters governing the overall yield of sorbic acid in this process. In the long-term projection, primary costs were almost equally shared amongst feedstock, separation, and catalysis. Improving yields for this process will be required to make this process economically feasible, but also vital will be improving all kinetic parameters in order to achieve cost competitiveness.
The second paper explored the development of a robust but simple spreadsheet model (BioPET) to perform early-stage TEA of candidate processes for biorenewable chemical production. In the early-stage development of new technologies, a feasibility study or order-of-magnitude evaluation TEA is conducted to determine whether further development of that technology is warranted. With the number of new technologies and pathways being developed in the realm of industrial biotechnology, a tool that can provide a rapid estimation of a new technology has great value in delivering feedback to scientists and companies alike. Using basic inputs governing fermentation (e.g. productivity, titer, yield), separation (e.g. distribution coefficient, relative volatility, purity, yield), and catalysis (e.g. selectivity, conversion, type of catalyst), an estimate of a production price can be determined. This early-stage TEA tool was built in Microsoft Excel® and evaluated for accuracy and precision against SuperPro Designer® and the BREW project from the EU, using ethanol, succinic acid, and adipic acid as target chemicals. Processes were simulated as close to the BREW assumptions as possible. BioPET had accurate results against SuperPro Designer®, providing an R2 between the two tools of 0.9995. BioPET had minor deviances from BREW project projected selling prices of the evaluated chemicals, but the results were within the range of error for BioPET-derived estimates.
The third paper describes the application of BioPET to the evaluation of bio-based styrene. Bio-based styrene is a drop-in replacement chemical that remains in the early stages of development. Given basic knowledge of the properties of chemicals used in the process and general knowledge of the biokinetic limitations of the host organism, the styrene process was evaluated in BioPET at conservative commercial-scale values to evaluate the competitiveness of such a method of production. The results suggest bio-based styrene could be competitive with current petroleum-based prices at predicted selling price of 1.82 USD kg-1. A Monte Carlo analysis provided insight into the uncertainty of the process and estimated an the standard deviation to be ±0.44 USD kg-1. The majority of the cost of bio-based styrene arises out of the feedstock due to the small maximum yield of fermentation and relatively simple process design. While current production values might not yet be commercially feasible, values of bio-based styrene have potential to surpass the current petroleum-based styrene production. Additional research into the metabolic pathways governing biostyrene production will enable a reduction in the uncertainty of the cost estimate. At present, the BioPET results on bio-based styrene, and rising prices of petroleum-based styrene, suggest that bio-based styrene may well be cost-competitive in the future.