Modelling and operation of reactors for enzymatic biodiesel production

In developing sustainable industrial processes, biochemical engineering, as a part of a broader field of chemical engineering is becoming an increasingly important as a tool in the chemical engineers toolbox. Its application is driven by consumer demand for new products and by industry wishing to increase profits while reducing operating cost, as well as meeting government and regulatory pressures for processes to be environmentally friendly and sustainable.

Current applications of biocatalysts, more specifically, enzymes for large scale bulk production of chemicals have been successfully applied to the production of high fructose corn syrup, upgrading of fats and oils and biodiesel production to name a few. Despite these examples of industrial enzymatic applications, it is still not “clear cut” how to implement biocatalyst in industry and how best to optimize the processes.

This is because the processing strategy is usually different to most traditional catalytic processes. In nature, enzymes operate at much lower substrate and product concentrations compared to most industrial chemical processes. What this means is that the natural conditions for biocatalysts are normally much different from conventional process-relevant conditions.

Also, the optimal process conditions can vary greatly from one biocatalyst to the next. Hence, to maximize product yields and reactor productivity then the type of reactor operation and downstream processing need to be able to address the aforementioned issues. One way to achieve this is through process modelling to help focus the experimental work needed for process understanding and to support further process development and optimization of the process.

To address how the reactors should be operated; a strategy using mechanistic modelling by combining the biological aspects of the enzyme with reaction/reactor engineering is performed. This strategy is applied to a case study of biodiesel production catalysed by a liquid enzyme formulation. The use of enzymes for biodiesel production is still in its infancy with non-optimized process designs.

Furthermore is it unclear how the process should be operated to ensure optimal economics given the relatively high cost of the enzyme and the low value of the products.