Semi-continuous production of biodiesel on pilot scale via enzymatic hydroesterification of waste material: Process and economics considerations

Abstract

Nowadays, the use of edible oils with elevate purity in the biodiesel production represents around 70% of the chain of feedstocks applied in the process by the main producing countries at world level. This occurs due, mainly, to reaction limitations of the traditional alkaline route employed industrially. Bypassing drawbacks of the chemical process, enzymatic technique is an effective alternative for the biodiesel synthesis. In this sense, this paper reports results to semi-continuous production of biodiesel on pilot scale, from waste cooking oil, via hydroesterification mediated by different commercial lipases in liquid formulation: Eversa® Transform and its novel thermostable successor Eversa® Transform 2.0. Data for yields, residual acidity, productivities, biocatalysts performance, kinetics and economic analysis are presented in this comprehensive research. Using the best reaction conditions found (40 °C, 0.7 wt% of Eversa® Transform 2.0, 4.0 wt% of water, methanol to oil molar ratio of 6.3:1 and 8 h at a two-step reaction system), 96.2% of FAME yield was achieved. A pseudo-first order model presented a good fit of the experimental data, where a kApp of 0.373∙h−1 was obtained for the process with the best performance. Moreover, for this process, an economic analysis indicated the feasibility of the system through a positive net return and operating cost of US$ 0.50 kg−1 of biofuel. This information served as foundation to conclude that enzymatic hydroesterification catalyzed by liquid lipases has the necessary tools to be implemented on industrial biodiesel production.