The fatty acid ester butyl butyrate is a promising substitute for diesel and jet engine fuel, thus being relevant in energy supply for land-based and aviation transport. The building blocks of the ester, n-butanol and butyric acid, are important platform chemicals themselves and can be produced in biotechnological processes based on renewable sources such as lignocellulosic biomass, thereby addressing the transition from a petroleum-based to a sustainable energy supply. Butanol and butyric acid production in bioreactors is hampered by the common challenges associated with biofuel production, such as product inhibition, high downstream processing costs, and low yields. Whilst earlier work suggested a one-reactor system, the INDNOR project EcoLodge was based on three reactors, one for the production of butanol, one for butyric acid, in two separate but coupled continuous Clostridium fermentations, and a third reaction system for the enzymatic esterification. The product separation was done with electrophoreses-supported membranes. A significant increase in sugar-to-product yields was achieved, not at least through the simultaneous digestion of C5 and C6 sugars.
Following up on these achievements, the project NanoLodge targeted the highly ambitious integration of all three operations by applying dedicated membranes separating the different reactive systems, with the obvious expectation to further increase the yield whilst generating a highly integrated facility that can be upscaled to serve at large-scale operation. Though a full integration could not be accomplished during the course of the project, the consortium of Jadavpur University and the CSIR-Central Glass and Ceramic Research Institute from Kolkata, India, and SINTEF industry and NTNU in Trondheim, Norway, accomplished functionalized bio-mimetic membranes that combine enzymatic esterification of butanol and butyric acid into butyl butyrate while efficiently separating the ester product from the educts. The membranes were successfully tested on simultaneously microbially produced butanol and butyric acid containing medium as an excellent basis for a future complete process integration in possible follow-up projects. The NanoLodge project was also linked to the Norwegian FME Bio4Fuel and various EC projects targeting sustainable fuel production.
The NanoLodge project generated and applied new competence on nano-selective bio-mimetic membranes for use in the conversion og biobased chemcials into fuel ingredients like butyl butyrate, e.g., as integral component of a future highly intensified multi-stage reactor system with increased bio-feed-to-product yield to the level where the operation becomes economically feasible or even competitive to the existing bio-fuel production facilities. Though the originally targeted degree of integration could not be accomplished in the frame of this project, the project has still made significant steps in the direction of this ultimate goal, e.g., by developing enzyme-polymeric membranes that efficiently and continuously synthesize and separate the product butyl butyrate from fermentation broth containing butanol and butyric acid. This represents a new component towards a more efficient production of biofuels and thus to reduce the CO2 footprint of transport, which currently still represents a major issue.
The fatty acid ester butyl butyrate is as a promising substitute for diesel and jet engine fuel, thus being of relevance in energy supply for both land-based and aviation transport. The building blocks of the ester, n-butanol and butyric acid, are important platform chemicals themselves and can be produced in biotechnological processes based on renewable sources such as lignocellulosic biomass, thereby addressing the transition from a petroleum-based to a sustainable energy supply.
The production of the butanol and butyric acid in bioreactors is hampered by the common challenges associated with biofuel production such as product inhibition and high downstream processing costs and low yields. Whilst earlier work suggested a one reactor system, the recently concluded INDNOR project EcoLodge was based on three reactors, one for the production of butanol, one for butyric acid, in two separate but coupled continuous Clostridium fermentations, and a third reaction system for the enzymatic esterification. The product separation was done with electrophoreses-supported membranes. A significant increase in sugar to product yields were achieved not at least through the simultaneous digestion of C5 and C6 sugars.
The project NanoLodge will now target integration of all three operations into one, with dedicated membranes separating the different reactive systems, with the obvious expectation to further increase the yield, whilst generating a highly integrated facility that can be upscaled to serve at large-scale operation. The project is a collaboration between Jadavpur University and the CSIR-Central Glass and Ceramic Research Institute (Kolkata, India), specialising in bio-reactors and membrane technology, and SINTEF industry with biotechnology, membrane technology and process technology groups involved, and NTNU adding in competence in process systems engineering. The project is linked to the Norwegian FME Bio4Fuel, but also various other ongoing EC projects.
