(455f) Process Design for the Synthesis of Biodiesel, Glycerol, 3-Hydroxypropionic Acid and 1,3-Propanediol

The current tendency towards the use of renewable biomass feedstocks instead of the use of non-renewable resources (for example, petroleum), has created the need for development of new, innovative production processes within the chemical and biochemical industries. Therefore, alternative solutions able to reduce the consumption of non-renewable resources and consequently minimize effects on climate change, waste, while, improving product yields, should be promoted. This replacement of petroleum with biomass as the primary material for fuel and chemical production is basically the idea behind the biorefinery concept.

This project is focusing on the ways that glycerol (an intermediate or by-product in a biorefinery) could be converted into value added platform chemicals so that its surplus production is not ending up as waste. The effective utilization of glycerol will ultimately contribute to the viability of biodiesel production since it will significantly lower its already high production cost. Thus, the design and development of a sustainable process to utilize this organic raw material becomes imperative.

The case of the simultaneous production of two platform chemicals with glycerol as a starting material has been investigated, namely of 3-hydroxypropionic acid (3HP) and 1,3-propanediol (1,3PDO). This process is part of a bigger one, where, by using vegetable oil as feedstock, the aim is to produce biodiesel. However, as glycerol is obtained as a by-product, it is then subjected to biotransformation with recombinant resting cells of Lactobacillus reuteri in an aqueous solution. The resting cells initially grow in the fermenter at 37^oC and then the biotransformation of glycerol is performed in a stirred-tank reactor. This biotransformation has 3 main products, 3-hydroxypropionic acid (3HP) and 1,3-propanediol (1,3PDO), that are of interest as well as significant amounts of 3-hydroxypropionaldehyde (3HPA) as by-product (that is not of interest and needs to be reduced).

L.reuteri is selected for biotransformation for several reasons, such as, it is a safe bacteria, has a great potential as a biocatalyst, and it cannot be used as a carbon source by glycerol, unlike other bacteria. Last but not the least, apart from 3HPA, no other by-products are formed during the bioconversion of glycerol by L.reuteri, thereby making the downstream process much simplified.

The goal of the project is to investigate the optimal production process towards 3HP and 1,3PDO simultaneously, in comparison to the existing methods that are oriented to the production of either only 3HP [Ramakrishnan Gopi et al.,2015] or only 1,3PDO [Nakamura and Whited, 2014]. The research is orientated towards a setup of the production process that produces equal amounts of the desired products, is economically and environmentally feasible and sustainable. In addition, the existence of significant amounts of the aldehyde by-product (3HPA) needs to be avoided. Two scenarios are investigated; one where 3HPA is isolated, purified and sold in the market as a by-product, and the other, where it is recycled back to the biotransformation reactor such that the production of 3HP and 1,3PDO are favoured.

According to the results regarding the production of 3HP and 1,3PDO, it is possible to determine the quantity of glycerol that needs to be allocated for the production 3HP and 1,3PDO and the remaining that will be allocated to the market. That is, the operation will depend on the function of the demand for glycerol, its current price, as well as the demands and prices of 3HP and 1,3PDO.

The presentation will provide the modelling and design details of the integrated process with a special focus on the increase of the atom efficiency of the processes involved, on the sustainability of the production process, the environmental impact versus the production and capital costs for different scenarios of product demand and price.