Sustainable biofuel production from organic waste via polyhydroxyalkanoates

Agroindustrial production processes are associated with the generation of enormous quantities of organic residues, often in a water diluted form. Effective valorization of these organic residues is of critical importance for the sustainability of agroindustrial production processes. Here we propose an innovative route for processing agroindustrial residues for the production of novel biofuels. The hybrid processing route proposed is based on two steps: In the first step a microbial ecology based biotechnological process is used to concentrate the water dissolved organic substrates in the form of intracellular storage polymers: polyhydroxyalkanoates (PHAs). This process has demonstrated to be capable of production of biomass that consists for 85-90% of PHAs, does not require aseptic conditions, and can be based on different types of ?waste? organic substrates. In the second step of the process, the PHAs are used for the chemical production of hydroxyalkanoate methyl esters (HAMEs). This esterification process has shown to yield HMEs with more than 95% purities, which can be used directly as fuel additives and have combustion heat values comparable to propanol and butanol. A major advantage of the HME production process is that it does not require highly purified PHA-based raw material, excluding the need for energy intensive PHA purification steps. For both steps in the HME production process a proof of principle has been established, but many questions remain to be answered to enable implementation of the process proposed. In this project Delft University of Technology will work on the influence of combinations of different substrates on the metabolic fluxes involved in PHA production and PHA-composition in a mixed microbial community. The relation between community stability and process stability will be evaluated. The objective of the work conducted at Tsinghua University is to optimize the HAME production process in terms of yields, solvent recovery, and upscaling. Both groups will work on the optimized process design and the interaction between e.g. PHA composition and fuel value.