Design einer Demonstrationsanlage zur photoautotrophen PHB-Produktion

Increasing costs and limited amounts of fossil fuels as well as increased interest in sustainability lead to high efforts regarding the substitution of fossil resources as basic product for fuel or plastics. One approach of an alternative plastic production process is performed within the CO2USE project. Carbon dioxide from exhaust gases is used as carbon source for photoautotrophic biomass growth. Then the production of bio-based and biodegradable polyesters (polyhydroxybutyrate PHB), within the biomass is induced by nutrient limitation of the medium. As the residual biomass is fermented in a biogas plant and the nutrient rich, fluid extract from fermentation residues is recycled in the cultivation process, a resource-friendly and sustainable PHB-production process was developed. So far this process was carried out at laboratory scale, which leads to a lack of any economic data foundation. To increase the knowledge and receive indicators for relevant cost factors, the whole process was notionally up-scaled and results for this up-scaled demonstration plant were calculated. The simulation of the production process was performed with spreadsheet software and the use of circular references, important information was derived from literature and project data and an adaption of the annuity method was used to receive values for the PHB production costs as well as single cost factors of the plant. To allow a comparison of specific advantages and disadvantages of different cultivation systems, two plants with different cultivation systems were designed. The analysis of the results shows, that for all cost factors (investment, demand-related costs, operation-related costs, etc.) the open thin-layer cultivation system is advantageous to a tubular photobioreactor. Nevertheless the production costs for PHB are extremely high for both options and approximately two orders of magnitude higher than the costs for heterotrophic produced PHB. For future efforts in realizing photoautotrophic PHB-production the following success was accomplished with this work: cost factors with the highest influence could be identified and defined as important reference points for further work and improvements.