The subject of the DGMK project 777 was the scientific penetration of a two-stage process for the conversion of the entire moist algae biomass into high-quality fuels or fuel components. In the first stage, the moist biomass is thermochemically converted into a heavy oil-like product – the so-called biocrude (hydrothermal liquefaction). A large part of the heteroelements contained in the biomass is already eliminated in this step without the use of hydrogen. In the second stage, upgrading to applicable fuel components is carried out by hydrogenating processes (hydrotreating). In the project fundamental investigations were carried out on the influence of parameters on both stages as well as on the dependence of the product yield and properties after hydrotreating on the reaction conditions in hydrothermal liquefaction. The goal was the optimization of the overall process chain with regard to yield and quality of the products as well as hydrogen consumption. By using various methods of instrumental analysis, it was possible to characterize the very complexly composed starting materials and products in chemical terms comprehensively and to deepen the understanding about the reactions taking place. The investigations have shown that about one third of the algae biomass can be converted into almost heteroatom-free naphtha and middle distillate fractions. The energetic yield with regard to the energy chemically bound in the microalgae amounts to approximately 60 %, even when taking the required hydrogen supply into account. An economic analysis based on the experimental results showed that for a production plant (capacity 100 kt hydrogenated product per year) at a biomass price of 0.30 €/kg, which is considered realistic in the future, fuel could be produced at a price of less than 2 € per liter. These costs are in the same range as those currently being discussed for power-to-liquid technologies.
The IGF project (18209 BR) of the research association DGMK Deutsche Wissenschaftliche Gesellschaft für Erdöl, Erdgas und Kohle e.V., Überseering 40, 22297 Hamburg was funded by the Federal Ministry for Economic Affairs and Energy via the AiF within the framework of the programme for the promotion of joint industrial research (IGF) on the basis of a resolution of the German Bundestag.