Conversion of Microalgae to Fuels or Fuel Components

Compared to land plants, algae have up to thirty times higher biomass productivity and, as autophotrophic organisms, have the ability to assimilate carbon dioxide in the growth phase and convert it into a broad spectrum of organic compounds. This makes microalgae interesting as a renewable raw material both for a sustainable energy industry and for the production of chemical products (e.g. dyes, polyunsaturated fatty acids). The aim is to develop a process for the production of drop-in-compatible fuels or fuel components from microalgae biomass.

The path proposed here envisages the use of the entire moist algal biomass. In the first step, the biomass is converted into a heavy oil-like "biocrude" in the presence of water under critical or near-critical conditions. In the process, a considerable proportion of the oxygen and nitrogen contained in the algae is already split off in the form of water, carbon dioxide and ammonia. Further refinement into high-grade fuels is carried out by hydrogenation processes and can in principle be integrated into existing refinery processes.

The project is based on the idea of producing a product that is basically suitable for further processing in a refinery and can optimally be fed into the system before crude oil distillation. The task is to coordinate and optimize the conditions of hydrothermal liquefaction and product upgrading in such a way that a crude oil-like product can be produced with the least possible effort (few process stages, low H2 requirement) and high yield, which is suitable for further processing in a crude oil refinery. To this end, it must be free of impurities (e.g. phosphorus, minerals, heavy metals), be capable of being evaporated as completely as possible under normal pressure and have a low residual content of hetero compounds. The project is divided into the investigations on hydrothermal liquefaction at the BTU Cottbus and the optimization of the biocrude upgrading carried out by the TU Bergakademie Freiberg.

The DGMK research report 777 is available. The project has been completed.