How is ethylene made from microalgae

Plastics from the wood and algae refinery

Renewable raw materials are now more of a topic of discussion than energy sources. Pure incineration would actually be a waste compared to material use. A biorefinery is now being built in the Leuna Chemical Park, in which biomass components are to be converted into raw materials for the chemical industry on a large-scale in the future.

"The new Fraunhofer Center for Chemical-Biotechnological Processes CBP closes a gap between laboratory and industry, we will be able to use bioreactors with a volume of up to 10,000 l here," says Prof. Thomas Hirth, head of the Fraunhofer Institute for Interfaces - and Bioprocess Engineering IGB, to which the CBP will be connected.

The aim of the research is to transfer the processes, which have so far only been tested on a laboratory scale, into industry: In three to five years, chemical raw materials such as ethylene, olefins and aromatics as well as technical gases and enzymes are to be produced from wood, algae or vegetable oils.

"By using biomass as a material, we can make a very significant contribution to reducing CO2 emissions and also increase energy and resource efficiency," Hirth assured VDI nachrichten. In addition, parts of the crude oil would be replaced, whereby the biomass used is generally not suitable for food or feed use.

More than € 45 million will flow into the new research center by the time it is completed in 2012, the majority of which will be used for technical equipment such as fermenters and continuous systems that can work at process pressures of up to 250 bar and temperatures of up to 750 ° C.

Around 30 partners from industry and research are already involved in the projects of the new center. For example, a subsidiary of the Linde Group acts as the general contractor for the engineering of the process engineering units. “As an open platform, we will also take up other projects,” promised Hirth.

The digestion of lignocellulose from wood is already being researched, whereby - unlike in the paper industry - not only one component is to be used as a material. “At first, only cellulose was of interest in papermaking. Lignin, glucose and xylose are used thermally to generate process heat, ”reported project manager Gerd Unkelbach.

But what sounded very efficient at first is by no means: For example, phenols can be obtained from the previously burned components, which, according to Unkelbach, bring in around four times more than the use of other energy sources would cost.

In the case of wood and straw, the individual building blocks can be broken down in such a way that they can then be used as bio-based synthetic building blocks and polymers or processed into plastics. The favorites are hardwoods - and especially beech, for whose wood there is otherwise only a comparatively low demand.

The starting materials - wood chips, bark, shavings or small wood - are not digested in the CBP with sodium compounds, but with organic solvents at around 200 ° C and 20 bar. The carbohydrate fractions obtained serve as a carbon source for fermentations on a scale of up to 10 m3.

In the future, microalgae will also be a raw material from which plastics or technical enzymes can be manufactured. Katja Patzsch from Bioprocess Engineering at the IGB explains that the new research center will create a cultivation system for those types of microalgae that are characterized by their robustness and strong growth in volume. “It will look like a forest of large slabs with pipes running through them,” says Patzsch. In the slowly flowing, nutrient-rich water, the biomass thrives, which is processed relatively easily in the fermenter after the water has been withdrawn.

Andreas Hiltermann, Managing Director of the site development company Infra-Leuna GmbH, is currently particularly confident about the potential of biochemistry. “When high-pressure synthesis was first installed here on a large scale in 1920, it was a stronghold of technology. Today we will have to think about how we can gradually replace the main raw material in the petrochemical industry, and we want to be at the forefront again, ”said Hiltermann, who is one of the main initiators of the new research center.

Products made from renewable raw materials are currently certainly more expensive than oil-based ones, but that is not just a question of the quantities sold. “Customers will also be willing to pay a little more for an organic product, especially since it is usually about specialty chemicals,” Hiltermann is certain.

For him, using the processes from the biorefinery is the beginning of a rethink. Lignite is also to be used as a material in Leuna in the future. For this purpose, 13 partners from industry have already come together, whose funding has now been approved by the Federal Ministry of Research. But that is “another goal than bringing the renewable raw materials into a refinery process,” says Hiltermann. M. SCHULZE

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