CELBICON – Cost-effective carbon dioxide conversion into chemicals

Initial situation and project goal

The recycling of the climate gas CO₂ as a carbon source is one of the main challenges of the 21^st century. The development of novel processes is of key importance to counterbalance the increasing CO₂ emissions and climate change [1]. Regenerative platform chemicals can be produced by integrating renewable energy in the operation of strategically important CO₂-neutral processes. Because of the geographical distribution of available regenerative energy and CO₂, the development of decentralized processes is of particular interest.

The EU project “Cost-effective CO₂ conversion into chemicals via combination of capture, ELectrochemical and BIochemical CONversion technologies – CELBICON” aims at the development of new CO₂-to-chemicals technologies by combining CO₂ capture, electrochemical CO₂ conversion into intermediates and fermentation of these intermediates into value-added chemicals. At the beginning of the project, the subsystems existed as individual technologies at a certain technology readiness level (TRL). During the CELBICON project, these technologies are to be further developed and integrated into a technology platform operated at TRL5. Key criteria for the developments are: (a) a modular and decentralized system, (b) high material and energy efficiency, (c) low investment and operating costs and (d) high robustness providing process variability.

Coupling electrochemistry and biotechnology in process cascades to convert CO₂ into value-added chemical products

The targeted process chain was first demonstrated on a laboratory scale.

Adsorption of CO₂ from air (direct air capture, DAC) is the first process step, achieved in a pilot plant provided by project partner Climeworks (Switzerland).

The captured CO₂ is then converted electrochemically into formic acid. For this step, Fraunhofer IGB has developed tin-based electrocatalysts and a phosphate-buffered electrolyte. The first conversion step involves electrochemical reduction of CO₂ to C₁ intermediates on the cathode, while wastewater treatment was chosen for the valorization of the anodic current.

The C₁ intermediates will be converted into higher-value chemicals such as lactic acid, isoprene and long-chain terpenes in an integrated fermentation process. In this way, the microorganisms used are optimized by tailor-made metabolic engineering aimed at efficient formation of the product and to support process performance.

Demonstration plant

During the last project year, the modules of the CELBICON plant were built and integrated into a single demonstration plant. For doing so, Fraunhofer IGB has designed and constructed the automated demonstration plant featuring an electrolytic cell from project partners Gaskatel (Germany) and Hysytech (Italy), in which the electrochemical conversion of CO₂ captured from air into formic acid could be tested in a relevant operational environment. Upon commissioning the demonstrator plant, process validation and optimization will be completed at the end of the project.

Summary

In the CELBICON project it was demonstrated that electrochemically generated formic acid can be applied as substrate in a fermentation process to yield a product from the terpenoid metabolism. A fed-batch process at 10 L scale has been developed, enabling promising biomass yields based on optimized operational parameters. Product purification was successfully established, and it was demonstrated that 14% of the fed formic acid can be converted into a terpenoid dye.

Literature

 [1] UNEP. (2017) The emissions gap report 2017. United Nations Environment Programme (UNEP), Nairobi.