ZSW scientist prepares a thermogravimetric analysis, © ZSW

Carbon dioxide may be a greenhouse gas, but it can also be a raw material source in industries such as plastics processing and renewable energy generation, where it could gradually replace natural gas and crude oil. Capturing carbon dioxide directly from air provides several advantages for combatting climate change. While limiting the atmospheric concentration of CO₂, it offers new opportunities in the chemical industry and in transportation and could dramatically lower harmful emissions by cutting into fossil fuel demand.

The aim of a new German project, CORAL, is to use a demonstration system for researching and analyzing the viability of individual carbon capture methods. Coordinated by ZSW, the Center for Solar Energy and Hydrogen Research Baden-Württemberg, it has been joined by the University of Stuttgart’s Institute of Polymer Chemistry and Heidelberg’s Institute for Energy and Environmental Research.

So far, the raw materials for most chemical products – be they plastics, gasoline, diesel or kerosene – have been crude oil and natural gas. To meet international climate targets, fossil fuels will need to be replaced by renewables as soon as possible. One option is to employ power-to-gas or P2G^®. Through electrolysis, it creates hydrogen that can later be used in combination with CO₂ to synthesize hydrocarbons.

Please note that P2G^® has been trademarked by ZSW.

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Search for the most efficient solution

There have already been several methods available to extract carbon dioxide from air and use it to synthesize raw materials. The aim of CORAL is to determine the most efficient and inexpensive technique. The next step would be to build a demonstration system and test the selected method, showing that key chemical compounds, such as methanol, dimethyl ether and propylene, could be created based on nothing but renewable resources in the future.

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From CO₂ supply to waste heat recovery

The last point also serves to distinguish air capture from similar, but very energy-consuming methods for extracting CO₂. It is their power demand that won’t allow them to leave the R&D stage. ZSW’s experience with cost-benefit analyses dates to 2009, when a pilot plant was built to demonstrate successfully that concentrated CO₂ can be extracted from air to produce methane using electric energy as part of our P2G^® process. However, it was a very power-hungry system, creating a drawback that we aim to overcome by setting up a new demonstration plant. The key to improved efficiency will be power-to-x (P2X) generating a considerable amount of waste heat.

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Renewable transportation by P2X

The first stage of all P2X methods is water electrolysis, as hydrogen is used as the raw material source for all subsequent stages. Converting this hydrogen into CNG, LNG or another renewable, carbon-based energy carrier primarily requires carbon dioxide.

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Author: Dr. Ulrich Zuberbühler, Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)