Making Biogas a CO2 Sink Using Carbon Mineralization

In order to reduce carbon emissions, lots of research has been conducted in the field of carbon capture and storage technologies.

Thereby the focus is mainly on technologies in which carbon dioxide is sequestrated and pressed into depleted oil fields, unmineable coal seams or saline aquifers. What all these technologies have in common is that they are energy-intensive and reduce the efficiency of fossil fired power plants. Also these technologies include long-term monitoring, verification, permanence and other unknown side effects and potential risks.

But there is another possibility of carbon capture, so far not so much in focus: Carbon mineralization processes use alkaline earth metals to capture and store carbon dioxide in the form of ecofriendly carbonates. The advantage of a solid reaction product makes liquefaction as well as the search for secure storage location unnecessary. Carbon dioxide is stored environmentally compatible and is stable long term. These are only some advantages of this alternative process.

The herewith introduced research project has the goal to use alkaline earth metals from combustion ashes like calcium and magnesium to upgrade biogas to natural gas level.

At the same time, calcium carbonate shall be separated as a recyclable material and process water pollution shall be reduced. Therefore a test field concept was developed and realized.

The carbon mineralization process is conducted as described and accelerated in a packed column. In this test field separating and storing carbon dioxide from continuous simulated biogas volume flows up to 5Nm³/h are possible.

The research includes an investigation of balance of test parameters in order to find the optimum of the upgrading process.

Additionally research in the field of heavy metal reduction from the process water was done using hydrogen sulfide from simulated biogas. The idea is to find the best environment for lead sulfide reaction. Thereby heavy metal pollution in ash and process water but also the hydrogen sulfide content in biogas is reduced.

The research project is part of the interdisciplinary Boysen-TU Dresden-research training group. In twelve projects from engineering and social science junior scientists are working and collaborating on sustainable energy systems. Future research collaboration in the field of economics, political and communication studies are planed.