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Keeping Tabs on Biogas Yields

Steinbeis develops biomass carousel as part of ZIM project

When biomass ferments, it produces biogas. Until now, determining biogas yields resulting from fermentation has involved a great deal of manual effort and time. Biogas yields were ascertained by hand using batch tests under VDI 4630 guidelines and DIN standard 38414-8. The Steinbeis Innovation Center for System Solutions in Measuring and Automation Technology has been working with the ATRES Group from the Bavarian city of Freising as part of a ZIM project to co-develop a biomass carousel for automatically measuring biogas yields.

Batch tests are used to assess the anaerobic degradability, the rate of degrading, and the degradability properties of organic liquids and solids, also testing for the quality and quantity of specific biogas yields. The results of tests are used for planning, monitoring, and documenting yields for third parties such as government departments who issue authorizations.

The team of experts working on the ZIM project developed an automatic measurement system in the form of a carousel. The device can hold up to 48 fermentation vials making it possible to measure the biogas production of biomass. The specialists at the Steinbeis Innovation Center for System Solutions in Measuring and Automation Technology were responsible for the design and engineering aspects of the project as well as the automation components.

Measurements are taken automatically by filling fermentation vials with biomass and heating them in a basin of water. An eudiometer (a device that

CAD model of a biomass carousel

measures gas volume) is connected to each vial with a glass tube for capturing emitted biogas. At the center of the carousel is a rotating arm with a volume measurement device and a medium infrared spectrometer (MIRS) for assessing gas properties. The volume measurement device consists of a forked photoelectric sensor and a linear unit. After each measurement, it travels to the next position (eudiometer). The MIRS can measure gas quality for biogas volumes of 150ml and higher. It is connected to each eudiometer by an airtight pneumatic coupling. The unit makes it possible to determine concentrations of carbon dioxide and methane in biogas and all 48 vials can be checked once every eight hours. The current 48-vial prototype is 2.15 meters in diameter and 2.5 meters high. The project team can also design smaller carousels.