Pure biogas from deepwater conditions

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With a total of 500 fermenters and a pilot plant, the University of Hohenheim is one of the leading research locations for biogas production. Source: Oskar Eyb/Universität Hohenheim

11.11.2011  - 

Like natural gas, biogas also consists mainly of methane. Nevertheless, only a tiny portion of the biogas produced in Germany is fed into the natural gas pipeline network, the main reason being that biogas requires thorough cleaning and compacting. Scientists at the University of Hohenheim have now navigated these hurdles by simulating deep sea conditions during production. The methane bacteria seem to enjoy the high pressure, producing gas of the highest quality. According to the researchers, the method can lead to energy costs savings of up to 40 percent. The next step in Hohenheim will be to develop a prototype of the new plant. The Federal Ministry of Education and Research (BMBF) is funding the research with 681,000 euros until 2013.
 

They remain something of an exotic sight: In Germany today there exist only around 50 biomethane plants that feed biogas into the gas grid. Per year by 2020, however, the federal government is aiming for the production and feeding-in to the network of around six billion cubic feet of biomethane per year. At current capacity, this would necessitate about 1,500 plants. Prior to feeding-in, the biogas must not only be cleaned of water, hydrogen sulphide, and carbon dioxide, but also condensed in a separate process - with high energy costs. Not surprisingly, few large companies have taken this leap to date. The vast majority of biogas produced in the more than 7,000 biogas plants in Germany is burned on location in cogeneration plants – for heat production, and to generate electricity for the grid. Even then, the generated heat is often only partially exploited.

No treatment required

At the University of Hohenheim, researchers are studying how the feeding-in process might be made more economical. The trick: The bacteria build up the pressure through their own methane output. This also eliminates many unwanted by-products. “Pressure and purity are not guaranteed during biomass fermentation, and must be produced in the downstream process, which is technically complicated,” says Andreas Lemmer, who heads the research project at the University of Hohenheim.

At the heart of the new approach is a new kind of fermenter that makes the methane bacteria feel simply snug as a bug. The local accommodation corresponds to a pressure of around ten times that of their natural deep sea environment. Indeed, one of the major technical challenges of the new reactor is to keep the pressure exactly constant. Here, the Hohenheim researchers have had to develop a unique control and regulation technology, and a prototype of the new facility is in the works.

Capital expenditure significantly lower

The research taking place in Hohenheim is part of the joint project “Innovative Erzeugung von gasförmigen Brennstoffen aus Biomasse” (Innovative Production of Gaseous Fuels from Biomass), which involves numerous industrial partners, alongside the University of Hohenheim and the Karlsruhe Institute of Technology (KIT), the University of Stuttgart, the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW). The BMBF is supporting the joint project within the framework of the initiative Bioenergy 2021 with a total of 2.6 million euros. Hohenheim has been granted 618,000 euros for the development of a procedure to combine biogas production and its processing into biomethane. Scientists estimate that this could save up to 40 percent in energy costs. In addition, total investment costs are further reduced because no extra stage is required for gas processing. This also allows systems to be much smaller, say the researchers.

Lemmer and his colleagues believe that their project has serious economic potential. “A lot is happening in natural biogas production,” says Lemmer. A number of companies have already made enquiries about their work, say the Hohenheim-based scientists.

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