Conventional biogas plants have the disadvantage that the production of energy cannot be controlled in a flexible way. Therefore, Großmann Ingenieur Consult GmbH (GICON) has developed a fast, simple method for controlling biogas production from renewable resources. In addition, the two-stage dry-wet fermentation process with split hydrolysis makes it possible to control the two stages independently. Heribert Krämer, head of the GICON subsidiary in Konstanz, is convinced that this method is a major step on the road towards the establishment of virtual power stations.
Conventional biogas plants take several days before they reach full capacity. This is seen as a major problem when it comes to creating virtual power stations, an idea that focuses on integrating small, decentralised power generation systems (e.g. photovoltaic plants, wind power plants or biogas plants) in order to do away with large power plants. "The only parameter that can be influenced during the power generation process is the generation of biogas, which needs to be controlled flexibly, and more importantly, quickly," said Heribert Krämer, head of the Department of Wet Fermentation at GICON GmbH. In cooperation with the BTU Cottbus and many other research institutions, GICON has developed a worldwide unique method with which it is possible to stop biogas generation and start it again within only a few hours. "This flexibility is a good solution for the lack of wind and also enables us to switch off the plant during the daytime," said Heribert Krämer. In addition, the two-stage energy production process is far more effective and environmentally friendly than conventional biogas plants due to the decoupling of hydrolysis and methane formation. The generation of regenerative energy using wet fermentation is based on organic substances from agricultural or food waste, branches and almost all plant substrates.
The greatest advantage of the GICON process is the decoupling of hydrolysis and methane formation. Initially, the substrate (e.g., organic waste or energy crops such as corn) is packed into big tanks known as percolators. In the first step, i.e. hydrolysis, the substrate is wetted with water which causes organic components to dissolve from the substrate matrix and to be converted into organic acids and other water-soluble products," said Krämer explaining the process. The resulting aqueous solution (hydrolysate) is then fed into the second stage, i.e. the formation of methane in a solid-bed reactor. The two processes can also be run independently from each other. "For example, it is possible to control the supply of biomass by increasing percolation and by temporarily storing the percolate. The percolate can be stored for several days before it is fed into the methane reactor," explained Heribert Krämer going on to add "it is also possible to reduce the quantity of percolate fed into the methane reactor, or to stop the process entirely."
A major aspect of the GICON process is the possibility to integrate it into existing structures. The biogas plant works particularly well in combination with composting plants because the waste can be used for the biogas plant and the substrate can be returned to the composting process after percolation. The time the substrate remains in the percolators is relatively short, between 14 and 20 days only. This means that around 15 to 30 thousand t of substrate can be processed per year. An ideal combination is a biogas plant with a solar power station, as this enables the modulated control of the processes. "For example, it is possible to operate the plant at night only in order to compensate for the non-productive periods of solar plants and wind power plants," said Krämer who envisages a great future for the combination of waste disposal and regenerative energies into virtual power stations that produce gas, heat and electrical energy 24h a day. "Due to the flexibility of the processes and a methane content that is 15 - 20 per cent higher than that of conventional plants, the GICON biogas method is an important factor in the establishment of virtual power stations."
In 2010, two new GICON process biogas plants were erected in Erfurt and Cottbus, each with a special focus on waste or corn fermentation. "In the future, our major focus will certainly shift towards the processing of waste since corn is expensive and because of limits set by the percolate," said the biologist. New tests are being carried out to assess the suitability of certain substrates for percolation and optimise the processes. For example, the percolate can be enriched with different enzymes or trace elements in order to increase the amount of energy generated. Another advantage of the GICON process is that different environmental conditions such as temperature or pH value can be separately controlled and optimised in the two process stages.
The GICON system is not only used in Germany; Harvest Power Inc., one of the most important American companies in the field of organic waste management, has licensed the process and obtained exclusive rights to sell the patented GICON biogas process in the USA.
Contact:Heribert KrämerTel.: +49 7531 81995-11Fax: +49 7531 81995-10E-mail: h.kraemer(at)gicon.de