Aarhus University Seal

Biogas plant at AU acquires organic authorisation

The biogas research plant at AU Foulum is the first plant in Denmark to have gained authorisation periodically to run organic biogas productions. This opens up new possibilities, particularly for organic farmers.

[Translate to English:] Forsøgsbiogasanlægget ved AU Foulum har fået autorisation til at køre med delvis økologisk drift. Foto: AU

The biogas plant at Aarhus University’s Research Centre Foulum is the first in Denmark to be granted authorisation to run periodic organic productions.

 

This is particularly important for organic farmers who often have a problem with sourcing organic manure. With the authorisation, it will be possible for organic farmers to increase the amount of nitrogen they can apply to their fields.

 

The manager of the biogas plant at AU Foulum, Mogens Møller Hansen, explains:

 

- The maximum amount of nitrogen that organic farmers can currently apply to their fields from conventional manure is 70 kg N per hectare. If they have an organic source of manure they may apply a maximum of 140 kg N per hectare, of which 70 kg may come from a conventional source. With the authorisation for the biogas plant to produce an organic fertiliser product, organic farmers can set up an arrangement with the biogas plant where they supply an organic biomass and in return they receive a fertiliser product with a certain percentage from the organic production line. If this product is 50% organic, they can therefore in future apply 140 kg N per hectare to their fields.

 

Quarantine period without GMO
In order for the biogas plant at AU Foulum to run a periodic organic production, they will need initially to undergo a GMO quarantine period, which means that the plant can no longer receive feedstocks containing GMO.

 

Mogens Møller Hansen reveals that past experiences with running a purely organic biogas production have not been all that good, but that there is on-going research into organic biomasses.

 

- Organic biomass plants face some real challenges because the biomasses often have a high dry-matter content and they got too little slurry. We have experience in using organic biomasses in Foulum, but it has not been without problems. However, we are adopting new technologies that enable these biomasses to be processed. Now we are working on optimising the processes so that we can make the production financially viable. But the bottom line is that it will make it easier for the organic farmer to obtain organic manures without having to build biogas plants that are based exclusively on organic production, explains Mogens Møller Hansen.

 

With the authorisation to run a periodic organic production, AU Foulum has been able to complete the organic cycle at the biogas plant. An extruder has already previously been connected to the plant, capable of handling biomasses such as meadow grass, hay, deep bedding material and grass-clover that all have a high dry-matter content. One of the advantages of the extruder is that it is very flexible as it is capable of handling dry-matter contents ranging from 20-85%. At the very high end of the scale, its capacity is, however, compromised and the next step is therefore to incorporate a straw briquette technology that has a large capacity at high dry-matter contents. There will therefore be two feed-in systems that supplement each other.

 

The BioM project at AU Foulum has been the prime motivation for the application for authorisation of the biogas plant. The project focuses on conservation of wetland areas in the Nørre Å valley near Viborg and production of organic manure for the arable farmers in the area. A cooperative of suppliers has been established in this connection, and they harvest the grass in the valley and sell it to the biogas plant at AU Foulum and in return receive anorganic manure.

 

- This is a good arrangement where we receive organic biomasses that we do not normally receive and are able to test them. The organic farmers on the other hand receive a manure that is partly organic and they can therefore increase the amount of nitrogen to their fields rather than relying on conventional manure, says Mogens Møller Hansen.

 

At the biogas plant in Foulum the organic biomasses are supplemented with conventional slurry from the nearby Cattle Research Centre. The addition of slurry is a necessity in order to have a sufficiently high water content for the mixture to be pumped into the digestor.

 

Further information: Plant manager Mogens Møller Hansen, Department of Engineering Science, telephone: +45 2076 2732, e-mail: mogensm.hansen@agrsci.dk