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Biogas Plant Acquires Organic Authorisation

04 April 2013
Aarhus University

DENMARK - 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 per cent 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 per cent.

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.

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