Using livestock bedding in new biogas plant

Xergi is working on processing large volumes of livestock bedding in several Danish biogas plants. We have looked at what this means for ground carbon levels and have spoken to several Danish dairy cattle farmers who are already working with a biogas plant.

Xergi is currently developing several Danish biogas projects where energy production is expected to become based largely on bedding from cattle.

"We can see that large volumes of livestock bedding are readily available. The bedding has a high energy content – and we have developed a new technology that enables us to utilise this energy," explains Managing Director Jørgen Ballermann about the development of the new biogas projects in Denmark.

Until now, it has not been possible to utilise livestock bedding efficiently in commercial biogas production. However, Xergi has now come so far with the development of NiX® - its pre-treatment technology which is able to handle livestock bedding - that the company has been busy developing several large biogas plants involving this technology.

Effect on ground carbon content?

During discussions with various livestock farmers, Xergi has been asked about how ground carbon levels will be affected by taking livestock bedding to be processed at a biogas plant rather than spreading it directly on the ground.

We passed this question on to Professor Jørgen E. Olesen, who is one of Denmark's leading experts on climate and environmental issues related to agricultural production.

"It does not make a great deal of difference using the bedding directly on fields instead of running it through a biogas plant. When the bedding is used in a biogas plant, slightly less carbon will be stored in the ground, but there is no great difference. This is because it is the easily convertible part of the carbon that is converted in the biogas plant while it is the more slowly convertible part of the carbon that it returned to the soil with the degassed biomass. If the bedding is spread directly on the ground, the easily convertible part of the carbon will also be converted relatively quickly. This means that after 3-4 years the difference will not be very great," explains Jørgen E. Olesen.

Nitrogen is more important

"Cattle farms usually have a cultivation system that favours the carbon content in the soil anyway. That is why, if anything, people should focus on the nitrogen in the animal manure," says the Professor from the University of Aarhus.

"The problem for cattle farms is utilising the nitrogen sufficiently well, and the biogas helps greatly with this problem," says Jørgen E. Olesen.

Two satisfied dairy cattle farmers

Biogas Nyt has also spoken to several cattle farmers who are already taking their manure to be processed at a biogas plant. They are all very satisfied with the arrangement and believe that it would be a good idea to include livestock bedding.

Two of the farmers are Peter Mamsen and Hans Gejl, who take their manure to Linkogas near Vejen in southern Jutland.

Peter Mamsen takes 150 cubic metres of manure from both cattle and pigs to be processed every week.

"I think the scheme is going really well. Compared to pure cattle manure, the degassed manure is a great deal easier to handle. The raw cattle manure is thick and sticky while the degassed manure is much thinner which makes it easier for the truck to pump. While the raw manure stays on top of the soil, the degassed manure dissolves much better. This is a particular benefit if you are spreading the manure on growing crops such as winter crops and larger fields," says Peter Mamsen.

The nitrogen in the manure is also converted from organic nitrogen to ammonium nitrogen which is easier for the plants to absorb. This is precisely the reason that Jørgen E. Olesen views the biogas positively.

Good logistics

Hans Gejl takes 150 cubic metres of primarily cattle manure to be processed every week. He emphasises that the degassed manure is easy to handle and that it hardly smells compared to raw manure. He is also very satisfied with the logistics involved.

"We have storage tanks for manure placed in different locations on our property. When the degassed manure is delivered, we get them to deliver it to the storage tanks close to the fields where the manure is to be used. In this way, we save on transporting the manure from the farm out to the field where it is needed," explains Hans Gejl.

Enhanced fertilising value

They would both like to take their bedding to the biogas plant to be processed.

"It would be an advantage if we could rid ourselves of our covered manure heap. We just need to remember that we use some of our livestock bedding as floating layers in our tanks of degassed manure that cannot themselves form floating layers," says Peter Mamsen.

"The bedding is not bad for the fields, but the degassed manure has a higher fertiliser value so we would very much like to take our bedding to the biogas plant to be processed," says Hans Gejl.

For further information, please contact:

Jørgen Ballermann, CEO, Xergi A/S
Tel: +45 99 35 16 00

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