Applying Filtralite® Air in a biological odour treatment filter is a simple and effective solution, allowing nature’s own bacteria to handle the purification. Therefore, this was the obvious solution for Nature Energy Nordfyn in Bogense, Denmark.


Nature Energy Nordfyn is a biogas plant near the town of Bogense on Funen, which treats approximately 300,000 tons of biomass per year.
Opened in 2016, it comprises of a biogas plant for degassing biomass and an upgrading plant, purifying the raw biogas so it can be led to the consumers via the existing natural gas grid.

Why Filtralite® Air in odour treatment filters?

As a filter material for the biological odour treatment of the plant, Leca Danmark A/S has supplied 750m3 of Filtralite® Air 10-20mm. The advantages of the product are:

  • The air volume/percentage of voids between the grains is large, between 40-45% therefore the air will have great space to move within. The air volume distributes itself as a network of air-filled passages between the Filtralite Air grains.
  • The surface of Filtralite Air is porous and the air will come in contact with a large surface area where the odorants can be removed. 
  • The pressure loss through large grains is considerably lower than for finer grading’s due to the size of the air-filled passages. This is important as the filter treats 40,000m3 air/hour. The lower the pressure loss, the lower the energy requirement for moving the air.
  • The coarse grading provides more room for storage of biofilm and maintain air movement so that the filter does not clog.


How does it work?

The principles of biological odour treatment with Filtralite Air are as follows:

When cleaned, the odour-filled air is sucked or pressed through the water-humidified layer of Filtralite Air After a few weeks, a large amount of nature’s own bacteria, which feed on the nutrients in the odour-filled air, will start growing on the surfaces of the Filtralite Air.

The appetite of the bacteria is in principle the key contributor to purifying odour. Filtralite Air provides a large surface for the bacteria to grow and provides a series of networks of air-filled corridors.

Pleased with the solution

Pernille Knudsen, Civil Engineer with PBJ Miljø ApS and Project Manager during the planning of the plant, is pleased with Filtralite Air as a solution in the filter:

“Before we knew of Filtralite Air we used bark in this type of filter. However, bark densifies when mixed with water and retains moisture with difficulty. The Filtralite Air filters do not collapse and they retain water well. Thus, the filter requires less water to provide optimum conditions for the bacteria. This, together with the recirculation, means annual water savings of approximately 60%” she explains.

As the lightweight aggregate is inactive and durable, Pernille Knudsen does not anticipate a replacement of the material for the next 8 - 10 years.

The annual production of the plant in Bogense is 10 million m3 of upgraded biogas, which is sold through Nature Energy under the name BioGas. This provides heat consumption to 6,000 home-units.