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From designer furniture to sustainable district heating

by Linda Bertelsen

A collaboration between Gelsted District Heating and the furniture factory Carl Hansen & Søn utilizes waste wood from designer furniture to produce sustainable district heating. And this results in a significant reduction in CO2 footprint and district heating prices.

Neither Y-chair, Arne Jacobsen, or Børge Mogensen rhymes with district heating. Nevertheless, the Danish design icons have become decisively important for heating the small town of Gelsted on Vestfyn.

DH company collaborates with a furniture manufacturer.

Here, the local district heating company, Gelsted Fjernvarme, has closely collaborated with the furniture manufacturer Carl Hansen & Søn, whose primary production is located in the town. The manufacturer is behind the production of some of the most iconic modern Danish furniture designs – the waste wood from that production now becomes sustainable district heating.

From waste wood to biomass

Carl Hansen & Søn press their wood waste into briquettes, which can then be used as biomass at Gelsted Fjernvarme’s biofuel plant. This replaces the wood chips used in the last few years. And the advantages for the two companies, according to Gelsted Fjernvarme’s operations manager, Torben Hjorth, are unmistakable.

CO2 and cost reduction

The district heating company gets cheaper and more sustainable heat production, while Carl Hansen & Søn uses all the wood from their furniture production.

– The project gives us a colossal CO2 and cost reduction. We save over 300 lorry trains in and out of Gelsted per year. Gelsted city gets a total CO2 reduction of around 40 percent, he says and continues:

– At the same time, we can maintain our heating price even though the price of wood chips and log chips has increased by 20-25 percent. The waste wood is much cheaper than fuel and will account for approximately half of our fuel consumption, corresponding to 10,000 MWh. It gives a very cash benefit to our consumers – and as biomass prices continue to rise, our system’s benefit also becomes greater.

Collaboration has been underway for a few years

The collaboration between Gelsted Fjernvarme and Carl Hansen & Søn has been underway for a few years. In fact, in the autumn of 2019, attempts were made to start the biofuel plant with the furniture factory’s waste wood.

At that time, however, the idea was that you would use the wood waste without treating it first. And it turned out to be far more complicated than first thought. So difficult, in fact, that the project was temporarily put on hold. In the meantime, Gelsted Fjernvarme had to switch to local wood chips in production while an alternative solution was searched for.

The challenge was a very high dust content in the wood waste, which created an explosive atmosphere in the district heating company’s equipment and fuel storage. In addition, there were poor opportunities to store the waste during the summer months. And after a more prolonged analysis and investigation, the choice was made to press the waste wood into briquettes instead.

– We have production up and running now and only need the final fine-tuning. And we can already see that it will be a great success. The wood briquettes are super good fuel, as they have a constant low moisture content of 6-7 percent. It gives a much higher calorific value than wood chips, which can fluctuate from 20 and up to 38 percent moisture, Torben Hjorth says and adds:

The briquettes also have a clear density advantage because the wood waste is compressed. The density is 1 kg/dm3, whereas it is only 0.2 kg/dm3 for wood chips. This means that we can store five times as much energy per room.

Bumps on the road

However, the operations manager also emphasizes that arriving at the collaboration has been a demanding process:

– Our two companies are from very different worlds. From a purely commercial point of view, we work based on different principles, as we are a cooperative supply company and must not burden our customers with unnecessary costs. It has therefore required a few rounds to find out.

Translated from the Danish District Heating Association