Measure the moisture content of the wood in three minutes – directly on the truck

The moisture content meter (blue) inserted into pulpwood, loaded onto a truck.Photo: Kari Hyll, Skogforsk

New microwave technology makes it possible to measure the moisture content of the wood directly on the truck – in just three minutes. The method can be a breakthrough for quality assessment and trade in roundwood and chips.

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FIND US ON

For three years, the Skogforsk-led project Intjning Fuktcontent has been working to further develop microwave-based technology to measure the moisture content of roundwood and wood chips directly on trucks. The Forestry Research Institute recently demonstrated the equipment at Johannes’ biocombined heat and power plant in Gävle, where it is installed.

The semi-automatic meter, which has been developed by the Gävle company Radarbolaget, can measure roundwood or wood chips directly on a truck. However, this assumes that there are no metal walls between the meter and the roundwood/chips.

“The measurement takes about three minutes before the result comes in, and then most of the time is spent pushing in and retracting the meter towards the truck. The microwaves detect the moisture content of the wood in a volume equivalent to about 2000 litres of wood chips or two cubic metres of round wood,” says project manager Kari Hyll.

So far, the meter has been evaluated on wood that is not frozen, and the moisture content can then be determined with an accuracy of about four percentage points. But within the project, several experiments have also been carried out on frozen wood.

Frozen or unfrozen has

an impact“An important part of the research has been to understand how the diameter of the wood affects the measurement. The more measurements that can be made on frozen, unfrozen and semi-frozen timber, the more accurate that calibration model will be. And it is the calibration model that translates the microwave signal into moisture content,” says Kari Hyll.

Among the 18 people who participated in the demo day, there were representatives from Sveaskog, Billerud, Mellanskog, Rundvirke skog, Stockholm Exergi and the financier Energimyndigheten. According to Kari Hyll, they considered the moisture content measurement to be particularly relevant for wood chips, where the moisture content can vary greatly, and for pulpwood (roundwood). Since there is currently no practical method for measuring moisture content in round wood, the method has the potential to change how round wood is quality assessed and sorted, both in Sweden and globally, they believed.

“The question is whether the technology opens up for trade in pulpwood in the future to be based on dry weight instead of volume. It will be interesting to follow the development going forward,” says Kari Hyll.

The three-year project, with a budget of SEK 7.1 million, was completed in September. After the completion of the project, Radarbolaget has expressed an ambition to continue developing the meter. The idea is that the development work will be done in collaboration with one or more interested industrial companies.

Source; Skogforsk