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Silva Fennica 1926-1997
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Acta Forestalia Fennica
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Articles by Lars Fridh

Category : Research article

article id 6993, category Research article
Lars Fridh, Lars Eliasson, Dan Bergström. (2018). Precision and accuracy in moisture content determination of wood fuel chips using a handheld electric capacitance moisture meter. Silva Fennica vol. 52 no. 5 article id 6993. https://doi.org/10.14214/sf.6993
Keywords: heating value; biofuels; payment
Highlights: The studied capacitance meter can provide accurate estimates of mean moisture content for chips with M < 50% if a large sample is taken; It should be possible to use the capacitance meter to measure moisture content even for calculating payments depending of the needed accuracy; However a calibration function for each assortment is needed.
Abstract | Full text in HTML | Full text in PDF | Author Info

According to the Swedish Timber Measurement Act, measurements affecting payments for wood fuels to landowners must be accurate and precise. In this regard, moisture content is an important quality parameter for wood chips which influences the net calorific value as received and thus the economic value. As standard practice moisture content is determined with the oven-drying method, which is cumbersome to use for deliveries to facilities without drying-ovens, which in turn necessitates that samples are taken elsewhere for measurement. An alternative solution is to use a portable moisture meter. Our aim was to evaluate the precision of a handheld capacitance moisture meter. Accuracy and precision of a capacitance meter was determined in the lab and a calibration function was made. Thereafter, the calibrated moisture meter was compared with the standard method for moisture content determination of truckloads of chips. The capacitance meter showed a moderate accuracy by underestimating moisture content by 6.0 percentage points (pp), compared to the reference method, at a precision of ±3.8 pp (CI 95%). For chips with M > 50%, both accuracy and precision decreased. Calibration increased the accuracy in the follow up study by 3 pp for chips with M < 50% but could not be made for wetter chips. The oven-drying method and the capacitance meter can provide equally accurate estimates of mean moisture content for chips with M < 50% if a larger sample is taken with the latter. It should be possible to use capacitance meters to measure moisture content even when used to calculate payments depending of the needed accuracy. A calibration function for each assortment is needed.

  • Fridh, Skogforsk, The Forestry Research Institute of Sweden, Uppsala Science Park, 751 83 Uppsala, Sweden; Skogsägarna Mellanskog, Uppsala Science Park, Box 127, 751 04 Uppsala, Sweden ORCID http://orcid.org/0000-0002-4721-1193 E-mail: lars.fridh@mellanskog.se
  • Eliasson, Skogforsk, The Forestry Research Institute of Sweden, Uppsala Science Park, 751 83 Uppsala, Sweden ORCID http://orcid.org/0000-0002-2038-9864 E-mail: lars.eliasson@skogforsk.se (email)
  • Bergström, Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, S-901 83 Umeå, Sweden E-mail: dan.bergstrom@slu.se

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