Two ways of settling wood chips by ATRO tonnes, compared
Wood chips settled by dry matter can be measured in two ways: with a weighbridge and a drying oven, which is the reference method, or with a humimeter BMA-2 on a measured sample. The figures below come from the manufacturer and rest on stated assumptions, so they are worth reading together with those assumptions rather than on their own.
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| Investment cost | €4,440 | €80,000 |
| Cost per measurement at 500 measurements a year | €2.70 | €24.70 |
| Total time of a measurement | a few minutes | at least 24 hours |
What the calculation assumes
- time of a measurement with a weighbridge and drying oven: about 15 minutes of work
- time of a measurement with the BMA-2: about 3 minutes
- personnel cost of €36 per hour
- depreciation of the weighbridge and drying oven over 12 years
On those assumptions the manufacturer reports a saving of 80 % in time and personnel cost (€1.80 against €9.00 per measurement) and of 96 % in maintenance and energy (€0.10 against €2.50 per measurement). The difference in total time comes from the reference method itself: oven drying takes at least 24 hours, which is why it documents a delivery after the fact rather than at the weighbridge.
The accredited testing laboratory
Schaller runs a testing laboratory meeting the requirements of EN ISO/IEC 17025. In 2016 it was accredited for the determination of water content according to EN ISO 18134-2, the oven-drying method for solid biofuels. The BMA-2 was developed together with that laboratory, and the manufacturer cites it in the "Bioenergy 2020" and "Holzforschung Austria" reports; the measuring method is covered by a patent registered in the European Union.
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Where the advantage actually lies
The money saved is the smaller part. The larger one is that a result available in minutes can be used at intake, while the lorry is still on site - a 24-hour result cannot. A measurement on a 12 litre sample also averages over a large volume, which matters with a material as uneven as wood chips, and leaves little room for manipulation.
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