MIKES-metrology at the VTT Technical Research Centre of Finland has developed the first primary standard for realising SI-traceability for moisture in biomass and other solid materials. At present, the reliability of moisture measurements in industry is based on reference measurements according to the oven dry method. In this method, the moisture content is determined as the mass loss of a sample due to drying by heating. The result is, however, distorted by non-aqueous volatiles. For biomass in particular this effect can be very significant. The system developed by MIKES-metrology is based on collecting the water vapour evaporated from a sample by heating into a cold trap and weighing the gained mass of the trap. The trapped water is analysed to determine if also non-aqueous volatiles are trapped during the measurement. The drying process is also monitored by a capacitive humidity sensor measuring the air exiting the sample container. Because the drying process is equivalent to the oven drying method, measurement results obtained with the system are given in terms of both water mass fraction with SI traceability and moisture content according to the standardised oven drying method.
This development is a part of a European research project METefnet coordinated by MIKES-metrology in which new methods are being developed for establishing and disseminating SI traceability to moisture measurements of solid materials (see www.metef.net). The work is supported by the European Metrology Research Programme (EMRP) jointly funded by the EMRP participating countries within EURAMET and the European Union.