The measurement of water content is generally carried out using two approaches: laboratory methods and rapid electrical measurement methods.

Measurement in the laboratory
In the laboratory method, the fuel is dried in a drying cabinet according to DIN EN ISO 18134-2 for at least 12 hours at a defined temperature until the fuel's remaining mass is constant. The water content of the fuel is calculated from the mass loss due to oven drying. This method is used in accredited testing laboratories and is usually used as a reference for quick measurement procedures. Due to its high complexity, this method is prone to errors. It should also be noted that not only water evaporates, but also other ingredients - such as resins.

Electrical measurement methods
Electrical measurement methods are ideal for practical applications. They enable fast, reliable measurement results directly on site. The two most important electrical methods are:

• Conductance based methods
  With this method, the material to be measured is not changed. The method measures the water content based on the electrical conductivity, which increases with higher water content. The more water there is, the more conductivity arises and the electrical resistance decreases. This measurement happens very quickly because only the probe needs to be brought into contact with the biomass. However, the conductance is strongly dependent on temperature. Therefore, it is necessary to carry out an accurate and correct temperature compensation of the measurement result.

• Dielectric processes
  In the dielectric process, the water content is calculated by measuring the dielectric constant of water in the biomass. By irradiating the measuring frequency into the material, it is possible to analyze larger quantities of biomass. In addition, the method is less temperature dependent than the conductance method.