All biomass contains Carbon (C), Oxygen (O), Hydrogen (H), Nitrogen (N) and various other trace elements. On average wood contains about 49 % C, 6 % H and 44 % O with some variation between wood species (Fengel and Wegener 2003).

A high carbon content is directly related to a high density and therefore a high calorific value and desirable for combustion and gasification.

The major elements contained in any biomass, such as C, N, H, can be determined with elemental analysis and/or x-ray fluorescence (XRF) as described by Perkel (2012).

C, N and H can be determined by combustion in a pure oxygen atmosphere at high temperatures, which converts the sample elements into CO2, H2O and N2. The amount of the product gases is proportional to the amount of C, N and H in the sample.

In the XRF technique a material is exposed to high energy x-rays, which eject electrons from the sample atoms. The transition of outer electrons to the vacant spaces results in photo energy that is characteristic for the element and can be detected by a fluorescence detector.