Characterisation of lignocellulosic biomasses

General informations

Each biomass presents particular properties. Its chemical composition, its structure and the organisation of the constitutive fibres are important criteria to determine its possibilities of valorisation.

Different methods of analysis are used to measure:

• The chemical composition by analysis of extractives, lignin and polysaccharides (cellulose and hemicelluloses) contents and of minerals content,
• The biomass quality by analysis of the dry matter content, the density, mass volume and the colour,
• The biomass structure by separation of the constitutive elements and analysis of the fibres obtained, by examination in optical and electronic microscopy.

Technical data

Chemical composition
Lignocellulosic biomass is first ground to obtain a sawdust. This grinding can be carry out under cold conditions to avoid the loss in volatile compounds.

• The extractives content is obtained by extraction of the sawdust with different solvents such as water and acetone with a ASE extraction system.
• The lignin content is obtained by determination of the insoluble in concentrated sulphuric acid or Klason method.
• The polysaccharides contents are obtained by acid hydrolysis and HPLC analysis of the constitutive sugars obtained. By calculation, it is then possible to determine the cellulose and hemicelluloses contents.
• The minerals content is the residue from calci-nation at 525°C (with carbonates) or at 900°C (without carbonates) of a biomass sample.

Biomass quality

• The humidity or the dry matter content is obtained by difference of weights after drying at 105°C.
• The infradensity of wood is measured on wood slices with the Archimède principle.
• The mass volume is measured by determination of the dry weight of a given volume of biomass.
• The biomass colour is determined by its brightness and its trichromatic coordinates (Lab) obtained by spectroscopy of the sawdust.

Biomass structure

• From ultrathin slices of biomass embedded in an epoxy resin, it is possible to examine the ultrastructure of fibres wall with different dying methods combined to transmission electron microscopy.