An extensive characterization of various treated waste wood for assessment of suitability with combustion process

- Extensive characterization was performed on a large panel of waste wood samples.
- Waste wood heterogeneity was confirmed.
- The pollutants concentration could be explained by the wood treatments.
- Ash, moisture and iron contents were mainly linked with external pollution.
- N, Cl and metals were found to be the main obstacles to combustion.

A representative set of treated waste wood was extensively characterized in order to evaluate its heterogeneity and its suitability with combustion process. Samples included both average samples made up of waste wood mixtures and specific waste wood classes. Untreated wood was also considered for comparison.As expected, neither heating value nor composition in C, H, O varied significantly compared to untreated wood. However, differences arose for minor elements, in relation with the chemical treatments undergone by waste wood.Particleboard was shown to be the main source of N with values up to 38 g/kg due to the presence of N-containing resins. Heavy metals like Ba, Ti or Zn were clearly associated to pigments used in painted wood or coatings and their amount reached respectively 2.6, 2.9 and 1.1 g/kg in painted wood. Cr and Cu were shown to come essentially from the chemical treatment undergone by impregnated wood with values of several thousands of mg/kg.A comparison between the minor elements contents found in waste wood and the specifications required in terms of feedstock composition and gas emissions in biomass combustion plants showed that the use of such feedstock would require either pretreatment before combustion to remove impurities or specific gas post-treatment.