Effects of mineral contamination on the ash content of olive tree residual biomass

• Mineral contamination affects the ash content, especially in the case of the leaves.
• Physical cleaning methods were able to reduce the ash content of olive leaves by 2%.
• Minerals from the soil were absorbed by the leaves, increasing their ash content.
• The storage conditions of olive leaves affected their final ash content.

The rise in energy consumption has made the use of alternative fuels a priority. Residual biomass is an abundant renewable energy resource whose use can lead to significant socioeconomic and environmental benefits. This biomass is destined to play an important role in the new energy model since agricultural residues are produced in huge amounts throughout the world. Consequently, converting this residue into an energy product increases the value of these waste materials and reduces the environmental impact of waste disposal. The generation of agricultural residues from the olive sector in the Mediterranean area is an important source of residual biomass highly suitable for thermal energy generation. This biomass comes from olive groves and olive oil production plants that generate by-products with high energy content. However, since the properties of biomass are dependent on a wide range of factors, the focus of our research was to analyse all of its forms (leaves, branches, bark and wood) separately in order to better understand their thermal behaviour and assure the quality of the final energy product. The determination of the ash content for each type of olive tree residual biomass indicated that olive leaves were responsible for the high ash content of this biomass. As a result, various cleaning methods were used to study the effect of the mineral contamination from leaves on the final ash content. The ashes were also analysed with a microscope to ascertain their composition.