Meso and Macroporosity in Carbonaceous Materials Prepared by Thermal Treatment from Lignocellulosic Wastes

This work analyses the improvement of the macroporous structure of coals made from olive wood waste (OWW) by means of thermal treatment between 400 ºC and 900 ºC. These coals will be used in the Biomethanization or Anaerobic Digestion process of wet residual biomass, as they act as bacteriological adherents, immobilising the microorganisms that participate in this process and increasing its energy yield. The carbonaceous adherends have been characterised by elemental analysis, mercury porosimetry, adsorption isotherms and SEM. The yield of the carbonisation process varies between 39.73% and 21.52%. For samples carbonised at 400 ºC the yield is usually higher than for those carbonised between 600 ºC and 900 ºC. The carbonisation temperature has a major influence on the porosity distribution in the meso- and macropore regions, and not so much the treatment time. In the mesopore region, in general, the porosity distribution is more heterogeneous, with the volume of mesoporosity increasing with increasing carbonisation temperature, according to: 900 ºC>600 ºC>400 ºC. However, as far as macropores are concerned, the size distribution is much more homogeneous and the volume of macroporosity decreases with increasing carbonisation temperature, being the sample prepared at 400 ºC for 15 min showing the highest porosity development, with a total volume of 0.60 cm3g−1.