The influence of organic matter on sewage sludge pyrolysis

Four sewage sludges (SL) with different origins were selected from the Ávila region (Spain). Sewage sludge 1 (SL1) was primary sewage sludge without biological stabilization, sewage sludge 2 (SL2) and sewage sludge 4 (SL4) were obtained after anaerobic stabilization and sewage sludge 3 (SL3) was collected from a natural wastewater lake. The organic matter of sewage sludges was characterized and fractionated into humic acids (HA) and fulvic acids (FA) in order to study their influence on pyrolysis behavior. Preparation of cheaper carbon adsorbents was performed by a new method, without chemical activation with H2SO4 or ZnCl2. Experimental results showed that carbon enrichment during pyrolysis treatment was well correlated (R2 > 0.95) with fulvic acid sewage sludge content for two temperatures and two reaction times used. Finally, the highest porosity development was obtained for SL2 (403 mI2/g) and SL4 (554 mgI2/g) both of which were found to have low HA/FA ratios.