Co-pyrolysis of biosolids with alum sludge: Effect of temperature and mixing ratio on product properties

Sustainable management of biosolids and alum sludge are becoming increasingly important due to the rapid growth in their production with increasing urbanization globally. Pyrolysis has been identified as a promising method for biosolids management. However, land application of biochar derived from pyrolysis of biosolids may be limited despite their significant agro-environmental benefits, mainly due to the potential increased concentration of heavy metal content in the biochar. Current study experimentally investigated co-pyrolysis of biosolids with alum sludge with an aim to produce high quality biochar with reduced heavy metal content. Moreover, it is further hypothesized that the addition of alum sludge may catalyze pyrolysis reactions, which may alter properties of pyrolysis products such as oil, gas and biochar. The results indicate that co-pyrolysis can reduce heavy metal concentrations in biochar while also improving oil and gas product qualities, suggesting beneficial synergistic effects. Furthermore, the process parameters such as pyrolysis temperature and alum sludge mixing ratio have a significant impact on the yield distribution and product (biochar, pyrolysis oil and gas) properties.