(2019) Environment International_Catalytic pyrolysis of swine manure using CO₂ and steel slag

Lee D.-J., Jeong K.-H., Lee D.-H., Lee S.-H., Jung M.-W., Jang Y.-N., Jo G.-G., Kwag J.H., Yi H., Park Y.-K., Kwon E.E.

(Elsevier Ltd) Environment International ISSN: 1604120 Vol.133 Issue. Article No.105204 DOI: 10.1016/j.envint.2019.105204

Pyrolysis of swine manure (SM) was conducted as a case study to establish an environmentally sound management of livestock manure. To build a more renewable pyrolysis platform for SM, this study selected carbon dioxide (CO₂) as the reaction medium. In addition, CO₂ was used in pyrolysis of SM to restrict the formation of toxic compounds, such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs). A series of thermo-gravimetric analysis (TGA) tests was done to understand the thermolysis of SM in the CO₂ environment. The TGA tests elucidated no occurrence of heterogeneous reactions between the SM sample and the CO₂. Moreover, the TGA tests of SM suggested that SM contains more volatile matter (VM) than lignocellulosic biomass. Non-catalytic transesterification of SM lipids confirmed that the dried SM sample contained 8.85 ± 0.05 wt% of lipids. This study also confirmed that the mechanistic role of CO₂ was realized through the gas phase reactions between volatile pyrolysates evolved from the thermolysis of SM and CO₂. In summary, CO₂ donates O, enhancing the generation of CO through homogeneous reactions. In parallel, this study confirmed that CO₂ suppress dehydrogenation. Therefore, the identified gas phase reactions between volatile pyrolysates and CO₂ led to the compositional modifications in the condensable pyrolysates. However, such mechanistic features arising from CO₂ only initiated at ≥520 °C. To expedite the reaction kinetics of the homogeneous reaction triggered by CO₂, steel slag (SS) was used as a catalyst. Hence, the reaction kinetics associated with the mechanistic role of CO₂ were substantially enhanced (up to 80%) when SS was used as a catalyst. Therefore, all experimental findings strongly suggest that CO₂ can be utilized as a raw material in a thermo-chemical process. More importantly, all observations suggest that CO₂ lopping can also be achieved in a thermo-chemical process. Lastly, this study shows that the high Cu content in SM was effectively immobilized through pyrolysis. Conclusively, this study experimentally proved that CO₂ could be promising for restricting the formation of toxic pollutant in the thermo-chemical treatment in that CO₂ offers an innovative and strategic means for controlling the ratio of C to H. Note that aromaticity and toxicity of chemical compounds are highly contingent on the ratio of C to H. © 2019 The Authors

This work was carried out with the support of “Cooperative Research Program for Agriculture Science & Technology Development (Project title: Development of optimal liquid fertilization process and utilizing technology for livestock farm, Project No. PJ01268502)” Rural Development Administration, Republic of Korea.