(2017) Applied Energy_Pyrolysis process of agricultural waste using CO₂ for waste management, energy recovery, and biochar fabrication

Lee J., Yang X., Cho S.-H., Kim J.-K., Lee S.S., Tsang D.C.W., Ok Y.S., Kwon E.E.

(Elsevier Ltd) Applied Energy ISSN: 3062619 Vol.185 Issue. Article No. DOI: 10.1016/j.apenergy.2016.10.092

This study focused on the mechanistic understanding of CO₂ in pyrolysis process of agricultural waste to achieve waste management, energy recovery, and biochar fabrication. In order to scrutinize the genuine role of CO₂ in the biomass pyrolysis, all pyrogenic products such as syngas, pyrolytic oil (i.e., tar), and biochar generated from pyrolysis of red pepper stalk in N₂ and CO₂ were characterized. Thermo-gravimetric analysis confirmed that during the thermolysis of red pepper stalk, the magnitude of exothermic reaction in CO₂ from 220 to 400 °C was substantially different from that in N₂, resulting in the different extents of carbonization. The physico-chemical properties of biochar produced in CO₂ were varied compared to biochar produced in N₂. For example, the surface area of biochar produced in CO₂ was increased from 32.46 to 109.15 m² g⁻¹. This study validates the role of CO₂ not only as expediting agent for the thermal cracking of volatile organic carbons (VOCs) but also as reacting agent with VOCs. This genuine influence of CO₂ in pyrolysis of red pepper stalk led to enhanced generation of syngas, which consequently reduced tar production because VOCs evolving from devolatilization of biomass served as substrates for syngas via reaction between CO₂ and VOCs. The enhanced generation of CO reached up to 3000 and 6000% at 600 and 690 °C, respectively, whereas 33.8% tar reduction in CO₂ was identified at 600 °C. © 2016 Elsevier Ltd

This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2014RA1A004893). This work was also supported by a National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. NRF-2015H1D3A1066513). Biochar characterization was performed at Central Laboratory of Kangwon National University.