Nitrogen fixation of municipal sewage sludge by co-pyrolysis with biomass and KH2PO4-modified biochar addition

In order to reduce nitrogen emissions during municipal sewage sludge (MSS) pyrolysis, the effects of co-pyrolysis of MSS with biomass and the second adsorption of KH2PO4-modified biochar were investigated. It was found that co-pyrolysis with cellulose inhibited the conversion of nitrogen into pyrolytic gas, and increased the N content in pyrolytic biochar. And the nitrogen fixation rate increased with cellulose addition increasing. Besides, compared with different biomass, MSS co-pyrolysis with 30% sugarcane bagasse had the optimal effect on nitrogen fixation (39%). Moreover, KH2PO4-modified biochar addition increased the second adsorption of nitrogenous volatiles and fixed nitrogen into oxides-N. The total nitrogen fixation rate reached maximum (47.65%) at 5% KH2PO4 impregnation. Thus, it is an effective nitrogen fixation method that MSS co-pyrolysis of 30% sugarcane bagasse with the second absorption of 5% KH2PO4-modified biochar. This study provided an effective solution to improve the treatment of municipal sewage sludge by pyrolysis technology.

Automated summary

This study investigated the co-pyrolysis of municipal sewage sludge (MSS) with biomass and the second adsorption of KH2PO4-modified biochar to reduce nitrogen emissions. Co-pyrolysis with cellulose was found to inhibit the conversion of nitrogen into pyrolytic gas and increase the nitrogen content in pyrolytic biochar. The nitrogen fixation rate increased with cellulose addition, and co-pyrolysis with 30% sugarcane bagasse showed the optimal effect on nitrogen fixation (39%). Furthermore, the addition of KH2PO4-modified biochar increased the adsorption of nitrogenous volatiles and fixed nitrogen into oxides-N, with the total nitrogen fixation rate reaching a maximum (47.65%) at 5% KH2PO4 impregnation. Thus, co-pyrolysis of MSS with 30% sugarcane bagasse and the second adsorption of 5% KH2PO4-modified biochar provided an effective nitrogen fixation method. This study offered a practical solution to improve the treatment of municipal sewage sludge through pyrolysis technology.