Co-pyrolysis of peanut shell with phosphate fertilizer to improve carbon sequestration and emission reduction potential of biochar

The carbon sequestration and emission reduction by co-pyrolysis of biomass with phosphate to produce biochar is a key carbon-negative technology. However, effect of phosphate on carbon sequestration and emission reduction during the biochar formation has been unclear. In this study, a typical phosphate compound, potassium dihydrogen phosphate (KH2PO4), was pre-mixed with peanut shell (PS) for biochar production through pyrolysis at 750 °C. Results showed that after adding KH2PO4, the carbon fixation capacity of biochar increased significantly with FCR = 1.18 to FCR = 1.82, resulting 54% yield when compared to non-catalytic pyrolysis. The KH2PO4 affected the emission reduction process of biochar from two aspects: (1) increasing the calorific value of pyrolysis by-products and (2) reducing the content of CO2 and CH4 in bio-gas. The output of the renewed energy increased to 5.42 × 103 MJ/t from 4.09 × 103 MJ/t and the volume fraction of CO2 and CH4 decreased by 78.17 mol% and 22.01 mol%, respectively. Moreover, the net energy balance and net CO2e balance of the process were found 3.76 × 103 MJ/t and 1.28 × 103 kg/t respectively, reflecting importance and superiority of this research work than other reported studies. Thus, KH2PO4 has efficient carbon sequestration and emission reduction potential.