Carbonization characteristics of co-pyrolysis of sewage sludge and corn stalks and its agricultural benefits

Purpose Conversion of sewage sludge and corn stalks into biochars via co-pyrolysis is a promising strategy for resource recycling. We hypothesized that the condition of co-pyrolysis would change the biochars' properties, which would have different agronomic benefits in coal mining area. The aims of this study were to (i) explore the difference in physicochemical properties, pore structure, and surface chemistry and (ii) identify agronomic benefits to promote corn growth and sequester C.Materials and methods Biochars were prepared via co-pyrolysis of sewage sludge and corn stalks using an orthogonal test (sewage sludge:corn stalks (w/w) (10:0, 7:3, 5:5), pyrolysis temperature (450 degrees C, 550 degrees C, 650 degrees C), and residence time (60 min, 90 min, 120 min)). We characterized biochars and investigated their effects on the germination rates of corn and SOC mineralization.Results and discussion The content of C and N in biochars increased with the addition of corn stalks. The pore structure of biochars was improved with the increases of corn stalks and pyrolysis temperature. The corn germination rates increased with the increases in pyrolysis temperature and the addition of corn stalks, which was consistent with the change of biochar pore structure. The optimized SSC9 (sewage sludge/corn stalks 5:5 (w/w), pyrolysis temperature 650 degrees C, and residence time 120 min) was simply produced where the key indicators germination rates reached 80%. Applying 1% and 2% SSC9 (H/C was 0.04 and O/C was 0.27) did not affect CO2 emissions.Conclusions Co-pyrolysis of sewage sludge and corn stalks produces different carbonization characteristics under different conditions, which has the agricultural benefit potential to promote corn growth and sequester C in coal mining area.

Automated summary

The conversion of sewage sludge and corn stalks into biochars through co-pyrolysis is a promising strategy for resource recycling. This study aimed to explore the differences in physicochemical properties and pore structure of the biochars, as well as their agronomic benefits in promoting corn growth and carbon sequestration in coal mining areas.