Environmental leaching of biochar: a full factorial analysis of composition and redundancy

To evaluate the changes in compositions and leaching components of different biochars under various environmental conditions, full factorial design experiments were conducted based on pyrolysis temperature (500-700 degrees C) (A), feedstock (dairy manure, wheat straw) (B), simulated environmental pH (4-10) (C), and simulated environmental temperature (15-45 degrees C) (D). The changes in biochar industrial and elemental composition and the leaching of dissolved organic carbon (DOC), dissolved organic matter (DOM), and soluble metals were characterized. Results showed that absolute value of significant effects (p < 0.01) affecting the change in H/C ratio followed the order of factor B (0.20) > factor A (0.14) > interaction A x B (0.11) > interaction A x C x D (0.02); the absolute value of significant effects affecting DOC leaching followed the order of factor A (46.80) > interaction A x B (24.25) > factor D (14.35), and pyrolysis temperature was the only effect affecting humic acid-like and protein-like DOM leaching (the absolute value of effect was 0.58); the leached contents of soluble metals were in the order of K > Ca > Mg > Al, Fe, and Zn, and the absolute value of significant effects affecting soluble K leaching followed the order of factor B (1267.90) > factor D (278.00). Redundancy analysis results revealed that biochar-derived H/C ratio and C were the most important interpreters for the changes in biochar compositions and leaching components. This study provides scientific data for further revealing the interaction between biochar and the environment in soil application systems and the potential of biochar application in carbon sequestration and agricultural production.