SPLIT APPLICATION OF BIOCHAR FOR HUMIC ACIDS STRUCTURAL CHARACTERISTICS ENHANCEMENT DURING CHICKEN MANURE COMPOSTING

Abstract

Applying biochar to composting substrates promotes more complexity and stability of the formed humic acids (HA). This study investigated how different biochar addition methods affect HA formation during chicken manure composting. Two methods of adding biochar were compared: split addition (2.5% for four times during the bio-oxidative phase) with mixing (A) and total addition (10% in one time) at the beginning of composting (B). The treatment without biochar addition was considered as a control. Compared to the control, A treatment had a HA with the highest oxygen/carbon (O/C) molar ratio (0.52), and it was the nearest to the O/C molar ratio of the soil HA (0.55). The FTIR, DTA, and TGA analyses indicated that HA isolated from the A compost exhibited the highest aromaticity, and it was similar to soil HA. These findings demonstrated that the split addition method of biochar could enhance the structural characteristics and stability of the formed HA during composting.