Effect of Biochar on 17β-Estradiol Degradation in Composted Poultry Manure: Residue and Bioassay Analysis

Abstract

While composting is normally a valid approach to decrease 17β-estradiol (E2) contents of manure prior to land application, E2 residues in compost pose a risk to the environment. Biochar is a useful material in composting due to its microstructure. The study aims to compare the effect of amending poultry manure (PM) with two different biochars at three levels on E2 degradation. The seven treatments consisted of compost with no biochar (control) and compost with 5%, 10%, or 15% wheat stalk biochar (WSB) or rice husk biochar (RHB). The results indicated composting with WSB and RHB reduced E2 extractable contents by 71.0–78.5% and 74.2–88.1%, versus 67.8% without biochar. The abundance of two bacteria capable of E2 degradation: Bacillus licheniformis and Bacillus subtilis, increased significantly (p < 0.05) over control in biochar-amended treatments. Moreover, the estrogenic activity (assessed by proliferative assay of MCF-7 cells) of the compost was diminished by the addition of biochar. Our results suggest that E2 degradation was accelerated by adding RHB, possibly by RHB’s provision of a better microenvironment due to larger surface area and pore volume than WSB. Thus, the addition of 15% RHB is recommended for the treatment of PM compost to enhance E2 degradation.