Elucidating the optimum added dosage of Diatomite during co-composting of pig manure and sawdust: Carbon dynamics and microbial community.

Six dosages of DM (0%, 2.5%, 5.0%, 10%, 15% and 20%) were added into initial mixtures for 42 days of aerobic composting to investigate the optimum added dosage of Diatomite (DM) during co-composting of pig manure and sawdust. The results showed that adding DM was beneficial for reducing CH4 emissions and greenhouse gas emission equivalent (GHGE) values by 15.63-24.25% and 14.33-69.08%, respectively. Meanwhile, the main contributor to the GHGE value was N2O (58.76-75.98%), followed by CH4 (17.22-29.16%) and NH3 (6.38-13.36%). Moreover, the maximum values in the degradation of total organic matter and the formation rate of humic acid were 20.46% and 82.19% in 10% DM added treatment (T3), respectively. Furthermore, the increase in spectral parameters, including the specific UV absorbance at 254 nm (SUVA254), the specific UV absorbance at 280 nm (SUVA280) and Fourier transform - infrared parameters were facilitated by DM amendment. Additionally, the higher values of the relative abundances of Proteobacteria (50.98%) and Bacteroidetes (12.73%), and related metabolisms such as carbohydrate metabolism and amino acid metabolism, as well as the lower value of methane metabolism reported in T3, supported the difference in CH4 and humification of the two treatments. In conclusion, DM was determined to be an eco-practical additive to improve the quality of end products and reduce potential risks, and the best treatment in this study was 10% added treatment based on dry weight.