Effects of biochar on enzyme activities during composting of cattle manure

With the rapid growth of livestock, they produce more and more waste, causing severe environmental damage. Biochar as a composting additive has several advantages, including improved performance and humification processes, increased enzyme activity, and reduced nitrogen (N) losses. To investigate the effect of biochar addition on compost quality and enzyme activity, we composted cattle manure with different biochar measures (2%, 5%, and 10%) and different types (rice husk and rice straw) of biochar. The results showed that adding biochar to the aerobic compost of cow manure effectively accelerated the temperature rise of the compost, decreased the total carbon (C) content of the compost, and the total N content increased from the mesophilic phase to the decaying period. The C-to-N compost showed a decreasing trend. The 5% rice husk biochar and 2% rice straw biochar treatments more effectively reduced the N loss during composting and played a better role in N fixation. The addition of rice husk biochar more effectively increased the urease activities compared with the addition of rice straw biochar. Adding 5% rice husk biochar increased the peroxidase and polyphenol oxidase activities by 78% and 38%, respectively. Therefore, adding 5% rice husk biochar effectively improved compost quality and enzyme activities and reduced N loss in the aerobic composting process of cattle manure for optimal compost production.