Comparative evaluation of biochar, pelelith, and garbage enzyme on nitrogenase and nitrogen-fixing bacteria during the composting of sewage sludge

This study investigated the effects of garbage enzyme (GE), pelelith (PL), and biochar (BC) on nitrogen (N) conservation, nitrogenase (Nase) and N-fixing bacteria during the composting of sewage sludge. Results showed that the addition of GE, PL, and BC reduced NH3 emissions by 40.9%, 29.3%, and 67.4%, and increased the NO3N contents of the end compost by 161.4, 88.2, and 105.8% relative to control, respectively, thus increasing the TN content. Three additives improved Nase, cellulase, and fluorescein diacetate hydrolase (FDA) activities and the abundances of nifH gene, and the largest increase was BC, followed by PL and GE. In addition, the additives also markedly influenced the succession of N-fixing bacteria, and significantly increased the abundance of Proteobacteria during the whole process. The BC and PL additions strengthened the sensitivity of N-fixing bacteria to environmental variables, and FDA, TN, moisture content, and NO3-N significantly affected the Nfixing bacteria at genus level.

Automated summary

The addition of garbage enzyme, pelelith, and biochar can reduce NH3 emissions and increase NO3N content during the composting of sewage sludge, leading to an increase in TN content. These additives also enhance Nase, cellulase, and FDA activities, as well as the abundance of nifH gene, with biochar showing the largest increase. The additions also influence the succession of N-fixing bacteria and increase the abundance of Proteobacteria, especially enhancing the sensitivity of N-fixing bacteria to environmental variables.