The biotic effects of lignite on humic acid components conversion during chicken manure composting.

Targeted regulation of composting to convert organic matter into humic acid (HA) holds significant importance in compost quality. Owing to its low carbon content, chicken manure compost often requires carbon supplements to promote the humification progress. The addition of lignite can increase HA content through biotic pathways, however, its structure was not explored. The Parallel factor analysis revealed that lignite can significantly increase the complexity of highly humified components. The lignite addition improved phenol oxidase activity, particularly laccase, during the thermophilic and cooling phases. The abundance and transformation functions of core bacteria also indicated that lignite addition can influence the activity of microbial transformation of HA components. The structural equation model further confirmed that lignite addition had a direct and indirect impact on enhancing the complexity of HA components through core bacteria and phenol oxidase. Therefore, lignite addition can improve HA structure complexity during composting through biotic pathways.

Effects of initial carbon-phosphorus ratio on phosphatase, and phosphorus availability in sludge composting.

Phosphorus in wastewater sludge is one of the important nutrients for biological growth and an important non-renewable resource. Most research in the composting field focuses on the C/N ratio, but there are few reports on initial carbon-phosphorus (C/P) ratio regulation. This study investigated the effects of different initial C/P ratios on phosphatase activity, key bacteria, and phosphorus availability in compost. In this study, the activity of phosphatase was measured, and key bacteria secreting phosphatase were identified. The results showed that adjusting the initial C/P ratio could prolong the cycle of action of key bacteria, thus affecting the activity of phosphatase and promoting the production of available phosphorus, but it was also inhibited by the feedback of available phosphorus. This study demonstrated the feasibility of adjusting the initial C/P ratio of sludge composting and provided theoretical support for optimizing the application of sludge composting products with different initial C/P ratios.