Precipitation sludge (PS) generated from cardboard production contains high metals (Al, Fe, Ca, Si) and organic components (starch, cellulose, xylan, and lignin). With high moisture and a mixture of organic and inorganic components, PS cannot be recycled and combusted for energy recovery, resulting in zero value and landfill disposal. This creates both environmental and economic challenges. Interestingly, observations of PS waste piles showed heat and odor, suggesting microbial activity within the sludge. To minimize waste sent to landfill and increase the chances of recycling, we are seeking a potential bioremediation route for organic matter degradation and resource recovery. In this study, microbial communities in PS were revealed using high-throughput DNA sequencing and their potential roles in breaking down organic components were investigated. Five experimental conditions were conducted by supplementing PS with the following 0.5% carbon sources to stimulate or enrich relevant microbial activities: no supplementation, cellulose, starch, xylan, and lignin. Samples were incubated at 25°C for ten weeks, and microbial diversity and profiles were monitored over time. The results revealed significant shifts in microbial composition. The genera Paludibacter, Propionicimonas, and Saccharimonadales were dominating the communities for the first two weeks, followed by the genera Leptolinea, Saccharofermentans, and Christensenellaceae R-7 group at later stages. Furthermore, organic composition analyses indicated that starch residue from the pulping process was rapidly degraded within the first two weeks, followed by degradation of the wood cell wall components xylan and cellulose. In contrast, lignin remained across all conditions due to its structural complexity and was enriched in the final slurry. These findings suggest that microbial activity can contribute to organic matter reduction in PS and enrich inorganic components for recycling. Additionally, this study enhances the value of PS for applications in fermentation, soil improvement, and material development. This exhibits the potential of microbial consortia for sustainability.