The Valorisation of the Solid Fraction of Buffalo Manure through the Vermicomposting Process

Introduction Vermicomposting is a method where earthworms break down organic wastes to create a nutrient-rich substrate, known as vermicompost or worm humus, which is both cost-effective and eco-friendly (Ferraz Ramos et al., 2022). This process, performed in controlled environments, produces vermicompost from the solid separation of buffalo manure, providing essential nutrients for sustainable agriculture (Lazcano et al., 2008)(Lim et al., 2015). Accurate quality evaluation ensures vermicompost’s efficacy and agricultural compatibility. This research aims to assess the benefits of vermicompost as an organic fertilizer through a detailed quality analysis focusing on chemical, physical, and biological aspects. The study compares vermicompost derived from raw buffalo manure and buffalo digestate Material and Methods Two vermicompost plants were sampled in different parts. The first plant (VPI) is located at a buffalo farm that uses the separated solids of the raw buffalo slurry as material/feed for vermicompost. The second plant (VPII) is a consortium plant to which three buffalo farms send their raw materials. The samples after collection were stored in a refrigerator at a temperature of 4°C and subsequently analysed for TS, VS, TAN, TKN, pH and GI. Results and Discussion Figure 1 shows the results of analyzed vermicompost units, with delta values indicating the difference between final and initial values (vermicompost and separated solids). In Figure 1 (left), the final vermicompost has lower organic matter and TAN content, but TKN increased by 68%, likely due to ammoniacal nitrogen immobilization. The pH value bis borderline, as good vermicompost should not exceed a pH of 8 per regulations. The GI is around 80%, indicating minimal inhibition and a 26% increase from the original material, suggesting reduced phytotoxicity after vermicomposting. Figure 1 (right) also shows a reduction in organic matter. TAN reduction is greater in VPII than VPI. TKN increases by 5% compared to the initial solids separation. The pH is lower in VPII, indicating more stable vermicompost. The GI is 92%, a 31% increase from the starting material. The separated digestate solids initially have high phytotoxicity, more than the raw sewage solids. However, pre-treatment, including hot process vapor insufflation, enhances the material by inactivating infested seeds, increasing the GI from the separated material at time 0 to the final material. Conclusions Vermicomposting is effective with both solids separated from raw buffalo manure and buffalo digestate. The analysis also shows that vermicomposting prior to applying the separated digestate solids or effluent to the field can result in a richer and more stable product.