Characterization of Matured Vermicompost Derived from Valorization of Palm Oil Mill Byproduct

The valorization process involves transforming low-value materials such as wastes into high-value-added products. The current study aims to determine the potential of using a valorization process such as vermicomposting technology to convert palm oil mill byproduct, namely, decanter cake (DC), into organic fertilizer or vermicompost. The maturity of the vermicompost was characterized through various chemical and instrumental characterization to ensure the end product was safe and beneficial for agricultural application. The vermicomposting of DC showed significantly higher nutrient recovery and decreases in C:N ratio in comparison with the controls, particularly in the treatment with 2 parts DC and 1 part rice straw (w/w) (2DC:1RS). 2DC:1RS vermicompost had a final C:N ratio of 9.03 ± 0.12 and reasonably high levels of calcium (1.13 ± 0.05 g/kg), potassium (25.47 ± 0.32 g/kg), magnesium (4.87 ± 0.19 g/kg), sodium (7.40 ± 0.03 g/kg), and phosphorus (3.62 ± 0.27 g/kg). In addition, instrumental characterization also revealed a higher degree of maturity in the vermicompost. Ratios of 2921:1633 and DTG2:DTG3 also showed significant linear correlations with the C:N ratio, implying that those ratios could be used to characterize the progression of vermicompost maturity during the valorization process of DC.