Vermicomposting with food processing waste mixtures of soybean meal and sugarcane bagasse

Abstract

Vermicomposting is considered a clean, sustainable, and effective technology to recycle food waste. However, the current knowledge of how different food waste combinations produce high-quality compost remains poor. Hence, the present study investigated the vermicomposting of soybean meal (SM) waste with sugarcane bagasse (SCB) in different ratios of SM:SMB (v/v, based on dry weight), i.e., 0:100, 25:75, 50:50, 75:25, and 100:0. Vermicompost quality was evaluated based on its maturity, agrochemical properties, earthworm ( Eisenia fetida ) biomass, and reproduction. The results showed that SM increased the activities of dehydrogenase, acid- and alkaline-phosphatase, and urease while decreasing the activity of cellulose. The β -glucosidase activity was highest with 25:75, followed by 50:50 of SM:SCB ratio. A higher proportion of SM increased the mineralization and nitrification rate during the vermicomposting, whereas total and available nutrients contents increased in the final product. The concentration of all heavy metals in the final vermicomposts was below than threshold. The degree of polymerization (DP) showed that all of the final vermicomposts were sufficiently mature for agricultural application. A higher percentage of SCB ( ≥ 50%) in SM:SMB mixtures, however, resulted in best vermicompost owing to reduced pH and EC, increased CEC and humic substance concentration, and higher germination index. So far, earthworm mass and abundance were highest in SM:SCB ratio of 50: 50. In short, a 50:50 mixture of SM:SCB promoted earthworm growth and produced the best quality vermicompost. • The addition of SM to SCB enhance mineralization and nitrogen transformation. • SCB in the mixtures improved product quality by increased CEC and humic substance. • Combination of 50% SCB and 50% SM promoted earthworm growth. • The content of total heavy metals increased in resulting vermicomposts.