Development of a novel co-composting system for empty fruit bunches using UASB-HCPB fermentor-derived effluent for sustainable palm oil waste management: Design, performance evaluation, and kinetic study

The exponential growth of Indonesia’s palm oil industry with annual production of 43.5 million tons generates substantial biomass waste, particularly empty fruit bunches (EFB), necessitating innovative waste management solutions. To address this challenge, an integrated approach to waste valorization through co-composting technologies was developed to transform agricultural waste into a valuable resource. This study introduces a novel cylindrical composting system integrating EFB with UASB-HCPB fermentor-derived effluent (FDE) as a co-composting accelerator. The study investigates the correlation between composter capacity (2, 5, and 10 kg) and process parameters for enhanced compost quality. The methodological framework encompassed optimum EFB size of ±2 cm, strategic FDE supplementation with moisture regulation (55–65%), and comprehensive physicochemical analysis including temperature, nutrient profiles, and degradation kinetics. A first-order model describing the decomposition rate constant (k = -2 × 10^–5C² + 2 × 10^–4C + 3 × 10^–4) was derived for precise prediction of organic matter degradation across varying composter capacities. The results showed that the 10 kg capacity demonstrated superior performance achieving notable parameters with temperature (30°C), moisture content (55.22%), pH (7.5), volatile suspended solids (208.011 mg/L), organic matter (94.23%), electrical conductivity (2.40 dS/m), water holding capacity (60%), and C/N ratio (17.20) with superior macro and micronutrient profiles (N: 1.69%, K₂O: 5.44%, P₂O₅: 0.63%). The organic matter degradation kinetics showed good correlation models across composters capacities, resulting in R² of 0.8800 for 2 kg composter, 0.9094 for 5 kg composter, and 0.9780 for 10 kg composter. The resultant compost characteristics exhibited adherence with Indonesian National Standard (SNI 19–7030–2004) specifications. This innovative approach presents a significant advancement in sustainable palm oil waste management for both environmental and agronomic benefits through efficient resource recovery and valorization.