Prediction of Optimal C: N Ratio in Different Palm Oil Mill Waste Mixtures and Its Evaluation of Earthworm Biomass

The oil palm industry has been recognized for its contribution towards economic
growth and rapid development, it has also contributed to environmental pollution due to the
production of huge quantities of by-products from the oil extraction process. Current research
reports prediction of optimal CN ratio of different mixture percentages of palm oil mill effluent
(POME) and palm pressed fiber (PPF) namely 100% (only POME), 90%, 80%, 70%, 60%,
50%, 40%, 30%, 20%, 10% and 0% (only PPF). Different mixture percentages with varying
initial characters results in different C:N ratio which could affect the earthworm growth and the
vermicomposting stability. Therefore, the present research aims to predict the optimal mixture
by establishing a 3D base model. The models were generated having an average unified
formula using mathematical software Matlab. The results obtained in this study indicates that
the 3D polynomial graph can explain the relationship between different POME-PPF
concentration with respect to earthworm growth and time showing ideal R2 value of 0.99. The
regression analysis showed positive correlation between different mixture percentages and
earthworm growth in 50% (r = 0.412), 60% (r = 0.509) and 70% (r = 0.441). Therefore, from
the model it can conclude that 60% mixture of POME-PPF is an optimal mixture for the
vermicomposting process.