Conclusion
Through composting SBE with agricultural and palm oil milling by-products, the physicochemical properties such as the acid reactivity and hydrophobic nature of the composted SBE improved drastically. The resulting compost exhibited some enhanced fertilizer properties such as the C:N ratio, water-holding capacity, CEC and OC content that was able to rejuvenate degraded soil, and to act as an efficient water/nutrients controlled release fertilizer in soil–fertilizer interaction. Results from the pot assays and field trial conducted further revealed a significant biomass growth and yield productivity for the tested crops. In general, the developed SBE compost can be used as a bio organic fertilizer for a wide range of crops.