3. Results and discussion
Bio fertilizer production in the oil palm industry has so far concentrated mainly on the by-products from palm oil mills but has excluded the refinery waste (namely SBE) discharged by the PORs. SBE was found to contain a fairly adequate quantity of NPK compared to various other bio materials such as oil palm biomass (e.g. POME, EFB, OPT and oil palm frond or OPF) and agricultural by-products (e.g. chicken litter) (Table 1), which is essentially required in any bio fertilizer production. The initial C:N ratio of 290 in SBE before composting was far too high compared to other bio materials which could decompose readily in the field as mulch. Though SBE contained a high C with limited N, the bioavailability of C could be low, thus the decomposition of SBE being slow. Hence, the direct application of SBE to soil would have caused a detrimental effect in limiting bioavailability of soil N for plant growth.