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 byproducts
(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.