2.3. Formulation and production of SBE-based bio organic fertilizer
The SBE collected was first sorted out to remove any unwanted substances arising from the dumping of other wastes during oil refining process. It was subjected to a 90 day co-composting phase with chicken litter (∼25%) and palm oil milling by-products (∼40%) i.e. empty fruit bunches (EFB), palm oil mill effluent (POME) and shredded oil palm trunks (OPT). The type and blending ratio of the feedstock used were dependent on the desired nitrogen–phosphorus–potassium (NPK) contents for the finished product formulated. Modification of C:N ratio was also conducted via different blending ratios. The composting was conducted at 30–50 °C in open door and closed door windrowing systems to facilitate aeration via mechanical turning and to encourage active microbial growth in SBE. Agitating with aeration was conducted regularly for a complete homogeneous and effective mixing