3.2. SBE-based bio organic fertilizer
Organic fertilizers are naturally occurring fertilizers or naturally occurring mineral deposits. In practice, organic fertilizers usually include mineral-based fertilizers as well, such as greensand or rock phosphate which is naturally occurring too. Organic fertilizer is produced naturally or via natural biological processes such as composting. The majority of nitrogen supplying organic fertilizers contain insoluble nitrogen and act as a slow-release fertilizer. SBE which is a naturally occurring montmorillonite/bentonite clay containing mineral deposits that is mined and physically treated into powder form without using chemicals. Hence, they can be considered organic. By co-composting SBE with other naturally occurring organic materials such as agricultural by-products and oil palm biomass, the composted finished products can still be considered as organic fertilizers.
Besides, a total pore volume of 0.165 cm3 g−1 for the SBE is indicative of a material that is not as good an adsorbent as activated carbon (0.459 cm3 g−1) but suffices to loosely bind the nutrients and release them slowly when needed by the crops. It shows adequate sorption/desorption capability. Once it is enhanced or composted, it increases water holding capacity, porosity and the adsorption capacity of nutrients. Unfortunately, there is not enough evidence at the moment to show that the structure and texture of composted SBE was indeed improved.