Digested empty fruit bunch as a fertilize
SMARTRI, IPB and WUR collaborate to demonstrate that digested empty fruit bunches can be used as a fertilizer. The parties met on July 8 in Libo (Sumatra).
Background
The SustainPalm programme is being executed to implement practices that increase sustainability of oil palm in Indonesia. One of the focus areas is the use of residues for added value products. This will spare land, reduce GHG emissions and increasing local welfare. Empty fruit bunch (EFB) is the residue after the oil fruits have been harvested. Currently EFB is incinerated, sometimes returned as such to the oil palm plantation and sometimes first composted and returned to the plantation. In SustainPalm the EFB will be anaerobically digested together with the palm oil mill effluent (POME) (in a mixture) to produce biogas. The biogas can be used to supply energy to the oil mill. As a result, the oil mill doesn’t need to use mesocarp fibre as fuel anymore and this can be sold and used for other purposes. After anaerobic digestion, a digestate is produced from the EFB and POME mixture that still contains valuable nutrients, such as nitrogen, phosphorus, potassium and more. Moreover, it will contain residue organic matter that is relatively recalcitrant with respect to biodegradation: this is the fraction that tends to stay in the soil for a longer time and improves soil structure (e.g. water holding capacity).
Our aim
We are demonstrating that the EFB/POME digestate can be used as a fertilizer and soil improver. We plan to compare four types of fertilizers: chemical/synthetic fertilizers, mulched EFB with added treated POME, composted EFB with added treated POME and EFB/POME digestate.
This demonstration is a collaboration of Sinar Mas (palm oil producing company), IPB and WUR at the site of SMARTRI (part of Sinar Mas) in Libo, near to Pekanbaru (Sumatra).
Progress
On July 8 (2024) Wolter Elbersen and Johan van Groenestijn (WUR) visited SMARTRI and discussed the trials with employees of SMARTRI (a.o. Pak Hasbullah) and IPB student Pak Syafiq.

Digestate was produced on site of SMARTRI in 200 L vessels and compost was produced in heaps. The first tests concerned the effect of the various fertilizer types on seed germination of radish in petri dishes and pots. In fact, this was a kind of toxicity test. Too high additions appeared to inhibit germination. This insight is important to design the next tests in which crop yields will be compared on a sandy soil (poor in nutrients and fibres) with added fertilizer types.
