Trials about composting of solid wastes from palm oil Mills in Indonesia
The solid wastes produced in palm oil mills are empty fruit bunch (EFB), mesocarp fibre, shell, and palm kernel cake. On an average the amount of EFB is 0,220 t of 1 t oil palm fruit bunch (Singh, 1994). In Indonesia, there will be about 2.9 million tonnes EFB (dry basis) in 2000 (Lubis et. al. 1994). At the moment, EFB in Indonesian palm oil mills are burnt in incinerators to reduce the mass and the volume of the biomass. The bunch ash that can be used as a valuable fertiliser (in 1 t dry ash: 414 kg K2O, 37 kg P2O5, 58 kg MgO, and 49 % CaO; 48 to 87 kg ash from 1 t EFB dm) (Singh, 1994). The negative effect of the incineration of EFB is the air pollution and the destroying of the organic matter and the nitrogen. In Malaysia, for example, the incineration is prohibited since 1990 (Teoh and Chia, 1993).
In a sustainable palm oil production the objective is the use of all valuable components of EFB without environmental pollution. Table 1 and 2 show the composition of EFB. They are characterised by a high content of organic matter and plant nutrients, especially potassium but also nitrogen, and a relatively wide C/N ratio. The content of holocellulose is about 70 % and 17 % is lignin (Goenadi et al. 1994).
The alternatives for the use of EFB are beneath fuel as mulch (Singh et al., 1989, Singh 1994) compost, and raw material for pulp and paper industry (Lubis et al., 1994; Goenadi et al., 1994; Guritno et al., 1995).
Composting of EFB is an interesting alternative, because this alternative can reuse not only the mineral plant nutrients, but also the organic matter with the positive impact on soil structure, improving water and air capacity. The nitrogen concentration of EFB is low compared to their carbon concentration, so added N source can be important to induce the micro-organisms growth.