Oil palm waste as pyrolysis feedstock - versatile biochar

What is it about?

Oil palm plantations occupy the largest sector of agriculture in Malaysia with approximately 5.7 million hectares of plantation area in 2016. The subsequent processing to produce palm oil inadvertently produces great amount of oil palm wastes (OPW) that generally comprise of 15% of mesocarp fibres (MF), 6% of palm kernel shells (PKS), and 23% of empty fruit bunches (EFB) in one ton of fresh fruit bunch (FFB) of oil palm. In view of the large production of OPW and the advantages shown by the biochar produced from pyrolysis process, this study was performed to investigate the potential of using OPW as a pyrolysis feedstock for recovery of biochar with desirable properties for use in multiapplications. This included some in-depth analyses of the elemental and proximate composition of the OPW. The wastes were then analyzed via a thermogravimetrical approach to examine the different types and stages of chemical reactions (e.g. moisture evaporation, devolatilization, fragmentation) that could occur during their thermal decomposition by pyrolysis, and to propose the suitable pyrolysis temperature for optimal recovery of biochar.

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Why is it important?

Oil palm wastes can be a suitable feedstock for pyrolysis conversion into biochar due to its high carbon content (up to 51 wt%). The OPW should be pyrolysed at a minimum temperature of 410 ◦C in order to remove the majority content of the volatile matter for recovery as a carbon-dense biochar. The biochar obtained at microwave power of 700 W (i.e. MC700) showed highly porous with ‘cleaner’ pores observed on its surface. Combined with the high BET surface area of 210 m2/g and low contents of moisture and ash (<3 wt%), this suggests that MC700 has many sites for adsorption processes. The biochar showed a 48 mg/g of adsorption efficiency on methylene blue dye adsorption, and provided good retention of water and nutrients to improve mushroom growth (450 g of Oyster mushroom yield obtained).