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Palm oil empty fruit bunch (EFB) is a by-product produced during palm oil processing. In South East Asian countries, EFB is abundant and can be utilized as a renewable energy source. Cofiring of EFB with coal can be beneficial for preserving coal and reducing CO2 emission. However, EFB has some weaknesses in its properties such as; low bulk density, high moisture content, high alkaline contents, etc. Moreover, high amount of silicon and potassium in EFB tend to increase ash agglomeration which causes slagging and fouling in the equipment. In this study, hydrothermal treatment (HT) was employed to improve the physicochemical properties of the EFB by turning into biochar. Biochars are obtained after EFB is treated hydrothermally at a temperature range of 200-300 oC for 60 minutes were characterized for their proximate and ultimate compositions, mineral composition, calorific values, and ash fusion temperature. The analyses showed that fixed carbon increased while volatile matter decreased after HT. These changes were more prominent with increasing reaction temperature. The calorific values of EFB increased from 19.05 MJ/kg to 29.31 MJ/kg after HT at 300 oC. The biochar was then mixed with coal at different ratios (1:1, 1:2, and 2:1) for cofiring. The results showed that the energy densification increased with increasing reaction temperature. XRF results showed that the contents of Na, K and Si in EFB decreased after HT, resulting in the increased ash melting temperature. Consequently, the fouling and agglomeration potential could be reduced. The optimum ratio for cofiring between biochar and coal was found to be 2:1, as the fouling and slagging indices were lowest. It can be concluded that HT is a promising method for upgrading EFB as a feedstock for cofiring with coal.

To enhance the physicochemical properties of the EFB in the form of biochar, torrefaction and hydrothermal treatment were used. The proximate and ultimate compositions, heating values, and mineral composition of the biochar were all determined. The results showed that after treatment, fixed carbon increased while volatile matter decreased. With increasing reaction temperature, the increase and decrease were more noticeable. After hydrothermal treatment at 300 oC, the heating values of EFB increased from 19.05 MJ/kg to 29.31 MJ/kg. As the reaction temperature rose, so did the energy densification. The contents of Na, K, and Si in EFB decreased after hydrothermal treatment, according to XRF results. In general, the ash content of biochar obtained through hydrothermal treatment was lower than that of EFB (4.54%) as a raw material and comparable to Indonesian coal (37.37%) as a comparison. As a result, hydrothermal treatment is preferable to torrefaction when it comes to converting biomass to high-quality solid fuel.

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