One of the problems commonly encountered during the gasification process for biomass is the agglomeration of residue associated with low efficiency, which occurs due to the use of low-quality fuels containing ash and alkali and alkaline earth metallic (AAEM) compounds. In this study, the empty fruit bunch (EFB), which is a byproduct of the palm oil industry that could potentially be used as fuel, was pretreated by washing with both tap water and a nitric acid solution (0.1 wt %) for different washing times to try to resolve this problem. The washing process decreased the ash content from 5.9 wt % to 1.5 wt % when all the washing pretreatments were employed, and over 80 wt % of the AAEM compounds, such as potassium (K), magnesium (Mg), calcium (Ca), and sodium (Na), were removed. Additionally, scanning electron microscopy (SEM) with Xray diffraction (XRD) was used to identify the composition and surface characteristics of the agglomerations produced during gasification. The proportion of agglomeration measured in washed EFB decreased by over half compared to the agglomeration produced by unwashed EFB, regardless of the type of washing solution used. Previous research has shown that syngas yields of approximately 70% can be achieved at a temperature range of 900 to 1000 degrees C. Thus, washed EFBs were applied to a bubbling fluidized bed reactor (BFB), and the optimum experimental conditions (temperature and equivalence ratio, ER) were chosen as 900 degrees C and ER = 0.6. The syngas yield of the washed EFB gasification was higher than that of the unwashed EFB. Additionally, agglomeration was reduced from 8.7 wt % to 1.3 wt %.