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Due to the tremendous amount of palm biomass residues produced during the palm oil extraction from fresh fruit bunch (FFB), it is inevitable to harness these biomass energy sources to cope with the depletion of fossil fuels and increase in global energy demand scenarios. Densification is one of the favourable techniques to improve the storage and transportation of biomass fuels in order to prevent dumped areas adjacent to palm mills and to prevent from becoming another waste product. This article reviews comprehensively on how type of palm biomass, compaction pressure and temperature, binder, pre- and post-treatments affect the physical and combustion properties of the palm biomass briquettes produced. Based on the previous researches, generally it can be said that the type of palm biomass, the compaction pressure and temperature, and type of binder affect both the physical and combustion performance of densified palm biomass. However, the effect of particle size could be observed only on the physical characteristics of densified products, whereas the effect on the combustion properties remains unclear. In addition, treatments such as pyrolysis, dry and wet torrefaction (hydrothermal treatment), and steam explosion have potential to be applied during briquette production in order to improve the combustion properties. In this review article, it is also suggested that the combination of densification and followed by wet torrefaction will enhance the combustion properties of palm biomass briquettes.

High global energy demand scenario has driven towards transformation from sole dependence on fossil fuels to utilization of inexhaustible renewable energy sources such as hydro, biomass, solar and wind. Renewable energy sources are abundant in Malaysia, especially palm biomass residues that are produced during the oil extraction process of fresh fruit bunch. Therefore, it is inevitable to harness these bioenergy sources, in order to prevent waste accumulation at adjacent to palm mills. Briquetting of palm biomass such as empty fruit bunch (EFB) with polyethylene (PE) plastics waste addition is expected not only could maximize the utilization of energy resources, but also could become as a potential solution for residue and municipal plastics waste disposal. In the present study, the physical and combustion properties of palm biomass briquettes that contain novel mixture of pulverized EFB and PE plastics waste were investigated experimentally. The briquettes were produced with different mixing ratio of EFB and PE plastics (weight ratios of 95:5, 90:10 and 85:15), under various heating temperatures (130-190 ) and at constant compaction pressure of 7 MPa. Based on the results, it can be said that heating temperature plays a significant role in affecting physical properties such as relaxed density and compressive strength. The values of relaxed density and compressive strength are within the range of 1100 to 1300 kg/m3 and 0.8 to 1.2 MPa, respectively. Meanwhile, mixing ratio does affect relaxed density and gross calorific value. All values of gross calorific (17900 to 21000 kJ/kg) and moisture content (7% to 9%) are found to fulfill the requirement for commercialization as stated by DIN51731 (gross calorific value>17500 kJ/kg and moisture content<10%). Even though the values of ash content (3% to 4%) exceed the limitation as stated by the standard (<0.7%), it is still considered very competitive if compared to the commonly used local briquette that contains mesocarp fibre and shell (5.8%). Finally, it can be concluded that the best quality of briquette can be achieved when highest composition of PE plastics (weight percentage of 15%) is used and the briquetting process is performed at the highest temperature (190 ).