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A physical and chemical characterization of three Colombian agricultural biomass residues was carried out to identify promising feedstocks for thermochemical energy production. The three chosen were sugar cane bagasse (SCB), rice husk (RH), and palm kernel shell (PKS). Results showed that SCB, has high volatile material (87.41 wt % daf), lignocellulosic composition high in hemicellulose (29.68 wt % daf) and cellulose (39.81 wt. daf), high alkali index (4.07), and soft morphology; these characteristics make it a good candidate for fast pyrolysis to produce bio-oil and gas. The RH, despite having a lignocellulosic composition similar to SCB, has slightly less volatile matter than SCB (75.73 wt % daf), a soft morphological structure, and high ash content (19.33 wt %) mainly of noncatalytic species, all of which make RH unattractive for pyrolysis; however, its fixed carbon content makes it very interesting for combustion and gasification processes. On the other hand, the PKS is the biomass with the highest content of fixed carbon (22.78 wt % daf) and lignin (58.30 wt %); its hard structure, low ash content (2.67 wt %), and high lignin content make it most suitable for high-temperature processes like combustion and gasification processes.

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Currently, there are many studies that analyze the co-gasification or co-combustion of biomass with coal in fluidized-bed reactors. Mixing these two materials takes advantage of particle segregation as a result of the differences in density, shape, and size; this phenomenon requires due attention because it can lead to reactor operation issues. Some common problems seen with biomass are gap flow, plug flow, and large bubbles that reduce mass and energy transport, thus lowering the quality of the syngas product. In this study, we found that mixing biomass palm kernel shell (PKS) with coal greatly reduces these problems. Furthermore, we propose that this technique can be applied to other biomasses than the biomass used in our study without observing fluid dynamic issues. Continuous feeding co-gasification tests were performed with PKS and sub-bituminous coal type A (sub-bA coal) in a pilot-scale fluidized-bed reactor using air as the gasifying agent.

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The effects of the binder amount and particle size on the quality and mechanical agglomeration of pellets produced from three biomasses of agroindustrial crops (rice husk, “RH”; coffee husk, “CH”; and palm rachis, “PR”) were studied. Pellet quality parameters, such as the production yield, bulk density, pellet size distribution (length), water resistance, impact resistance, and ultimate and proximate analyses, were analyzed according to the European standards and were related to a possible energy exploitation. In addition, pellet morphology was evaluated by scanning electron microscopy and stereoscope visualization. The connectivity between the biomass particles is explained by mean of mechanical interlock for PR, whereas for CH and RH, a combination of mechanisms, such as adhesion and interparticle attraction forces, provides the connectivity between the biomass particles. The results showed that, for the smallest particle size analyzed (0.6 mm), pellets from laminar-shaped biomasses (RH and CH) showed a high impact resistance and water resistance. Likewise, pellets from the fibrous biomass (PR) showed a high impact resistance but a low water resistance.