(159h) Granulation of Lime Pretreated Switchgrass Powders
Densification of switchgrass will reduce handling, transport and storage issues in the biorefinery due to low bulk density and poor flowability by improving the physical and flow characteristics. Conventionally, switchgrass is densified into pellets and briquettes, but the densification process requires high pressure, energy and cost for compaction. Hence, a novel low-pressure wet granulation method of densification was proposed to evaluate the quality of densified products. Wet granulation is a process of agglomerating fine particles into granules by addition of liquid binders and application of shear/vibrating forces. In this study, switchgrass was ground into fine powders and pretreated with calcium oxide at three loading rates (0.05, 0.1, 0.2 g/g of biomass) at 121°C for 30 min and at room temperature (23-25°C) for 72 hours. Pretreated powders were granulated using cornstarch and sodium alginate combination binder in a pan granulator with standard operating procedures. Structural changes occurred during pretreatment of switchgrass were analyzed by scanning electron microscopy and autofluorescence microscopy. The physical, flow and chemical properties of pretreated switchgrass granules were determined and compared with untreated switchgrass granules. Switchgrass granules made from pretreatment of calcium oxide (0.2 g/g of switchgrass powder) at both autoclave and room temperature conditions had higher single granule density and lower binder to powder percentage compared to untreated switchgrass granules. Granulation of biomass can be a viable alternative to improve biomass quality compared to energy intensive pelleting technology.