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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Agricultural and Biosystems Engineering

First Advisor

Kasiviswanathan Muthukumarappan


Switchgrass, com stover, and prairie cord grass are three important biomass materials that are widely used as alterative energy resources because of their abundant availability and renewable nature. These materials are rich in lignin and cellulose and, therefore, are considered as lignocellulosic materials. These materials can be used in the future in commercial production of renewable fuels (ethanol), combined heat and power, chemicals, and bio-products. Efficient conversion of biomass into bioenergy relies heavily on the effective, consistent, and economical transport of biomass from the field to the biorefinery. Due to the high moisture content, irregular shape and size, and low bulk density, biomass can, potentially, be very difficult to handle, transport, store, and utilize in its original form. This major issue faced by contemporary ethanol producers needs to be solved.
To address this problem, biomasses need to be condensed. In this project, switchgrass, corn stover, and prairie cord grass are ground into 2 mm, 4 mm, and 8 mm samples and pretreated by the Ammonia Fiber Expansion (AFEX) pretreatment process and subsequently run through comPAKco equipment (PAKed). Physical properties can show characteristics of the transition and storage of these biomass materials. These physical properties, which include moisture content, bulk density, true density, porosity, water activity, thermal properties, and glass transition temperature, were measured using 2 mm, 4 mm, and 8 mm control, AFEX treated, and AFEX-PAKed switchgrass, com stover, and prairie cord grass. After storage in the open air for six months, the physical properties were tested again and compared with the physical properties of the biomasses before storage. After being AFEX-PAKed, the bulk density of the three biomass materials increased 2-3 times, which indicated AFEX-PAKed biomass materials are more effective to transport and handle. AFEX-PAKed biomasses also have better durability, which indicated that during handling and transport AFEX-PAKed biomass products are less likely to break. After storage in the open air for 6 months, the moisture content of all AFEX treated and AFEX-PAKed biomass materials decreased, while the durability of all AFEX-PAKed biomasses increased. The glass transition temperature (Tg) of all AFEX treated and AFEX-PAKed biomass materials decreased except AFEX-PAKed switchgrass. The WAI and WSI changing showed mix trends. The thermal property values and true density values stayed the same after storage.
To understand the flow characteristics of switchgrass, corn stover, and prairie cord grass, flowability and floodability analysis of 2 mm, 4mm and 8mm of all three mentioned biomass materials were done. Flowability includes angle of repose (AoR), aerated bulk density (ABD), packed bulk density (PBD), compressibility, angle of spatula (AoS), cohesion, and uniformity. Floodability includes angle of fall (AoF), angle of difference (AoD), and dispersibility. The flowability and the floodability were evaluated by the index of the flow properties and the flood properties. From the results, the flowability and the floodability of all these three biomasses showed a similar trend. AFEX treatment didn't influence the flowability or the floodability of the biomass materials. In addition, there was no significant difference noted in the value of floodability between control, AFEX treated, and AFEX-PAKed biomasses. but, the AFEX-PAKed biomassesshowed lower value flowability.
Moisture adsorption characteristics of biomass materials at various relative humidity and temperature values are important in the storage process to optimize the conditions. High moisture adsorption of biomass products has been known to increase the presence of fungi and molds, which tend to be damaging to the stored materials. Moisture adsorption of 8 mm control, AFEX treated and AFEX-PAKed switchgrass, corn stover, and prairie cord grass, under three temperatures (20, 30, and 40°C) and four relative humidity values ranging (60, 70, 80, and 90%) was measured and modeled. Three commonly used models of Peleg, Pilosof, and Page were used to fit the experimental data. The Peleg and Page models were found to be more suitable to describe the dynamic moisture adsorption of control, AFEX treated, and AFEX-PAKed switchgrass, com stover, and prairie cord grass. The Modified Henderson model was more reasonable to describe the relationship of RH, temperature, and EMC in comparison to the Modified Chung-Pfost; Modfied Halsey; Modified Oswin, and Modified GAB (Guggenheim-Anderson-de Boer) models.

Library of Congress Subject Headings

corn stover
ethanol as fuel
biomass conversion
biomass energy


Includes bibliographical references (128-140)



Number of Pages



South Dakota State University


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