¦PELLET DEPARTMENT
PHOTO: PENN STATE UNIVERSITY
From Recipe to Scientific Formula A solid understanding of energy crops and their densification behavior could remove much of the guesswork in creating a quality pellet. BY CHRIS HANSON
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reating a pellet or briquette from energy crops may seem more like a secret family recipe than an exact process. Begin with a selected feedstock, dry accordingly, add binders if necessary and compress generously. Sometimes, even if the recipe is dead-on, the end product may turn out differently than expected. Densifying energy crops presents unique challenges to producers seeking to use grassy feedstocks, such as miscanthus and switchgrass, for pellet production. Moisture, binder and energy requirements are just a few of the issues inherent in creating a pellet or briquette made from energy crops, says Emily Heaton, assistant professor of biomass crop production at Iowa State University. “Sometimes there is not enough moisture or enough binder, depending on the pelleting process and getting it to stick together, and then the energy that is required to get it to stick together,” Heaton says. “You can always get it to stick together, but what does it take to do that?” Heaton says she believes the challenge involved in densifying dedicated energy crops is simply gaining enough experience 22 BIOMASS MAGAZINE | FEBRUARY 2014
and know-how—making more kinds of pellets more often, and having a reason to begin producing them at scale to evaluate in more detail. Researchers at Penn State University are working to do just that, by engaging in a continuous study of pelletizing biomass energy crops in small-scale pellet machines. “The project is working from two directions,” says Daniel Ciolkosz, research associate at Penn State. “One direction starts at the fundamental science of particulate materials and how they behave during the densification process.” Heading up the fundamental side of the project, researchers Apoorva Karamchandani, Hojae Yi and Virendra Puri apply their particulate compaction background to investigate solutions for problems including pelletizer clogging and crumble-prone pellets. “What we envision is to have more consistent throughput in terms of the process, and less issues during pelletization,” says Yi, research associate of powder mechanics at Penn State. By bringing more science into the equation, the user will have greater control and insight over feedstock selection, and pro-