Doctor of Philosophy (PhD) 
in
Biomaterials Engineering
Research

Three lignocellulosic materials were utilized for this research: Shrub Willow, Miscanthus, and Wheat Straw [pictured left to right]. Each biomass was pretreated with hot water extraction prior to the pelletization process [pictured in bottom row].

Hot water extraction resulted in two main streams: solid lignocellulosic biomass and liquid hydrolysate. The solid biomass was air dried and utilized for fuel pellets [pictured top left]. The liquid hydrolysate contained hemicellulosic sugars and lignin [pictured top right]. The hydrolysate was acidified to pH-2 to precipitate the lignin from the hydrolysate. The hydrolysate was then decanted from the container and the lignin was recovered [pictured  bottom left] to be washed, dried [pictured bottom right], and applied to biomass during the pelletization process.

Two pelletizers were used for making fuel pellets of different treatments. The large-scale pelletizer was a flat-die pelletizer located off-site in Tully, NY [pictured right]. A small-scale ring-die pelletizer was located on-site in Syracuse, NY [pictured left]. Each lignocellulosic material was ground into 6 mm and 3 mm particle size prior to large-scale pelletization, and 3 mm and 1 mm particle size for small scale pelletization. Lignin-addition pelletization occurred only with the small-scale pelletizer.

Hot water extraction was performed at the pilot scale for each of the three lignocellulosic materials. The pilot scale reactor had a volume of 65 cubic feet or 1841 Liters [pictured above]. The process used steam and pressure to remove hemicelluloses (particularly xylans) from biomass, notably angiosperms. A portion of lignin was also removed during the process. The extraction occurred for two hours at approximately 160 degrees Celsius. 

Biomass was ground to various particle sizes utilizing two hammermills. One hammermill was a small-scale machine capable of reducing particle size to 6 mm, 3 mm, and approximately 1 mm dimensions [pictured left]. The other hammermill was a large-scale device capable of reducing particle size to 6 mm at a quicker speed than the small-scale hammermill [pictured right]. 

Various pellet properties were tested to examine the impact of the hot water extraction and lignin addition treatments. These properties included: 

• Bulk Density 

• Pellet Density and Dimensions

• Durability

• Moisture Content

• Ash Content

• Moisture Absorption

• Calorific Value

• Carbon Monoxide (CO) Emissions

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Most of these properties were measured following an associated ISO method with limited modifications where necessary. Moisture Absorption and CO emissions did not follow an ISO method, but did utilize methods influenced by literature in the field. An example of an emissions apparatus is pictured above.