Abstract
A. R. Elniski. The Effect of Hot Water Extraction of Lignocellulosic Biomass and Recovered Lignin Addition on Fuel Pellet Properties, 300 pages, 42 tables, 75 figures, 2023. CSE style guide used.
Lignocellulosic biomass (LCB) is a renewable resource considered as an attractive alternative source of energy. Low bulk density, high ash content, and lack of uniformity are hurdles towards incorporating LCB into energy applications. Pelletizing densifies LCB into fuel pellets that have a higher bulk density, higher energy density, and are more uniform. However, they are more susceptible to degradation from moisture exposure, have unfavorable ash, and are hazardous in the emission of carbon monoxide (CO) in storage.
Hot water extraction (HWE) is a mild hydrothermal treatment process that is most effective on angiosperms such as shrub willow, miscanthus, and wheat straw in removing hemicelluloses (xylans). HWE results in lower ash content and increased lignin content when used on willow, miscanthus, and wheat straw. HWE has the potential to reduce CO emissions from pellets based on the partial removal of hemicelluloses and increase in lignin content. Lignin can be recovered from HWE and used as a feedstock additive for fuel pellets as well. Literature has yet to explore the utilization of HWE and lignin addition on the reduction of CO emissions.
In this study, shrub willow, miscanthus, and wheat straw were hot water extracted (HWEed) and pelletized. Ash content, energy content, bulk density, durability, pellet length, moisture absorption, and CO emissions of pellets made from LCB and HWEed LCB were measured. Lignin recovered from the HWE of shrub willow (RecL) and commercially available softwood kraft LignoBoost lignin (ComL) were added to willow and pelletized. The same pellet properties were measured.
The effect of HWE and lignin addition on pellet properties is not universal; it is dependent upon the LCB and the type of lignin utilized as an additive. Findings regarding HWE that have not been previously reported in other studies were the CO emissions of HWEed LCB pellets: HWEed LCB pellets emitted significantly more CO than LCB pellets with nearly all HWEed LCB samples. Regarding RecL and ComL as feedstock additives, pellets with RecL or ComL emitted significantly less CO than willow pellets without additional lignin. Future work should examine the addition of lignin to HWEed LCB to reduce CO emissions.