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A Biomass Carol: Bioenergy for The Future

Ekramul Ehite

FFAR Fellow, University of Tennessee-Knoxville

Knoxville, TN

An Abundance of Potential Agricultural By Products

Imagine you are in a modern-day reproduction of Charles Dickens’ classic “A Christmas Carol” — instead of Victorian London, you are in a rural cornfield in the Midwest. The ghost of the Christmas past shows you the barren cornfield after the harvest with an abundance of corn stover (corn stalks, leaves, and cobs) lying in the field. All this while the ghost rides a diesel-run tractor clogging the air with smoke. You ask, “Is there no beneficial use for corn stover that will also not harm the environment?”

Agricultural Waste Material as Biomass Feedstock

Well, that is when the ghost of the Christmas present shows up and tells you about using agricultural waste materials as lignocellulosic biomass feedstock in biorefineries to produce bioenergy, biofuel and biochemical products. Apart from agricultural waste like corn stover, lignocellulosic biomass can be sourced from forestry residues (pine, poplar), dedicated energy crops (switchgrass, Salix), and aquatic plants (water hyacinth). Since lignocellulosic biomass comes from non-edible sources, they do not compete with human and animal food. Additionally, certain bioenergy crops can be potentially grown in marginal lands without competing with croplands, which is especially relevant for countries with limited land and forest resources. As such, lignocellulosic biomass materials are the key to a future world that will be environment-friendly, zero-waste, and not dependent on fossil fuel sources.

Then why is that not the case right now? The ghost responds that a major limitation hindering the commercial viability of lignocellulosic biomass is the high degree of variability in their physiomechanical and morphological properties, making their processing in biorefinery plants highly challenging. They get stuck in the flow equipment during the flow, stopping the biorefining operation and harming the overall bioenergy economics. And thus, lignocellulosic biomass materials cannot fulfill its potential as a game-changer for the energy industry.

A scientist in a lab conducting an experiment using switchgrass.
FFAR Fellow, Ekramul Ehite, conducts an experiment using switchgrass.

Biomass Flow Issues and the Future

But wait, where’s the ghost of the Christmas future? That is where my doctoral research comes in, as it deals with investigating the underlying reason behind biomass flow issues. I hypothesize that the flow behavior is directly related to the biomass cell wall’s unique microstructure and structural constituents. The lignocellulosic biomass cell wall has a compound, non-uniform, three-dimensional matrix structure formed by three polymers: the polysaccharides cellulose and hemicellulose, and the phenolic polymer lignin, with trace amounts of other chemical compounds. In addition to the compositional varieties, the biomass feedstock is highly variable in their morphology, i.e., their physical size, shape, and distribution, further worsening flow issues. Yet, the state-of-the-art biomass industry does not have comprehensive information about the connection between biomass structural constituents and morphology to the flow.

My target was to develop a fundamental understanding of the relationship between structural constituents and the morphology of lignocellulosic biomass materials and the impact of the structure and morphology on flow behavior. I experimentally investigated biomass particles of different structural compositions through classical physical flow characterization tests and computationally through high-fidelity discrete element modeling. The experimental and computational works provided insights into the fundamental flow physics of biomass feedstock and knowledge about macro-scale flow and micro-scale interaction.

Ultimately, my doctoral research established a direct link between lignocellulosic biomass structural constituents and their strength and frictional properties, developed a mechanism for capturing biomass particle morphology and flow in high-fidelity computational models, and provided a statistical analysis process for validating the results. The next generation of scientists and producers can use the developed experimental, computational and statistical framework to predict diverse biomass flow behavior, apply corrective actions and efficiently utilize lignocellulosic biomass materials.

FFAR Fellow Ekramul Ehite spreading the word about agricultural biomass-derived bioenergy
FFAR Fellow Ekramul Ehite spreading the word about agricultural biomass-derived bioenergy

The outcomes of my research align directly with the Foundation for Food and Agriculture Research’s Next Generation Crops Challenge Area of developing unconventional crops and creating novel economic applications of conventional crops for enhanced crop diversity and farm profitability. My work will hopefully contribute to a clean, sustainable circular energy system and financial future for the global community. And just like Scrooge, I hope that possibility makes your heart laugh.