Award Date

12-1-2024

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Mechanical Engineering

First Committee Member

Jaeyun Moon

Second Committee Member

Kwang Kim

Third Committee Member

Brendan O'Toole

Fourth Committee Member

Erica Marti

Number of Pages

150

Abstract

Climate change and wildfires are two interconnected crises that present a great danger to the American southwest. Anthropogenic greenhouse gases including carbon dioxide have warmed the earth, creating droughts and altering weather patterns so that wildfires have increased in severity and intensity within the region. Wildfires in turn release stored carbon from biomass into the atmosphere, creating a dangerous feedback loop that destroys vast swaths of land in areas including the Great Basin Desert of northern Nevada and surrounding states. Fuel breaks offer a method to slow the spread of wildfires but are costly and generate large amounts of waste biomass material. This material can be transformed into biochar (BC), a porous carbonaceous material that sequesters carbon and can adsorb CO2 to assist in stopping climate change. In this thesis, four materials found in the Great Basin Desert (pinyon pine wood and needles, big sagebrush, and cheatgrass) were transformed into biochar at pyrolysis temperatures of 500 C, 600 C, and 700 C and studied for their materials characteristics. These biochars were then tested for their CO2 adsorption abilities via thermogravimetric analysis (TGA) and a column study. Materials characterizations found that cheatgrass biochar had an especially high BET surface area (428.73 m2/g at 700 C), while pinyon pine needle biochar had a high nitrogen content, which is linked to increased material basicity. Additionally, Fourier transform infrared spectroscopy analysis indicated a decrease in the acidic oxygen functional group O-H bend (carboxylic acid) for all materials as pyrolysis temperature increased. TGA testing showed that all materials had similar adsorption properties at the same pyrolysis temperatures with adsorption increasing as temperature increased, while column studies measured lower adsorption values but suggested that cheatgrass BC had a significantly higher adsorption than the other tested materials. These results indicate that physisorption through high surface area and chemisorption through high basicity are both strong influencing factors to CO2 adsorption. Additionally, this study shows that higher pyrolysis temperatures are beneficial to adsorption for these four materials, with cheatgrass pyrolyzed at 700 C having the highest adsorption value of 73.3 mg CO2/g BC via TGA testing. This study can be expanded in the future to include a greater range of pyrolysis temperatures and times, an expanded column study, and adsorption testing under different gas conditions.

Keywords

Adsorption; Biochar; Carbon Dioxide; Climate Change; Pyrolysis; Wildfires

Disciplines

Engineering Science and Materials | Environmental Engineering | Materials Science and Engineering | Mechanical Engineering

File Format

PDF

File Size

4,100 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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Available for download on Monday, December 15, 2031


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