Date of Publication

7-2025

Document Type

Master's Thesis

Degree Name

Master of Science in Mechanical Engineering

Subject Categories

Engineering

College

Gokongwei College of Engineering

Department/Unit

Mechanical Engineering

Thesis Advisor

Aristotle T. Ubando

Defense Panel Chair

Ivan Henderson V. Gue

Defense Panel Member

Robby B. Manrique

Niño Rigo Emil G. Lim

Abstract/Summary

With the growing studies on microalgae as a sustainable source of biomass and other high-value products, the demand for microalgal biomass has increased. Hence, microalgae waste accumulation has become a growing environmental issue, threatening marine ecosystems and water quality. Torrefaction has been explored as a potential solution to convert microalgal biomass into solid biofuel, offering a means to capture carbon and mitigate greenhouse gas emissions. In recent years, inert and oxidative torrefaction have become the primary methods to convert microalgae into a solid product called biochar. However, these methods face challenges mainly due to high energy consumption and the extended processing times required to burn the biomass. Catalysts help mitigate these issues by enhancing carbon retention, upgrading aromatics, and improving the energy density of biofuels. This study utilizes zeolite ZSM-5-assisted torrefaction to produce biochar from Chlorella sp. under inert and oxidative atmospheres. A multi-objective optimization approach, combining the Taguchi method, composite desirability function, and principal component analysis, is applied to optimize biomass-to-zeolite ratio, oxygen concentration, temperature, and residence time. Key performance indicators include solid yield, higher heating value (HHV), and electricity input. Results show that temperature and catalyst concentration significantly affect solid yield and HHV, while oxygen concentration primarily influences HHV. Optimal conditions (1:3 biomass–zeolite ratio, 12% O2, 220 °C, 15 min) result in an HHV of 23.08 MJ·kg-1, a solid yield of 65.01%, and low electricity input (0.049 kWh). Compared to non-catalytic torrefaction, ZSM-5 improves HHV by 5.24% but reduces yield by 23.63%, reflecting a trade-off between energy content and mass retention. Lastly, ZSM-5 demonstrates stable reusability over five cycles. These findings highlight ZSM-5-assisted torrefaction as a practical approach for producing high-quality biochar from microalgae, supporting sustainable renewable energy systems.

Abstract Format

html

Language

English

Format

Electronic

Keywords

Biomass energy; Microalgae

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Embargo Period

7-2028

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Available for download on Saturday, July 01, 2028

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