A study on microalgal biorefinery system with use phase uncertainty and allocation analysis

Date of Publication


Document Type

Master's Thesis

Degree Name

Master of Science in Mechanical Engineering

Subject Categories

Energy Systems | Mechanical Engineering


Gokongwei College of Engineering


Mechanical Engineering

Thesis Advisor

Alvin B. Culaba
Aristotle T. Ubando

Defense Panel Chair

Archie B. Maglaya

Defense Panel Member

Neil Stephen Lopez
Anthony Shun Fung Chiu


The biorefinery concept presents a way towards achieving economic and environmental feasibility for biofuels as means of satisfying global energy demand through synergies within the supply chain. Biodiesel and bioethanol have been mandated for inclusion into diesel and gasoline fuel blends in the Philippines since 2007 via the Philippine Biofuels Act. Microalgal biofuels have yet to be subject to a well-to-wheel life cycle assessment (LCA) that accounts for environmental impacts not only from production, but also from its use phase. The probabilistic nature of such usage is addressed through the Monte Carlo simulation. Moreover, the allocation of environmental burdens for pathways common to 2 or more products remains a matter of methodological debates in the field of LCA. As such, 3 allocation methodologies (mass, energy, and economic value) are used with system expansion in this study to analyze the sensitivity of environmental assessments to such methodological choices for pathways common to microalgae-based biodiesel and bioethanol. SimaPro LCA software is used to assess and present the environmental performance of biofuels across a wide range of environmental impacts based on the 2016 ReCiPe Endpoint criteria. Microalgal biofuel production is found to have energy intensive processes that must be optimized. Allocation analysis found that environmental performance lags behind fossil fuel counterparts. Local energy supply dominated by conventional fuels adversely impacts biorefinery environmental viability. A direct linear relationship between fuel consumption rate and environmental impact is discovered through uncertainty analysis using the Monte Carlo simulation. Recommendations are given to adopt better technologies, to study allocation methods further, and to formulate economic framework for the development of a local microalgal biofuels sector.

Abstract Format







Biodiesel fuels—Refining; Biomass energy—Refining

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