Economic and environmental performance of microalgal energy products – A case study exploring circular bioeconomy principles applied to recycled anaerobic digester waste flows

Jin Wook Ro, Cody Yothers, Alissa Kendall, Annaliese Franz, Ruihong Zhang

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

This study quantifies the financial and environmental impacts of a microalgal bioenergy system that attempts to maximize circular flows by recovering and reusing the carbon, nutrients, and water within the system. The system produces microalgal biomass using liquid digestate of an anaerobic digester that processes 45 metric tons of food waste and generates 28.6 m3 of permeate daily in California, and three energy production scenarios from the biomass are considered: producing biodiesel, electricity, and both. In all scenarios, the resulting energy products delivered only modest reductions in environmental impacts as measured by carbon dioxide equivalent emissions. The carbon intensities (CIs) of biodiesel from this study were 91.0 gCO2e/MJ and 93.3 gCO2e/MJ, which were lower than 94.71 gCO2e/MJ of conventional petroleum diesel, and the CI of electricity from this study was 70.6 gCO2e/MJ, lower than the average electricity grid CI in California (82.92 gCO2e/MJ). The economic analysis results show that generating electricity alone can be profitable, while biodiesel produced via this system is not cost competitive with conventional diesel due to high capital expenses. Thus, generating electricity in lieu of biodiesel appears to be a better option to maximize the use of waste flows and supply lower-carbon energy.

Original languageEnglish
Article number120802
JournalJournal of Environmental Management
Volume358
DOIs
StatePublished - May 2024
Externally publishedYes

Funding

This research was supported by a grant from the California Energy Commission , Award Number ARV-15-008. We acknowledge Dr. Tyler J. Barzee, Dr. Hamed M. El Mashad, Kayla Rude, and Jiayong Liang for their assistance with the laboratory experiments.

Keywords

  • Anaerobic digestion
  • Bioenergy
  • Circular economy microalgae
  • Life cycle assessment
  • Techno-economic analysis

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