Reduction in Energy Requirement and CO 2 Emission for Microalgae Oil Production Using Wastewater

Riaru Ishizaki, Ryozo Noguchi, Agusta Samodra Putra, Sosaku Ichikawa, Tofael Ahamed and Makoto M Watanabe
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Riaru Ishizaki: Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan
Ryozo Noguchi: Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan
Agusta Samodra Putra: Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan
Sosaku Ichikawa: Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan
Tofael Ahamed: Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan
Makoto M Watanabe: Algae Biomass and Energy System R&D Center, University of Tsukuba, Ibaraki 305-8572, Japan

Energies, 2020, vol. 13, issue 7, 1-20

Abstract: A comparative evaluation of energy requirement and CO 2 emission was performed for native polyculture microalgae oil production in a wastewater treatment plant (WWTP). The wastewater provided nutrients for algae growth. Datasets of microalgae oil production and their details were collected from the Minamisoma pilot plant. Environmental impact estimation from direct energy and material balance was analyzed using SimaPro ® v8.0.4. in two scenarios: existing and algal scenarios. In the existing scenario, CO 2 emission sources were from wastewater treatment, sludge treatment, and import of crude oil. In the algal scenario, CO 2 emission with microalgae production was considered using wastewater treatment, CO 2 absorption from growing algae, and hydrothermal liquefaction (HTL) for extraction, along with the exclusion of exhausted CO 2 emission for growing algae and use of discharged heat for HTL. In these two scenarios, 1 m 3 of wastewater was treated, and 2.17 MJ higher heating value (HHV) output was obtained. Consequently, 2.76 kg-CO 2 eq/m 3 -wastewater in the existing scenario and 1.59 kg-CO 2 eq/m 3 -wastewater in the algal scenario were calculated. In the HTL process, 21.5 MJ/m 3 -wastewater of the discharged heat energy was required in the algal scenario. Hence, the efficiency of the biocrude production system will surpass those of the WWTP and imported crude oil.

Keywords: biocrude; exhausted CO 2; oxygen ditch method; polyculture microalgae (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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