Energy balance of algal biomass production in a 1-ha “Green Wall Panel” plant: How to produce algal biomass in a closed reactor achieving a high Net Energy Ratio

M.R. Tredici, N. Bassi, M. Prussi, N. Biondi, L. Rodolfi, G. Chini Zittelli and G. Sampietro

Applied Energy, 2015, vol. 154, issue C, 1103-1111

Abstract: The annual productivity of Tetraselmis suecica in a 1-ha Green Wall Panel-II (GWP-II) plant in Tuscany (Italy) is 36t (dry weight)ha−1year−1, which corresponds to an energy output of 799GJha−1year−1. The energy inputs necessary to attain that productivity amount to 1362GJha−1year−1, mainly given by the embodied energy of the reactor (about 30%), mixing (about 40%), fertilizers (11%) and harvesting (10%). The Net Energy Ratio (NER) of T. suecica production is thus 0.6. In a more suitable location (North Africa) productivity nearly doubles, reaching 66tha−1year−1, but the NER increases only by 40% and the gain (difference between output and inputs) remains negative. In a GWP-II integrated with photovoltaics (PV), the NER becomes 1.7 and the gain surpasses 600GJha−1year−1. Marine microalgae cultivation in a GWP plant, in a suitable location, can attain high biomass productivities and protein yields 30times higher than those achievable with traditional crops (soya). When the GWP reactor is integrated with PV, the process attains a positive energy balance, which substantially enhances its sustainability.

Keywords: NER; GWP; Tetraselmis; Algae food; Biofuels; Protein (search for similar items in EconPapers)
Date: 2015
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Citations: View citations in EconPapers (15)

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DOI: 10.1016/j.apenergy.2015.01.086

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