A biorefinery from Nannochloropsis sp. microalga – Energy and CO2 emission and economic analyses

• Published in: Bioresource technology 2013-06, Vol.138, p.235-244
• Main Authors: Ferreira, Ana F., Ribeiro, Lauro A., Batista, Ana P., Marques, Paula A.S.S., Nobre, Beatriz P., Palavra, António M.F., da Silva, Patrícia Pereira, Gouveia, Luísa, Silva, Carla
• Format: Article
• Language: English
• Subjects: Biofuels - economics; Biological and medical sciences; Biomass; Biotechnology - economics; Biotechnology - methods; Carbon dioxide; Carbon Dioxide - metabolism; Chromatography, Supercritical Fluid; CO2; Costs and Cost Analysis; Economical evaluation; Economics; Electricity; Emission analysis; Energy; Energy consumption; Extraction; Feasibility Studies; Fermentation; Fundamental and applied biological sciences. Psychology; Hydrogen - metabolism; Life cycle; Microalga biorefinery; Microalgae - metabolism; Nannochloropsis; Oils - metabolism; Pathways; Pigments, Biological - metabolism; Portugal; Refining; Thermodynamics
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2013.03.168

•Oil obtained by SE has the lowest energy and CO2 values per MJprod.•Oil obtained by SFE proved to be more economically viable, with a cost of 365€/kgoil.•Biorefinery 2 (biodiesel SFE+bioH2) has the best energy/CO2/economy compromise.•The bioH2 as co-product may be advantageous in terms of product yield or profit.•High-value pigments can be produced by SFE which is a clean technology. Are microalgae a potential energy source for biofuel production? This paper presents the laboratory results from a Nannochloropsis sp. microalga biorefinery for the production of oil, high-value pigments, and biohydrogen (bioH2). The energy consumption and CO2 emissions involved in the whole process (microalgae cultivation, harvest, dewater, mill, extraction and leftover biomass fermentation) were evaluated. An economic evaluation was also performed. Oil was obtained by soxhlet (SE) and supercritical fluid extraction (SFE). The bioH2 was produced by fermentation of the leftover biomass. The oil production pathway by SE shows the lowest value of energy consumption, 177-245MJ/MJprod, and CO2 emissions, 13–15kgCO2/MJprod. Despite consuming and emitting c.a. 20% more than the SE pathway, the oil obtained by SFE, proved to be more economically viable, with a cost of 365€/kgoil produced and simultaneously extracting high-value pigments. The bioH2 as co-product may be advantageous in terms of product yield or profit.