Article

Embiruçu M and Ghirardi ML, Comparative energy life-cycle analyses of microalgal biomass production in open ponds and photobioreactors

Department of Environmental Engineering, Bahia Center for Clean Technologies, Federal University of Bahia, Rua Aristides Novis No. 2, 4 degrees andar, Polytechnique Institute, Salvador 40.210-630, BA, Brazil.
Bioresource Technology (Impact Factor: 4.49). 10/2009; 101(4):1406-13. DOI: 10.1016/j.biortech.2009.09.038
Source: PubMed

ABSTRACT

An analysis of the energy life-cycle for production of biomass using the oil-rich microalgae Nannochloropsis sp. was performed, which included both raceway ponds, tubular and flat-plate photobioreactors for algal cultivation. The net energy ratio (NER) for each process was calculated. The results showed that the use of horizontal tubular photobioreactors (PBRs) is not economically feasible ([NER]<1) and that the estimated NERs for flat-plate PBRs and raceway ponds is >1. The NER for ponds and flat-plate PBRs could be raised to significantly higher values if the lipid content of the biomass were increased to 60% dw/cwd. Although neither system is currently competitive with petroleum, the threshold oil cost at which this would occur was also estimated.

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    • "Closed PBRs are either naturally or artificially illuminated and aimed at mainly culturing single species of microalgae under controlled operating conditions. Closed PBRs are superior to open-pond systems in many aspects, such as lower water and CO 2 loss, less risk contamination of undesirable microorganisms (Jorquera et al., 2010; Posten, 2009; Wang et al., 2012; Yoo et al., 2012). However, they have not been fully scaled up due to the higher capital and operating costs compared to open-pond systems. "
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    ABSTRACT: Microalgae have been used as energy resources in recent decades to mitigate the global energy crisis. As the demand for pure microalgae strains for commercial use increases, designing an effective photobioreactor (PBR) for mass cultivation is important. Chlorella vulgaris, a local freshwater microalga, was used to study the algal biomass cultivation and lipid production using various PBR configurations (bubbling, air-lift, porous air-lift). The results show that a bubbling column design is a better choice for the cultivation of Chlorella vulgaris than an air-lift one. The highest biomass concentration in the bubbling PBR was 0.78 g/L while the air-lift PBR had a value of 0.09 g/L. Key operating parameters, including draft-tube length and bubbling flowrate, were then optimized based on biomass production and lipid yield. The highest lipid content was in the porous air-lift PBR and the air-lift PBR with shorter draft tube (35 cm) was also better than a longer one (50 cm) for algal cultivation, but the microalgae attached on the inner tube of PBR always occurred. The highest biomass concentration could be produced under the highest gas flowrate of 2.7 L/min whereas the lowest dry cell mass was under the lowest gas flowrate of 0.2 L/min.
    Full-text · Article · Jan 2016 · Water Environment Research
    • "This value translated into energy per volume shows energy consumptions in the range of 3–6 W/m 3 for raceway ponds and 25–60 W/m 3 for photobioreactors . Jorquera et al. (2010) indicates an energy consumption of 3.7 W/m 3 for raceway ponds and 53 W/m 3 for photo-bioreactors using air pumping for mixing. Similar values were given for paddlewheel raceway ponds and flat panel photo-bioreactors (Brentner et al., 2011). "
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    ABSTRACT: Large-scale microalgae cultivations for CO2 bio-sequestration from power plants can be an alternative process to conventional technologies if the capital investments associated with carbon capture, transport and storage can be reduced or avoided. In order to counterbalance the costs required to operate massive microalgae cultivations, it is necessary to create additional revenues through biomass sales. This manuscript examines the techno-economics of microalgae cultivations for the integration with three power plant technologies using an artificial neural network model. The economics are estimated using the net present value approach. The assessment is carried out at photosynthesis efficiencies ranging from 2% to 6%. The sensitivity assessment shows microalgae selling prices in the range of $440-1028/t at a photosynthetic efficiency of 4% for low and high cost scenarios in order to achieve an electricity price similar to that from a conventional power plant without a CO2 capture and storage.
    No preview · Article · Jan 2016 · Computers & Chemical Engineering
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    • "Closed PBRs are either naturally or artificially illuminated and aimed at mainly culturing single species of microalgae under controlled operating conditions. Closed PBRs are superior to open-pond systems in many aspects, such as lower water and CO 2 loss, less risk contamination of undesirable microorganisms (Jorquera et al., 2010; Posten, 2009; Wang et al., 2012; Yoo et al., 2012). However, they have not been fully scaled up due to the higher capital and operating costs compared to open-pond systems. "

    Full-text · Dataset · Dec 2015
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