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: 5.04). 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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Available from: Orlando Jorquera, Aug 16, 2015
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    • "Furthermore, the assumption that a higher areal biomass productivity of 6 g m −2 day −1 can be reached (personal communication) and more biomass could be harvested (5% instead of 1.9%), possibly by small modifications to the coalescers, is made. According to the studies of Jorquera et al. (2010) and Lardon et al. (2009), even higher biomass productivities can be achieved in open pond systems (e.g., 11 g m −2 day −1 and 24 g m 2 day −1 , respectively). However, accounting for the climate conditions of The Netherlands, it is assumed that a maximum of approximately 20 t DM ha −1 year −1 could be established. "
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    ABSTRACT: Keywords: Biorefinery Life cycle analysis (LCA) Protein-rich feed ingredient Algae Soybeans a b s t r a c t Sustainability in terms of the natural resource demands of protein-rich algal meal for livestock feed applications was examined. In The Netherlands, an integrated microalgal biorefinery delivered the following products: digestate, electricity, heat available for a nearby bio-ethanol facility and algae oil and meal. Pilot scale (500 m 2) data were used to conduct an exergy analysis (EA), which revealed the process inefficiencies of energy-intensive processes such as drying (44.01%) and inoculum production (54.98%). An attributional life cycle assessment (LCA) using system expansion exposed the high contribution of biomass digestion to the total resource footprint of the biorefinery (72.74%) due to the high daily demand for biomass and electricity consumption of the dosage system. In this study, algal meal was compared with soybean meal, which is the most commonly used protein-rich animal feed ingredient; it is produced in Brazil and transported to The Netherlands. Because algae production is a young, small-scale technology , the resource footprint of the large-scale soy meal production was a factor of 10 2 lower, mainly as a result of the energy-intensive algae cultivation stages. A sensitivity analysis showed that the resource footprint of algal meal production could be comparable with soy meal when, overall, the areal biomass productivity increases, electricity production is based on more renewable sources (wind) and the energy consumption from mixing and blowing flue gases into the ponds decreases.
    Resources Conservation and Recycling 05/2015; 101:61-72. DOI:10.1016/j.resconrec.2015.05.013 · 2.69 Impact Factor
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    • "Functional unit Perimeter Location I C H T U [42] Kad Production of 1 MW h of electricity X X X X X USA (New Mexico) [6] Lar Combustion of 1 MJ of biodiesel X X X X X France [7] Bal Production of 1 L of biodiesel X X X X USA (New York) [8] Bat10 Production of 1 MJ of biodiesel X X X X USA (Colorado) [9] Cla10 Production of 317 GJ of algae X X X USA (Virginia, Iowa, California) [67] Jor Production of 100 t DM of algae X X Global [70] Luo Production of 1 MJ of bioethanol X X X X X USA (Texas) [10] San Production of 1000 MJ of biodiesel X X X X X USA (unspecified) [11] Ste Combustion of 1 t of biodiesel X X X X X UK [12] Bre Production of 10 GJ of algal methylester X X X X USA (Arizona) [66] Cam Carriage of 1 t km X X X X X Australia (coastal land) [3] "
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    ABSTRACT: Many studies have used the Life Cycle Assessment (LCA) methodology to assess the environmental impacts and energetic suitability of microalgal biofuels. This paper presents a critical review focused on goal and scope, system boundaries, functional unit, Life Cycle Inventories (LCI) and environmental impacts of 41 LCA of algal biofuels. The comparison between these LCA has been made difficult by the heterogeneity of their underlying hypotheses and perimeters. Hence we propose to define methodological guidelines to harmonize results presentation in order to improve the validity of each new contribution and to ease its comparison to other studies. LCA allows detecting pollution transfers between production stages as well as between distinct environmental impacts. At the Life Cycle Inventory (LCI) level, a special attention should be paid to the perimeter of the study (e.g. inclusion of infrastructures) and to the handling of the co-products (allocation or substitution). Moreover the inventory data have to be treated in a consistent way in order to guarantee the comparability of LCI between different studies. Hence we recommend that data of all the production steps should be given at a unit process level, i.e. the smallest element for which input and output data can be quantified. At the Life Cycle Impact Assessment level, other impacts than the greenhouse gases balance have to be taken into account, like impacts related to the use of fertilizers (acidification and eutrophication) and phytosanitary products (human toxicity and ecotoxicity), impacts of direct and indirect land use change, and water consumptions. Finally, as biofuel is aiming at replacing existing energy productions, an energy balance should always be carried out; the Cumulative Energy Demand Ratio offers a convenient framework in that regard.
    Applied Energy 04/2015; DOI:10.1016/j.apenergy.2015.03.056 · 5.61 Impact Factor
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    • "This high value is the result of a very high productivity (100 t ha À1 year À1 ) and the fact that important energy inputs (cooling, harvesting, nutrients) and conversion of electric energy input to primary energy were not considered. Besides that, in the Jorquera et al. [13] analysis, a biomass with a 30 MJ kg À1 caloric content is attained as output product, which will require a relatively high lipid content. A productivity of 100 t ha À1 year À1 of a lipid-rich biomass is unlikely, even at the small scale. "
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    ABSTRACT: The annual productivity of Tetraselmis suecica in a 1-ha Green Wall Panel-II (GWP-II) plant in Tuscany (Italy) is 36 t (dry weight) ha−1 year−1, which corresponds to an energy output of 799 GJ ha−1 year−1. The energy inputs necessary to attain that productivity amount to 1362 GJ ha−1 year−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 66 t ha−1 year−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 600 GJ ha−1 year−1. Marine microalgae cultivation in a GWP plant, in a suitable location, can attain high biomass productivities and protein yields 30 times 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.
    Applied Energy 03/2015; DOI:10.1016/j.apenergy.2015.01.086 · 5.61 Impact Factor
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