Review
Various potential techniques to reduce the water footprint of microalgal biomass production for biofuel—A review

https://doi.org/10.1016/j.scitotenv.2020.142218Get rights and content

Highlights

  • Water footprint of microalgal biofuel production is lesser than popular fuel crops.

  • Reciprocal relation exists between biomass productivity and water footprint.

  • Strategies such as recycling and high cell density significantly reduce water footprint.

  • Surface and biofilm cultivation can consume low water as well as economic.

Abstract

Due to their rapid growth rates, high lipid productivity, and ability to synthesize value-added products, microalgae are considered as the potential biofuel feedstocks. However, among the several bottlenecks that are hindering the commercialization of microalgal biofuel synthesis, the issue of high water consumption is the least explored. This analysis, therefore, examines the factors that decide water use for the production of microalgae biofuel. Microalgae biodiesel water footprint varies from 3.5 to 3726 kg of water per kg of biodiesel. The study further investigates the cause for large variability in the estimation of the water footprint for microalgae fuel. Various strategies, including the reuse of harvested water, the use of high density cultivation that could be adopted for low water consumption in microalgal biofuel production are discussed. Specifically, the review identified a reciprocal relationship between biomass productivity and water footprint. On the basis of which the review emphasizes the significance of high density cultivation, which can be inexpensive and feasible relative to other water-saving techniques. With the setback of water scarcity due to the rapid industrialization in developing countries, the implementation of the cultivation system with a focus on minimizing the water consumption is inevitable for a successful large scale microalgal biofuel production.

Introduction

Microalgae are photosynthetic organisms with a low doubling time and having extensive applications such as biodegradation, bioremediation, biofuel, fish and animal feed (Ma et al., 2018b; Nagappan and Verma, 2016a; Nagappan and Verma, 2018; Vergara et al., 2016). Moreover, microalgae can fix the CO2 and thus can be used in the industrial set-up for reducing the carbon footprint (Singh et al., 2016; Thawechai et al., 2016). Besides, the adoption of a suitable lipid extraction based biorefinery approach can lead to the production of several high-value products (González-Fernández et al., 2016; Nagappan et al., 2018; Nagappan and Verma, 2016b; Park et al., 2013; Perazzoli et al., 2016). It is also noteworthy that, due to the various reasons, the microalgal products are not yet commercialized and among which the high water consumption is the least addressed issue.

Water is essential for microalgal growth as it helps in maintaining the temperature and also serves as a medium for nutrient delivery. As biofuel applications require large scale biomass production, the water demand is very high for such products (De Bhowmick et al., 2019; Guieysse et al., 2013). Water used for microalgae cultivation competes with human use of water for essential purposes such as drinking and irrigation (Delrue et al., 2012). This, in turn, leads to food vs. fuel scenario, which arises mainly in the case of the use of fresh water. Therefore, water management is essential in the successful commercialization of microalgal fuel. In this context, recycling of growth medium and use of adherent growth systems such as biofilm reactors can possibly overcome the above problem.

Section snippets

Water consumption in industrial production of microalgae

A typical microalgal biomass production for various industrial purposes involves microalgae cultivation (in a suitable growth system such as an open pond, photobioreactor, etc.) followed by drying, harvesting, lipid extraction, and esterification (Batan et al., 2016; Lardon et al., 2009). The loss of water is mainly observed during the stages of drying, harvesting, and cultivation (Delrue et al., 2012; Feng et al., 2016). The replacement or avoiding the loss of water is not possible especially

Calculation of water demand and water footprint

A water footprint is a term adopted by UNESCO in 2002 to signify the quantity of fresh water used by people, organisations or companies to manufacture products or offer facilities that the population needs. In this study, the water footprint means the consumption of water for the production a biofuel. In the case of microalgal biofuel production, the water footprint is comprised of three components: grey water, blue water, and white water. The blue water footprint is the amount of water

Water footprint of conventional crops and microalgae for biomass production

A comparison of the water footprints allied with the conventional crops and microalgae based on biofuel production is presented in this section. Table 1 compares the total water footprint of biomass production using different fuel crops including microalgae. Among conventional crops, the water footprints of sorghum and soybean were far higher (between 13,000 and 16,000 kg of water per kg of biodiesel) than sugar cane and sugar beet, which are estimated to be between 2000 and 4000 kg of water

Location and environmental conditions

Water consumption for microalgal biomass production depends on the location and environmental conditions prevailing in that area. A region with higher solar radiation and temperature will generally have a more giant water footprint than the one with lower solar radiation and temperature. This is primarily due to a higher rate of evaporation, as in the case of tropical and equatorial regions. Microalgae cultivation in arid regions consumes more water than tropical regions. For example, the water

Recycling

Nearly a six-fold reduction in the consumption of water can be achieved if the harvested water is recycled during the microalgal cultivation (Huang et al., 2016). Furthermore, the consumption of water can be reduced also if wastewater and seawater is used along with the recycling process. Besides the advantage of the reduction in the consumption of water, the recycling of water reduces the requirement of the nutrient since recycled medium contains unused nutrients. It has been estimated that

Economics of recycling and surface cultivation vs reduction of water footprint

Surface cultivation, including algal biofilm reactor, generates comparable or even higher biomass than the conventional suspended culture. Moreover, by simple scrapping, biomass can be easily detached from the surface. Since surface cultivation does not have a harvesting burden, the net energy ratio seems more promising. It has been estimated that the biomass density of the harvested biomass in an algal biofilm photobioreactor is 96.4 kg m−3, which is significantly higher than biomass

Key challenges and perspective

Large scale open ponds requiring a massive area for cultivation contribute to high water utilization. Also, water is, to a great extent, lost by evaporation in open pond type cultivation. On the other hand, photobioreactors, even though they do not experience the ill effects of these issues, the expense of establishment is high. Therefore, procedures, including inexpensive reactors expending less volume of water must be developed. In such manner, novel systems, for example, capillary-driven

Conclusion

The use of recycling systems and high density cultures, as proposed in this review, are an efficient technique with a low water footprint. Recycling systems significantly reduce the use of water but also reduce the production of biomass in subsequent recycling steps. While high-density cultivation, including non-suspended methods, such as surface and biofilm cultivation and suspended cultivation, including trophic-based methods, does not encounter these problems. In addition to low water

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors are thankful to the Ministry of Science and Technology, Taiwan (MOST107-2113-M-037-007-MY2), Kaohsiung Medical University (KMU)-Taiwan, Research Center for Environmental Medicine-KMU, and NSYSU-KMU collaboration research project (NSYSU-KMU 107-I004)-Taiwan for research grant support. The authors are thankful to Sri Venkateswara College of Engineering – Sriperumpudur, India for supporting the work. This work also supported by the Research Center for Environmental Medicine, Kaohsiung

References (117)

  • M.J. Cooney et al.

    Bio-oil from photosynthetic microalgae: case study

    Bioresour. Technol.

    (2011)
  • M. Cowling et al.

    An alternative approach to antifouling based on analogues of natural processes

    Sci. Total Environ.

    (2000)
  • P. Das et al.

    Microalgae harvesting by pH adjusted coagulation-flocculation, recycling of the coagulant and the growth media

    Bioresour. Technol.

    (2016)
  • G. De Bhowmick et al.

    Performance evaluation of an outdoor algal biorefinery for sustainable production of biomass, lipid and lutein valorizing flue-gas carbon dioxide and wastewater cocktail

    Bioresour. Technol.

    (2019)
  • L.E. De-Bashan et al.

    Immobilized microalgae for removing pollutants: review of practical aspects

    Bioresour. Technol.

    (2010)
  • F. Delrue et al.

    An economic, sustainability, and energetic model of biodiesel production from microalgae

    Bioresour. Technol.

    (2012)
  • M. Erkelens et al.

    Microalgae digestate effluent as a growth medium for Tetraselmis sp. in the production of biofuels

    Bioresour. Technol.

    (2014)
  • W. Farooq et al.

    Water use and its recycling in microalgae cultivation for biofuel application

    Bioresour. Technol.

    (2015)
  • L. Fortunato et al.

    Evaluation of membrane fouling mitigation strategies in an algal membrane photobioreactor (AMPBR) treating secondary wastewater effluent

    Sci. Total Environ.

    (2020)
  • C.C. Gaylarde et al.

    A comparative study of the major microbial biomass of biofilms on exteriors of buildings in Europe and Latin America

    Int. Biodeterior. Biodegradation

    (2005)
  • P. Gerbens-Leenes et al.

    The blue and grey water footprint of construction materials: steel, cement and glass

    Water Resources and Industry

    (2018)
  • F. Gladis et al.

    Influence of material properties and photocatalysis on phototrophic growth in multi-year roof weathering

    Int. Biodeterior. Biodegradation

    (2011)
  • C. González-Fernández et al.

    Impact of temperature and photoperiod on anaerobic biodegradability of microalgae grown in urban wastewater

    Int. Biodeterior. Biodegradation

    (2016)
  • C. González-López et al.

    Medium recycling for Nannochloropsis gaditana cultures for aquaculture

    Bioresour. Technol.

    (2013)
  • S. Görs et al.

    Fungal and algal biomass in biofilms on artificial surfaces quantified by ergosterol and chlorophyll a as biomarkers

    Int. Biodeterior. Biodegradation

    (2007)
  • M. Gross et al.

    Development of a rotating algal biofilm growth system for attached microalgae growth with in situ biomass harvest

    Bioresour. Technol.

    (2013)
  • B. Guieysse et al.

    Variability and uncertainty in water demand and water footprint assessments of fresh algae cultivation based on case studies from five climatic regions

    Bioresour. Technol.

    (2013)
  • F. Hadj-Romdhane et al.

    The culture of Chlorella vulgaris in a recycled supernatant: effects on biomass production and medium quality

    Bioresour. Technol.

    (2013)
  • R.M. Handler et al.

    Evaluation of environmental impacts from microalgae cultivation in open-air raceway ponds: analysis of the prior literature and investigation of wide variance in predicted impacts

    Algal Res.

    (2012)
  • Y. Huang et al.

    Improvement on light penetrability and microalgae biomass production by periodically pre-harvesting Chlorella vulgaris cells with culture medium recycling

    Bioresour. Technol.

    (2016)
  • O. Jorquera et al.

    Comparative energy life-cycle analyses of microalgal biomass production in open ponds and photobioreactors

    Bioresour. Technol.

    (2010)
  • L. Katarzyna et al.

    Non-enclosure methods for non-suspended microalgae cultivation: literature review and research needs

    Renew. Sust. Energ. Rev.

    (2015)
  • D.-G. Kim et al.

    Harvest of Scenedesmus sp. with bioflocculant and reuse of culture medium for subsequent high-density cultures

    Bioresour. Technol.

    (2011)
  • T.P. Lam et al.

    Strategies to control biological contaminants during microalgal cultivation in open ponds

    Bioresour. Technol.

    (2018)
  • F. Lananan et al.

    Optimization of biomass harvesting of microalgae, Chlorella sp. utilizing auto-flocculating microalgae, Ankistrodesmus sp. as bio-flocculant

    Int. Biodeterior. Biodegradation

    (2016)
  • F. Lehr et al.

    Closed photo-bioreactors as tools for biofuel production

    Curr. Opin. Biotechnol.

    (2009)
  • L. Leng et al.

    Use of microalgae to recycle nutrients in aqueous phase derived from hydrothermal liquefaction process

    Bioresour. Technol.

    (2018)
  • Y. Li et al.

    The effect of recycling culture medium after harvesting of Chlorella vulgaris biomass by flocculating bacteria on microalgal growth and the functionary mechanism

    Bioresour. Technol.

    (2019)
  • S.K. Liehr et al.

    A modeling study of the effect of pH on carbon limited algal biofilms

    Water Res.

    (1988)
  • J. Liu et al.

    Freshwater microalgae harvested via flocculation induced by pH decrease

    Biotechnology for biofuels

    (2013)
  • T. Liu et al.

    Attached cultivation technology of microalgae for efficient biomass feedstock production

    Bioresour. Technol.

    (2013)
  • X. Miao et al.

    Biodiesel production from heterotrophic microalgal oil

    Bioresour. Technol.

    (2006)
  • A. Mishra et al.

    Isolation and characterization of extracellular polymeric substances from micro-algae Dunaliella salina under salt stress

    Bioresour. Technol.

    (2009)
  • W. Mulbry et al.

    Treatment of dairy manure effluent using freshwater algae: algal productivity and recovery of manure nutrients using pilot-scale algal turf scrubbers

    Bioresour. Technol.

    (2008)
  • N.-H. Norsker et al.

    Microalgal production—a close look at the economics

    Biotechnol. Adv.

    (2011)
  • A. Ozkan et al.

    Reduction of water and energy requirement of algae cultivation using an algae biofilm photobioreactor

    Bioresour. Technol.

    (2012)
  • K.Y. Park et al.

    Anaerobic digestion of microalgal biomass with ultrasonic disintegration

    Int. Biodeterior. Biodegradation

    (2013)
  • S. Perazzoli et al.

    Optimizing biomethane production from anaerobic degradation of Scenedesmus spp. biomass harvested from algae-based swine digestate treatment

    Int. Biodeterior. Biodegradation

    (2016)
  • B. Podola et al.

    Porous substrate bioreactors: a paradigm shift in microalgal biotechnology?

    Trends Biotechnol.

    (2017)
  • A. Pugazhendhi et al.

    A review on chemical mechanism of microalgae flocculation via polymers

    Biotechnology Reports

    (2019)
  • Cited by (45)

    • Introduction to renewable energy-water-environment nexus

      2023, The Renewable Energy-Water-Environment Nexus: Fundamentals, Technology, and Policy
    View all citing articles on Scopus
    View full text