state of the art research report in Mechanical engineering field

Ethanol is one plant-based biofuel that makes serves as a substitute for fossil fuels. Other current prominent sources of plant-based biofuel are oil-producing plants such as soybeans, oilseed rape, and palm (Amaro et al., 2011). However, these forms of biofuel are not commercially viable on a large-scale because they have high production costs compared to their usable energy output (Abou-Shanab et al., 2011).

Therefore, scientists are exploring the use of algae as an alternative source of biofuel production (Abou-Shanab et al., 2011; Amaro et al., 2011; Bull & Collins, 2012; Chisti & Yan, 2011; Park & Craggs, 2011; Pate, Klise, & Wu, 2011; Snow & Smith, 2012). According to Abou-Shanab et al. (2011), there are several advantages to using algae, specifically microalgae, for biofuel production, most notably, its “higher photosynthetic efficiency, higher biomass production, and higher growth rates, as compared to other energy crops” (p. 3300). There are numerous varieties of algae and microalgae, which offer a plethora of research opportunities for discovering the optimal strains for the variety of ecological conditions found in the diverse regions of earth (Abou-Shanab et al, 2011; Snow & Smith, 2012).

Scope

This paper will focus on research aimed at developing biofuel from algal strains, including microalgal strains, as an alternative energy source. Specifically, the paper will discuss the scientific and engineering challenges that need to be addressed in order to bring this research concept to fruition. Although the Background section of this paper provided information on other forms of plant-based biofuel for context, these forms of biofuel will not be addressed in-depth and will be considered tertiary to the main discussion of algal biofuel. Furthermore, other alternative forms of energy, such a wind, tidal, and solar, will not be discussed.

DISCUSSION

Scientific Inquiry into Biofuel Derived from Algae

As the search to identify sustainable alternative energy sources intensifies, scientists are at the forefront of discovery. One of the most difficult challenges that scientists face in the development of algae and microalgae into biofuel is determining which strain(s) are viable candidates for scale-up of commercial production (Amaro et al., 2011; Snow & Smith, 2012). Candidate strains can either be naturally occurring in fresh water or salt water (wild strains; Amaro et al., 2011) or genetically engineered (GE, Amaro et al., 2012; Snow & Smith, 2012). There are thousands of strains of algae and microalgae that are candidates for scientific inquiry (Snow & Smith, 2012). Scientists have begun profiling algal strains for lipid content and lipid productivity, both of which are essential to production of algal biofuels. Scientists are interested in algae as a source of biofuel production for many reasons, including algae’s versatility—it can be cultivated from either fresh water or salt water stocks, wastewater, or stagnant or rushing water (Abou-Shanab et al., 2011). Furthermore, there are a number of advantages to using microalgae because it is hardy, reproduces quickly (within mere hours), is more efficient during the photosynthesis process compared to other plants, and produces more biomass after oil extraction that can be used in the production of ethanol or methane or can be used as feed for livestock or as an organic fertilizer (Amaro et al., 2011)

Amaro et al. (2011) cautioned that in addition to the high productivity and fatty acid content of algal species, “selection of the most adequate species for biodiesel production should take other factors into account—e.g. the ability to uptake available nutrients or grow under specific environmental conditions” (p. 3403). These specific environmental conditions vary from ecological region and algal production process, and they include amount of natural sunlight, amount of artificial light necessary for closed-system production, amount of naturally occurring carbon dioxide, amount of supplemental carbon dioxide generated by industrial processes and naturally occurring methane production, air temperature, water temperature, etc. (Park & Craggs, 2011; Pate et al., 2011).

Engineering Challenges Presented by Bringing Algal Biofuel to Commercial Scale

If scientists are at the forefront of discovery, then engineers are at the forefront of innovation as they work to optimize genetically modified algal strains (Snow & Smith, 2012) or to design optimal environments within which algae can grow (Adey, Kangas, & Mulbry, 2011; Albou-Shanab et al., 2011; Amaro et al., 2011; Park & Craggs, 2011).

Genetic Engineering of Algae and Microalgae. Some of the challenges that engineers face in the genetic engineering of suitable algal and microalgal strains include lack of a fully defined genome for most algal strains (which limits the engineers’ ability to fully understand the genome sequencing of suitable strains); a limited understanding of the “of the mechanisms underlying regulation of gene expression; and lack of specific molecular biology tools—e.g. efficient nuclear transformation, availability of promoter and selectable maker genes, and stable expression of transgenes” (Amaro et al., 2011, p. 3404). Given that there are thousands of algal strains, advances in genetic engineering of the most viable strains may take considerable time and resources.

Engineering of Algal and Microalgal Processes. Because microalgae naturally optimize nutrients in their environment for metabolic efficiency, “microalgae depend critically on a sufficient supply of a carbon source and of light to carry out photosynthesis” for biomass growth (Amaro et al., 2011, p. 3304). Therefore, engineers are examining methods to increase carbon and light and to regulate pH and by-product removal in algal growing environments to optimize algal production.

One method of optimizing the cultivation of algae for biofuel purposes is consideration of the reactor design, which could either be closed photobioreactors or open ponds or water sources (Amaro et al., 2011). Figure 1a shows a closed photobioreactor system, whereas Figure 1b shows algae growing in an open-pond configuration. Closed photobioreactors are preferred over open ponds due to the ponds’ susceptibility to contamination and poor regulation of temperature and light (Amaro et al., 2011). According to Amaro et al. (2011), “[u]nlike ponds, photobioreactors offer the opportunity to optimize the light path, so distinct configurations have been proposed and built to improve light supply, and thus microalga biomass productivity” (Amaro et al., 2011, p. 3405).

Figure 1b: Open algae ponds for biofuel production.

Source: www.guarduian.co.uk/environment/2008/oct/23/biofuels-energy

Figure 1a: Closed algae system for production.

Source: www.treehugger.com

CONCLUSION

Supplies of fossil fuels such as petroleum are dwindling, prompting the scientific and engineering communities to search for alternative sources of energy. Algae have been identified as promising biofuel material, yet identification of suitable strains and the development of the optimal cultivation technologies are still in their nascent stages. Some of the challenges faced by scientists are mapping the genomes of the thousands of potential strains to discover which are optimal for fuel production. Engineers are challenged by the design of the processes to be used during cultivation.

Works Cited

Abou-Shand, R. A. I., Hwang, J.-H., Cho, Y., Min, B., & Jeon, B.-H. (2011). Characterization of microalgal species isolated from fresh water bodies as a potential source for biodiesel production. Applied Energy, 88, 3300-3306.

Adey, W. H., Kangas, P. C., & Mulbry, W. (2011). Algal turf scrubbing: Cleaning surface waters with solar energy while producing a biofuel. Bioscience, 61(6), 434-441. doi: 10.1525/bio.2011.61.6.5

Amaro, H. M., Guedes, A. C., & Malcata, F. X. (2011). Advances and perspectives in using microalgae to produce biodiesel. Applied Energy, 88, 3402-3410.

Bull, J. J., & Collins, S. (2012). Algae for biofuel: Will the evolution of weeds limit the enterprise? Evolution, 66(9), 2983-2987.

Chisti, Y., & Yan, J. (2011). Energy from algae: Current status and future trends. Algal biofuels—A status report. Applied Energy, 88, 3277-3279.

Park, J. B. K., & Craggs, R. J. (2011). Algal production in wastewater treatment high rate algal ponds for potential biofuel use. Water Science and Technology, 63(10), 2403-2410.

Pate, R., Klise, G., & Wu, B. (2011). Resource demand implications for US algae biofuels production scale-up. Applied Energy, 88, 3377-3388.

Snow, A. A., & Smith, V. H. (2012). Genetically engineered algae for biofuels: A key role for ecologists. Bioscience, 62(8), 765-768. doi: 10.1525/bio.2012.62.8.9

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