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ARS Home » Research » Publications at this Location » Publication #162004


item Mulbry, Walter

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 5/30/2004
Publication Date: 6/5/2005
Citation: Blersch, D., Mulbry III, W.W., Kangas, P. 2005. Emergy of algae revisited: comparisons of algal-based wastewater treatment systems. Meeting Abstract. pp 435-444.

Interpretive Summary:

Technical Abstract: After World War II, there was a high level of interest in using algal systems in bioengineering designs. Much of this interest was stimulated by the space program where algae were being examined for use in bioregenerative life support systems. A variety of laboratory studies with algal bioengineering were undertaken that demonstrated high and efficient levels of photosynthesis under artificial light conditions. In some cases, the magnitudes of photosynthesis were higher than found in nature. These results lead some researchers to imagine that algae might provide an important source of food for humans. At the same time that early studies were being undertaken, H.T. Odum was developing field techniques and making measurements of primary productivity (photosynthesis at the scale of the ecosystem) in a number of different systems. Odum developed one of the first examples of energy analysis and used this method to compare laboratory scale algal systems with other agricultural systems. Evaluations of energy resources and their transformations use a unit of measure called emergy, and involve calculation of all energy and material flows in and out of the system studied. Odum's analysis quantified the magnitudes of energy subsidies to a biomass yield system that had previously been ignored in assessments of the system. In this study, we re-evaluated Odum's original analysis with more recent approaches of emergy analysis. We evaluated three experimental studies of algal turf scrubbers (ATS) with emergy analysis. Overview energy diagrams were developed for laboratory-scale ATS systems using artificial lighting or sunlight. Our results show that all of the ATS transformities were similar, demonstrating that transformity is not qualitatively affected by the use of artificial lighting versus sunlight. Byproducts of the ATS treatment systems are clean water and algal biomass. Our calculations show that both of these byproducts have similar transformities.