EMERGY SYNTHESIS 3: Theory and Applications of the Emergy Methodology

Transcription

1 EMERGY SYNTHESIS 3: Theory and Applications of the Emergy Methodology Proceedings from the Third Biennial Emergy Conference, Edited by Mark T. Brown University of Florida Managing Editor Eliana Bardi University of Florida, Associate Editors Daniel E. Campbell US EPA Narragansett, Rhode Island Vito Comar State University of Mato Grosso do Sul Dourados, Brazil Shu-Li Haung National Taipei University Taipei, Taiwan Torbjorn Rydberg Centre for Sustainable Agriculture Uppsala, Sweden David Tilley University of Maryland College Park, Maryland Sergio Ulgiati University of Siena Siena, Italy November 2005 The Center for Policy Department of Engineering Sciences University of Florida Gainesville, FL ii

2 46 Economy: A Microcosm Valuation Karla L. Cozza, Antonio L. Philomena, and Jorge A.V. Costa ABSTRACT One of the most important discussions on species cultivation is the ecological-economic costs involved. A study of media diversity is presented that tests the real values embodied in artificial and natural sources. platensis development on several nutritional sources was modeled and the emergy synthesis of the microcosm experiment was calculated. Successful mesocosm design was proposed to create an ecological economic balance of inputs-outputs. Scale differences were compared and judged in relation to production and sustainability. Both experiments were built in Southern Brazil. INTRODUCTION One of the most important decisions about species cultivation is the ecological-economic costs involved in the process. To check the system costs, experiments could be run at the microcosm level simulating natural conditions (Bayers & Odum, 1993). Showing high productivity (24 ton/ha/year) and being a source of γ-linolenic oil ( mg/kg), platensis is a promising organism to be cultivated and a source of protein in countries where this is scarce so that a new food alternative could be available. Today, this blue-green algae can be used biotechnologically in the clean method, where the biomass is added in human food or in the wasted method, when the spirulina biomass is developed to filter industrial, urban, and rural effluents. Large-scale production is done by private enterprises in, for example, California (USA) and Hawaii (USA). The aim of this study was to compare different energy inputs to spirulina production and verify their costs at the mesoscale. MATERIAL & METHODS platensis was supplied by the University of São Paulo. Three different cultivation designs were carried out (Cozza, 1999). Treatment I involved a Zarrouk medium with a variable nitrogen source and 672 hours of cultivation time/growing time. Treatment II was a semi-continuous cultivation design with the best nutrient sources found in Treatment I. These experiments ran for a total of 2,782 hours. Treatment III was a cultivation design receiving natural water from Mangueira Lagoon (located at the southernmost state of Brazil - Rio Grande do Sul, with natural high alkalinity and ideal conditions (a mean minimum depth of 7.4 m) for cyanobacteria growth). Treatment III had an experi time of 720 hours. The whole experiment occurred inside a greenhouse with 12-hour light periods under 1,900 Lux intensity, a temperature of 30 C, and 0.1 g/l initial cellular conditions. The experi progress was measured through biomass concentration, carbonate, bicarbonate, and ph parameters. During Treatment I the following nitrogen sources were monitored: urea, sodium nitrate, ammonium nitrate, ammonium chloride, ammonium sulfate, and ammonium phosphate. Treatment II -569-

3 Chapter 46. Economy: A Microcosm Evaluation received sodium nitrate, ammonium nitrate, or urea, which were replaced after each parcel was collected and analysed. In Treatment III, water from Mangueira Lagoon was utilized to find out if the addition of bicarbonate was necessary, as well as the effects of different nitrogen sources and micro nutrients. The Newman-Keuls Statistical Test was applied to the values biomass concentration of platensis found during Treatments I, II, and III. Based on the result, three models (see Figures 1, 2, and 3) were chosen from thirty three experiment combinations and all data was calculated in emergy units (Beyers & Odum, 1993, and Odum, 1996). Cost comparisons and productivity variation were scaled up to 100,000 liter tanks (mesocosms). RESULTS AND DISCUSSION An environment created to reproduce the complexity of the natural world needs several inputs of matter, energy and biomass. Especially at a microcosm scale, the requirements and management of the organisms under study require huge efforts to obtain high productivity. In Table 1, matter, energy, labor, and biomass can be compared among the three treatments. Table 2 shows the emergy of each experiment input in Treatments I, II and III. Experiments showed very clearly the high productivity (Emergy and biomass ratio) obtained with the natural water from Mangueira Lagoon (even the addition of nitrate, bicarbonate and micronutrients did not change the high productivity of natural water). Economically, the medium used in Treatment III had a cost of US 0.87/kg at a 100,000 L mesoscale plant including medium composition and maintenance. This low cost, compared to US /kg for Treatment I and US /kg for Treatment II at the same scale of the former, was expected due to the high ecological-economic efficiency embodied in the Lagoon water, and costs magnification when system needs nutrients complementation and external energy. In the international market spirulina (dried powder) is sold at US /kg. Treatment I and II carried the highest total emergy involved with the cultivation technologies. Source Zarrouk Medium Without N source 2.37 E E E E E 14 atory 3.49 E 14 Figure 1. General Emergy Model of cultivation until 672 h Treatment I. Units = sej -570-

4 Chapter 46. Economy: A Microcosm Evaluation Sources Zarrouk Medium without atory Frozen Algae Figure 2. General Model of cultivation until 2,782 h Treatment II. Source Micronutrients NaHCO 3 Mangueira Lagoon Water atory Figure 3. General Model of cultivation until 720 h Treatment III

5 Chapter 46. Economy: A Microcosm Evaluation Table 1. Comparison of matter, energy, labor, and biomass among Treatments I, II and III. Topics Treatment I Treatment II Treatment III Added nutrients (kg) 255 1,369 0 Water (L) 100, , ,000 Energy (KW) 120, ,589 50,468 (h) 672 2, Biomass (kg)* *at 672 hours Modified from Cozza (1999). Table 2. Emergy proportion of matter, energy, labor, and biomass among Treatments I, II and III expressed in sej. Topics Treatment I Treatment II Treatment III Added Nutrients 2.67 E E11 0 Water 2.43 E E E12 Energy 6.90 E E E E E E14 Total Emergy 6.95 E E E16 Total Emergy/Biomass (sej/kg) 3.50E E E14 Modified from Cozza, Obs.: The amount of water used is the same for Treatments I and III, but the emergy value is different because the former is treated water from the system, and the latter is natural water from Mangueira Lagoon. All transformities are from Odum, CONCLUSION Due to the great input of the natural services (sun, wind and nutrients) the Treatment III cultivation had the lowest cost. At the microcosm level the cultivation medium is used in an effort to emulate nature, as shown by the higher costs incurred in Treatment I and II. REFERENCES Beyers, R.J. and Odum, H.T Ecological Microcosms. Springer-Verlag, New York, 557 p. Cozza, K.L platensis em meios naturais e sintéticos: fatores nutricionais e custos experimentais. Master thesis, FURG, Rio Grande. 204 p. Odum, H.T Accounting. John Wiley & Sons, New York. 369 p