A Life Cycle Assessment Based Evaluation of a Coupled Wastewater Treatment and Biofuel Production Paradigm
- 1 Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, USA
- 2 School of Sustainable Engineering and the Built Environment, Global Institute of Sustainability, Arizona State University, Engineering G-Wing, Tempe, USA
- 3 School of Sustainable Engineering and the Built Environment, Global Institute of Sustainability, Arizona State University, Engineering G-Wing, Tempe, USA
- 4 Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, USA
- 5 Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, USA
- 6 Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, USA
- 7 Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, USA
- 8 De- partment of Systems Engineering and Management, Air Force Institute of Technology, WPAFB, USA
Abstract
A laboratory experiment was performed to determine the feasibility of coupling a conventional wastewater treatment system with an algal photobioreactor (PBR) for the removal of nutrients from wastewater and production of renewable resources. An activated sludge batch reactor was set up in series with an algal PBR to feed synthetic wastewater to Chlorella vulgaris . The nutrient concentration in the water as well as lipid content, carbohydrate content, and growth rate of the algal biomass were tested over 10 cycles to determine the capabilities of the coupled system. The study revealed complete nutrient removal in some cycles, with the average final nutrient content of 2 mg-P/L and 3 mg-N/L in effluent of the PBR. The algae biomass contained 24% ± 3% lipids and 26% ± 7% carbohydrates by dry weight. A life cycle assessment revealed the highest energy demand occurred during harvesting of the algal mixture through centrifugation or filtration, but the highest global warming and eutrophication impacts were due to CO 2 use and PBR construction material production. It is feasible for the system to treat wastewater while generating renewable resources, but the system must be optimized to reduce life cycle environmental impacts and result in a net energy gain before large-scale implementation is possible.
- R. Frischknecht, PRé Consultants, 2004.
- R. Frischknecht, et al., “The Ecoinvent Database: Overview and Methodological Framework (7 pp),” The International Journal of Life Cycle Assessment, Vol. 10, No. 1 2005, pp. 3-9. doi:10.1065/lca2004.10.181.1
- USLCI, National Renewable Energy Laboratory, 2008.
- R. Spriensma, PRe Consultants, 2004.
- G. A. Norris, PRé Consultants and Sylvatica, 2003.
- L. Lardon, A. Hélias, B. Sialve, J.-P. Steyer and O. Bernard, “Life-Cycle Assessment of Biodiesel Production from Microalgae,” Environmental Science & Technology Vol. 43, No. 17, 2009, pp. 6475-6481. doi:10.1021/es900705j
- P. M. Schenk, et al., “Second Generation Biofuels: High-Efficiency Microalgae for Biodiesel Production,” Bioenergy Research, Vol. 1, No. 1, 2008, pp. 20-43.
- A. P. Carvalho, L. A. Meireles and F. X. Malcata, “Microalgal Reactors: A Review of Enclosed System Designs and Performances,” Biotechnology Progress, Vol. 22, No. 6, 2006, pp. 1490-1506.
- M. Eddy and H. D. Stensel, “Wastewater Engineering: Treatment and Reuse,” McGraw Hill, New York, 2004.
- M. Maurer and T. A. L. Schwegler, “Nutrients in Urine: Energetic Aspects of Removal and Recovery,” Water Science and technology, Vol. 48, No. 1, 2003, pp. 37-46.
- K. L. Kadam, “Environmental Implications of Power Generation via Coal-Microalgae Cofiring,” Energy, Vol. 27, No. 10, 2002, pp. 905-922. doi:10.1016/S0360-5442(02)00025-7
- G. Shelef, A. Sukenik and M. Green, “Microalgae Harvesting and Processing: A Literature Review,” Solar Energy Research Institute, Golden, 1984. doi:10.2172/6204677
- L. Batan, J. Quinn, T. Bradley and B. Willson, “Net Energy and Greenhouse Gas Emissions Evaluation of Biodiesel Derived from Microalgae,” Environmental Science & Technology, Vol. 45, No. 3, 2010, p. 1160. doi:10.1021/es1038479
- J. C. Bare, “Traci,” Journal of Industrial Ecology, Vol. 6, No. 3-4, 2002, pp. 49-78. doi:10.1162/108819802766269539
- V. Riis and W. Mai, “Gas Chromatographic Determination of Polyhydroxybutyric Acid in Microbial Biomass after Hydrochloric Acid Propanolysis,” Journal of Chromatography, Vol. 44, 1988, pp. 285-289.