Sustainability Evaluation of Immobilized Acid-Adapted Microalgal Technology in Acid Mine Drainage Remediation following Emergy and Carbon Footprint Analysis |
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Authors: | Kuppan Praveen Sudharsanam Abinandan Kadiyala Venkateswarlu Mallavarapu Megharaj |
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Institution: | 1.Global Centre for Environmental Remediation (GCER), ATC Building, College of Engineering Science and Environment, University of Newcastle, Callaghan, NSW 2308, Australia; (K.P.); (S.A.);2.Cooperative Research Centre for Contamination Assessment and Remediation of Environment (CRC CARE), ATC Building, University of Newcastle, Callaghan, NSW 2308, Australia;3.Formerly Department of Microbiology, Sri Krishnadevaraya University, Anantapuramu 515003, India; |
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Abstract: | Sustainability evaluation of wastewater treatment helps to reduce greenhouse gas emissions, as it emphasizes the development of green technologies and optimum resource use rather than the end-of-pipe treatment. The conventional approaches for treating acid mine drainages (AMDs) are efficient; however, they need enormous amounts of energy, making them less sustainable and causing greater environmental concern. We recently demonstrated the potential of immobilized acid-adapted microalgal technology for AMD remediation. Here, this novel approach has been evaluated following emergy and carbon footprint analysis for its sustainability in AMD treatment. Our results showed that imported energy inputs contributed significantly (>90%) to the overall emergy and were much lower than in passive and active treatment systems. The microalgal treatment required 2–15 times more renewable inputs than the other two treatment systems. Additionally, the emergy indices indicated higher environmental loading ratio and lower per cent renewability, suggesting the need for adequate renewable inputs in the immobilized microalgal system. The emergy yield ratio for biodiesel production from the microalgal biomass after AMD treatment was >1.0, which indicates a better emergy return on total emergy spent. Based on greenhouse gas emissions, carbon footprint analysis (CFA), was performed using default emission factors, in accordance with the IPCC standards and the National Greenhouse Energy Reporting (NGER) program of Australia. Interestingly, CFA of acid-adapted microalgal technology revealed significant greenhouse gas emissions due to usage of various construction materials as per IPCC, while SCOPE 2 emissions from purchased electricity were evident as per NGER. Our findings indicate that the immobilized microalgal technology is highly sustainable in AMD treatment, and its potential could be realized further by including solar energy into the overall treatment system. |
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Keywords: | immobilized microalgae AMD bioremediation sustainability emergy carbon footprint NGER IPCC |
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