Sustainable Energy Bio-Sources, An Environmental Performance Approach: Life Cycle Assessment From WWTP to BESs

Sustainable energy bio-sources, an environmental performance approach: life cycle assessment from WWTP to BESs

G. Blejman¹, R. Pacciani^1,2, S. Guri^1,2, and L.F. Vega^1,2

¹ MATGAS Research Center, Campus UAB, 08193 Bellaterra, Barcelona, Spain

² Carburos Metálicos, Air Products Group, C/ Aragón  300, 08009 Barcelona, Spain

There is a huge impetus for developing new technologies for the production of both energy and bioproducts in a sustainable way. For example, Bio-Electrochemical Systems (BESs), such as Microbial Fuel Cells (MFCs) and Microbial Electrolysis Cells (MECs) are novel technologies which promise to replace energy intensive wastewater treatment processes (WWTPs) by converting the organic waste fraction present in wastewater into hydrogen or electricity. Their potential as sustainable technologies for combined energy and biofuel production is very high, considering the huge amount of sludge generated (average 30 kg dry matter/inhabitant·year). Moreover, defining the characteristics and the environmental burdens of the wastewater coming into a WWTP plays a key role in understanding the possible applications of the sludge for generating energy and hydrogen with MFCs and MECs, respectively.

In this work we analyse the environmental impact of (i) a Wastewater Treatment Plant and (ii) the production of Hydrogen and biogas from the sludge generated in the WWTP itself.

Firstly we assess the environmental impact of 1 m3 of water entering the Waste Water Treatment (WWTP) process using Life Cycle Assessment methodology. We then identify the environmental hot spots in the process chain, focusing on the most important environmental burdens of a WWTP: energy use, main pollutants from personal care products, heavy metals and final utilization of sludge as a bioproduct.

The environmental impact is assessed with Simapro, Version 7.2, with CML2000 method. The impact categories considered are: AP (acidification potential, global, kg SO2 eq.), GWP100a (global warming potential, kgCO2 eq.), EP (eutrophication potential, global, kg PO₄ eq.), PHO (photochemical oxidation, kg formed ozone), DAR (depletion of abiotic resources, kg antimony eq.), ODP (ozone depletion potential, kg CFC-11 eq.), ETP (ecotoxicity potential, kg 1,4-DCB eq.) as well as CED (Cumulative Energy Demand). Bearing in mind that water reuse and reclamation is one of the main issues of water sustainability, we add to the standard CML impact categories the Freshwater Ecosystem Indicator, (direct effect on biodiversity of freshwater ecosystem) and the Freshwater Depletion (FD), to properly estimate the impact of the process in the water cycle.

This project is partially financed by Carburos Metálicos and the Spanish Government, CDTI, in the CENIT BIOSOS, belonging to the Program Ingenio 2010.