(314e) Eco-LCA Methodolgy for Sustainability Assessment of Bio-Wwts Focused on Energy Recovery

Introduction. The energy potential of agro-industrial effluents receiving biological treatment is often not much exploited, particularly in emergent regions because this alternative energy is forced to compete disadvantageously with conventional energy sources from an economic point of view. Consequently, smart strategies are required to prove the environmental/economic potential of biological wastewater treatment systems (Bio-WWTs) depolluting agro-industrial effluents committed with improved energy recovery. In this context, the following contribution introduces a methodological framework for refined sustainability assessment of Bio-WWTs treating agro-industrial effluents. It combines life cycle assessment (LCA) and ecological economics methods, specifically the emergy accounting approach. Results of a first proof of concept of this methodology are presented here using a Bio-WWTs of the poultry sector and a Bio-WWTs treating beer production effluents as case studies.

Methods. The methodology is developed as follows:

(i) Obtaining of Net Environmental Benefits Indicators-(NEB) by means LCA. The analyses includes avoided or shifted conventional energy in the borders of Bio-WWTs (Godin et al. 2012.) by the recovery of biogas from the Bio-WWTs operation. For each case study the NEB indicators were calculated for two life cycle scenarios considering different energy recovery routes in order to transform these NEBs in Environmental Influence Indicators (IAM). Application of the analytical identification method enables obtaining a reduced set ofIAM (Grunwald-Rosch, 2011).

(ii) Identification of potential co-benefits or “add-values” related with changes in the ecosystem services offer, which are promoted by differences between life cycle scenarios. These “add-values” are specifically appraised by emergy methods (Zhang Y, 2010). Then a set of normalized add-value indicators (NAV) are proposed to assess the "eco-economic" dimension of sustainbility.

Results. A set of Sustainable-Development Indicators (SDIs) has been obtained and defined as NAV/IAM ratios, similarly to ecoefficiency indicators. These SDIs are related to: CO₂-capture capacity, resources utilization, water pollutants and airborne emissions dilution. An overall sustainability indicator NAV_T/IAM_P has been also tailored from the contribution of single SDIs. Charts as presented in figure 1 were obtained and used to identify sustainability conditions.

Discussion and conclusions.A methodology unique for sustainability assessment of Bio-WWTs focused on energy recovery has been developed. This is based on integration of LCA/emergy methods (Eco-LCA) and allows to build representative SDIs for Bio-WWTs. These SDIs are dimensionless quantities because emergy (NAV) and environmental (IAM) terms are normalised values ranging from -1 to 1. Positive values of SDIs indicate “additionality”, potential “add-value” or a co-benefit obtained, which is promoted by reducing a direct environmental impact (positive IAM). A strong non-additional condition as far as an individual SDI results from both emergy and environmental terms minus numbers. A weak non-additional condition is produced when the emergy term is negative but the respective environmental is not. Results show that sustainability requires synergy among different SDIs and is not only dependent of climate change control/mitigation, which is the more generalized and accepted sustainbility criteria for wastewater treatment systems. Bio-WWTs focused on energy recovery increase resources utilization, this is an “emergy cost” which is “not additional” but it is required to promote additionality through other SDIs. The study shows that sustainability of Bio-WWTs with higher energy availability or production (beer case) is more dependent on the contribution to climate change control than Bio-WWTs with lower energy potential (poultry case). The baseline choice and the application of the NEB approach are key aspects to prove additionality of Bio-WWTs by means the outlined methodology.

References.

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