Lifecycle sustainability assessment for the comparison of traditional and sustainable drainage systems.

Urban drainage is a topic of increasing interest due to its key role for managing water-related disasters, which are being exacerbated by the effects of Climate Change and urbanization. Since traditional drainage systems struggle to deal with the combined action of these phenomena, Sustainable Drainage Systems (SuDS) are gaining attention as an alternative to help manage these high-water management demands. In this context, this research aimed at conducting a lifecycle sustainability assessment for comparing the economic, environmental and social performance of both drainage systems. The three dimensions of sustainable development were addressed with the support of the concepts of Net Present Value (NPV), Life Cycle Assessment (LCA) and a combination of the Leopold matrix and a semi structured interview, respectively. The results of applying this approach to the case study of the Rancho Bellavista housing development (Querétaro, Mexico) showed that SuDS outperformed traditional drainage systems in environmental and social terms; however, their high maintenance costs and shorter life expectancy hindered its economic feasibility. As such, future urban plans should focus on complementary designs whereby the strengths of both drainage alternatives are combined to boost their contributions to achieving sustainable development.

Eco-efficiency evaluation in wastewater treatment plants considering greenhouse gas emissions through the data envelopment analysis-tolerance model.

The eco-efficiency evaluation in wastewater treatment plants (WWTPs) is used to know and improve the environmental and economic efficiency of these processes, systems, products, and services. The eco-efficiency evaluations in WWTP contemplate the inputs to be minimized, the desirable results to be maximized, and the undesired results to be minimized. Data envelopment analysis (DEA) is a widely used method to evaluate the eco-efficiency of WWTPs; integrating several approaches in a single index, traditional DEA models do not take into account the uncertainty in the data. This study evaluates the eco-efficiency of a sample of Catalan WWTPs, considering the uncertainty of the data (DEA tolerance model), and it is for the first time that together with CO2, other greenhouse gas (GHG) such as CH4 and N2O are considered as part of the process outputs. GHG emissions were quantified using methods reported in the literature. Seven hundred twenty-nine eco-efficiency scores were estimated for each WWTP instead of a single score like conventional DEA models, analyzing optimistic and pessimistic scenarios. The WWTPs were classified according to the estimated eco-efficiency scores, accounting for the uncertainty in each of the scenarios, and demonstrating the changes in the performance of the WWTPs in the different scenarios. Only two WWTPs were eco-efficient in all the scenarios evaluated. This approach provides essential information to improve efficiency and innovation in the wastewater sector.

Analysis of empirical methods for the quantification of N2O emissions in wastewater treatment plants: Comparison of emission results obtained from the IPCC Tier 1 methodology and the methodologies that integrate operational data.

Wastewater is a source of N2O emission that is generated, both directly from advanced treatment plants and indirectly from the discharge of wastewater into the natural environment, due to its remaining nitrogen content. There are a variety of methods based on different parameters used to calculate N2O emission in wastewater treatment plants. The methodology proposed by the IPCC is used as an international reference for national inventories. In this work, we use five international methodologies to calculate the N2O emission of the WWTPs in two areas with high population density: The Metropolitan Area of Barcelona (MAB) and Mexico City (MXC). The MAB has 100% population served and has advanced treatment plants (five WWTP) and traditional wastewater treatment plants (two WWTP), the MXC served 14% of its population and had advanced treatment plants (six WWTP) and traditional plants (nineteen WWTP) in 2016. The results obtained show that the IPCC and Das methodologies underestimate the emission of N2O by considering the per capita consumption of proteins as a constant nitrogen value and also by the suggested emission factors. The methodologies that use the operational data of each plant provide emission results closer to those found in the literature. The value of TN should be the parameter to be considered for a correct estimate of the N2O emission in the WWTPs. The emission factors currently used are very low, with a low level of confidence of up to 1.3%. The range currently used should be increased and have a minimum range of 0.03 kg N2O-N/kg N. The emission factors reported in the literature are very variable and with very high levels of uncertainty, and therefore underestimate the emission of N2O in WWTPs. More research should be done to obtain higher and more reliable emission factors than those currently used.

Environmental assessment of energy production from anaerobic digestion of pig manure at medium-scale using life cycle assessment.

This study assessed the potential environmental effects of energy production from pig manure treatment by anaerobic digestion at medium-scale based on the Life Cycle Assessment of a farm in Puebla, Mexico. It also compared the results from common practices of biogas flaring and conventional management. The analysis was based on one ton of pig manure in 4 systems: two with energy production, one with biogas flaring, and the last one conventional management. The use of biogas for electricity production combined with composting techniques generated the lowest net impacts on climate change of 272 kg CO2eq and photochemical oxidation of 0.056 kg ethylene eq, while the biogas flaring registered impacts of 344 kg CO2eq and 0.095 kg ethylene eq. The systems with energy production had environmental benefits on fossil resources depletion by avoiding the consumption of -863 MJ and -1608 MJ, but systems that burned biogas required fossil fuel consumption of 246 MJ from the grid. The conventional management generated the greatest environmental impacts, with eutrophication being the most important negative effect due to the manure discharge into water bodies (5.97 kg PO4eq). Sensitivity analysis shown that energy production could generate greater impacts on global warming compared to the case in which manure was used directly in crop fields, if emissions from unintentional releases and a poor digestate management are not avoided. Results are relevant for developing countries in which processes are carried out in rural and semi-industrial areas with lack of technical knowledge and economic resources.

Environmental and social life cycle assessment of urban water systems: The case of Mexico City.

Mexico City and its metropolitan area have suffered problems of sustainability in the water system. The main goals of this study were to assess the environmental and social impacts of the water system in Mexico City using Life Cycle Assessment (LCA), identify the significant impacts and their sources, and provide a new perspective for a sustainable water system in the city. The entire water system was considered, including the following stages: water abstraction and treatment, transport, distribution, use, sewage collection and wastewater treatment. Social Life Cycle Assessment was performed considering the UNEP/SETAC Guidelines for the Social-LCA of products and the water system workers. We used five subcategories (working hours, fair wage, health and safety conditions, social security and professional development) and 30 indicators of labor conditions. The results of LCA show that the processes of abstraction, water treatment, transport and distribution combined to produce between 83.9 and 89.6% of the impacts in four of six categories. However, the transportation stage generates the highest environmental impacts due to energy consumption. The wastewater treatment stage avoids environmental impacts in freshwater eutrophication (-69.9%) and non-carcinogenic effects (-86.2%) due to Atotonilco, the new centralized WWTP. The social life cycle assessment results indicated that the transport stage had the best social performance score, with a value of 0.3 on a scale of zero to one. The total system exhibited regular performance in health and safety conditions, with a value of 0.6 in this category. Moving toward a sustainable water system in Mexico City requires analyze future scenarios on the decentralization of potable water services and the implementation of renewable energy technologies in water abstraction and transport to reduce electrical energy consumption and mitigate global warming impacts. Regarding the social dimension, the water system requires stricter policies to monitor the health and safety conditions of workers according to the definition of decent work toward recent sustainable development goals. This study allowed us to identify the stages with high and low environmental impacts with LCA and, with S-LCA, the best and worst social performance in working conditions. The next step is to complete a sustainability assessment that includes the economic dimension, develop a framework to integrate the three dimensions and propose scenarios to improve environmental and social performance.

Life cycle assessment of Mexican polymer and high-durability cotton paper banknotes.

This study compares the environmental performance of Mexican banknotes printed on high-durability cotton paper (HD paper) and thermoplastic polymer (polymer) through a life cycle assessment to appraise the environmental impacts from the extraction of raw materials to the final disposal of the banknotes. The functional unit was defined considering the next parameters: 1) lifespan of the banknotes, stablished in 31.5 and 54months for HD paper and polymer, respectively; 2) denomination, selecting $200 pesos banknotes; 3) a 5year time frame and 4) a defined amount of money, in this case stablished as the monthly cash supply of an average Mexican household, equaling $12,708 pesos. Accordingly, 121 pieces for the HD paper and 71 pieces for the polymer banknotes were analyzed. The results favor the banknotes printed on polymer substrate primarily because of the longer lifespan of this type of material; however, there is a considerable environmental impact in the stages of distribution, followed by the extraction of the raw materials (crude oil) during manufacturing. Regarding the HD cotton paper, the major impact corresponds to extraction of the raw materials, followed by the distribution of the banknotes. The inclusion of the automatic teller machines (ATMs) in the life cycle assessment of banknotes shows that the electricity required by these devices became the largest contributor to the environmental impacts. Additionally, the sensitivity analysis that the average lifetime of the banknotes is a determining factor for the environmental impacts associated with the whole life cycle of this product. The life cycle stages that refer to the extraction of the raw materials, combined with the average lifetime of the banknotes and the electricity required during the usage stage, are determining factors in the total environmental impact associated with Mexican banknotes.