A comparison and methodological proposal for hybrid approaches to quantify environmental impacts: A case study for renewable energies.

The transition towards a more sustainable and decarbonised energy system is mandatory for achieving global climate objectives, and counting on proper tools to evaluate sustainability is essential. Among sustainability assessment methodologies, hybrid approaches integrating Input-Output analysis (IOA) and Life Cycle Assessment (LCA) are often proposed to overcome limitations and take advantage of strengths of both methodologies. In this paper we propose a new hybrid tiered approach, named Identification and Subtraction Method (ISM). Through a case study of Concentrated Solar Power (CSP) technology, we test the proposed method assessing seven environmental indicators and compare the results obtained by different methodological approaches: Environmental Extended Multiregional Input-Output (EMRIO), LCA and two hybrid approaches. Results showed that, in general, LCA and EMRIO provide the lowest and uppest impact values, respectively. The ISM method expands the LCA boundaries by including indirect impacts, avoiding double-counting and retaining the technological detail and representativeness of the LCA. The main advantage is the ability to establish with high accuracy the impact coming from the LCA system boundaries. Furthermore, ISM is easy to undertake for LCA practitioners, is a low time-consuming hybrid approach once the LCA and EMRIO models are run, and it does not require the alteration of the IO matrix as other hybrid methods. However, the need to perform the EMRIO and LCA analysis could imply high detailed data needs. An additional limitation of the model is that it is not be able to include partial contributions from EMRIO sectors. The highest differences between results obtained by the different methods are found in the assessment of local impacts and the resources depletion, while the methods tend to agree more on global and regional impacts quantification. However, there are limitations to the implementation of the impact characterization methods that should be borne in mind when comparing the results of the different methods.

Estimates of population exposure to atmospheric pollution and health-related externalities in a real city: The impact of spatial resolution on the accuracy of results.

Health impacts of atmospheric pollution is an important issue in urban environments. Its magnitude depends on population exposure which have been frequently estimated by considering different approaches relating pollutant concentration and population exposed to it. However, the uncertainties due to the spatial resolution of the model used to estimate the pollutant concentration or due to the lack of representativeness of urban air quality monitoring station (AQMS) have not been evaluated in detail. In this context, NO2 annual average concentration at pedestrian level in the whole city of Pamplona (Spain) modelled at high spatial resolution (~1 m) by Computational Fluid Dynamic (CFD) simulations is used to estimate the total population exposure and health-related externalities by using different approaches. Air pollutant concentration and population are aggregated at different spatial resolutions ranging from a horizontal grid cell size of 100 m × 100 m to a coarser resolution where the whole city is covered by only one cell (6 km × 5 km). In addition, concentrations at AQMS locations are also extracted to assess the representativeness of those AQMS. The case with a spatial resolution of 100 m × 100 m for both pollutant-concentration distribution and population data is used as a reference (Base case) and compared with those obtained with the other approaches. This study indicates that the spatial resolution of concentration and population distribution in the city should be 1 km × 1 km or finer to obtain appropriate estimates of total population exposure (underestimations <13%) and health-related externalities (underestimations <37%). For the cases with coarser resolutions, a strong underestimation of total population exposure (>31%) and health-related externalities (>76%) was found. On the other hand, the use of AQMS concentrations can induce important errors due to the limited spatial representativeness, in particular in terms of population exposure.

Assessing sustainability performance in the educational sector. A high school case study.

This paper provides a detailed assessment of the environmental performance of a High school student in the city of Madrid, as well as the associated external costs. Life Cycle Assessment was used to evaluate the potential environmental impacts. Environmental external costs were also estimated using a simplified application of the impact pathway approach. The inventory of environmental loads included the consumption of resources in the school building operation and maintenance (O&M) activities, in the educational activities and in the transport activities. The activity of one student in one school year is the functional unit. The results showed that the emissions contributing to Climate Change are quantified in 461 kg CO2 eq·year-1·student-1, being the transport responsible for the 69% of the total impact, the O&M of the school building for the 20% and the educational activities for the remaining 11%. According to the results, the O&M of the facilities is the largest contributor to ozone depletion and water resource depletion. The educational activity is the main contributor to human toxicity, freshwater eutrophication and ecotoxicity, land use and resource depletion. Transport activities are responsible for most of the impacts related to the exposure to particular matter, ionizing radiation, and those impacts related to photochemical ozone formation, acidification, and terrestrial and marine eutrophication. Furthermore, the quantification of the external costs showed that these costs could reach a value of 34 euro·year-1·student-1 being transport the main contributor with a 52% of the external costs.