Dr Jaume Albertí

Dietary choices, a main driver of food production, play a significant role within the climate change arena. Consequently, there is a growing trend on publishing research assessing the environmental impacts of diets and dietary shifts, mainly following the life cycle assessment (LCA) methodology. However, several methodological issues still bring a challenge, especially in the definition of the function and the quantification of the functional unit (FU).
The FU is the reference unit of an LCA study, and it is the basis for allowing comparison among different systems. This short communication defines the function of diets as the supply of the daily required amount of calories and nutrients, and it proposes a novel FU that accounts for the energy intake and the nutritional quality of the diet. In order to compare the performance of the proposed FU to the most commonly ones used for diet LCAs (mass-based and isocaloric), dietary scenarios within the Spanish context are assessed. On the one hand, using a mass-based FU, greenhouse gas (GHG) emissions are underestimated, since the nutrition properties of food are not considered, and, on the other hand, the isocaloric substitution does not allow comparison among diets with different levels of energy intake. In contrast, the proposed caloric-and nutrient-corrected FU allows to compare diets that differ in energy and nutritional quality in a fairer way. Finally, it is recommended to use this FU for future diet LCAs.

The use of industrial solid wastes with a high content of SiO2 and Al2O3, called “precursors”, is often studied in the construction industry when combined with NaOH as “activator”. The precursor and activator system is generally proposed as a binder material with similar characteristics to Portland cement. In this work, we technically and environmentally evaluated such a system elaborated with an industrial waste: coal ash with caustic soda in solid state. This product, mixed with the soil, acts as a stabilizer to increase the capacity of load support, allowing the improvement of the conditions of performance in low volume traffic roads. An experimental design applied to the stabilizing product showed the incidence of different factors on the load carrying capacity response: packaging material, type of seal, baling moisture and storage humidity. The application of the stabilizer product was found to increase the resistance of the ground over a 500%. Finally, the environmental aspects were evaluated through a simplified Life Cycle Assessment methodology (LCA), the scope of the study was restricted to cradle to gate, collecting data up to the packaged stabilizing product. The results showed that the highest impacts were caused, for most impact categories, by NaOH production, and transport was relevant as well.

Research on Life Cycle Assessment (LCA) was initially performed to analyze specific products; however, it evolved to assess environmental impacts of more complex systems, such as roads. In this, the construction, use and maintenance stages are usually considered. The results of different studies revealed that all stages have relevant environmental impacts like topsoil loss, change in the use of land, modification of natural drainage and groundwater patterns, landslides, erosion, sedimentation, landscape degradation, increase in noise and dust levels, fuel and oil spills, waste generation, and air, soil and water pollution.

This paper presents the results of a literature review on the application of LCA in road construction as a tool to quantify the potential impacts derived from the use of traditional and alternative materials. The research showed that the most common materials found were recycled asphalt (concrete and bitumen), fly ash, and polymer. In addition, the environmental impact categories more commonly assessed were energy consumption and global warming potential (GWP). These results claimed that the construction of roads should be directed towards the fulfilment of technical, social, economic and environmental criteria. Finally, it was found that most of the studies were performed for high traffic volume roads; therefore, for developing countries, research is needed focussed on low traffic ones.

Tourism is a key industry in the Spanish economy. Spain was in the World top three ranking by international tourist arrivals and by income in 2015. The development of the tourism industry is essential to maintain the established economic system. However, if the environmental requirements were not taken into account, the country would face a negative effect on depletion of local environmental resources from which tourism depends. This case study evaluates, through a life cycle perspective, the average carbon footprint of an overnight stay in a Spanish coastland hotel by analyzing 14 two-to-five-stars hotels. Inventory and impact data are analyzed and presented both for resource use and greenhouse gases emissions, with the intention of helping in the environmental decision-making process. The main identified potential hotspots are electricity and fuels consumption (6 to 30 kWh/overnight stay and 24 to 127 MJ/overnight stay respectively), which are proportional to the number of stars and unoccupancy rate and they produce more than 75% of the impact. It is also revealed that voluntary implementation of environmental monitoring systems (like EMAS regulation) promotes collection of more detailed and accurate data, which helps in a more efficient use of resources. A literature review on LCA and tourism is also discussed. Spanish hotels inventory data presented here for the first time will be useful for tourism related managers (destination managers, policy makers and hotel managers among others) to calculate sustainability key indicators, which can lead to achieve real sustainable-tourism goals. Further data collection will be needed in future projects to gather representative data from more hotels, other accommodation facilities and also other products/services offered by tourist sector in Spain (like transport of tourists, food and beverage, culture-sports & recreation and others).

This study highlights the need and suggests some basis for working on the Life Cycle Assessment (LCA) of cities with a sustainability perspective. Cities are relevant actors in sustainable development and contribute to the generation of significant environmental impacts upstream and downstream their internal activity. LCA is precise in assessing environmental aspects of sustainability but lacks social and economic inputs. It is important to avoid problem shifting, even between the different dimensions of sustainability.

A systematic literature review has been performed so as to extract the procedure for defining the goal, function, functional unit, and reference flow of a complex system. The existing literature is mainly product focused, although services are also considered somehow. The procedure for defining the abovementioned items is previously applied to a relatively simple system, a power generation plant, so as to find parallelisms to define those items for a complex system such as a city.

To obtain a feasible (i.e., simplified) city Life Cycle Sustainability Assessment, the authors propose to introduce the social and economic aspects through the use of the City Prosperity Index (CPI) as technical performance within the FU of the city LCA. The CPI combined with the number of inhabitants is the normalization factor which is found to be more suitable to avoid problem shifting among sustainability dimensions and to avoid the interference of the number of inhabitants when comparing two different cities. An exemplification of the variation of the results after the application of these two factors in 18 cities' CO2-eq emissions is described. Even though this is not a large sample, it includes cities from different continents and levels of development and, thus it can be useful to see the how the suggested method is affecting cities' ranking.

This article is a step forward in the definition of the goal and scope of city Life Cycle Assessments (LCA). We contribute to city LCA by proposing procedures (i) to set city boundaries and (ii) for allocating burdens among cities.

The study has been based on a systematic literature review of existing guidelines and standards as well as academic work linked to system boundary definition and to allocation procedures setting. Internationally accepted guidelines provide a basis on how current city assessments should be performed. LCA-based and LCA ISO 14040 compliant case studies of other types of systems provide background knowledge to analyse the applicability of existing methods to define the system boundaries and to apply allocation procedures to the case of a city LCA. The analysis and proposal of procedures is complemented with a survey sent to environmental and urban management researchers and specialists.

Geographical boundaries and functional boundaries compose the city LCA boundaries. Three methods for setting the boundaries for a city LCA are proposed: (i) administrative-based boundaries, defined by the area delineated for the purpose of local administration; (ii) density-based boundaries, defined by the continuity of the population density of an urban area; and (iii) service-based boundaries, defined by the density-based boundaries plus those services induced by the city.

Four allocation methods are proposed: (i) monetary-based allocation, which uses the added value generated at each stage in the life cycle to distribute the burden; (ii) producer-based allocation, which assigns impacts to the city that holds the production of the good; (iii) consumer-based allocation, which assigns impacts to the city that hosts the final user/consumer of the good; and (iv) category-based allocation, proposed by the authors, according to which, global impacts are assigned to the city where consumption takes place, while local impacts are allocated to the city where the impacts occur.

Density- and service-based boundaries are the most parsimonious as we see it is the simplest way to simulate the complexity and interdependency of cities. Geographical boundaries of a city LCA should be defined through the density-basedprocedure, which should include cities, towns and suburbs connected with a continuous density of population. However, the functional boundaries of the city LCA should be defined through service-based procedure, which would help to include, in the city system, those induced activities that happen out of the geographical boundaries of the city.

The chosen allocation procedure should follow the causality principle between the impact and the activity performed. The proposed method for allocating impacts to the producer or the consumer, depending on whether the impact category under consideration is local or global, has been found through a survey to be the most preferred way to share responsibilities along the supply chain. Thus, the category-based allocation procedure is the suggested one.

The survey results show how density- and service-based boundaries are the preferred by the panel of experts, by giving best marks in lifelikeness and accuracy. They also prefer the category-based allocation procedure, by giving best marks in informativeness, lifelikeness, and accuracy, and second in influence.

This article analyses whether existing LCA and sustainability methods can be used in the assessment of a city or an urban region. The approach is performed through the review of current existing LCA-based and sustainability standards and guidelines. A focus is put into those LCA-based standards specially designed for the built environment. Moreover, a review of non-LCA based standards, indices and guides for the assessment of the sustainability of countries, cities or urban regions is done. The purpose is to check if these assessment tools can provide good results in the absence of LCA-based assessments for cities and urban regions. This review demonstrates the lack of consensus in the definition of both, the city and its boundaries, which hinders the development of useful sustainability standards. Furthermore, it is concluded that current sustainability assessment tools miss, at least, one of these aspects: (i) holistic point of view, (ii) focus on various environmental impacts, (iii) a Life Cycle (LC) perspective, and (iv) the possibility to compare the results among different cities or urban regions. From the LCA perspective, the deficiencies found also include the need for a definition of the function, functional unit (FU), and reference flow (RF) of neighbourhoods, cities, and urban regions.