Gara Villalba

• Bachelor of Engineering
• Autonomous University of Barcelona

Introduction The Green Corridors Plan (Eixos Verds Plan), proposed by the Barcelona City Council, aims to enhance urban well-being, environmental sustainability, and resilience by transforming one in every three streets into green corridors. Although initially designed for city-wide implementation, only the first phase, focused on the centric Eixam...

Heat and drought events are increasing in frequency and intensity, posing significant risks to natural and agricultural ecosystems with uncertain effects on the net ecosystem CO2 exchange (NEE). The current Vegetation Photosynthesis and Respiration Model (VPRM) was adjusted to include soil moisture impacts on the gross ecosystem exchange (GEE) and...

The previously proposed Vegetation Photosynthesis and Respiration Model was changed to include soil moisture impacts on ecosystem carbon fluxes. A modest annual increase of net carbon sink of 0.69 gC m-2 yr-1 is found in southwestern Europe but with high spatial and annual variability. The inter-annual variability in net ecosystem exchange is more...

Monitoring CO 2 concentrations in urban areas is crucial for determining the efficacy of climate change mitigation policies. However, highly heterogeneous land use, local geography, and local convection patterns, which vary throughout the urban landscape, complicate this task. To establish continuous monitoring programs, it is important to first de...

Cities face the challenges of supplying food and managing organic municipal solid waste (OMSW) sustainably amid increasing urbanization rates. Urban agriculture (UA) can help with this effort by producing local crops that are fertilized with nutrients recovered from compost generated from OMSW. This research aims to determine the potential of OMSW...

Due to urban population growth during recent decades, the food supply chain has become one of the key material flows in the metabolism of cities. Urban agriculture (UA) can be an alternative for mitigating food supply impacts. UA can provide environmental benefits, but current concepts and strategies do not reflect its full potential. The circular...

With the latest IPCC report, dramatic global climate action must be taken immediately to limit global warming to 1.5 oC, or face more frequent and extreme weather events with catastrophic implications. Cities must invest in climate resilience development; however, government policies are only effective if they are supported by the society in which...

Urban design is currently promoting the inclusion of plants in buildings. However, plants emit biogenic volatile organic compounds (BVOCs), which alone or in combination with other airborne molecules such as CO2, may result in a general increase in tropospheric pollution. Many studies have documented the effects of biotic and abiotic factors on pla...

Carbonyl sulfide (OCS) is used to quantify the carbon capture potential of the biosphere because of its direct correlation with CO2 uptake during photosynthesis. However, to constrain the urban biosphere signal, it is necessary to evaluate potential anthropogenic sources. We conducted two sampling campaigns in the Metropolitan Area of Barcelona (AM...

Urban agriculture (UA) activities are increasing in popularity and importance due to greater food demands and reductions in agricultural land, also advocating for greater local food supply and security as well as the social and community cohesion perspective. This activity also has the potential to enhance the circularity of urban flows, repurposin...

Tropospheric ozone (O3) is an important surface pollutant in urban areas, and it has complex formation mechanisms that depend on the atmospheric chemistry and on meteorological factors. The severe reductions observed in anthropogenic emissions during the COVID-19 pandemic can further our understanding of the photochemical mechanisms leading to O3 f...

Carbonyl sulfide (OCS) is used to quantify the carbon capture potential of the biosphere because of its direct correlation with CO2 uptake during photosynthesis. However, to constrain the urban biosphere signal, it is necessary to evaluate potential anthropogenic sources. We conducted two sampling campaigns in the Metropolitan Area of Barcelona (AM...

Improving air quality in highly polluted cities is a challenge for today’s society. Most of the proposed strategies include green policies that aim to introduce green infrastructures helping to improve air quality. To design new cities with more green infrastructures, the WRF-Chem model is used to analyze the evolution of the most common pollutants...

Heatwaves (HWs) are expected to increase both in duration and intensity in the next decades, but little is known about their synoptic and mesoscalar behavior, which is especially important in mid-latitude regions. Most climate research has focused on temperature analysis to characterize HWs. We propose that a combination of temperature and synoptic...

The external resource dependency of urban areas results in the externalization of environmental and socioeconomic impacts. Implementing food, energy and water production systems on urban rooftops (roof mosaics) can potentially help cities become more self-sufficient but depends on the city's urban morphology. We studied the supply potential and imp...

Tropospheric ozone (O3) is an important surface pollutant in urban areas, and it has complex formation mechanisms that depend on the atmospheric chemistry and meteorological factors. The severe reductions observed in anthropogenic emissions during the COVID-19 pandemic can further our understanding of the photochemical mechanisms leading to O3 form...

Heatwaves (HWs) are expected to increase both in duration and intensity in the next decades, but little is known about their synoptic and mesoscalar behavior, which is especially important in mid-latitude regions. Most climate research has focused on temperature analysis to characterize HWs. We propose that a combination of temperature and synoptic...

Urban green installations are extensively promoted to increase sustainable and accessible food production and simultaneously improve the environmental performance and liveability of city buildings. In addition to the multiple benefits of plant retrofitting, these installations may lead to a consistent increase in biogenic volatile organic compounds...

Severe measures concerting the mobility of people have been implemented worldwide to contain the spread of COVID-19. This exceptional situation during COVID-19 can serve as a chemical experiment that expands our understanding of photochemical processes in the atmosphere. In this study, we analyze changes in the urban air quality during COVID lockdo...

Street trees are an important driver of street microclimate through shading and transpirative cooling, which are key mechanisms for improving thermal comfort in urban areas. Urban canopy models (UCM) with integrated trees are useful tools because they represent the impacts of street trees on neighborhood-scale climate, resolving the interactions be...

Peri urban agriculture (peri-UA) can supply food locally and potentially more sustainably than far-away conventional agricultural systems. It can also introduce significant environmental impacts depending on the local biophysical conditions and resources required to implement it and, Fon the practices used to manage crops, which could vary widely a...

Meteorological and climate prediction models at the urban scale increasingly require more accurate and high-resolution data. The Local Climate Zone (LCZ) system is an initiative to standardize a classification scheme of the urban landscape, based mainly on the properties of surface structure (e.g., building, tree height, density) and surface cover...

The transition to clean energy will require significant increases in electricity sourced from renewable energy technologies. While wind and solar photovoltaic sources are generally expected to overtake hydropower to dominate the renewable electricity supply market, numerous other technologies vie for a share in this rapidly evolving arena. To date,...

A paradigm shift is needed in wastewater treatment plants (WWTPs) to progress from traditional pollutant removal to resource recovery. However, whether this transformation produces overall environmental benefits will depend on the efficient and sustainable use of resources by emerging technologies. Given that many of these technologies are still be...

Hydroponic systems are an attractive form of urban agriculture due to their low weight load, inert substrate conditions, and overall better control of plant nutrition and growth. However, gaining urban food sovereignty cannot be at the cost of increasing environmental impacts, such as eutrophication and nonrenewable resource depletion, associated w...

Geographically explicit datasets reflecting local management of crops are needed to help improve direct nitrous oxide (N2O) emission inventories. Yet, the lack of geographically explicit datasets of relevant factors influencing the emissions make it difficult to estimate them in such way. Particularly, for local peri-urban agriculture, spatially ex...

Purpose New environmental strategies are emerging for cities to become more self-sufficient, such as hydroponic crop production. The implementation of such systems requires materials that usually originate in countries with low labour costs and other legal regulations. To what extent could these strategies be shifting problems across the globe? To...

Due to increased urbanization and global warming, cities are experiencing more heat wave (HW) events that cause extreme heat stress. To mitigate such effects, a better understanding of the impact of urban morphology on the boundary layer development is needed. This study investigates the sensitivity of mesoscale simulations using the WRF model coup...

The rigorous traffic limitations during COVID-19 have forced many people to work from home, reaching an outstanding degree of teleworking and reduction in air pollution. This exceptional situation can be examined as a large-scale pilot test to determine the potential of improving urban air quality through teleworking. Based on observed traffic redu...

Urban agriculture (UA) is a means for cities to become more resilient in terms of food sovereignty while shortening the distance between production and consumption. However, intensive soilless UA still depends on the use of fertilizers, which relies on depleting non-renewable resources such as phosphorous (P) and causes both local and global impact...

The rise of population in urban areas makes it ever more important to promote urban agriculture (UA) that is efficient in terms of water and nutrients. How to meet the irrigation demand of UA is of particular concern in urban areas where water sources are often limited. With the aim of determining how to reduce water use for irrigation while mainta...

Air pollution exposure is a major environmental risk to health and has been estimated to be responsible for 7 million premature deaths worldwide every year. This is of special concern in cities, where there are high levels of pollution and high population densities. Not only is there an urgent need for cities to monitor, analyze, predict and inform...

With the overall aim to design successful implementation strategies of food-energy-water production systems on urban roofs, we propose an integrated process that includes participatory processes and a multi-dimensional sustainability assessment of environmental, social and economic indicators. The proposed framework was applied to a typical housing...

Soilless crop production is a viable way to promote vertical agriculture in urban areas, but it relies extensively on the use of mineral fertilizer. Thus, the benefits of fresher, local food and avoiding the transportation and packaging associated with food import could be counteracted by an increase in nutrient-rich wastewater, which could contrib...

Urban agriculture, while being a promising solution to increase food sovereignty in cities, can lead to an unprecedented discharge of nutrient and fertilizer-related emissions into the urban environment. Especially relevant are nitrogen (N) and phosphorus (P), due to their contribution to marine and freshwater eutrophication. Therefore, alternative...

The frequency and intensity of heat waves (HW) in cities are on the rise due to climate change as well as urban fabric materials and anthropogenic activities that affect heat accumulation. The efficacy of HW mitigation strategies depends on a city's specific and unique morphology, land use, building materials, climate and geography. In this study,...

BACKGROUND Urban agriculture contributes to meeting the growing food production demand in cities. In the context of low water availability, it is important to consider alternatives that are able to maintain production. Through a circular economy vision, this study aimed to assess the use of substrates made from local materials as an alternative for...

Housing estates, that is, mass social housing on middle‐ and high‐rise apartment blocks, in urban areas are found all over the world with very similar constructive patterns and a multiplicity of environmental and socio‐economic problems. In this regard, such areas are optimal for the implementation of a roof mosaic which involves applying a combina...

Local food production through urban agriculture (UA) is promoted as a means to make cities more sustainable. However, UA does not come free of environmental impacts. In this sense, optimizing urban resources through circular economy principles offers the opportunity to close loops and improve production systems, but an assessment of these systems t...

Urban agriculture systems can significantly contribute towards mitigating the impacts of inefficient and complex food supply chains and increase urban food sovereignty. Moreover, improving these urban agriculture systems in terms of nutrient management can lead to a better environmental performance. Based on a rooftop greenhouse in the Barcelona re...

Urban development and the sprawl of transport infrastructures have disregarded the crucial function of metropolitan landscape in provisioning human well-being and biodiversity. This research aims to contribute to the challenges of Planning for Sustainability by proposing a Socioecological Integrated Analysis (SIA) to support the Land Use Master Pla...

Phosphorus (P) resources are decreasing at an alarming rate due to global fertilizer use and insufficient nutrient recovery strategies. Currently, more circular approaches are promoted, such as recovering P from wastewater in the form of struvite. This is especially attractive for urban areas, where there is a growing trend of local crop production...

Green spaces are known to provide a number of benefits to urban areas. In order to make green spaces more accessible to people in urban regions, the EU has launched some important initiatives that place green infrastructure (GI) development as a top priority in urban planning, contributing to the paradigm of making more sustainable and smarter citi...

Urban agriculture systems, such as rooftop greenhouses, are attractive alternatives for mitigating the impacts of the extensive food supply chains that currently feed cities. In this study, we study the opportunity that nutrient recirculation offers to improve the environmental performance of agricultural systems. In particular, we analyze the envi...

Purpose Rooftop greenhouses (RTGs) are agricultural systems that can improve the food supply chain by producing vegetables in unused urban spaces. However, to date, environmental assessments of RTGs have only focused on specific crops, without considering the impacts resulting from seasonality, combinations of crops and nonoperational time. We ana...

In light of global population growth and the increasing food demand in cities, new food production strategies have been developed to promote a more resource-efficient urban agriculture. Greenhouses with hydroponic systems have been proposed as sustainable systems for growing food in urban areas with a better control of plant growth. However, nutrie...

The European Union (EU) is developing strategies for fostering electric mobility (EM); however, there are risks that threaten the development of this emergent technology which must be considered and evaluated. In this study, we analyse the use and potential recovery of the four rare earth elements, which are used in the permanent magnets (PMs) of t...

A recent study helps city planners find the greenest and most effective way of producing renewable energy, crops and water on rooftops. The researchers developed a method for analysing the performance and environmental impacts of different combinations of rooftop rainwater-harvesting-, energy- and food systems. It could aid efforts to promote urban...

Purpose Due to population growth, urban water demand is expected to increase significantly, as well as the environmental and economic costs required to supply it. Rainwater harvesting (RWH) systems can play a key role in helping cities meet part of their water demand as an alternative to conventional water abstraction and treatment. This paper pres...

Cities are rapidly growing and need to look for ways to optimize resource consumption. Metropolises are especially vulnerable in three main systems, often referred to as the FEW (i.e., food, energy, and water) nexus. In this context, urban rooftops are underutilized areas that might be used for the production of these resources. We developed the Ro...

This deliverable entitled “Concise description of application fields for different MFA a pproaches and indicators” describes the various methods of material flow analysis (MFA) applied to raw materials, and analyses existing indicators in terms of a characterization scheme that was developed by the MinFuture partners (chapter 4). Chapter 5 gives va...

The main objective of this article is to introduce an open‐source, online software tool called OMAT as a teaching tool for performing economy wide‐material flow analysis (EW‐MFA) at urban or regional level in industrial ecology curricula. To that intent, we present a classroom and project activity that was developed for a masters‐level industrial e...

Decentralized wastewater treatment and reuse (DWTRU) using small-scale on-site sewage treatment plants (STPs) is an attractive solution addressing the problems of water pollution and scarcity, especially in rapidly urbanizing cities in developing countries, where centralized infrastructure for wastewater treatment is inadequate. But decentralized s...

Due to population growth and the subsequent increase in the demand for food, low carbon food chain production systems are a necessity to reduce the effects on climate change as much as possible. Urban agriculture is of great interest because of its potential in reducing the indirect CO2 emissions of a city's food supply by reducing transportation d...

This study presents a life cycle assessment of a crop sequence of cauliflower and tomato that is subjected to three different fertilization treatments; the crops were cultivated in a Mediterranean region. The main objective of this study is the assessment of organic and mineral fertilizers that are applied to a crop sequence of tomato and cauliflow...

Sewers are known as longitudinal reactors where gases such as methane, nitrous oxide and hydrogen sulphide can be produced. However, gaseous emissions have been mainly assessed in wastewater treatment plants (WWTP). This article presents a critical review of studies that quantify the generation of these gases in sewers and to identify the existing...

Direct gas emissions from wastewater collection and treatment systems have become a topic of increasing interest, given their contribution to the urban carbon footprint, as well as, to the problems associated to odours. Most studies have focused on wastewater treatment plants (WWTPs), disregarding the significant role of sewer networks in the produ...

The environmental impacts resulting from sewer networks are best analysed from a life-cycle perspective to integrate the energy requirements into the infrastructure design. The energy requirements for pumping wastewater depend on the configuration of the city (e. g., climate, population, length of the sewer, topography, etc.). This study analyses a...

Managing sanitation infrastructures is of paramount importance in order to meet the demand of an increasing urban population. From a life-cycle perspective, the operation stage of the wastewater collection and treatment results in 2 different types of contributions to the Global Warming Potential (GWP). On the one hand, the indirect impacts consist...

A sewer network can be considered as a biological reactor where each constructive element can lead to different environmental conditions. Depending on these conditions, several biological reactions could take place resulting in gas formation, such as nitrous oxide (N2O), methane (CH4) and hydrogen sulphide (H2S). Problems like corrosion and odour a...

This study provides a global substance flow analysis for gallium (Ga), germanium (Ge), and indium (In) for 2011, quantifying the amount of metal lost during extraction, beneficiation/smelting/refining, manufacturing of intermediate products, and the amount embodied in end-use products. Thus far, studies illustrating their cradle to end-use life cyc...

Biogas is rich in methane and can be further purified through biogas upgrading technologies, presenting a viable alternative to natural gas. Landfills and anaerobic digestors treating municipal solid waste are a large source of such biogas. They therefore offer an attractive opportunity to tap into this potential source of natural gas while at the...

This paper studies the potential application of a novel biogas upgrading technology called alkaline with regeneration (AwR). This technology uses an alkaline solution, along with carbon mineralization, to remove and store CO2 from biogas in order to create biomethane, a substitute of natural gas. Three different applications of biogas were explored...

The industrial system now utilizes many more elements, especially rare metals, than was the case even a half century ago. Most are not mined for themselves but are obtained as by-products or "hitchhikers" of the more familiar industrial metals, such as iron, aluminum, copper, nickel, and zinc. This imposes a limit on the production of by-product me...

For many companies, the greenhouse gas (GHG) emissions associated with their purchased and consumed electricity form one of the largest contributions to the GHG emissions that result from their activities. Currently, hourly variations in electricity grid emissions are not considered by standard GHG accounting protocols, which apply a national grid...

A Life Cycle Assessment (LCA) of two home composts with low and high gaseous emissions of the composting process is presented. The study focused on the gaseous emissions of the composting process. Gaseous emissions of methane, nitrous oxides, ammonia and volatic organic compounds of the composting process were experimentally measured in field real...

Previous studies assessing the environmental impacts of drinking water supply networks have considered a bottom-up approach, analysing single case studies. This paper presents a top-down approach for the assessment of the operational phase of a water supply network. A representative sample of 50 cities was statistically analysed to find relations b...

Carbon mineralization is a promising process for carbon dioxide (CO2) capture and storage, and it can also be applied for biogas upgrading. This paper uses a life cycle assessment to identify possible methods of improving and reducing the environmental impact of novel biogas upgrading technologies. The two novel pilot-scale technologies that are as...

In the context of transition to sustainability, one of the main challenges facing societies today is the supply of water. By integrating different methodological tools and studies we developed the innovative software program Plugrisost® (rainwater, greys and sustainability), a simulation model, that facilitates the economic evaluation and the poten...

Meeting the growing water demand, especially in urban areas, is becoming a high economic cost for society. With 9 billion inhabitants prospected by 2050 (70% in urban areas), water demand for human use and consumption is expected to greatly increase, leading to unachievable economic and social costs. Rainwater harvesting systems could play an impor...

Despite efforts to increase the selective collection of municipal solid waste (MSW) in developed countries, the amount of unsorted waste remains high, with the consequent difficulty of material recovery and recycling. In 2010, 61% of the MSW generated in the European Union (EU) ended up in landfill and incineration facilities. Autoclaving is a nove...

To bring sustainable resource use into practice, it is important to have concrete measurement tools. Material flow analysis (MFA) has become a useful tool for analyzing the metabolism of social systems, such as countries, regions and cities. This contribution proposes to use the Life Cycle Assessment (LCA) and the MFA methodologies to analyze the m...

Expected population growth will result in increasing water demand. The consequences could potentially jeopardise water resource availability especially in urban areas and significantly increase costs. Rainwater harvesting (RWH) systems can aid not only in meeting water demand partially, but also doing so in a more cost-effective and environmentally...

Proper recycling of mobile phones and other electronic products is important in order to reduce the generation of large amounts of hazardous waste, lessen environmental and social problems associated to the extraction of minerals and primary production of materials, and also minimize the depletion of scarce materials that are often difficult to sub...

In a world with an increasing urban population, analysing the construction impacts of sanitation infrastructures through Life Cycle Assessment (LCA) is necessary for defining the best environmental management strategies. In this study, the environmental impacts of one linear meter of sewer constructive solution were analysed for different pipe mate...

An alternative source of methane that can also reduce the greenhouse gas effect is one that comes from the upgrading of biogas. This paper studies eight technologies through life cycle assessment (LCA). Six of the technologies are ones that are already on the market and the two others are novel technologies that use carbon mineralization to store C...

In 2010, the generation of municipal solid waste (MSW) by the European Unión (EU-27) was 252 million tons, with an estimated organic content of 30–40% by weight. Composting this organic matter would significantly improve waste reduction and mineral fertilizer substitution. We present a Life Cycle Analysis (LCA) and agronomical assessment of the fol...

This study presents the application of exergetic efficiency analysis in assessing how effectively resources are utilized in the current industrial processes of construction material manufacturing. The role of exergy is discussed from several key perspectives such as quality, energy conservation, and process improvement potentials. Both primary and...

This chapter presents an overview of the mass balance principle and its applications. It is an important tool for quantifying wastes which are produced by economic processes. These wastes are equal in mass to the difference between total raw material inputs to the process and useful material outputs. Products are becoming more complex which results...

Until now, few studies had focused on the environmental impact of the construction phase of a drinking water transport and distribution network (DWTDN). Using the life cycle assessment (LCA) methodology, this article compares the environmental impact of pipes made of different materials as constructive solutions for the DWTDN. Two pipe diameters (9...

Like cities, many large national parks in the United States often include "urban" visitor and residential areas that mostly demand (rather than produce) energy and key urban materials. The U.S. National Park Service has committed to quantifying and reducing scopes 1 and 2 emissions by 35% and scope 3 emissions by 10% by 2020 for all parks. Current...

The use of rare earth metals (REMs) for new applications in renewable and communication technologies has increased concern about future supply as well as environmental burdens associated with the extraction, use, and disposal (losses) of these metals. Although there are several reports describing and quantifying the production and use of REM, there...

The demand for lithium has increased significantly during the last decade as it has become key for the development of industrial products, especially batteries for electronic devices and electric vehicles. This article reviews sources, extraction and production, uses, and recovery and recycling, all of which are important aspects when evaluating li...

Environmental improvements (environmental dimension) have been developed to be applied in industrial activities (economic dimension), nowadays, these are moving to urban areas (social dimension). Population in urban areas will increase significantly during the next decades as well as water demand. On the other hand, water resources availability is...

In our continued effort in reducing resource consumption, greener technologies such as rainwater harvesting could be very useful in diminishing our dependence on desalinated or treated water and the associated energy requirements. This paper applies exergy analysis and exergetic efficiency to evaluate the performance of eight different scenarios of...

A number of metals that are now important to the electronic industry (and others) will become much more important in the future if current trends in technology continue. Most of these metals are byproducts (or hitch-hikers) of a small number of important industrial metals (attractors). By definition, the metals in the hitch-hiker group are not mine...

We used a thermodynamic framework to characterize the resource consumption of the construction sector in 2001 in Catalonia, the northeast region of Spain. The analysis was done with a cradle-to-product life cycle approach using material flow analysis (MFA) and exergy accounting methodologies to quantify the total material and energy inputs in the s...