Literature review on the potential of urban waste for the fertilization of urban agriculture: A closer look at the metropolitan area of Barcelona.

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, repurposing nutrients from waste sources, increasing their self-sufficiency, reducing nutrient loss into the environment, and avoiding environmental cost of nutrient extraction and synthetization. The present work is aimed at defining recovery technologies outlined in the literature to obtain relevant nutrients such as N and P from waste sources in urban areas. Through literature research tools, the waste sources were defined, differentiating two main groups: (1) food, organic, biowaste and (2) wastewater. Up to 7 recovery strategies were identified for food, organic, and biowaste sources, while 11 strategies were defined for wastewater, mainly focusing on the recovery of N and P, which are applicable in UA in different forms. The potential of the recovered nutrients to cover existing and prospective UA sites was further assessed for the metropolitan area of Barcelona. Nutrient recovery from current composting and anaerobic digestion of urban sourced organic matter obtained each year in the area as well as the composting of wastewater sludge, struvite precipitation and ion exchange in wastewater effluent generated yearly in existing WWTPs were assessed. The results show that the requirements for the current and prospective UA in the area can be met 2.7 to 380.2 times for P and 1.7 to 117.5 times for N depending on the recovery strategy. While the present results are promising, current perceptions, legislation and the implementation and production costs compared to existing markets do not facilitate the application of nutrient recovery strategies, although a change is expected in the near future.

Assessment of greenhouse emissions of the green bean through the static enclosure technique.

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 (BVOCs) in the urban environment, especially indoors. Accordingly, health concerns could limit the implementation of building-integrated agriculture. In a building-integrated rooftop greenhouse (i-RTG), throughout the whole hydroponic cycle, green bean emissions were dynamically collected in a static enclosure. Four representative BVOCs, α-pinene (monoterpene), ß-caryophyllene (sesquiterpene), linalool (oxygenated monoterpene) and cis-3-hexenol (LOX derivate), were investigated in the samples collected from two equivalent sections of a static enclosure, one empty and one occupied by the i-RTG plants, to estimate the volatile emission factor (EF). Throughout the season, extremely variable BVOC levels between 0.04 and 5.36 ppb were found with occasional but not significant (P > 0.05) variations between the two sections. The highest emission rates were observed during plant vegetative development, with EFs equivalent to 78.97, 75.85 and 51.34 ng g-1 h-1 for cis-3-hexenol, α-pinene, and linalool, respectively; at plant maturity, all volatiles were either close to the LLOQ (lowest limit of quantitation) or not detected. Consistent with previous studies significant relationships (r ≥ 0.92; P < 0.05) were individuated within volatiles and temperature and relative humidity of the sections. However, correlations were all negative and were mainly attributed to the relevant effect of the enclosure on the final sampling conditions. Overall, levels found were at least 15 folds lower than the given Risk and LCI values of the EU-LCI protocol for indoor environments, suggesting low BVOC exposure in the i-RTG. Statistical outcomes demonstrated the applicability of the static enclosure technique for fast BVOC emissions survey inside green retrofitted spaces. However, providing high sampling performance over entire BVOCs collection is recommended to reduce sampling error and incorrect estimation of the emissions.

Increasing resource circularity in wastewater treatment: Environmental implications of technological upgrades.

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 being tested at the pilot scale, there is a lack of environmental assessments quantifying their impacts and benefits. In particular, an integrated approach to energy and nutrient recovery can elucidate the potential configurations for WWTPs. In this study, we conduct a life cycle assessment (LCA) of emergent wastewater treatment technologies aimed at increasing resource circularity in WWTPs. We focus on increasing energy self-sufficiency through biogas upgrades and a more radical circular approach aimed at nutrient recovery. Based on a case-study WWTP, we compare its current configuration with (1) implementing autotrophic nitrogen removal in the mainstream and deriving most of the organic matter for biogas production, which increases the quality and quantity of biogas available for energy production; (2) implementing struvite recovery through enhanced biological phosphorus removal (EBPR) as a radical approach to phosphorus management, offering an alternative to mineral fertilizer; and (3) a combination of both approaches. The results show that incremental changes in biogas production are insufficient for compensating for the environmental investment in infrastructure, although autotrophic nitrogen removal is beneficial for increasing the quality of the effluent. Combined phosphorus and energy recovery reduce the environmental impacts from the avoided use of fertilizers and phosphorus and the nitrogen release into water bodies. An integrated approach to resource management in WWTPs is thus desirable and creates new opportunities toward the implementation of circular strategies with low environmental impact in cities.

Recovered phosphorus for a more resilient urban agriculture: Assessment of the fertilizer potential of struvite in hydroponics.

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 for its production and application. With the aim to reduce such impacts and encourage a more efficient use of nutrients, this study assesses the feasibility of using struvite precipitated from an urban wastewater treatment plant as the unique source of P fertilizer. To do so, we apply various quantities of struvite (ranging from 1 to 20 g/plant) to the substrate of a hydroponic Phaseolus vulgaris crop and determine the yield, water flows and P balances. The results show that treatments with more than 5 g of struvite per plant produced a higher yield (maximum of 181.41 g/plant) than the control (134.6 g/plant) with mineral fertilizer (KPO4H2). On the other hand, P concentration in all plant organs was always lower when using struvite than when using chemical fertilizer. Finally, the fact that different amounts of struvite remained undissolved in all treatments denotes the importance to balance between a correct P supply to the plant and a decrease of P lost through the leachates, based on the amount of struvite and the irrigated water. The findings of this study show that it is feasible for UA to efficiently use locally recovered nutrients such as P to produce local food.

Optimizing irrigation in urban agriculture for tomato crops in rooftop greenhouses.

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 maintaining productivity and reducing environmental impacts in UA, this study explores the agronomic performance and environmental life cycle impacts and benefits of three different fertigation management practices used in a rooftop greenhouse for tomato crop in Barcelona: 1) open management (OP); 2) recirculation (RC), in which 30% of the drained, unused water is used to irrigate the crop; and 3) the same recirculated management of RC with a further reduction in fresh water input of 15%(RR). Despite the recirculation and reduction of water and nutrients, all three irrigation management practices resulted in similar yields: 16.2, 17.9, and 16.8·kg·m-2 for OP, RC, and RR, respectively. In terms of water-use efficiency, RR management was the most efficient, requiring 48.7·liters·kg-1 of tomato, followed by RC (52.4·L·kg-1) and OP (75.2·L·kg-1). RR presented an improvement of 7% in water-use efficiency. In terms of environmental performance, RC had the best performance in almost all impact categories during the operational phase, especially in regard to marine and freshwater eutrophication, with 44% and 93% fewer impacts than OP due to the recirculation of nutrients and reduced nutrient loss through leachates. In terms of infrastructure, even though recirculation management requires additional equipment, the materials present better performance in the range from 0.2 to 14% depending on the impact category. This study can support evaluation of agricultural projects in the city, through yields and water consumption presented, incentivizing good practices aligned with the sustainability of UA.

Comparison of organic substrates in urban rooftop agriculture, towards improving crop production resilience to temporary drought in Mediterranean cities.

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 urban agriculture in periods of low water availability, due to water supply cuts. The substrates used were coir commercial organic substrate, vegetable compost from urban organic waste and perlite commercial standard substrate; a mixture of the urban compost and perlite (1:1) was used for three consecutive crop cycles of lettuce (Lactuca sativa L. var. crispa). The crop cycles were performed in the spring and summer periods of 2018 to observe the performance during warmer periods of the year in an integrated rooftop greenhouse near Barcelona. Each substrate was assessed under conventional irrigation (0-5 kPa) and temporary water restricted conditions (irrigation stopped until the water tension reached -20 kPa perlite). RESULTS: In terms of yield, our results show that the compost and mixture were similar to those obtained from perlite (11.5% and 3.7% more production under restricted water conditions). Organic substrates increased the crop's resilience to water restriction, in contrast to the perlite. In particular, water loss took longer in coir (one- and two-crop cycle); however, when dryness began, it occurred quickly. CONCLUSION: The vegetable compost and the substrate mixture presented tolerance to temporary water restriction when water restriction reached -20 kPa. © 2021 Society of Chemical Industry.

Assessing the environmental behavior of alternative fertigation methods in soilless systems: The case of Phaseolus vulgaris with struvite and rhizobia inoculation.

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 methods of fertilization need to be put into practice to avoid such impacts to the surrounding environment. Struvite, has been studied as a potential slow releasing fertilizer due to its high P content, while the bacteria rhizobium has been used to fix N directly from the atmosphere. Legumes, like the common bean are N-demanding crops capable of symbiosis with the bacteria rhizobium and have previously shown positive responses to fertilization with struvite. This study aims to analyze the environmental performance of plant production in hydroponic systems combining rhizobium inoculation and struvite (2 g, 5 g, 10 g, 20 g) irrigated with a N and P deficient nutrient solution, using life cycle analysis (LCA). The nutrient content of in- and out-going irrigation was analyzed as well as in plants and beans. The functional unit for the LCA was 1 kg of fresh beans. The results obtained indicate a yield reduction of 60% to 50% in comparison to the control which was irrigated with a full nutrient solution. The impacts from operational stage are less in all impact categories, where most significant reductions up to 69% and 59% are seen in marine-eutrophication and global warming respectively. Although the infrastructure does not change between treatments, its impacts increase due to the lower yields. We determine that below a 10% of the control yield, the alternative systems have more impact than the use of conventional mineral fertilizers in almost all impact categories, thus pointing to the importance of infrastructure to truly reduce environmental impacts for urban agriculture.

Closed-Loop Crop Cascade to Optimize Nutrient Flows and Grow Low-Impact Vegetables in Cities.

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 region, we propose a cascade system where the leachates of a tomato cycle from January to July (donor crop) are used as the main irrigation source for five successive lettuce cycles (receiving crop). By determining the agronomic performance and the nutrient metabolism of the system, we aimed to define the potential of these systems to avoid nutrient depletion and mitigate eutrophication, while scaling the system in terms of nutrient supply between the donor and the receiving crops. The results showed that low yields (below 130 g per lettuce plant) are obtained if a cascade system is used during the early stage of the donor crop, as the amount of nutrients in donor's leachates, specially N (62.4 mg irrigated per plant in the first cycle), was not enough to feed the lettuce receiving crop. This effect was also observed in the nutrient content of the lettuce, which increased with every test until equaling the control (4.4% of N content) as the leachates got richer, although too high electrical conductivity values (near 3 dS/m) were reached at the end of the donor crop cycle. Findings on the uptake of the residual nutrient flows showed how the cascade system was able to take advantage of the nutrients to produce local lettuce while mitigating the effect of N and P in the freshwater and marine environments. Considering our case study, we finally quantified the scale between the donor and receiving crops and proposed three major ideas to optimize the nutrient flows while maintaining the yield and quality of the vegetables produced in the receiving crop.

Can wastewater feed cities? Determining the feasibility and environmental burdens of struvite recovery and reuse for urban regions.

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 and large volumes of wastewater are treated in centralized wastewater treatment plants (WWTPs). This research aims to assess the technical and environmental feasibility of applying a struvite recovery and reuse strategy to meet the P requirements to fertilize the agricultural fields of an urban region. To do so, we analyze the potential P recovery and the environmental impacts of integrating three recovery technologies (REM-NUT®, Ostara® and AirPrex®) in the two biggest WWTPs of the Àrea Metropolitana de Barcelona. The results show that all technologies are able to recover between 5 and 30 times the amount of P required to fertilize the agricultural area of the region annually (36.5 t). As can be expected, including P recovery technologies result in additional impacts per m3 of wastewater due to increased electricity consumption and chemicals required for the struvite precipitation. However, struvite recovery results in less eutrophication potential, especially in the REM-NUT® case, with an average reduction of 5.4 times. On the other hand, Ostara®, that recovers P from the digestate, had the lowest impacts (9 kgCO2eq/kgP), even compared to the production of mineral fertilizer. When we apply our findings to the whole region, we can see that chemical use for struvite precipitation and energy consumption during the wastewater treatment process are the elements with the greatest impact. Thus, choosing the most appropriate technology in the most suitable WWTP is the most efficient strategy to diminish the environmental impacts of the system.

Analysis of urban agriculture solid waste in the frame of circular economy: Case study of tomato crop in integrated rooftop greenhouse.

Within urban agriculture (UA), integrated rooftop greenhouses (i-RTG) have great growth potential as they offer multiple benefits. Currently it is intended to improve environmental benefits by taking advantage of the water, nutrients and gases flows. On the other hand, solid waste (SW) generated by the UA is a new type of waste within cities that has not well been classified or quantified for its use. This could become a new problem for the waste management system within cities in the future, mainly the organic fraction. The objective of this research is to identify what type of i-RTG SW has the potential to be used from a circular economy (CE) perspective and propose a type of management for its material valorization. The results of the case study show that, of the SW generated in i-RTG, the biomass has the greatest potential to be used locally as an eco-material, particularly the tomato stems. Its use is proposed as a substrate for two experimental lettuce crops in i-RTG. The results show that tomato stems have a better yield as a substrate after a prewash treatment, since at first the values of electrical conductivity (EC) are very high with respect to the control substrate, which is expanded perlite. In conclusion, we can say that it is possible to increase the environmental benefits of i-RTG by taking advantage of its biomass locally, helping to foresee a possible future problem regarding the management of the residual biomass of i-RTG within cities. In this way, the paradigm about the perception of the SW of the UA could be changed to give them a by-product treatment from the beginning.

Towards Productive Cities: Environmental Assessment of the Food-Energy-Water Nexus of the Urban Roof Mosaic.

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 Roof Mosaic approach, which combines life cycle assessment with two rooftop guidelines, to analyze the technical feasibility and environmental implications of producing food and energy, and harvesting rainwater on rooftops through different combinations at different scales. To illustrate, we apply the Roof Mosaic approach to a densely populated neighborhood in a Mediterranean city. The building-scale results show that integrating rainwater harvesting and food production would avoid relatively insignificant emissions (13.9-18.6 kg CO2 eq/inhabitant/year) in the use stage, but their construction would have low environmental impacts. In contrast, the application of energy systems (photovoltaic or solar thermal systems) combined with rainwater harvesting could potentially avoid higher CO2 eq emissions (177-196 kg CO2 eq/inhabitant/year) but generate higher environmental burdens in the construction phase. When applied at the neighborhood scale, the approach can be optimized to meet between 7% and 50% of FEW demands and avoid up to 157 tons CO2 eq/year. This approach is a useful guide to optimize the FEW nexus providing a range of options for the exploitation of rooftops at the local scale, which can aid cities in becoming self-sufficient, optimizing resources, and reducing CO2 eq emissions.

Agronomic and Environmental Assessment of a Polyculture Rooftop Soilless Urban Home Garden in a Mediterranean City.

Urban planning has been focusing its attention on urban rooftop agriculture as an innovative way to produce local and reliable food in unused spaces in cities. However, there is a lack of quantitative data on soilless urban home gardens and their contribution to self-sufficiency. The aim of the present study is to provide quantitative agronomic and environmental data on an actual soilless urban garden to estimate its degree of self-sufficiency and sustainability. For this purpose, an 18 m2 soilless polyculture rooftop urban home garden in the city center of Barcelona was analyzed. From 2015 to 2017, 22 different crops were grown to feed 2 people in an open-air soilless system, and a life cycle assessment was performed. A total productivity of 10.6 kg/m2/year was achieved, meaning that 5.3 m2 would be needed to fulfill the yearly vegetable requirements of an average citizen (in terms of weight). Considering the vegetable market basket of Catalonia, an 8.2 m2 soilless garden would be needed to cover 62% of the market basket for one person. The top 5 most productive crops were tomato, chard, lettuce, pepper and eggplant, accounting for 85.5% of the total production. The water consumption was 3.7 L/m2/day, and 3.3 kg/year/m2 of waste was generated. A high degree of self-sufficiency was achieved, although adjustments could be made to adapt the production to the market basket. The environmental assessment showed that the fertilizers and their associated leachates accounted for the highest environmental impacts in all the studied impact categories. Overall, 0.6 kg CO2 eq. was generated per kg of vegetables produced. The quantitative data provided by the present study offer a reference from which urban planners and researchers can project future implementations of rooftop urban agriculture (UA) on a large scale.

Ecological network analysis of growing tomatoes in an urban rooftop greenhouse.

Urban agriculture has emerged as an alternative to conventional rural agriculture seeking to foster a sustainable circular economy in cities. When considering the feasibility of urban agriculture and planning for the future of food production and energy, it is important to understand the relationships between energy flows throughout the system, identify their strengths and weaknesses, and make suggestions to optimize the system. To address this need, we analyzed the energy flows for growing tomatoes at a rooftop greenhouse (RTG). We used life cycle assessment (LCA) to identify the flows within the supply chain. We further analyzed these flows using ecological network analysis (ENA), which allowed a comparison of the industrial system to natural systems. Going beyond LCA, ENA also allowed us to focus more on the relationships between components. Similar to existing ENA studies on urban metabolism, our results showed that the RTG does not mimic the perfect pyramidal structure found in natural ecosystems due to the system's dependency on fossil fuels throughout the supply chain and each industry's significant impact on wasted energy. However, it was discovered that the RTG has strong foundational relationships in its industries, demonstrating overall positive utility; this foundation can be improved by using more renewable energy and increasing the recycling rates throughout the supply chain, which will in turn improve the hierarchy of energy flows and overall energy consumption performance of the system.

Low-carbon electricity production through the implementation of photovoltaic panels in rooftops in urban environments: A case study for three cities in Peru.

Urban environments in Latin America must begin decarbonizing their activities to avoid increasing greenhouse gases (GHGs) emissions rates due to their reliance on fossil fuel-based energy to support economic growth. In this context, cities in Latin America have high potential to convert sunlight into energy. Hence, the main objective of this study was to determine the potential of electricity self-sufficiency production and mitigation of GHG emissions in three medium-sized cities in Peru through the revalorization of underutilized rooftop areas in urban environments. Each city represented a distinct natural area of Peru: Pacific coast, Andean region and Amazon basin. More specifically, photovoltaic solar systems were the technology selected for implementation in these rooftop areas. Data on incident solar energy, temperature and energy consumption were collected. Thereafter, ArcGis10.3 was used to quantify the total usable area in the cities. A series of correction factors, including tilt, orientation or roof profiles were applied to attain an accurate value of usable area. Finally, Life Cycle Assessment was the methodology chosen to calculate the reduction of environmental impacts as compared to the current context of using electricity from the regional grids. Results showed that the cities assessed have the potential to obtain their entire current electricity demand for residential, commercial and public lighting purposes, augmenting energy security and resilience to intermittent natural disasters, with the support of decentralized storage systems. This approach would also translate into substantial reductions in terms of GHG emissions. Annual reductions in GHG emissions ranged from 112ton CO2eq in the city of Ayacucho to over 523kton CO2eq in Pucallpa, showing that cities in the Amazon basin would be the ones that benefit the most in terms of climate change mitigation.

Life cycle and hydrologic modeling of rainwater harvesting in urban neighborhoods: Implications of urban form and water demand patterns in the US and Spain.

Water management plays a major role in any city, but applying alternative strategies might be more or less feasible depending on the urban form and water demand. This paper aims to compare the environmental performance of implementing rainwater harvesting (RWH) systems in American and European cities. To do so, two neighborhoods with a water-stressed Mediterranean climate were selected in contrasting cities, i.e., Calafell (Catalonia, Spain) and Ukiah (California, US). Calafell is a high-density, tourist city, whereas Ukiah is a typical sprawled area. We studied the life cycle impacts of RWH in urban contexts by using runoff modeling before (i.e. business as usual) and after the implementation of this system. In general, cisterns were able to supply >75% of the rainwater demand for laundry and toilet flushing. The exception were multi-story buildings with roofs smaller than 200m2, where the catchment area was insufficient to meet demand. The implementation of RWH was environmentally beneficial with respect to the business-as-usual scenario, especially because of reduced runoff treatment needs. Along with soil features, roof area and water demand were major parameters that affected this reduction. RWH systems are more attractive in Calafell, which had 60% lower impacts than in Ukiah. Therefore, high-density areas can potentially benefit more from RWH than sprawled cities.

Urban rainwater runoff quantity and quality - A potential endogenous resource in cities?

Rainwater harvesting might help to achieve self-sufficiency, but it must comply with health standards. We studied the runoff quantity and quality harvested from seven urban surfaces in a university campus in Barcelona according to their use (pedestrian or motorized mobility) and materials (concrete, asphalt and slabs). An experimental rainwater harvesting system was used to collect the runoff resulting from a set of rainfall events. We estimated the runoff coefficient and initial abstraction of each surface and analyzed the physicochemical and microbiological properties, and hydrocarbon and metal content of the samples. Rainfall intensity, surface material and state of conservation were essential parameters. Because of low rainfall intensity and surface degradation, the runoff coefficient was variable, with a minimum of 0.41. Concrete had the best quality, whereas weathering and particulate matter deposition led to worse quality in asphalt areas. Physicochemical runoff quality was outstanding when compared to superficial and underground water. Microorganisms were identified in the samples (>1 CFU/100 mL) and treatment is required to meet human consumption standards. Motorized traffic mostly affects the presence of metals such as zinc (31.7 µg/L). In the future, sustainable mobility patterns might result in improved rainwater quality standards.

Are we preventing flood damage eco-efficiently? An integrated method applied to post-disaster emergency actions.

Flood damage results in economic and environmental losses in the society, but flood prevention also entails an initial investment in infrastructure. This study presents an integrated eco-efficiency approach for assessing flood prevention and avoided damage. We focused on ephemeral streams in the Maresme region (Catalonia, Spain), which is an urbanized area affected by damaging torrential events. Our goal was to determine the feasibility of post-disaster emergency actions implemented after a major event through an integrated hydrologic, environmental and economic approach. Life cycle assessment (LCA) and costing (LCC) were used to determine the eco-efficiency of these actions, and their net impact and payback were calculated by integrating avoided flood damage. Results showed that the actions effectively reduced damage generation when compared to the registered water flows and rainfall intensities. The eco-efficiency of the emergency actions resulted in 1.2kgCO2eq. per invested euro. When integrating the avoided damage into the initial investment, negative net impacts were obtained (e.g., -5.2E+05€ and -2.9E+04kgCO2eq. per event), which suggests that these interventions contributed with environmental and economic benefits to the society. The economic investment was recovered in two years, whereas the design could be improved to reduce their environmental footprint, which is recovered in 25years. Our method and results highlight the effects of integrating the environmental and economic consequences of decisions at an urban scale and might help the administration and insurance companies in the design of prevention plans and climate change adaptation.

Contribution of plastic waste recovery to greenhouse gas (GHG) savings in Spain.

This paper concentrates on the quantification of greenhouse gas (GHG) emissions of post-consumer plastic waste recovery (material or energy) by considering the influence of the plastic waste quality (high or low), the recycled plastic applications (virgin plastic substitution or non-plastic substitution) and the markets of recovered plastic (regional or global). The aim is to quantify the environmental consequences of different alternatives in order to evaluate opportunities and limitations to select the best and most feasible plastic waste recovery option to decrease the GHG emissions. The methodologies of material flow analysis (MFA) for a time period of thirteen years and consequential life cycle assessment (CLCA) have been integrated. The study focuses on Spain as a representative country for Europe. The results show that to improve resource efficiency and avoid more GHG emissions, the options for plastic waste management are dependent on the quality of the recovered plastic. The results also show that there is an increasing trend of exporting plastic waste for recycling, mainly to China, that reduces the GHG benefits from recycling, suggesting that a new focus should be introduced to take into account the split between local recycling and exporting.

Upgraded biogas from municipal solid waste for natural gas substitution and CO2 reduction--a case study of Austria, Italy, and Spain.

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 same time minimizing the global warming impact resulting from methane emissions in waste management schemes (WMS) and fossil fuel consumption reduction. This study looks at the current municipal solid waste flows of Spain, Italy, and Austria over one year (2009), in order to determine how much biogas is generated. Then it examines how much natural gas could be substituted by using four different biogas upgrading technologies. Based on current waste generation rates, exploratory but realistic WMS were created for each country in order to maximize biogas production and potential for natural gas substitution. It was found that the potential substitution of natural gas by biogas resulting from the current WMS seems rather insignificant: 0.2% for Austria, 0.6% for Italy and 0.3% for Spain. However, if the WMS is redesigned to maximize biogas production, these figures can increase to 0.7% for Austria, 1% for Italy and 2% for Spain. Furthermore, the potential CO2 reduction as a consequence of capturing the biogas and replacing fossil fuel can result in up to a 93% reduction of the annual national waste greenhouse gas emissions of Spain and Italy.

An uncertainty and sensitivity analysis applied to the prioritisation of pharmaceuticals as surface water contaminants from wastewater treatment plant direct emissions.

In this study, the concentration probability distributions of 82 pharmaceutical compounds detected in the effluents of 179 European wastewater treatment plants were computed and inserted into a multimedia fate model. The comparative ecotoxicological impact of the direct emission of these compounds from wastewater treatment plants on freshwater ecosystems, based on a potentially affected fraction (PAF) of species approach, was assessed to rank compounds based on priority. As many pharmaceuticals are acids or bases, the multimedia fate model accounts for regressions to estimate pH-dependent fate parameters. An uncertainty analysis was performed by means of Monte Carlo analysis, which included the uncertainty of fate and ecotoxicity model input variables, as well as the spatial variability of landscape characteristics on the European continental scale. Several pharmaceutical compounds were identified as being of greatest concern, including 7 analgesics/anti-inflammatories, 3 ß-blockers, 3 psychiatric drugs, and 1 each of 6 other therapeutic classes. The fate and impact modelling relied extensively on estimated data, given that most of these compounds have little or no experimental fate or ecotoxicity data available, as well as a limited reported occurrence in effluents. The contribution of estimated model input variables to the variance of freshwater ecotoxicity impact, as well as the lack of experimental abiotic degradation data for most compounds, helped in establishing priorities for further testing. Generally, the effluent concentration and the ecotoxicity effect factor were the model input variables with the most significant effect on the uncertainty of output results.