This paper presents research concerning the environmental analysis of the selective collection management of municipal solid waste. The main goal of this study is to quantify and to compare, by means ...of Life Cycle Assessment (LCA), the potential environmental impacts of three selective collection systems modelled on densely populated urban areas. These systems are: the mobile pneumatic, the multi-container and the door-to-door. Impact assessment method based on CML 2 baseline 2000 is applied to the different systems. The study separates and analyzes the collection systems in substages: two urban substages and one inter-city substage. At the urban level, the multi-container system has the least environmental impact of all systems. The mobile pneumatic system has greater environmental impacts in terms of global warming, fresh water aquatic ecotoxicity, terrestrial ecotoxicity, acidification and eutrophication. In this system, the pipes and the pneumatic transport have the greatest impacts. The door-to-door system has a greatest environmental impact in terms of abiotic depletion, ozone layer depletion and human toxicity. An overall evaluation of the three substages, with a sensitivity analysis, indicates that the mobile pneumatic system at an inter-city distance of 20
km shows the greatest environmental impacts and the greatest energy demand. Inter-city transport is key; the results show that from an inter-city distance of 11
km onwards, this becomes the substage which most contributes to global warming impact and energy demand, in all the systems.
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.
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•Nutrient circularity is key due to losses into the environment and depleting resources.•Urban agriculture can serve as a link to increase nutrient circularity in cities.•Urban waste can be divided into two streams wastewater and organic, bio, food waste.•Existing structures like WWTP can supply great amounts of key nutrients like N and P.•Social perception and legal constraints are key in the future of nutrient recovery.
This study is a quantitative description of Brazil's copper life cycle, comprising mining, refining, manufacturing, use and waste generation in the year 2005. A substance flow analysis is presented ...and the results are compared with existing values for other countries and economic regions (Europe, Asia, Latin America, and Africa).
The results show that Brazil is a net importer of copper both in concentrate and in the form of finished goods (total net weight 64
kt). Internal copper consumption is 1.44
kg per inhabitant per year and 0.52
kg/inhab/year is accumulated in the form of stock. Otherwise, the amount of waste generated (1.4
t/inhab/year) is close to that generated in Europe (1.9
t/inhab/year).
The copper distribution profile in waste flow is characterized by similar values for waste flow from construction and demolition (27.8%) and from electrical and electronic equipments (27.7%), whilst municipal solid waste and non-dangerous and industrial waste present 19.7% and 13.2%, respectively. Waste from electrical and electronic equipment and motor vehicles sent to scrap, in spite of representing just 1% of all waste in terms of mass, contain almost 38% of all residual copper (28% and 10%, respectively).
Brazil presents a secondary copper-recycling rate of around 25%, differing from that of other developing countries because it imports little scrap copper and releases 142
kt into the biosphere (0.75
kg/inhab).
We make the case that Brazil's government can feasibly encourage reductions in demand for this metal while increasing copper recycling rates through a two-edged strategy based on education and public awareness on the one hand – making a case for the unsustainability of current copper production and consumption models – and on the other, implementing economic tools to transfer costs of post-use recovery to manufacturers and consumers.
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.
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•Solid waste (SW) from urban agriculture (UA): a new typology of waste within cities•Use of UA SW from a circular economy (CE) perspective•Biomass as a by-product of integrated rooftop greenhouse (i-RTG)•Use of tomato stems from i-RTG as a substrate for lettuce crops•Reduction of the UA SW within the cities and closure of the UA life cycle
The environmental impacts derived from the urban water system of the municipality of Aveiro (Portugal) were analysed in this study using the Life Cycle Assessment (LCA) methodology. In addition, ...those stages and processes with the largest environmental impacts were identified and improvement scenarios were proposed. The entire water system was considered, including the following stages: water abstraction and treatment, water distribution, sewage collection, wastewater treatment and disposal, and water administration.
The results show that the stage of water abstraction and treatment was the most relevant for the majority of impact categories because most of the electricity consumption happened during this stage. For marine eutrophication and marine ecotoxicity, the stage of wastewater treatment and disposal alone carried almost the entire burden because of the release of nitrogen and phosphorus into the sea.
Electricity consumption and discharge of nutrients to the sea have been identified as the largest contributors to the environmental impacts. Therefore, scenarios focused on changing these burdens were assessed in order to prioritise those actions that would bring the greatest improvements. The proposed improvement actions could be a basis for the decision-making process regarding future investments towards environmental sustainability of the urban water system.
•Water savings are significant in humid climates with intelligent irrigation systems.•Further analysis on intelligent irrigation should be completed in arid climates.•New CSIS Index provides ...summarized information on both water usage and yield.
Intelligent irrigation is one sustainable solution to reduce demands on water resources and adverse environmental impacts from irrigation. Specific case studies have quantified water savings with intelligent irrigation, however, water savings have not yet been quantified for urban agriculture or compared across climates. Before urban agriculture implements intelligent irrigation, requiring an added cost and knowledge requirements of the control system, the effects of the system must first be estimated for a broad range of climatic conditions. We hypothesized that an intelligent irrigation system will decrease water use without reducing crop yield. With CROPWAT, we modeled an urban tomato garden irrigated conventionally to one irrigated intelligently in each of the nine climatic regions of the United States. Tomatoes were selected because they are sensitive to water stress. The intelligent irrigation system included a wireless sensor network and controllable valves. In addition, we created the Conventional-Scenario Intelligent-Scenario Index to compare the overall performance of an intelligent irrigation strategy to a conventional one. Our simulations showed that the intelligent irrigation scenario decreased water use on average by 59% in all sub-humid climates while maintaining yield (0% reduction). All sub-humid climates (7 of 9 total zones) fell within the “fair” to “good” index categories. Based on these results, urban agricultural sites should consider installing intelligent irrigation systems if they are in sub-humid climates. In the two semi-arid climates, our intelligent irrigation scenario eliminated the 6–10% crop yield reductions of the conventional scenario but did not reduce water consumption. Both locations fell within the “fair” index category. The minor improvements in the semi-arid climates may not outweigh the added system costs.
As a result of the integration of different methodological tools (life cycle assessment and dynamics simulation) and studies to evaluate the economic cost and the potential environmental impact of ...alternative water supplies (rainwater and greywater) for urban use, the software program Plugrisost (pluvials, greys and sustainability) has been developed. This modelling tool aims to contribute to urban water planning for smart city development. Plugrisost is a simulation model that facilitates the evaluation of rainwater harvesting (RWH) and greywater systems at different scales of urban planning. It is the only tool known thus far to integrate structural elements such as the sizing of storage tanks, estimated cost and quantitative environmental analysis. Plugrisost can be an adequate tool in the design stage because it provides environmental and economic information related to rainwater tank sizing and its estimates are more conservative than those of other tools. Plugrisost contributes to the design of urban infrastructure of low environmental impact, such as infrastructure that incorporates the use of rainwater, and the self-sufficiency analysis of water in cities. Using Plugrisost, we have found that on the single-house scale, the economic viability of an RWH system would be possible if the price of water is greater than 4 Euros/m3; and the environmental analysis would be favourable to tanks with less than 5 m3 of storage capacity. On the apartment-building scale, the results are 1.4 Euros/m3 and 33 m3, respectively.
•Plugrisost is a good tool for urban planning of RWH.•Environmental indicators are more conservative than the financial indicators.•Economic and environmental analysis can help avoid oversizing tanks.•The scale of analysis is a main factor.•Rainfall simulation using stochastic models is a factor that must be analysed.
PURPOSE: Urban water cycle construction processes are an important element to consider when assessing the sustainability of urban areas. The present study focuses on a structural and environmental ...analysis of cylindrical water tanks. The goal is to optimise cylindrical water tanks from both an environmental (environmental impacts due of life cycle assessment (LCA)) and a geometric perspective (building material quantities for construction purposes depending on the tank characteristics). METHODS: A sample of 147 cases was defined based on different positions (buried, superficial and partially buried), dimensions (combinations of heights and radii) and storage capacities (between 100 and 10,000 m³). A structural analysis was conducted for a defined set of cases to determine the quantities of steel and concrete required for its construction. The environmental impacts of the entire life cycle were assessed through a life cycle assessment (LCA). Additionally, environmental standards (the less impactful option for each dimension assessed: geometry, storage capacity and position) defined in the study were applied to realistic cases to evaluate potential environmental savings. RESULTS AND DISCUSSION: The LCA shows that materials are the main contributor to environmental impacts (more than transport, installation and end of life cycle stages). For this reason, the results of the structural and environmental assessments coincide. Taller water tanks have shown to be less impactful (60 to 70 % less impact for a 10.000-m³ tank). Regarding the position, superficial water tanks have shown to have between 15 and 35 % less impact than buried ones. The environmentally preferred water storage capacity is between 1000 and 2500 m³, being between 20 and 40 % less impact. For instance, an 8000-m³ tank would emit 1040 t of CO₂ eq. Applying the environmental standards 170.5 t of CO₂ eq could be saved (16 % of the total amount). CONCLUSIONS: The results of this study show that among the cases analysed, superficially positioned cylindrical water tanks of 8.5 m in height and of between 1000 and 2500 m³ in storage capacity present fewer impacts. The use of these standards in municipal water tanks construction projects may significantly reduce environmental impacts (10 to 40 %) in all impact categories.
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 and models the effect of such site-specific features on energy consumption and related effects in a sample of Spanish cities. The results show that the average annual energy used by sewers (6.4 kWh/capita and 0.014 kWh/m
3
of water flow) must not be underestimated because they may require up to 50 % of the electricity needs of a typical treatment plant in terms of consumption per capita. In terms of Global Warming Potential, pumping results in an average of 2.3 kg CO
2
eq./capita. A significant positive relationship was demonstrated between the kWh consumed and the length of the sewer and between other factors such as the population and wastewater production. In addition, Atlantic cities can consume 5 times as much energy as Mediterranean or Subtropical regions. A similar trend was shown in coastal cities. Finally, a simple predictive model of the electricity consumption was presented that considers the analysed parameters.
Roofs are the first candidates for rainwater harvesting in urban areas. This research integrates quantitative and qualitative data of rooftop stormwater runoff in an urban Mediterranean-weather ...environment. The objective of this paper is to provide criteria for the roof selection in order to maximise the availability and quality of rainwater. Four roofs have been selected and monitored over a period of 2 years (2008–2010): three sloping roofs – clay tiles, metal sheet and polycarbonate plastic – and one flat gravel roof. The authors offer a model for the estimation of the runoff volume and the initial abstraction of each roof, and assess the physicochemical contamination of roof runoff. Great differences in the runoff coefficient (RC) are observed, depending mostly on the slope and the roughness of the roof. Thus, sloping smooth roofs (RC
>
0.90) may harvest up to about 50% more rainwater than flat rough roofs (RC
=
0.62). Physicochemical runoff quality appears to be generally better than the average quality found in the literature review (conductivity: 85.0
±
10.0
μS/cm, total suspended solids: 5.98
±
0.95
mg/L, total organic carbon: 11.6
±
1.7
mg/L, pH: 7.59
±
0.07
upH). However, statistically significant differences are found between sloping and flat rough roofs for some parameters (conductivity, total organic carbon, total carbonates system and ammonium), with the former presenting better quality in all parameters (except for ammonium). The results have an important significance for local governments and urban planners in the (re)design of buildings and cities from the perspective of sustainable rainwater management. The inclusion of criteria related to the roof’s slope and roughness in city planning may be useful to promote rainwater as an alternative water supply while preventing flooding and water scarcity.
► The quantitative and qualitative water harvesting potential of four roofs is assessed. ► The initial abstraction is highest in flat rough roofs (3.8
mm). ► Sloping smooth roofs may harvest up to 50% more rainwater than flat rough ones. ► Rooftop runoff water quality is better in sloping smooth than flat rough roofs.
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