Life cycle assessment of granite application in sidewalks

Purpose

Sidewalks are important built areas for promoting environmental sustainability in cities since they support walking as a zero emission form of transportation contributing to protect the environment and the health of individuals. However, sidewalk management is typically focused on assessing their suitability for users without applying any environmental criteria on the infrastructure design. The paper aims to quantify the environmental impact that sidewalks can contribute to the urban space if no environmental criteria are applied in sidewalk design.

Methods

This study focuses on the environmental assessment of a very common sidewalk system found in cities to support pedestrian and light motorized traffic for over 45 years. The constructive solution consists of granite slabs (top layer) fixed on a mortar layer (3-cm thick) that is settled on a base of concrete (15-cm thick). The life cycle methodology was employed to conduct the environmental assessment of the system. The results are compared with the environmental outcomes of a sidewalk system that has the same function but is paved with concrete slabs to identify the environmentally optimal sidewalk design. The impact assessment method was CML Baseline 2001, and the inventory data were compiled from manufacturers associations, local authorities, and literature review.

Results and discussion

Construction materials have the highest environmental impact (48?C87%) in the sidewalk life cycle, where the granite top layer is the first contributor, although the amount of granite in the sidewalk system represents the 30% of the total weight of the construction materials used. A granite sidewalk has from 25% to 140% higher impact than a concrete one. The energy required to produce slabs is the key factor that characterizes the environmental impact of granite. Electricity and diesel consumption in stone cutting and moving represent over the 70% of the environmental burden of granite. The transportation of granite slabs is also relevant to the environmental impact. The use of imported granite could account for up to 76?C177% of the total environmental impact of the sidewalk life cycle.

Conclusions

Although granite is a natural material, using granite slabs as flooring material is not an environmentally suitable alternative over using concrete ones for paving sidewalks. The results have shown that if no environmental criteria are applied during sidewalk design and management, urban planners may be unconsciously contributing to an important environmental burden on the built environment. The ecodesign is a strategic opportunity to promote environmentally suitable urban infrastructures that contribute to promote urban sustainability in cities.

Recommendations

Energy efficiency techniques, water management, and well-considered transportation management should be developed and implemented in the granite industry to minimize the environmental impact of using it for paving. Additionally, further research is needed to quantify the environmental performance of other construction materials used in sidewalk construction in order to identify the best environmental alternatives and design improvements by optimizing the use of materials to the sidewalks functions.     

A life cycle comparison of disposal and beneficial use of coal combustion products in Florida

Background, aim, and scope  Beneficial use of coal combustion products (CCPs) in industrial or construction operations has the potential to minimize environmental and human health impacts that would otherwise be associated with disposal of CCPs in the life cycle of coal used for electricity generation. To assess opportunities for reducing impacts associated with four CCP materials considered in this study, fly ash, bottom ash, boiler slag, and flue gas desulfurization (FGD) material, this paper reports results of expanding a life cycle inventory of raw material and emissions (part 1 of this series of papers) by performing life cycle impact assessment on five scenarios of CCP management. Materials and methods  SimaPro 5.1 software (PRé Consultants) was used to calculate comparative environmental impacts of all scenarios using CML2001 and Environmental Design of Industrial Products 1997 midpoint impact assessment methods and Heirarchist and Individualist levels of the Eco-indicator 99 end point method. Trends were compared for global and local environmental and human health impact categories of global warming, acidification, smog formation, human toxicity, and ecotoxicity. Results  In each impact category, beneficial use of fly ash, bottom ash, and FGD material resulted in a reduced impact compared to disposal of these materials. The extent to which beneficial use reduced impacts depended on several factors, including the impact category in consideration, the magnitude of potentially avoided impacts associated with producing raw materials that CCPs replace, and the potential impact of CCP disposal methods. Global warming impacts were reduced by the substitution of fly ash for Portland cement in concrete production, as production of Portland cement generates large quantities of CO₂. However, for categories of global warming, smog formation, and acidification, impact reductions from CCP beneficial use are small, less than 6%, as these impacts were attributable, in greater part, to upstream processes of coal mining, transportation, and combustion. Human toxicity and ecotoxicity categories showed larger but more varied reductions, from 0% to 50%, caused by diverting CCPs from landfills and surface impoundments. Discussion  When comparing beneficial use scenarios, the four impact assessment methods used showed similar trends in categories of global warming, acidification, and smog formation. However, results diverged for human toxicity and ecotoxicity categories due to the lack of consensus among methods in classification and characterization of impacts from heavy metal release. Similarly, when assessing sensitivity of these results to changes in assumptions or system boundaries, human toxicity and ecotoxicity categories were most susceptible to change, while other impact categories had more robust results. Conclusions  Impact assessment results showed that beneficial use of CCPs presented opportunities for reduced environmental impacts in the life cycle of coal combusted for electricity generation, as compared to the baseline scenario of 100% CCP disposal, although the impact reductions varied depending on the CCPs used, the ultimate beneficial use, and the impact category in consideration. Recommendations and perspectives  As regulators and electric utilities increasingly consider viability and economics of the use of CCPs in various applications, this study provides a first-basis study of selected beneficial use alternatives. With these initial results, future studies should be directed towards beneficial uses that promise significant economic and environmental savings, such as use of fly ash in concrete, to quantify the currently unknown risk of these applications.     

Environmental Impact Assessment of Wood Use in Japan through 2050 Using Material Flow Analysis and Life Cycle Assessment

In this study, we used material flow analysis and life cycle assessment to quantify the environmental impacts and impact reductions related to wood consumption in Japan from 1970 to 2013. We then conducted future projections of the impacts and reductions until 2050 based on multiple future scenarios of domestic forestry, wood, and energy use. An impact assessment method involving characterization, damage assessment, and integration with a monetary unit was used, and the results were expressed in Japanese yen (JPY). We found that environmental impacts from paper consumption, such as climate change and urban air pollution, were significant and accounted for 56% to 83% of the total environmental impacts between 1970 and 2013. Therefore, reductions of greenhouse gas, nitrogen oxide, and sulfur oxide emissions from paper production would be an effective measure to reduce the overall environmental impacts. An increase in wood use for building construction, civil engineering, furniture materials, and energy production could lead to reductions of environmental impacts (via carbon storage, material substitution, and fuel substitution) amounting to 357 billion JPY in 2050, which is equivalent to 168% of the 2013 levels. Particularly, substitution of nonwooden materials, such as cement, concrete, and steel, with wood products in building construction could significantly contribute to impact reductions. Although an increase of wood consumption could reduce environmental impacts, such as climate change, resource consumption, and urban air pollution, increased wood consumption would also be associated with land‐use impacts. Therefore, minimizing land transformations from forest to barren land will be important.     

Regional normalisation figures for Australia 2005/2006—inventory and characterisation data from a production perspective

Background, aim, and scope  Under ISO 14040, normalisation is an optional step in life-cycle impact assessment designed to provide environmental context by indicating the relative contribution that the product system under investigation makes in the various impact categories, in comparison to a suitable reference scenario. The challenge for many studies, however, is to provide the appropriate context by adopting a normalisation reference scenario that is well matched to the product system’s parent environment. Australia has a highly urbanised population, mainly contained in just eight capital cities. In the context of normalising environmental impacts against the profile of an ‘average’ Australian, this poses a unique problem, compared to other industrialised regions of the world. This study aims to use publicly available data on environmentally relevant emissions and non-renewable resource consumption in 2005/2006 to develop regional normalisation data for Australia, at both inventory and characterisation levels. Methods  The regionalised inventory of emissions and resources production is constructed using a framework of 60 regional Statistical Divisions from the Australian Standard Geographical Classification system. Data from the National Pollutant Inventory, Australian Greenhouse Emissions Information System and the Australian Bureau of Agricultural and Resource Economics (energy and mineral statistics) are used as the basis for the inventories. These data could subsequently be used by any LCA practitioner to construct characterisation or normalisation data by impact category, according to any preferred life-cycle impact assessment methodology, for any of 60 regions in the country. In this study, the regionalised inventory data were assessed using the CML 2001 baseline and IMPACT 2002+ life-cycle impact assessment methods in SimaPro v.7.1.5. Results  Characterisation results from the two LCIA methods for Australia’s eight state and territory capital cities are presented, together with an overall national profile. These data are also shown on a per capita basis to highlight the relative environmental profiles of citizens in the different cities. Interestingly, many significant impacts occur outside of the capital cities but are linked to facilities providing the majority of their services and products to these urban centres (e.g. power stations, minerals processing). Comparison of the average Australian data with the Netherlands, Western Europe and the World shows the results to be broadly similar. Discussion  Analysis of the CML 2001 baseline characterisation results, on a per capita basis, shows substantial differences between the major cities of the country. In each impact category, these differences can be successfully traced to specific emissions in the raw data sources, the influence of prevailing climate conditions, or factors such as the mix of non-renewable energy resources in each state. Some weaknesses are also evident in the collection and estimation techniques of the raw data sources and in the application of European-based impact assessment models. Australia is a net exporter of many products, particularly natural resources. Therefore, a significant part of the characterisation data presented here for Australia represents products that will be consumed in other parts of the world. Similarly, at a regional level, there will be many inventory items produced in one area yet consumed in another. In this way, the impacts associated with consumption (particularly in densely populated but largely industry-free cities) are dissipated into other production centres. Conclusions  This study provides the first set of comprehensive inventory and characterisation data for Australia from a production perspective, disaggregated at a regional level. Despite Australia’s unique spatial demography, it is now possible to properly characterise the relative significance of environmental impacts occurring in any of 60 specific regions across the country. Recommendations and perspectives  Australia’s unique concentration of urban populations demonstrates the importance of regionally specific environmental assessments. Whilst the data presented in this study will be of most use to Australian LCA practitioners, it is also demonstrative of the broader global distribution of environmental impacts between urban and non-urban areas. The disconnection of environmental impacts between the place of production and the place of consumption is highlighted by this study and should be considered in any studies using these normalisation data for environmental profiling. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Hybrid Emergy-LCA (HEML) based metabolic evaluation of urban residential areas: The case of Beijing,China

In this paper, metabolic evaluation has been employed for better understanding the trends in urban environmental changes. Due to the urban activities cause impacts not only on local level but also a broader scale, Hybrid Emergy-LCA (HEML), a combining approach of Emergy Analysis (EMA) and Life Cycle Assessment (LCA) is structured to quantitatively investigate the mechanism. For the similarity across many emerging cities in China, a large-scale sub-urban residential area named Tian Tongyuan (TTY) in Beijing was chosen for testing the HEML. Objective indicators of live quality and negative impacts are both considered. Analysis indicates that the household Emergy input of TTY is 1.76E+16 sej/yr, while the prominent environmental impact is induced by Photochemical Oxidant Creation Potentials (POCP), 4.58E+05 g ethane eq./yr. The sustainable performance constructed by its live quality and environmental impacts of TTY is found as 98.80% as that of Beijing average. Mitigation polices on the building sector should be proposed because of its dominating impacts among various consuming ends of energy and materials.     

Comparative life-cycle impact assessment of concrete manufacturing in Singapore

Purpose

For countries like Singapore that is highly dependent on imported goods, it is essential to consider the consequences of consumption of imported cement and other concrete constituents for a fair carbon trading at global and regional levels. Recently, as a result of reduction in trade barriers and costs of materials and fuels, Singapore does not have much incentive in reducing environmental impacts of these imported goods. However, Singapore has set high environmental targets nationally to reduce impacts from building and construction. In addition to its national efforts, Singapore also needs to take action in trade-related consequences of importing energy-intensive products like cement and aggregates to Singapore. The purpose of this study is to quantify and suggest alternatives for reducing the embodied energy and life-cycle impacts of concrete consumption in Singapore on the basis of current trading volumes of these materials from Singapore’s importers.

Methods

A detailed life-cycle assessment of concrete manufacturing in Singapore is performed to suggest possible ways to reduce the environmental impacts from importing cement and aggregates from Singapore’s trade partners based on an earlier life-cycle inventory developed for Singapore and its neighboring countries. Life-cycle impact assessment (LCIA) impact characterization factors are based on a midpoint-oriented and hierarchist approach as defined by ReCiPe method. Following the LCIA, a scenario analysis is conducted to select the best combination of cement and aggregate importers of Singapore based on their environmental performance.

Results and discussion

Results from the scenario analysis show that overall impacts can be reduced by importing the materials from a nearer source with efficient production technologies and greener fuel mixes. About 10–34 % reduction is estimated in embodied energy, acidification, eutrophication, global warming potential, smog, and health impacts by importing from a closer and technologically greener source.

Conclusions

Despite the limitations due to data and modeling uncertainties, this study constitutes a baseline/benchmark for addressing the current cement and aggregate markets and associated environmental impacts of concrete consumption in Singapore based on historical import quantities of cement and aggregates from neighboring countries of Singapore. In the near future, policy-related action would be influential in achieving Singapore’s national and global environmental targets in buildings and construction sector. Incorporation of an LCA approach into Green Mark Scheme (GMS) by the Building and Construction Authority (BCA) is recommended for Singapore to comply both with its national goals and with its new climate action plan to the UN Framework Convention on Climate Change.

     

Impact of the selection of functional unit on the life cycle assessment of green concrete

Purpose

The objectives of this study are to evaluate life cycle assessment (LCA) for concrete mix designs containing alternative cement replacement materials in comparison with conventional 100% general use cement concrete and to evaluate the interplay and sensitivity of LCA for four concrete mix designs and six functional units which range in degrees of complexity and variables.

Methods

Six functional units with varying degrees of complexity are included in the analysis: (i) volume of concrete, (ii) volume and 28-day compressive strength, (iii) volume and 28-day rapid chloride permeability (RCP), (iv) volume and binder intensity, (v) volume and a combination of compressive strength and RCP and (vi) volume and a combination of binder intensity and RCP. Four reference flows are included in the analysis: three concrete mix designs containing slag, silica fume and limestone cement as cement replacement and one concrete mix design for conventional concrete.

Results and discussion

All three alternative mix designs were evaluated to have lower environmental impacts compared with the base 100% general use cement and so are considered to be ‘green’ concrete. Similar LCA results were observed for FU₁, FU₂ and FU₄, and relatively similar results were obtained for FU₃, FU₅ and FU₆. LCA conducted with functional units which were a function of durability exhibited markedly different (lower) LCA compared with the functional units that did not capture long-term durability.

Conclusions

Outcomes of this study portray the interplay between concrete mix design materials, choice of functional unit and environmental impact based on LCA. The results emphasize (i) the non-linearity between material properties and environmental impact and (ii) the importance of conducting an LCA with a selected functional unit that captures the concrete’s functional performance metrics specific to its application and expected exposure conditions. Based on this study, it is recommended that a complete LCA for a given concrete mix design should entail examination of multiple functional units in order to identify the range of environmental impacts or the optimal environmental impacts.

     

基于ENVI-met的道路绿带规划设计对PM2.5消减作用的模拟研究

城市道路绿地是城市绿地系统重要的组成部分,道路绿带承担着城市道路重要的生态环境改善功能,道路绿带的断面布局是道路绿地规划设计的核心内容。首次将ENVI-met运用于城市道路断面绿带规划设计模拟中,定量研究城市道路绿带断面形式对PM2.5的消减作用,结果表明: 1）道路横断面绿化类型对PM2.5分布有显著影响。道路绿化导致机动车道PM2.5浓度增加,非机动车道及人行道PM2.5浓度减少;2）道路绿化能明显消减人行道PM2.5浓度。从PM2.5的消减面积来看,四板五带式>两板三带式>一板两带式>三板四带式;从PM2.5的消减程度来看,两板三带式>四板五带式> 一板两带式>三板四带式。3）两板三带式、四板五带式绿化消减效果最佳,人行道消减率最大提高了18%。研究证实了道路绿化确能改善非机动车道及人行道的颗粒物污染,为绿色基础设施消减PM2.5浓度提供了有力的支撑。     

Design of concrete : Setting a new basis for improving both durability and environmental performance

CO₂ emissions from cement production currently represent around 6% of global CO₂ emissions. However, cement concrete absorbs CO₂ from the atmosphere because of carbonation (i.e., penetration of atmospheric CO₂ inside bulk concrete). Carbonation has beneficial effects on the mechanical resistance of cement concrete. However, carbonation also has adverse effects because it provokes a decrease in pH that favors later corrosion of reinforcing bars and thus reduces service life. Current European standards provide recommendations concerning reinforcing concrete covers, but these are not based on actual service‐life durations. Thanks to a previously developed carbonation model combined with sensitivity analysis and LCA, we compare Climate Change indicators of 1 m² of reinforced concrete cover over a 100‐years service life exposed to XC4 conditions in Madrid, obtained on one hand by using current standards and on the other hand with concrete‐cover depths calculated with our carbonation model. Our results show that cement strength class is a key parameter to both increase durability and decrease climate‐change impacts. When the carbonation model is used to optimize both durability and climate‐change impacts, it drives to considerable and significant improvements. Finally, climate‐change indicators predicted from our carbonation model are not linearly linked to carbon intensity of cements, which is a current argument of so‐called “green cements.” The values of indicators presented in this article cannot be generalized: They mainly depend on the geographical location. However, the model and key action levers are general. Using high cement strength classes and low water‐to‐cement ratios allows use of lower concrete‐cover depths and thus save amounts of concrete compared to the standard. This generates an important benefit in terms of climate‐change impacts for identical service lives and improved mechanical resistance. Thus, considering the huge impact of cement and construction industry on climate change, we plead for a revision of standards which, instead of thresholds based on simplified models, should provide certified tools enabling the best design for every situation. This article met the requirements for a gold/gold JIE data openness badge described at http://jie.click/badges.     

LEED v4: Where Are We Now? Critical Assessment through the LCA of an Office Building Using a Low Impact Energy Consumption Mix

Various green building rating systems (GBRSs) have been proposed to reduce the environmental impact of buildings. However, these GBRSs, such as Leadership in Energy and Environmental Design (LEED) v4, are primarily oriented toward a building's use stage energy consumption. Their application in contexts involving a high share of renewable energy, and hence a low‐impact electricity mix, can result in undesirable side effects. This paper aims to investigate such effects, based on an existing office building in Quebec (Canada), where more than 95% of the electricity consumption mix is renewable. This paper compares the material impacts from a low‐energy context building to material considerations in LEED v4. In addition to their contributions to the building impacts, material impacts are also defined by their potential to change impacts with different material configurations. Life cycle assessment (LCA) impacts were evaluated using Simapro 8.2, the ecoinvent 3.1 database, and the IMPACT 2002+ method. The building LCA results indicated higher environmental impact contributions from materials (>50%) compared to those from energy consumption. This is in contrast with the LEED v4 rating system, as it did not seem to be as effective in capturing such effects. The conclusions drawn from this work will help stakeholders from the buildings sector to have a better understanding of building environmental profiles, and the limitations of LEED v4 in contexts involving a low‐impact energy mix. In addition, this critical assessment can be used to further improve the LEED certification system.     

Environmental life cycle assessment of a commercial office building in Thailand

Background, aim, and scope  To minimize the environmental impacts of construction and simultaneously move closer to sustainable development in the society, the life cycle assessment of buildings is essential. This article provides an environmental life cycle assessment (LCA) of a typical commercial office building in Thailand. Almost all commercial office buildings in Thailand follow a similar structural, envelope pattern as well as usage patterns. Likewise, almost every office building in Thailand operates on electricity, which is obtained from the national grid which limits variability. Therefore, the results of the single case study building are representative of commercial office buildings in Thailand. Target audiences are architects, building construction managers and environmental policy makers who are interested in the environmental impact of buildings. Materials and methods  In this work, a combination of input–output and process analysis was used in assessing the potential environmental impact associated with the system under study according to the ISO14040 methodology. The study covered the whole life cycle including material production, construction, occupation, maintenance, demolition, and disposal. The inventory data was simulated in an LCA model and the environmental impacts for each stage computed. Three environmental impact categories considered relevant to the Thailand context were evaluated, namely, global warming potential, acidification potential, and photo-oxidant formation potential. A 50-year service time was assumed for the building. Results  The results obtained showed that steel and concrete are the most significant materials both in terms of quantities used, and also for their associated environmental impacts at the manufacturing stage. They accounted for 24% and 47% of the global warming potential, respectively. In addition, of the total photo-oxidant formation potential, they accounted for approximately 41% and 30%; and, of the total acidification potential, 37% and 42%, respectively. Analysis also revealed that the life cycle environmental impacts of commercial buildings are dominated by the operation stage, which accounted for approximately 52% of the total global warming potential, about 66% of the total acidification potential, and about 71% of the total photo-oxidant formation potential, respectively. The results indicate that the principal contributor to the impact categories during the operation phase were emissions related to fossil fuel combustion, particularly for electricity production. Discussion  The life cycle environmental impacts of commercial buildings are dominated by the operation stage, especially electricity consumption. Significant reductions in the environmental impacts of buildings at this stage can be achieved through reducing their operating energy. The results obtained show that increasing the indoor set-point temperature of the building by 2°C, as well as the practice of load shedding, reduces the environmental burdens of buildings at the operation stage. On a national scale, the implementation of these simple no-cost energy conservation measures have the potential to achieve estimated reductions of 10.2% global warming potential, 5.3% acidification potential, and 0.21% photo-oxidant formation potential per year, respectively, in emissions from the power generation sector. Overall, the measures could reduce approximately 4% per year from the projected global warming potential of 211.51 Tg for the economy of Thailand. Conclusions  Operation phase has the highest energy and environmental impacts, followed by the manufacturing phase. At the operation phase, significant reductions in the energy consumption and environmental impacts can be achieved through the implementation of simple no-cost energy conservation as well as energy efficiency strategies. No-cost energy conservation policies, which minimize energy consumption in commercial buildings, should be encouraged in combination with already existing energy efficiency measures of the government. Recommendations and perspectives  In the long run, the environmental impacts of buildings will need to be addressed. Incorporation of environmental life cycle assessment into the current building code is proposed. It is difficult to conduct a full and rigorous life cycle assessment of an office building. A building consists of many materials and components. This study made an effort to access reliable data on all the life cycle stages considered. Nevertheless, there were a number of assumptions made in the study due to the unavailability of adequate data. In order for life cycle modeling to fulfill its potential, there is a need for detailed data on specific building systems and components in Thailand. This will enable designers to construct and customize LCAs during the design phase to enable the evaluation of performance and material tradeoffs across life cycles without the excessive burden of compiling an inventory. Further studies with more detailed, reliable, and Thailand-specific inventories for building materials are recommended.     

Comparative LCA of recycled and conventional concrete for structural applications

Purpose

Construction and demolition (C&D) waste recycling has been considered to be a valuable option not only for minimising C&D waste streams to landfills but also for mitigating primary mineral resource depletion. However, the potentially higher cement demand due to the larger surface of the coarse recycled aggregates challenges the environmental benefits of recycling concrete. Furthermore, it is unclear how the environmental impacts depend on concrete mixture, cement type, aggregates composition and transport distances.

Methods

We therefore analysed the life cycle impacts of 12 recycled concrete (RC) mixtures with two different cement types and compared it with corresponding conventional concretes (CC) for three structural applications. The RC mixtures were selected according to laws, standards and construction practice in Switzerland. We compared the environmental impacts of ready-for-use concrete on the construction site, assuming equal lifetimes for recycled and conventional concrete in a full life cycle assessment. System expansion and substitution are considered to achieve the same functionality for all systems.

Results and discussion

The results show clear (～30 %) environmental benefits for all RC options at endpoint level (ecoindicator 99 and ecological scarcity). The difference is mainly due to the avoided burdens associated to reinforcing steel recycling and avoided disposal of C&D waste. Regarding global warming potential (GWP), the results are more balanced and primarily depend on the additional amount of cement needed for RC. Above 22 to 40 kg additional cement per cubic metre of concrete, RC exhibits a GWP comparable to CC. Additional transport distances above 15 km for the RC options do result in environmental impacts higher than those for CC.

Conclusions

In summary, the current market mixtures of recycled concrete in Switzerland show significant environmental benefits compared to conventional concrete and cause similar GWP, if additional cement and transport for RC are limited.

     

Environmental impact of thin-film GaInP/GaAs and multicrystalline silicon solar modules produced with solar electricity

Background, aim, and scope  The environmental burden of photovoltaic (PV) solar modules is currently largely determined by the cumulative input of fossil energy used for module production. However, with an increased focus on limiting the emission of CO₂ coming from fossil fuels, it is expected that renewable resources, including photovoltaics, may well become more important in producing electricity. A comparison of the environmental impacts of PV modules in case their life cycle is based on the use of PV electricity in contrast to conventional electricity can elucidate potential environmental drawbacks in an early stage of development of a solar-based economy. The goal of this paper is to show for ten impact categories the environmental consequences of replacing fossil electricity with solar electricity into the life cycle of two types of PV modules. Materials and methods  Using life cycle assessment (LCA), we evaluated the environmental impacts of two types of PV modules: a thin-film GaInP/GaAs tandem module and a multicrystalline silicon (multi-Si) module. For each of the modules, the total amount of fossil electricity required in the life cycle of the module was substituted with electricity that is generated by a corresponding PV module. The environmental impacts of the modules on the midpoint level were compared with those of the same modules in case their life cycle is based on the use of conventional electricity. The environmental impacts were assessed for Western European circumstances with an annual solar irradiation of 1000 kWh/m². For the GaInP/GaAs module, the environmental impacts of individual production steps were also analysed. Results  Environmental burdens decreased when PV electricity was applied in the life cycle of the two PV modules. The impact score reductions of the GaInP/GaAs module were up to a factor of 4.9 (global warming). The impact score reductions found for the multi-Si module were up to a factor of 2.5 (abiotic depletion and global warming). Reductions of the toxicity scores of both module types were smaller or negligible. This is caused by a decreased use of fossil fuels, on the one hand, and an increased consumption of materials for the production of the additional solar modules used for generating the required PV electricity on the other. Overall, the impact scores of the GaInP/GaAs module were reduced more than the corresponding scores of the multi-Si module. The contribution analysis of the GaInP/GaAs module production steps indicated that for global warming, the cell growth process is dominant for supply with conventional electricity, while for the solar scenario, the frame becomes dominant. Regarding freshwater aquatic ecotoxicity scores associated with the life cycle of the GaInP/GaAs module, the cell growth process is dominant for supply with conventional electricity, while the reactor system for the cell growth with the associated gas scrubbing system is dominant for the solar scenario. Discussion  There are uncertainties regarding the calculated environmental impact scores. This paper describes uncertainties associated with the used economic allocation method, and uncertainties because of missing life cycle inventory data. For the GaInP/GaAs module, it was found that the global warming impact scores range from −66% to +41%, and the freshwater aquatic ecotoxicity scores (for an infinite time horizon) range from −40% to +300% compared to the default estimates. For both impact categories, the choices associated with the allocation of gallium, with the electricity mix, with the conversion efficiency of the commercially produced GaInP/GaAs cells, and with the yield of the cell growth process are most influential. For freshwater aquatic ecotoxicity, the uncertainty concerning the lifetime of the reactor system for the GaInP/GaAs cell growth process and the gas scrubbing system is particularly relevant. Conclusions  Use of PV electricity instead of fossil electricity significantly reduces the environmental burdens of the GaInP/GaAs and the multi-Si module. The reductions of the toxicity scores, however, are smaller or negligible. Toxicity impacts of the GaInP/GaAs cells can be reduced by improvement of the yield of the cell growth process, a reduced energy demand in the cell growth process, reduction of the amount of stainless steel in the cell growth reactor system and the gas scrubbing system, and a longer lifetime of these systems. Recommendations and perspectives  Because the greenhouse gas emissions associated with the production of fossil-fuel-based electricity have an important share in global warming on a world-wide scale, switching to a more extensive use of solar power is helpful to comply with the present international legislation on the area of global warming reduction. As reductions in toxicity impact scores are smaller or negligible when fossil electricity is replaced by PV electricity, it is desirable to give specific attention to the processes which dominantly contribute to these impact categories. Furthermore, in this study, a shift in ranking of several environmental impacts of the modules has been found when PV electricity is used instead of fossil electricity. The results of a comparative LCA can thus be dependent of the electricity mix used in the life cycles of the assessed products. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

气候地砖——针对未来城市的可扩展气候适应系统落成典礼

一个名为“气候地砖”的创新气候适应项目如今在赫姆德斯给特22号咖啡馆前的人行道上进行了试点。“气候地砖”是一个适用于未来城市的新型可扩展气候适应系统。它为我们熟知的人行道装备了一系列附加功能,其处理水的方式不仅限于单纯的技术性方法,同时也注重了水作为一种宝贵的资源的特性。“气候地砖”通过一个简单的过程收集与管理来自屋顶和人行道的雨水,并确保水流向如种植池和蓄水池等正确的位置,为现有的城市重新引入自然水循环。这个系统可以收集并疏导由于气候变化而产生的预计额外30%的雨水,以免现有的排水基础设施过载。     

Assessing potential desertification environmental impact in life cycle assessment

Background, aim and scope  

Life cycle assessment (LCA) enables the objective assessment of global environmental burdens associated with the life cycle of a product or a production system. One of the main weaknesses of LCA is that, as yet, there is no scientific agreement on the assessment methods for land-use related impacts, which results in either the exclusion or the lack of assessment of local environmental impacts related to land use. The inclusion of the desertification impact in LCA studies of any human activity can be important in high-desertification risk regions.     

Utilization of woody biomass in Singapore: technological options for carbonization and economic comparison with incineration

Background, aim and scope  The interest in the use of biomass as a renewable energy resource has rapidly grown over the past few years. In Singapore, biomass resources are mostly from waste wood. This article presents a few technological options, namely carbonization, for the conversion of woody biomass into a solid fuel, charcoal. Materials and methods  In the first stage, a life cycle assessment (LCA) ‘gate-to-gate’ system was developed for a conventional carbonizer system, a modern carbonizer from Japan, and a proposed four-stage partial furnace carbonizer from Tunisia. The potential environmental impacts were generated for global warming potential, acidification, human toxicity and photochemical oxidant potential. Based on the first set of results, the second LCA investigation was carried out comparing the selected carbonizer from Japan and an existing incinerator in Singapore. The second LCA adopted a unique approach combining social costs of pollution with the economic factors of the two biomass conversion technologies. Results  The carbonizer from Japan resulted in approximately 85% less greenhouse gases than the conventional carbonization system and 54% less than the proposed four-stage carbonizer from Tunisia. In terms of acidification and human toxicity, the carbonizers from Japan and Tunisia display nearly similar results—both were considerably lower than the conventional carbonizer. For photochemical oxidant potential, very minimal emissions are generated from the four-stage carbonizer and nearly zero impact is realized for the carbonization technology from Japan. Discussion  From the first set of LCA results, the Japanese carbonizer is favored in terms of its environmental results. The highest environmental impacts from the conventional carbonizer were due to large and uncontrolled emissions of acidic gases, greenhouse gases (particularly CO₂ and CH₄), particulates, and non-methane volatile organic compounds from both fugitive sources and energy requirements. The second LCA addressed the performance of the carbonizer from Japan against an existing incinerator in terms of environmental as well as cost performances. This unique approach translated pollution emissions into monetary costs to highlight the impacts of social health. Conclusions  For the first LCA, the accumulated impacts from the Japanese carbonizer proved to display significantly lower environmental impacts, especially for global warming potential. The overall environmental performance of the four-stage carbonizer from Tunisia ranked slightly lower than the one from Japan and much higher than the conventional carbonizer. The second LCA results displayed a noteworthy improvement of 90% for human health from the modern Japanese carbonizer technology—when compared against conventional incinerators. Without considering health issues or social costs, the total value per ton of wood treated is nearly similar for both incinerator and carbonizer. Recommendations and perspectives  The interest in biomass as raw material for producing energy has emerged rapidly in many countries. However, careful analysis and comparison of technologies are necessary to ensure favorable environmental outcomes. A full life cycle study, along with costs and the impact of pollution on society, should be performed before any large-scale biomass conversion technology is implemented. LCA can be applied to quantify and verify the overall environmental performance of a particular technology of interest as well as further explore the proposed technology in terms of costs and social implications.     

Accounting for transportation impacts in the environmental assessment of waste management plans

Background, aim, and scope  Many recent studies on waste management have described in detail the potential impacts of recycling and final treatment of municipal waste. In public debates, the attention has also been focused on the choice of final disposal technologies (e.g. landfilling vs. incineration). However, a comprehensive assessment of the impacts of waste collection and transport was still lacking. In the present study, we use LCA to evaluate the potential impact of the provincial waste management plan of Varese (northern Italy). Particular attention is devoted to the estimation of environmental impacts generated during waste transport. Materials and methods  A detailed Life Cycle Inventory was built for the transportation phase, based on primary data collected by interviewing the agencies involved in waste collection. To model the recycling and final disposal phase we relied on the BUWAL 250 database. Impacts were evaluated with the Eco-Indicator 99 method in its egalitarian formulation. Results  The results of our analysis reveal that the major potential impacts of the plan are associated with waste collection and transport. These impacts are partially compensated by reduced resource consumption through recycling and energy recovery through incineration. Discussion  The outputs of the LCIA were compared with those obtained by using other ecoindicators (Eco-Indicator 99 hierarchist and individualist, CML2, EPS2000). Although not comparable on a quantitative basis, they are qualitatively consistent. Conclusions  Neglecting the effects of collection and transport might result in a severe underestimation of the environmental impacts of a waste management system, especially as refers to depletion of fossil fuels, emission of respiratory inorganics and climate change. To reduce the environmental impact of waste management systems, an accurate optimisation of waste transport is required. Recommendations and perspectives  Effective waste management planning requires the explicit inclusion of waste collection and transport when comparing alternative management policies.     

Life cycle assessment of 3D printing geo‐polymer concrete: An ex‐ante study

Three‐dimensional (3D) printing and geo‐polymers are two environmentally oriented innovations in concrete manufacturing. The 3D printing of concrete components aims to reduce raw material consumption and waste generation. Geo‐polymer is being developed to replace ordinary Portland cement and reduce the carbon footprint of the binder in the concrete. The environmental performance of the combined use of the two innovations is evaluated through an ex‐ante life cycle assessment (LCA). First, an attributional LCA was implemented, using data collected from the manufacturer to identify the hotspots for environmental improvements. Then, scaled‐up scenarios were built in collaboration with the company stakeholder. These scenarios were compared with the existing production system to understand the potential advantages/disadvantages of the innovative system and to identify the potential directions for improvement. The results indicate that 3D printing can potentially lead to waste reduction. However, depending on its recipe, geo‐polymer likely has higher environmental impacts than ordinary concrete. The ex‐ante LCA suggests that after step‐by‐step improvements in the production and transportation of raw materials, 3D printing geo‐polymer concrete is able to reduce the carbon footprint of concrete components, while it does still perform worse on impact categories, such as depletion of abiotic resources and stratospheric ozone depletion. We found that the most effective way to lower the environmental impacts of 3D concrete is to reduce silicate in the recipe of the geo‐polymer. This approach is, however, challenging to realize by the company due to the locked‐in effect of the previous innovation investment. The case study shows that to support technological innovation ex‐ante LCA has to be implemented as early as possible in innovation to allow for maintaining technical flexibility and improving on the identified hotspots.