A Carbon Footprint of Textile Recycling: A Case Study in Sweden

Global population growth and rising living standards are increasing apparel consumption. Consequently, consumption of resources and generation of textile waste are increasing. According to the Swedish Environmental Protection Agency, textile consumption increased by 40% between the years 2000 and 2009 in Sweden. Given that there is currently no textile recycling plant in Sweden, the aim of this article is to explore the potential environmental benefits of various textile recycling techniques and thereby direct textile waste management strategies toward more sustainable options. Three different recycling techniques for a model waste consisting of 50% cotton and 50% polyester were identified and a life cycle assessment (LCA) was made to assess the environmental performance of them. The recycling processes are: material reuse of textile waste of adequate quality; separation of cellulose from polyester using N‐methylmorpholine‐N‐oxide as a solvent; and chemical recycling of polyester. These are compared to incineration, representing conventional textile waste treatment in Sweden. The results show that incineration has the highest global warming potential and primary energy usage. The material reuse process exhibits the best performance of the studied systems, with savings of 8 tonnes of carbon dioxide equivalents (CO₂‐eq) and 164 gigajoules (GJ) of primary energy per tonne of textile waste. Sensitivity analyses showed that results are particularly sensitive to the considered yields of the processes and to the choice of replaced products. An integration of these recycling technologies for optimal usage of their different features for treatment of 1 tonne of textile waste shows that 10 tonnes CO₂‐eq and 169 GJ of primary energy could be saved.     

Uncertainty and Sensitivity in the Carbon Footprint of Shopping Bags

Carbon footprints for several shopping bag alternatives (polyethylene, paper, cotton, biodegradable modified starch, and recycled polyethylene) were compared with life cycle assessment. Stochastic uncertainty analysis was used to study the sensitivity of the comparison to scenario and parameter uncertainty. On the basis of the results, we could give only a few robust conclusions without choosing a waste treatment scenario or limiting the parameter space. Given the scenario of current waste infrastructure in Finland, recycled polyethylene bags seem to be the most preferable (?7 to 24 g CO₂ eq./bag) and biodegradable bags the least preferable (38 to 60 g CO₂ eq./bag) option. In each analyzed waste treatment scenario, a few parameters dominated the uncertainty of results. Most of these parameters were downstream of the shopping bag manufacturing (consumer behavior, landfill conditions, method of waste combustion, etc.). The choice of waste treatment scenario had a greater effect on the ranking of bags than parameter uncertainty within scenarios. This result highlights the importance of including several scenarios in comparative life cycle assessments.     

Exploring the Use of Ecological Footprint in Life Cycle Impact Assessment

Ecological footprint (EF) is a metric that estimates human consumption of biological resources and products, along with generation of waste greenhouse gas (GHG) emissions in terms of appropriated productive land. There is an opportunity to better characterize land occupation and effects on the carbon cycle in life cycle assessment (LCA) models using EF concepts. Both LCA and EF may benefit from the merging of approaches commonly used separately by practitioners of these two methods. However, few studies have compared or integrated EF with LCA. The focus of this research was to explore methods for improving the characterization of land occupation within LCA by considering the EF method, either as a complementary tool or impact assessment method. Biofuels provide an interesting subject for application of EF in the LCA context because two of the most important issues surrounding biofuels are land occupation (changes, availability, and so on) and GHG balances, two of the impacts that EF is able to capture. We apply EF to existing fuel LCA land occupation and emissions data and project EF for future scenarios for U.S. transportation fuels. We find that LCA studies can benefit from lessons learned in EF about appropriately modeling productive land occupation and facilitating clear communication of meaningful results, but find limitations to the EF in the LCA context that demand refinement and recommend that EF always be used along with other indicators and metrics in product‐level assessments.     

The Carbon Footprint of Norwegian Seafood Products on the Global Seafood Market

Greenhouse gas emissions caused by food production are receiving increased attention worldwide. A problem with many studies is that they only consider one product; methodological differences also make it difficult to compare results across studies. Using a consistent methodology to ensure comparability, we quantified the carbon footprint of more than 20 Norwegian seafood products, including fresh and frozen, processed and unprocessed cod, haddock, saithe, herring, mackerel, farmed salmon, and farmed blue mussels. The previous finding that fuel use in fishing and feed production in aquaculture are key inputs was confirmed. Additional key aspects identified were refrigerants used on fishing vessels, product yield, and by‐product use. Results also include that product form (fresh or frozen) only matters when freezing makes slower transportation possible. Processing before export was favorable due to the greater potential to use by‐products and the reduced need for transportation. The most efficient seafood product was herring shipped frozen in bulk to Moscow at 0.7 kilograms CO₂ equivalents per kilogram (kg CO₂‐eq/kg) edible product. At the other end we found fresh gutted salmon airfreighted to Tokyo at 14 kg CO₂‐eq/kg edible product. This wide range points to major differences between seafood products and room for considerable improvement within supply chains and in product choices. In fisheries, we found considerable variability between fishing methods used to land the same species, which indicates the importance of fisheries management favoring the most resource‐efficient ways of fishing. Both production and consumption patterns matter, and a range of improvements could benefit the carbon performance of Norwegian seafood products.     

Using the Lashof Accounting Methodology to Assess Carbon Mitigation Projects With Life Cycle Assessment

As governments elaborate strategies to counter climate change, there is a need to compare the different options available on an environmental basis. This study proposes a life cycle assessment framework integrating the Lashof accounting methodology, which enables the assessment and comparison of different carbon mitigation projects (e.g., biofuel use, a sequestering plant, an afforestation project). The Lashof accounting methodology is chosen amid other methods of greenhouse gas (GHG) emission characterization for its relative simplicity and capability to characterize all types of carbon mitigation projects. Using the unit of megagram‐year (Mg‐year), which accounts for the mass of GHGs in the atmosphere multiplied by the time it stays there, the methodology calculates the cumulative radiative forcing caused by GHG emission within a predetermined time frame. Basically, the developed framework uses the Mg‐year as a functional unit and isolates impacts related to the climate mitigation function with system expansion. The proposed framework is demonstrated with a case study of tree ethanol pathways (maize, sugarcane, and willow). The study shows that carbon mitigation assessment through life cycle assessment is possible and that it could be a useful tool for decision makers, as it can compare different projects regardless of their original context. The case study reveals that system expansion, as well as each carbon mitigation project's efficiency at reducing carbon emissions, are critical factors that have a significant impact on the results. Also, the framework proves to be useful for treating land‐use change emissions, as they are considered through the functional unit.     

A Carbon Footprint of High‐Speed Railways in China: A Case Study of the Beijing‐Shanghai Line

A carbon footprint (CF) assessment of Chinese high‐speed railways (HSRs) can help guide further development of the world's longest HSR network. In this research, a hybrid economic input‐output and life cycle assessment (EIO‐LCA) method was applied to estimate the CF of the Beijing‐Shanghai HSR line. Specific CFs were analyzed of different subsystems of the line, different stages of production, and three calculation scopes. Results showed that the annual CF of the Beijing‐Shanghai HSR is increasing, whereas the per‐passenger CF constantly declined between 2011 and 2014. Scope 1 emissions account for an average of 4% of the total annual CF, Scope 2 contribute 71%, and Scope 3 comprise 25%. Among the different stages, operation contributes the largest (71%), followed by construction (20%) and maintenance (9%). In the construction stage, the bridges have the largest CF, followed by trains, and then rails. A trade‐off exists between the increase in carbon emissions due to construction of bridges and the reduction in operation emissions affected by leveling changes in terrain. The Beijing‐Shanghai HSR line has a relatively higher per‐passenger CF than eight other HSR lines, which is largely due to China's coal‐based carbon‐intensive energy mix of electricity generation, high proportion of bridges, higher operating speed, and heavier train body. In the future, cleaner electricity supply options, more efficient raw material production, and improvement of trains are keys to reducing the CF of Chinese HSRs.     

Modeling Corn Ethanol and Climate

New fuel regulations based on life cycle greenhouse gas (GHG) emissions have focused renewed attention on life cycle models of biofuels. The BESS model estimates 25% lower life cycle GHG emissions for corn ethanol than does the well-known GREET model, which raises questions about which model is more accurate. I develop a life cycle metamodel to compare the GREET and BESS models in detail and to explain why the results from these models diverge. I find two main reasons for the divergence: (1) BESS models a more efficient biorefinery than is modeled in the cases to which its results have been compared, and (2) in several instances BESS fails to properly count upstream emissions. Adjustments to BESS to account for these differences raise the estimated global warming intensity (not including land use change) of the corn ethanol pathway considered in that model from 45 to 61 g CO₂e MJ⁻¹. Adjusting GREET to use BESS's biorefinery performance and coproduct credit assumptions reduces the GREET estimate from 64 to 61 g CO₂e MJ⁻¹. Although this analysis explains the gap between the two models, both models would be improved with better data on corn production practices and by better treatment of agricultural inputs.     

Global Warming Potential of Carbon Dioxide Emissions from Biomass Stored in the Anthroposphere and Used for Bioenergy at End of Life

There is growing interest in understanding how storage or delayed emission of carbon in products based on bioresources might mitigate climate change, and how such activities could be credited. In this research we extend the recently introduced approach that integrates biogenic carbon dioxide (CO₂) fluxes with the global carbon cycle (using biogenic global warming potential [GWP_bio]) to consider the storage period of harvested biomass in the anthroposphere, with subsequent oxidation. We then examine how this affects the climate impact from a bioenergy resource. This approach is compared to several recent methods designed to address the same problem. Using both a 100‐ and a 500‐year fixed time horizon we calculate the GWP_bio factor for every combination of rotational and anthropogenic storage periods between 0 and 100 years. The resulting GWP_bio factors range from ?0.99 (1‐year rotation and 100‐year storage) to +0.44 (100‐year rotation and 0‐year storage). The approach proposed in this study includes the interface between biomass growth and emissions and the global carbon cycle, whereas other methods do not model this. These results and the characterization factors produced can determine the climate change benefits or impacts associated with the storage of biomass in the anthroposphere, and the subsequent release of biogenic CO₂ with the radiative forcing integrated in a fixed time window.     

Life cycle assessment comparison of wooden and plastic pallets in the grocery industry

Wooden and plastic pallets are used extensively in global trade to transport finished goods and products. This article compares the life cycle performance of treated wooden and plastic pallets through a detailed cradle‐to‐grave life cycle assessment (LCA), and conducts an analysis of the various phytosanitary treatments. The LCA investigates and evaluates the environmental impacts due to the resources consumed and emissions of the product throughout its life cycle. The environmental impacts of the pallets are compared on a one‐trip basis and a 100,000‐trips basis. Impact categories are chosen with respect to environmental concerns. The results show that on a one‐trip basis, wooden pallets with conventional and radio frequency (RF) heat treatment incur an overall carbon footprint of 71.8% and 80.3% lower, respectively, than plastic pallets during their life cycle; and in comparison with wooden pallets treated with methyl bromide fumigation, they incur 20% and 30% less overall carbon footprint. Theoretical calculations of the resource consumption and emissions of RF treatment of pallets suggest that dielectric technology may provide a lower‐carbon alternative to both current ISPM 15‐approved treatments and to plastic pallets. Methyl bromide fumigation (15.95 kg CO₂ equivalent [eq.]) has a larger carbon footprint than conventional heat treatment (12.69 kg CO₂ eq.) of pallets. For the 100,000‐trips basis, the differences are even more significant. The results recommend that wooden pallets are more environmentally friendly than plastic pallets, and conventional and RF heat treatment for wooden pallets is more sustainable than methyl bromide fumigation treatment.     

Linear Approaches to Characterization of Delayed Emissions of Methane

It is becoming more common to include the effects of delayed greenhouse gas emissions as an additional aspect in carbon footprinting. Although full dynamic assessment is the only accurate option to calculate those effects, the linear approach as outlined in, for example, the International Reference Life Cycle Data System (ILCD) Handbook, which is a popular reference. This approach overestimates the benefits of delayed emissions in all cases, but, for methane, the deviation is orders of magnitude. An alternative linear approach is proposed that does not start at t = 0. When using a time horizon of 100 years, an initial no‐accounting period of 75 years is found to be appropriate for delayed emissions of methane, in most cases. The difference between the two approaches, when applying the concept of temporary carbon storage or delayed emissions to landfill, is considerable.     

The Blue Water Footprint of Primary Copper Production in Northern Chile

Water consumption related to the life cycle of metals is seldom reported, even though mines are often situated in very dry regions. In this study we quantified the life cycle consumption of groundwater and fresh surface water (blue water footprint [WF_blue]) for the extraction and production of high‐grade copper refined from both a copper sulfide ore and a copper oxide ore in the Atacama Desert of northern Chile. Where possible, we used company‐specific data. The processes for extracting copper from the two types of ore are quite different from each other, and the WF_blue of the sulfide ore refining process is 2.4 times higher than that of the oxide ore refining process (i.e., 96 cubic meters per metric ton [tonne] of copper versus 40 cubic meters per tonne of copper). Most of the water consumption (59% of WF_blue) in the sulfide ore process occurred at the concentrator plant, via seepage, accumulation, and also by evaporation. In the oxide ore process, the main user of water is the heap‐leaching process, with 45% of WF_blue. The crushing and agglomeration operations, electrowinning cells, and solution pools are also significant contributors to the total consumption of water in the oxide ore process. Most of the water consumed in the oxide ore process was lost to evaporation. The WF_blue of the oxide ore process can be reduced by preventing water evaporation and using more sophisticated devices during irrigation of the leaching heaps. The WF_blue of the sulfide ore refining process can be reduced by improving water recovery (i.e., reducing seepage, accumulation, and evaporation) from the tailings dam at the concentrator plant. Using seawater in the production of copper is also a promising option to reduce the WF_blue by up to 62%.     

Carbon Nanofiber Production

Holistic understanding of nanotechnology using systems analysis tools is essential for evaluating claims about the potential benefits of this emerging technology. This article presents one of the first assessments of the life cycle energy requirements and environmental impact of carbon nanofibers (CNFs) synthesis. Life cycle inventory data are compiled with data reported in the open literature. The results of the study indicate relatively higher life cycle energy requirements and higher environmental impact of CNFs as compared to traditional materials, like primary aluminum, steel, and polypropylene, on an equal mass basis. Life cycle energy requirements for CNFs from a range of feedstock materials are found to be 13 to 50 times that of primary aluminum on an equal mass basis. Similar trends are observed from the results of process life cycle assessment (LCA), as conveyed by different midpoint and endpoint damage indicators. Savings in life cycle energy consumption and, hence, reductions in environmental burden are envisaged if higher process yields of these fibers can be achieved in continuous operations. Since the comparison of CNFs is performed on an equal mass basis with traditional materials, these results cannot be generalized for CNF‐based nanoproducts. Quantity of use of these engineered nanomaterials and resulting benefits will decide their energy and environmental impact. Nevertheless, the life cycle inventory and the results of the study can be used for evaluating the environmental performance of specific CNF‐based nanoproducts.     

Energy Requirements of Carbon Nanoparticle Production

Energy requirements for fullerene and nanotube synthesis are calculated from literature data and presented for a number of important production processes, including fluidized bed and floating catalyst chemical vapor deposition (CVD), carbon monoxide disproportionation, pyrolysis, laser ablation, and electric arc and solar furnace synthesis. To produce data for strategic forward‐looking assessments of the environmental implications of carbon nanoparticles, an attempt is made to balance generality with sufficient detail for individual processes, a trade‐off that will likely be inherent in the analysis of many nanotechnologies. Critical energy and production issues are identified, and potential improvements in industrial‐scale processes are discussed. Possible interactions with industrial ecosystems are discussed with a view toward integrating synthesis to mitigate the impacts of large‐scale carbon nanoparticle manufacture. Carbon nanoparticles are found to be highly energy‐intensive materials, on the order of 2 to 100 times more energy‐intensive than aluminum, even with idealized production models.     

Fast Carbon Footprinting for Large Product Portfolios

Publicly Available Specification 2050‐2011 (PAS 2050), the Green House Gas Product Protocol (GHGPP) standard and forthcoming guideline 14067 from the International Organization for Standardization (ISO) have helped to propel carbon footprinting from a subdiscipline of life cycle assessment (LCA) to the mainstream. However, application of carbon footprinting to large portfolios of many distinct products and services is immensely resource intensive. Even if achieved, it often fails to inform company‐wide carbon reduction strategies because footprint data are disjointed or don't cover the whole portfolio. We introduce a novel approach to generate standard‐compliant product carbon footprints (CFs) for companies with large portfolios at a fraction of previously required time and expertise. The approach was developed and validated on an LCA dataset covering 1,137 individual products from a global packaged consumer goods company. Three novel techniques work in concert in a single approach that enables practitioners to calculate thousands of footprints virtually simultaneously: (i) a uniform data structure enables footprinting all products and services by looping the same algorithm; (ii) concurrent uncertainty analysis guides practitioners to gradually improve the accuracy of only those data that materially impact the results; and (iii) a predictive model generates estimated emission factors (EFs) for materials, thereby eliminating the manual mapping of a product or service's inventory to EF databases. These autogenerated EFs enable non‐LCA experts to calculate approximate CFs and alleviate resource constraints for companies embarking on large‐scale product carbon footprinting. We discuss implementation roadmaps for companies, including further road‐testing required to evaluate the effectiveness of the approach for other product portfolios, limitations, and future improvements of the fast footprinting methodology.     

Environmental Damage Assessment of Carbon Capture and Storage

An end‐point life cycle impact assessment is used to evaluate the damages of electricity generation from fossil fuel‐based power plants with carbon dioxide capture and storage (CCS) technology. Pulverized coal (PC), integrated gasification combined cycle (IGCC), and natural gas combined cycle (NGCC) power plants are assessed for carbon dioxide (CO₂) capture, pipeline transport, and storage in a geological formation. Results show that the CCS systems reduce the climate change‐related damages but increase the damages from toxicity, acidification, eutrophication, and resource consumption. Based on the currently available damage calculation methods, it is concluded that the benefit of reducing damage from climate change is larger than the increases in other damage categories, such as health effects from particulates or toxic chemicals. CCS significantly reduces the overall environmental damage, with a net reduction of 60% to 70% in human health damage and 65% to 75% in ecosystem damage. Most of the damage is due to fuel production and combustion processes. The energy and infrastructure demands of CCS cause increases in the depletion of natural resources by 33% for PC, 19% for IGCC, and 18% for NGCC power plants, mostly due to increased fossil fuel consumption.     

Using Attributional Life Cycle Assessment to Estimate Climate‐Change Mitigation Benefits Misleads Policy Makers

Life cycle assessment (LCA) is generally described as a tool for environmental decision making. Results from attributional LCA (ALCA), the most commonly used LCA method, often are presented in a way that suggests that policy decisions based on these results will yield the quantitative benefits estimated by ALCA. For example, ALCAs of biofuels are routinely used to suggest that the implementation of one alternative (say, a biofuel) will cause an X% change in greenhouse gas emissions, compared with a baseline (typically gasoline). However, because of several simplifications inherent in ALCA, the method, in fact, is not predictive of real‐world impacts on climate change, and hence the usual quantitative interpretation of ALCA results is not valid. A conceptually superior approach, consequential LCA (CLCA), avoids many of the limitations of ALCA, but because it is meant to model actual changes in the real world, CLCA results are scenario dependent and uncertain. These limitations mean that even the best practical CLCAs cannot produce definitive quantitative estimates of actual environmental outcomes. Both forms of LCA, however, can yield valuable insights about potential environmental effects, and CLCA can support robust decision making. By openly recognizing the limitations and understanding the appropriate uses of LCA as discussed here, practitioners and researchers can help policy makers implement policies that are less likely to have perverse effects and more likely to lead to effective environmental policies, including climate mitigation strategies.     

The Water Withdrawal Footprint of Energy Supply to Cities

Water footprints traditionally estimate water lost as a result of evapotranspiration (or otherwise unavailable for downstream uses) associated with producing a certain good, and the same embodied in trade across regions is used to estimate regional and national water footprints. These footprints, however, do not address risk posed to city energy supplies characterized by insufficient streamflow to support energy production, such as cooling water intake (e.g., withdrawals) at thermoelectric power plants. Water withdrawal intensity factors for producing goods and services are being developed at the national scale, but lack sufficient spatial resolution to address these types of water‐energy challenges facing cities. To address this need, this article presents a water withdrawal footprint for energy supply (WWFES) to cities and places it in the context of other water footprints defined in the literature. Analysis of electricity use versus electricity generation in 43 U.S. cities highlights the need for developing WWFES to estimate risks to transboundary city energy supplies resulting from water constraints. The magnitude of the WWFES is computed for Denver, Colorado, and compared to the city's direct use of water to offer perspective. The baseline WWFES for Denver is found to be 66% as large as all direct water uses in the city combined (mean estimate). Minimum, mean, and maximum estimates are computed to demonstrate sensitivity of the WWFES to selection of water withdrawal intensity factors. Finally, scenario analysis explores the effect of energy technology and energy policy choices in shaping the future water footprint of cities.     

Accounting for Emissions and Sinks from the Biogeochemical Cycle of Carbon in the U.S. Economic Input‐Output Model

Biogeochemical cycles are essential ecosystem services that continue to degrade as a result of human activities, but are not fully considered in efforts toward sustainable engineering. This article develops a model that integrates the carbon cycle with economic activities in the 2002 U.S. economy. Data about the carbon cycle, including emissions and sequestration flows, is obtained from the greenhouse gas inventory of the U.S. Environmental Protection Agency. Economic activities are captured by the economic input‐output model available from the Bureau of Economic Analysis. The resulting model is more comprehensive in its accounting for the carbon cycle than existing methods for carbon footprint (CF) calculations. Examples of unique flows in this model include the effect of land‐use and land‐cover change on carbon dioxide flow within the U.S. national boundary, carbon sequestration in urban trees, and emissions resulting from liming. This model is used to gain unique insight into the carbon profile of U.S. economic sectors by providing the life cycle emissions and sequestration in each sector. Such insight may be used to support policies, manage supply chains, and be used for more comprehensive CF calculations.     

Environmental Assessment of Single‐Walled Carbon Nanotube Processes

The environmental assessment of nanomanufacturing during the initial process design phase should lead to the development of competitive, safe, and environmentally responsible engineering and commercialization. Given the potential benefits and concerns regarding the use of single‐walled carbon nanotubes (SWNTs), three SWNT production processes have been investigated to assess their associated environmental impacts. These processes include arc ablation (arc), chemical vapor deposition (CVD), and high‐pressure carbon monoxide (HiPco). Without consideration of the currently unknown impacts of SWNT dispersion or other health impacts, life cycle assessment (LCA) methodology is used to analyze the environmental impact and provide a baseline for the environmental footprint of each manufacturing process. Although the technical attributes of the product resulting from each process may not be fully comparable, this study presents comparisons that show that the life cycle impacts are dominated by energy, specifically the electricity used in production. Under base case yield conditions, HiPco shows the lowest environmental impact, while the arc process has the lowest impact under best case yield conditions.     

碳足迹核算的国际标准概述与解析

各种层面上的碳足迹核算在全球气候变化控制领域得到了越来越多的关注。但是,这些关于碳足迹核算的相关国际标准繁多,彼此之间的关系复杂,不利于研究领域和工业界对这些标准进行应用与交流,限制了碳足迹核算的发展进度与深度。对目前已有的国际主要碳足迹核算标准及生命周期评价标准进行了整理,梳理出这些国际标准的一些基本特征,绘制了国际标准之间的关系图;并进一步从生命周期评价步骤的角度出发,解析了各种国际标准在这些阶段上的相关内容,以及每一个阶段上各标准相关规定中的不同特点及逻辑关系。对促进我国碳足迹核算相关研究与实践工作具有一定的理论与现实参考意义。