Showing papers in "International Journal of Life Cycle Assessment in 2009"

Assessing freshwater use impacts in LCA: Part I—inventory modelling and characterisation factors for the main impact pathways

Abstract: Freshwater is a basic resource for humans; however, its link to human health is seldom related to lack of physical access to sufficient freshwater, but rather to poor distribution and access to safe water supplies. On the other hand, freshwater availability for aquatic ecosystems is often reduced due to competition with human uses, potentially leading to impacts on ecosystem quality. This paper summarises how this specific resource use can be dealt with in life cycle analysis (LCA). The main quantifiable impact pathways linking freshwater use to the available supply are identified, leading to definition of the flows requiring quantification in the life cycle inventory (LCI). The LCI needs to distinguish between and quantify evaporative and non-evaporative uses of ‘blue’ and ‘green’ water, along with land use changes leading to changes in the availability of freshwater. Suitable indicators are suggested for the two main impact pathways [namely freshwater ecosystem impact (FEI) and freshwater depletion (FD)], and operational characterisation factors are provided for a range of countries and situations. For FEI, indicators relating current freshwater use to the available freshwater resources (with and without specific consideration of water ecosystem requirements) are suggested. For FD, the parameters required for evaluation of the commonly used abiotic depletion potentials are explored. An important value judgement when dealing with water use impacts is the omission or consideration of non-evaporative uses of water as impacting ecosystems. We suggest considering only evaporative uses as a default procedure, although more precautionary approaches (e.g. an ‘Egalitarian’ approach) may also include non-evaporative uses. Variation in seasonal river flows is not captured in the approach suggested for FEI, even though abstractions during droughts may have dramatic consequences for ecosystems; this has been considered beyond the scope of LCA. The approach suggested here improves the representation of impacts associated with freshwater use in LCA. The information required by the approach is generally available to LCA practitioners The widespread use of the approach suggested here will require some development (and consensus) by LCI database developers. Linking the suggested midpoint indicators for FEI to a damage approach will require further analysis of the relationship between FEI indicators and ecosystem health.

Carbon footprinting—opportunities and threats

Abstract: There are surprisingly many people out there that obviously think that carbon footprinting is a new thing. They obviously are not aware of the fact that it has been around for decades—just being called differently, i.e. the result of the life cycle impact category indicator global warming potential (GWP). However, carbon footprinting (CFP) is really fashionable these days. Like with all fashion, not all that glitters is gold. Taking carbon footprinting as the one and only yardstick, one has to face life-threatening trade-offs. If carbon footprint is the way to go, we need to shut down each waste-water treatment plant in the world, because it leads to an increased carbon footprint. You should also tear out the catalytic converter and diesel particulate filters from cars, because they lead to a higher CFP. Nuclear power would be obviously a most preferable energy generation option, because it has a lower carbon footprint than even most renewable energy sources—at least based on information provided by pertinent EPDs (Vattenfall 2005; 2007a, b). Recycling paper should be stopped, because compared to virgin paper with a carbon footprint close to ‘zero’, it comes with a higher burden—unless renewable energy is used for the processes necessary (Carbon Trust 2006). But, on the other hand, we have the market demand. Whether it is real or just perceived or just desired seems not so important. There is enough momentum for numerous international, national and sectoral initiatives underway to deal with CFP:

Allocation issues in LCA methodology: a case study of corn stover-based fuel ethanol

Abstract: Facing the threat of oil depletion and climate change, a shift from fossil resources to renewables is ongoing to secure long-term low carbon energy supplies. In view of the carbon dioxide reduction targets agreed upon in the Kyoto protocol, bioethanol has become an attractive option for one energy application, as transport fuel. Many studies on the LCA of fuel ethanol have been conducted, and the results vary to a large extent. In most of these studies, only one type of allocation is applied. However, the effect of allocation on outcomes is of crucial importance to LCA as a decision supporting tool. This is only addressed in a few studies to a limited extent. Moreover, most of the studies mainly focus on fossil energy use and GHG emissions. In this paper, a case study is presented wherein a more complete set of impact categories is used. Land use has been left out of account as only hectare data would be given which is obviously dominated by agriculture. Moreover, different allocation methods are applied to assess the sensitivity of the outcomes for allocation choices. This study focuses on the comparison of LCA results from the application of different allocation methods by presenting an LCA of gasoline and ethanol as fuels and with two types of blends of gasoline with ethanol, all used in a midsize car. As a main second-generation application growing fast in the USA, corn stover-based ethanol is chosen as a case study. The life cycles of the fuels include gasoline production, corn and stover agriculture, cellulosic ethanol production, blending ethanol with gasoline to produce E10 (10% of ethanol) and E85 (85% of ethanol), and finally the use of gasoline, E10, E85, and ethanol. In this study, a substantially broader set of eight environmental impacts is covered. LCA results appear to be largely dependent on the allocation methods rendered. The level of abiotic depletion and ozone layer depletion decrease when replacing gasoline by ethanol fuels, irrespective of the allocation method applied, while the rest of the impacts except global warming potential are larger. The results show a reduction of global warming potential when mass/energy allocation is applied; in the case of economic allocation, it gives contrary results. In the expanded systems, global warming potential is significantly reduced comparing to the ones from the allocated systems. A contribution analysis shows that car driving, electricity use for cellulase enzyme production, and ethanol conversion contribute largely to global warming potential from the life cycle of ethanol fuels. The reason why the results of global warming potential show a reverse trend is that the corn/stover allocation ratio shifts from 7.5 to 1.7 when shifting from economic allocation to mass/energy allocation. When mass/energy allocation is applied, both more credits (CO2 uptake) and more penalties (N2O emission) in agriculture are allocated to stover compared to the case of economic allocation. However, more CO2 is taken up than N2O (in CO2 eq.) emitted. Hence, the smaller the allocation ratio is between corn and stover, the lower the share of the overall global warming emissions being allocated to ethanol will be. In the system expansion approach, global warming potentials are significantly reduced, resulting in the negative values in all cases. This implies that the system expansion results are comparable to one another because they make the same cutoffs but not really to the results related to mass, energy, and economic value-based allocated systems. The choice of the allocation methods is essential for the outcomes, especially for global warming potential in this case. The application of economic allocation leads to increased GWP when replacing gasoline by ethanol fuels, while reduction of GWP is achieved when mass/energy allocation is used as well as in the system where biogenic CO2 is excluded. Ethanol fuels are better options than gasoline when abiotic depletion and ozone layer depletion are concerned. In terms of other environmental impacts, gasoline is a better option, mainly due to the emissions of nutrients and toxic substances connected with agriculture. A clear shift of problems can be detected: saving fossil fuels at the expense of emissions related to agriculture, with GHG benefits depending on allocation choices. The overall evaluation of these fuel options, therefore, depends very much on the importance attached to each impact category. This study focuses only on corn stover-based ethanol as one case. Further studies may include other types of cellulosic feedstocks (i.e., switchgrass or wood), which require less intensive agricultural practice and may lead to better environmental performance of fuel ethanol. Furthermore, this study shows that widely used but different allocation methods determine outcomes of LCA studies on biofuels. This is an unacceptable situation from a societal point of view and a challenge from a scientific point of view. The results from applying just one allocation method are not sufficient for decision making. Comparison of different allocation methods is certainly of crucial importance. A broader approach beyond LCA for the analysis of biorefinery systems with regard to energy conservation, environmental impact, and cost–benefit will provide general indications on the sustainability of bio-based productions.

Life cycle assessment of corn grain and corn stover in the United States

Abstract: The goal of this study is to estimate the county-level environmental performance for continuous corn cultivation of corn grain and corn stover grown under the current tillage practices for various corn-growing locations in the US Corn Belt. The environmental performance of corn grain varies with its farming location because of climate, soil properties, cropping management, etc. Corn stover, all of the above ground parts of the corn plant except the grain, would be used as a feedstock for cellulosic ethanol. Two cropping systems are under investigation: corn produced for grain only without collecting corn stover (referred to as CRN) and corn produced for grain and stover harvest (referred to as CSR). The functional unit in this study is defined as dry biomass, and the reference flow is 1 kg of dry biomass. The system boundary includes processes from cradle to farm gate. The default allocation procedure between corn grain and stover in the CSR system is the system expansion approach. County-level soil organic carbon dynamics, nitrate losses due to leaching, and nitrogen oxide and nitrous oxide emissions are simulated by the DAYCENT model. Life cycle environmental impact categories considered in this study are total fossil energy use, climate change (referred to as greenhouse gas emissions), acidification, and eutrophication. Sensitivities on farming practices and allocation are included. Simulations from the DAYCENT model predict that removing corn stover from soil could decrease nitrogen-related emissions from soil (i.e., N2O, NO x , and NO3 − leaching). DAYCENT also predicts a reduction in the annual accumulation rates of soil organic carbon (SOC) with corn stover removal. Corn stover has a better environmental performance than corn grain according to all life cycle environmental impacts considered. This is due to lower consumption of agrochemicals and fuel used in the field operations and lower nitrogen-related emissions from the soil. The primary source of total fossil energy associated with biomass production is nitrogen fertilizer, accounting for over 30% of the total fossil energy. Nitrogen-related emissions from soil (i.e., N2O, NO x , and NO3 − leaching) are the primary contributors to all other life cycle environmental impacts considered in this study. The environmental performance of corn grain and corn stover varies with the farming location due to crop management, soil properties, and climate conditions. Several general trends were identified from this study. Corn stover has a lower impact than corn grain in terms of total fossil energy, greenhouse gas emissions, acidification, and eutrophication. Harvesting corn stover reduces nitrogen-related emissions from the soil (i.e., N2O, NO x , NO3 −). The accumulation rate of soil organic carbon is reduced when corn stover is removed, and in some cases, the soil organic carbon level decreases. Harvesting only the cob portion of the stover would reduce the negative impact of stover removal on soil organic carbon sequestration rate while still bringing the benefit of lower nitrogen-related emissions from the soil. No-tillage practices offer higher accumulation rates of soil organic carbon, lower fuel consumption, and lower nitrogen emissions from the soil than the current or conventional tillage practices. Planting winter cover crops could be a way to reduce nitrogen losses from soil and to increase soil organic carbon levels. County-level modeling is more accurate in estimating the local environmental burdens associated with biomass production than national- or regional-level modeling. When possible, site-specific experimental information on soil carbon and nitrogen dynamics should be obtained to reflect the system more accurately. The allocation approach between corn grain and stover significantly affects the environmental performance of each. The preferred allocation method is the system expansion approach where incremental fuel usage, additional nutrients in the subsequent growing season, and changes in soil carbon and nitrogen dynamics due to removing corn stover are assigned to only the collected corn stover.

Life cycle assessment of two baby food packaging alternatives: glass jars vs. plastic pots

Abstract: This paper compares the life cycle assessment (LCA) of two packaging alternatives used for baby food produced by Nestle: plastic pot and glass jar. The study considers the environmental impacts associated with packaging systems used to provide one baby food meal in France, Spain, and Germany in 2007. In addition, alternate logistical scenarios are considered which are independent of the two packaging options. The 200-g packaging size is selected as the basis for this study. Two other packaging sizes are assessed in the sensitivity analysis. Because results are intended to be disclosed to the public, this study underwent a critical review by an external panel of LCA experts. The LCA is performed in accordance to the international standards ISO 14040 and ISO 14044. The packaging systems include the packaging production, the product assembly, the preservation process, the distribution, and the packaging end-of-life. The production of the content (before preservation process), as well as the use phase are not taken into account as they are considered not to change when changing packaging. The inventory is based on data obtained from the baby food producer and the suppliers, data from the scientific literature, and data from the ecoinvent database. Special care is taken to implement a system expansion approach for end-of-life open and closed loop recycling and energy production (ISO 14044). A comprehensive impact assessment is performed using two life cycle impact assessment methodologies: IMPACT 2002+ and CML 2001. An extensive uncertainty analysis using Monte Carlo as well as an extensive sensitivity study are performed on the inventory and the reference flows, respectively. When looking at the impacts due to preservation process and packaging (considering identical distribution distances), we observe a small but significant environmental benefit of the plastic pot system over the glass jar system. Depending on the country, the impact is reduced by 14% to 27% for primary energy, 28% to 31% for global warming, 31% to 34% for respiratory inorganics, and 28% to 31% for terrestrial acidification/nutrification. The environmental benefit associated with the change in packaging mainly results from (a) production of plastic pot (including its end-of-life; 43% to 51% of total benefit), (b) lighter weight of packaging positively impacting transportation (20% to 35% of total benefit), and (c) new preservation process permitted by the plastic system (23% to 34% of total benefit). The jar or pot (including cap or lid, cluster, stretch film, and label) represents approximately half of the life cycle impacts, the logistics approximately one fourth, and the rest (especially on-site energy, tray, and hood) one fourth. The sensitivity analysis shows that assumptions made in the basic scenarios are rather conservative for plastic pots and that the conclusions for the 200-g packaging size also apply to other packaging sizes. The uncertainty analysis performed on the inventory for the German market situation shows that the plastic pot system has less impact than the glass jar system while considering similar distribution distances with a confidence level above 97% for most impact categories. There is opportunity for further improvement independent of the type of packaging used, such as by reducing distribution distances while still optimizing lot size. The validity of the main conclusions presented in this study is confirmed by results of both impact assessment methodologies IMPACT 2002+ and CML 2001. For identical transportation distances, the plastic pot system shows a small but significant reduction in environmental burden compared to the glass jar system. As food distribution plays an important role in the overall life cycle burdens and may vary between scenarios, it is important to avoid additional transportation of the packaged food in order to maintain or even improve the advantage of the plastic pot system. The present study focuses on the comparison of packaging systems and directly related consequences. It is recommended that further environmental optimization of the product also includes food manufacturing (before preservation process) and the supply chain of raw materials.

Life cycle assessment of soybean-based biodiesel in Argentina for export

Abstract: Regional specificities are a key factor when analyzing the environmental impact of a biofuel pathway through a life cycle assessment (LCA). Due to different energy mixes, transport distances, agricultural practices and land use changes, results can significantly vary from one country to another. The Republic of Argentina is the first exporter of soybean oil and meal and the third largest soybean producer in the world, and therefore, soybean-based biodiesel production is expected to significantly increase in the near future, mostly for exportation. Moreover, Argentinean biodiesel producers will need to evaluate the environmental performances of their product in order to comply with sustainability criteria being developed. However, because of regional specificities, the environmental performances of this biofuel pathway can be expected to be different from those obtained for other countries and feedstocks previously studied. This work aims at analyzing the environmental impact of soybean-based biodiesel production in Argentina for export. The relevant impact categories account for the primary non-renewable energy consumption (CED), the global warming potential (GWP), the eutrophication potential (EP), the acidification potential (AP), the terrestrial ecotoxicity (TE), the aquatic ecotoxicity (AE), the human toxicity (HT) and land use competition (LU). The paper tackles the feedstock and country specificities in biodiesel production by comparing the results of soybean-based biodiesel in Argentina with other reference cases. Emphasis is put on explaining the factors that contribute most to the final results and the regional specificities that lead to different results for each biodiesel pathway. The Argentinean (AR) biodiesel pathway was modelled through an LCA and was compared with reference cases available in the ecoinvent® 2.01 database, namely, soybean-based biodiesel production in Brazil (BR) and the United States (US), rapeseed-based biodiesel production in the European Union (EU) and Switzerland (CH) and palm-oil-based biodiesel production in Malaysia (MY). In all cases, the systems were modelled from feedstock production to biodiesel use as B100 in a 28 t truck in CH. Furthermore, biodiesel pathways were compared with fossil low-sulphur diesel produced and used in CH. The LCA was performed according to the ISO standards. The life cycle inventory and the life cycle impact assessment (LCIA) were performed in Excel spreadsheets using the ecoinvent® 2.01 database. The cumulative energy demand (CED) and the GWP were estimated through the CED for fossil and nuclear energy and the IPCC 2001 (climate change) LCIA methods, respectively. Other impact categories were assessed according to CML 2001, as implemented in ecoinvent. As the product is a fuel for transportation (service), the system was defined for one vehicle kilometre (functional unit) and was divided into seven unit processes, namely, agricultural phase, soybean oil extraction and refining, transesterification, transport to port, transport to the destination country border, distribution and utilisation. The Argentinean pathway results in the highest GWP, CED, AE and HT compared with the reference biofuel pathways. Compared with the fossil reference, all impact categories are higher for the AR case, except for the CED. The most significant factor that contributes to the environmental impact in the Argentinean case varies depending on the evaluated category. Land provision through deforestation for soybean cultivation is the most impacting factor of the AR biodiesel pathway for the GWP, the CED and the HT categories. Whilst nitrogen oxide emissions during the fuel use are the main cause of acidification, nitrate leaching during soybean cultivation is the main factor of eutrophication. LU is almost totally affected by arable land occupation for soybean cultivation. Cypermethrin used as pesticide in feedstock production accounts for almost the total impact on TE and AE. The sensitivity analysis shows that an increase of 10% in the soybean yield, whilst keeping the same inputs, will reduce the total impact of the system. Avoiding deforestation is the main challenge to improve the environmental performances of soybean-based biodiesel production in AR. If the soybean expansion can be done on marginal and set-aside agricultural land, the negative impact of the system will be significantly reduced. Further implementation of crops’ successions, soybean inoculation, reduced tillage and less toxic pesticides will also improve the environmental performances. Using ethanol as alcohol in the transesterification process could significantly improve the energy balance of the Argentinean pathway. The main explaining factors depend on regional specificities of the system that lead to different results from those obtained in the reference cases. Significantly different results can be obtained depending on the level of detail of the input data, the use of punctual or average data and the assumptions made to build up the LCA inventory. Further improvement of the AR biodiesel pathways should be done in order to comply with international sustainability criteria on biofuel production. Due to the influence of land use changes in the final results, more efforts should be made to account for land use changes others than deforestation. More data are needed to determine the part of deforestation attributable to soybean cultivation. More efforts should be done to improve modelling of interaction between variables and previous crops in the agricultural phase, future transesterification technologies and market prices evolution. In order to assess more accurately the environmental impact of soybean-based biodiesel production in Argentina, further considerations should be made to account for indirect land use changes, domestic biodiesel consumption and exportation to other regions, production scale and regional georeferenced differentiation of production systems.

USES-LCA 2.0—a global nested multi-media fate, exposure, and effects model

Abstract: 1 The USES-LCA 2.0 modelThe Uniform System for the Evaluation of Substancesadapted for LCA purposes, in short USES-LCA, is a multi-media fate, exposure, and effects model (Huijbregts et al.2000). The model USES-LCA is based on the (E)USESmodel family applied for risk assessment purposes in theEuropean Union (Vermeire et al. 2005). It is one of themodels involved in the development of LCIA toxicityconsensus model USEtox (Rosenbaum et al. 2008). USES-LCA has recently been updated to USES-LCA 2.0 andcontains a database of 3,396 chemicals. With this version,the user has now access to an easy-to-use model thatcalculates characterization factors for ecotoxicity andhuman toxicity on both the midpoint and endpoint level.For human toxicity, characterization factors for carcino-gens, for non-carcinogens, and overall characterizationfactors are provided. Separate ecotoxicological character-ization factors are provided for terrestrial, freshwater, andmarine ecosystems. To obtain an overall ecotoxicologicalcharacterization factor on endpoint level, they are furtheraggregated on the basis of species density of terrestrial,freshwater, and marine ecosystems separately. Figure 1gives a schematic overview of USES-LCA 2.0.Compared to consensus model USEtox, the main extrafeatures of USES-LCA are (a) next to midpoint character-ization factors, endpoint characterization factors are alsocalculated; (b) next to freshwater ecotoxicity, seawater andterrestrial ecotoxicity are also addressed; and (c) variousscenario assumptions can be tested by changing scenariosettings (further details described below).This note summarizes the USES-LCA 2.0 model asdeveloped from the junction of the individual fate andintake part (Huijbregts et al. 2005b), human toxicologicalpart (Huijbregts et al. 2005a), and ecotoxicological part(Van de Meent and Huijbregts 2005; Van Zelm et al. 2007;Van Zelm et al. 2009). Any further information on thecalculation of the separate parts of the characterizationfactors can be found in these articles.2 Fate and exposure factorsFor ten emission compartments, including urban air, rural air,freshwater,andagriculturalsoil,USES-LCA2.0calculatesbydefault environmental fate and exposure factors in multiplecompartmentsandhumanintakefactorsforinhalationandoralintake using an infinite time horizon. Environmental fate andexposure factors express the change in the dissolved concen-tration in an environmental compartment due to an emissionchange. Human intake factors express the change in exposureof the total human population at continental, moderate, arctic,or tropic scale via ingestion, or inhalation due to an emissionchange in a compartment. Rain–no rain conditions areimplemented in USES-LCA 2.0 according to the intermittentrain model as outlined by Jolliet and Hauschild (2005).Due to the large uncertainty of modeling metal behaviorin the environment, USES-LCA 2.0 includes the possibilityto test the sensitivity of the metal characterization factorsaccording to the following user-specific scenario options:1. Oral intake via food by humans can be excluded for allmetals, as it has been shown that the concept ofbioconcentration, generally applicable for organic pollu-

Lifecycle assessment of fuel ethanol from sugarcane in Brazil

Abstract: Background, aim, and scope This paper presents the lifecycle assessment (LCA) of fuel ethanol, as 100% of the vehicle fuel, from sugarcane in Brazil. The functional unit is 10,000 km run in an urban area by a car with a 1,600-cm3 engine running on fuel hydrated ethanol, and the resulting reference flow is 1,000 kg of ethanol. The product system includes agricultural and industrial activities, distribution, cogeneration of electricity and steam, ethanol use during car driving, and industrial by-products recycling to irrigate sugarcane fields. The use of sugarcane by the ethanol agribusiness is one of the foremost financial resources for the economy of the Brazilian rural area, which occupies extensive areas and provides far-reaching potentials for renewable fuel production. But, there are environmental impacts during the fuel ethanol lifecycle, which this paper intents to analyze, including addressing the main activities responsible for such impacts and indicating some suggestions to minimize the impacts.

Socioeconomic indicators as a complement to life cycle assessment : An application to salmon production systems

Abstract: There is a growing recognition on the part of industry, policymakers, and consumers that sustainable industry practices are needed to maintain environmental and social well being. Life cycle assessment (LCA) is an internationally standardized analytical framework that has traditionally focused on evaluation of the environmental impacts of processes or products using a cradle-to-grave approach. Yet, sustainability, defined generally, requires that assessments consider not only environmental but also social and economic impacts—the other two pillars of sustainability. Even though the LCA methodology has the potential to include both social and economic indicators, and SETAC guidelines recommend the inclusion of such impact categories in all detailed LCAs, no established set of metrics exists to describe the relationship between socioeconomic indicators (SEIs) and a specific product or process; nor is there a common understanding on how such metrics might be developed. This article presents the methods for and development of a suite of socioeconomic indicators that complement the LCA methodology and provides a comprehensive approach for assessing the cradle-to-grave sustainability of a product or process. A combined top-down and bottom-up approach serves as the basis for development of the set of socioeconomic indicators presented here. Generally recognized societal values, industry specific issues, and financial constraints associated with collection of data necessary for measurement of the indicators are all factors considered in this approach. In our categorization, socioeconomic indicators fall into two types: additive indicators and descriptive indicators. Indicators are categorized based on fundamental methodological differences and then used to describe the socioeconomic impacts associated with salmon production. Additive indicators (e.g., production costs and value added) and descriptive indicators (e.g., fair wage and contribution to personal income) are both discussed. There is a need to further develop and refine methods to assess the results of socioeconomic indicators using a life cycle perspective. It would be most interesting to conduct additional case studies that focus on such methodological development, particularly trade-offs between stakeholder groups and pillars of sustainability. Additional areas of discussion are (1) the need for data to populate socioeconomic indicators and (2) defining system boundaries for socioeconomic indicators. This article presents a set of socioeconomic indicators designed to serve as a complement for the LCA framework, thus, increasing the framework’s effectiveness as a measure of the overall sustainability of a product or process. Development of socioeconomic indicators as a complement to LCA is still in its early stages, however, and further research is required. The SEIs presented here are discussed theoretically within the context of salmon food production systems, but a test of the practicability and validity of the indicators (i.e., a practical application) is also necessary. The practical application of the topic will be presented in a forthcoming paper.

Life-cycle assessment of a 2-MW rated power wind turbine: CML method

Abstract: Renewable energy sources nowadays constitute an increasingly important issue in our society, basically because of the need for alternative sources of energy to fossil fuels that are free of CO2 emissions and pollution and also because of other problems such as the diminution of the reserves of these fossil fuels, their increasing prices and the economic dependence of non-producers countries on those that produce fossil fuels. One of the renewable energy sources that has experienced a bigger growth over the last years is wind power, with the introduction of new wind farms all over the world and the new advances in wind power technology. Wind power produces electrical energy from the kinetic energy of the wind without producing any pollution or emissions during the conversion process. Although wind power does not produce pollution or emissions during operation, it should be considered that there is an environmental impact due to the manufacturing process of the wind turbine and the disposal process at the end of the wind turbine life cycle, and this environmental impact should be quantified in order to compare the effects of the production of energy and to analyse the possibilities of improvement of the process from that point of view. Thus, the aim of this study is to analyse the environmental impact of wind energy technology, considering the whole life cycle of the wind power system, by means of the application of the ISO 14040 standard [ISO (1998) ISO 14040. Environmental management—life cycle assessment—principles and framework. International Standard Organization, Geneva, Switzerland], which allows quantification of the overall impact of a wind turbine and each of its component parts using a Life Cycle Assessment (LCA) study. The procedures, details, and results obtained are based on the application of the existing international standards of LCA. In addition, environmental details and indications of materials and energy consumption provided by the various companies related to the production of the component parts are certified by the application of the environmental management system ISO 14001 [ISO (2004) ISO 14001 Environmental management systems—requirements with guidance for use. International Standard Organization, Geneva, Switzerland]. A wind turbine is analysed during all the phases of its life cycle, from cradle to grave, by applying this methodology, taking into account all the processes related to the wind turbine: the production of its main components (through the incorporation of cut-off criteria), the transport to the wind farm, the subsequent installation, the start-up, the maintenance and the final dismantling and stripping down into waste materials and their treatment. The study has been developed in accordance with the ISO 14044 standard [ISO (2006) ISO 14044: Environmental management—life cycle assessment—requirements and guidelines. International Standard Organization, Geneva, Switzerland] currently in force. The application of LCA, according to the corresponding international standards, has made it possible to determine and quantify the environmental impact associated with a wind turbine. On the basis of this data, the final environmental effect of the wind turbine after a lifespan of 20 years and its subsequent decommissioning have been studied. The environmental advantages of the generation of electricity using wind energy, that is, the reduction in emissions and contamination due to the use of a clean energy source, have also been evaluated. This study concludes that the environmental pollution resulting from all the phases of the wind turbine (manufacture, start-up, use, and dismantling) during the whole of its lifetime is recovered in less than 1 year. From the developed LCA model, the important levels of contamination of certain materials can be obtained, for instance, the prepreg (a composite made by a mixture of epoxy resin and fibreglass). Furthermore, it has been concluded that it is possible to reduce the environmental effects of manufacturing and recycling processes of wind turbines and their components. In order to achieve this goal in a fast and effective way, it is essential to enlist the cooperation of the different manufacturers.

Influence of assumptions about selection and recycling efficiencies on the LCA of integrated waste management systems

Abstract: Life cycle assessment (LCA) applied to alternative waste management strategies is becoming a commonly utilised tool for decision makers. This LCA study analyses together material and energy recovery within integrated municipal solid waste (MSW) management systems, i.e. the recovery of materials separated with the source-separated collection of MSW and the energy recovery from the residual waste. The final aim is to assess the energetic and environmental performance of the entire MSW management system and, in particular, to evaluate the influence of different assumptions about recycling on the LCA results. The analysis uses the method of LCA and, thus, takes into account that any recycling activity influences the environment not only by consuming resources and releasing emissions and waste streams but also by replacing conventional products from primary production. Different assumptions about the selection efficiencies of the collected materials and about the quantity of virgin material substituted by the reprocessed material were made. Moreover, the analysis considers that the energy recovered from the residual waste displaces the same quantity of energy produced in conventional power plants and boilers fuelled with fossil fuels. The analysis shows, in the expanded model of the material and energy recovering chain, that the environmental gains are higher than the environmental impacts. However, when we reduce the selection efficiencies by 15%, the impact indicators worsen by a percentage included between 10% and 26%. This phenomenon is even more evident when we consider a substitution ratio of 1:<1 for paper and plastic: The worsening is around 15–20% for all the impact indicators except for the global warming for which the worsening is up to 45%. Hypotheses about the selection efficiencies of the source-separated collected materials and about the substitution ratio have a great influence on the LCA results. Consequently, policy makers have to be aware of the fact that the impacts of an integrated MSW management system are highly dependent on the assumptions made in the modelling of the material recovery, as well as in the modelling of the energy recovery. LCA allows to evaluate the impacts of integrated systems and how these impacts change when the assumptions made during the modelling of the different single parts of the system are modified. Due to the significant impacts that hypotheses about material recovery have in the results, they should be expressed in a very transparent way in the report of LCA studies, together with the assumptions made about energy recovery. The results suggest that the hypotheses about the value of the substitution ratio are very important, and the case of wood should therefore be better analysed and a substitution ratio of 1:<1 should be used, as for paper and plastic. It seems that the assumptions made about which material is replaced by the recycled one are very important too, and in this sense, more research is needed about what the recycled plastic may effectively substitute, in particular the polyolefin mix.

The contribution of PAS 2050 to the evolution of international greenhouse gas emission standards

Abstract: The assessment of greenhouse gas (GHG) emissions arising from products (goods and services) is emerging as a high profile application of life cycle assessment (LCA), with an increasing desire from retailers and other supply chain organizations to better understand, and in some cases communicate, the carbon footprint of products. Publicly Available Specification 2050:2008, Specification for the assessment of the life cycle greenhouse gas emissions of goods and services, addresses the single-impact category of global warming to provide a standardized and simplified implementation of process LCA methods for assessing GHG emissions from products. This paper briefly reviews the development process followed for PAS 2050, before examining the treatment of GHG-specific contribution of PAS 2050 to product carbon footprinting. PAS 2050 was jointly sponsored by the Carbon Trust and the UK Department for Environment, Food and Rural Affairs and was published by the British Standards Institution on 29 October 2008. An independent steering group oversaw the development of the specification, including the establishment of an expert workgroup program, comprehensive international consultation, and expert input on the requirements of the specification. The development process for PAS 2050 resulted in a specification that includes specific requirements that limit the interpretation of the underlying LCA approach to product carbon footprinting. These requirements, including goal setting and life cycle inventory assessment, aspects of system boundary identification and temporal aspects of GHG emissions, clarify the approach to be taken by organizations implementing product carbon footprinting, and simplify the application of LCA procedures in relation to product carbon footprinting. Assessment of the emissions arising from the life cycle of products has a clear international component, and delivering consistent results across the supply chain requires the application of consistent methods. There is an emerging recognition that further standardization of methods for product carbon footprinting is needed, and the specific requirements resulting from the PAS 2050 development process make a valuable contribution across a range of GHG assessment issues. The widespread interest in PAS 2050 from individuals and organizations, together with the development of similar guidance by other organizations, confirmed that there is a need for clarification, certainty, and requirements in the field of product carbon footprint analysis. The use of PAS 2050 to refine, clarify, and simplify existing LCA methods and standards has resulted in specific approaches to key GHG assessment issues being developed; it is important that future standards development work considers the impact of these approaches and their further refinement. It is the consumption of goods and services by individuals around the world that drives global GHG emission, and PAS 2050 is a first attempt to provide integrated, consistent approaches that directly address the role of consumption at the product level in contributing to GHG emissions. Climate science and GHG assessment techniques are both evolving areas and it will be necessary to review the approach taken by PAS 2050 in the future: a formal review process for PAS 2050 will commence towards the end of 2009 and practitioners are encouraged to participate in this review process.

A spatially explicit life cycle inventory of the global textile chain

Abstract: Life cycle analyses (LCA) approaches require adaptation to reflect the increasing delocalization of production to emerging countries. This work addresses this challenge by establishing a country-level, spatially explicit life cycle inventory (LCI). This study comprises three separate dimensions. The first dimension is spatial: processes and emissions are allocated to the country in which they take place and modeled to take into account local factors. Emerging economies China and India are the location of production, the consumption occurs in Germany, an Organisation for Economic Cooperation and Development country. The second dimension is the product level: we consider two distinct textile garments, a cotton T-shirt and a polyester jacket, in order to highlight potential differences in the production and use phases. The third dimension is the inventory composition: we track CO2, SO2, NO x , and particulates, four major atmospheric pollutants, as well as energy use. This third dimension enriches the analysis of the spatial differentiation (first dimension) and distinct products (second dimension). We describe the textile production and use processes and define a functional unit for a garment. We then model important processes using a hierarchy of preferential data sources. We place special emphasis on the modeling of the principal local energy processes: electricity and transport in emerging countries. The spatially explicit inventory is disaggregated by country of location of the emissions and analyzed according to the dimensions of the study: location, product, and pollutant. The inventory shows striking differences between the two products considered as well as between the different pollutants considered. For the T-shirt, over 70% of the energy use and CO2 emissions occur in the consuming country, whereas for the jacket, more than 70% occur in the producing country. This reversal of proportions is due to differences in the use phase of the garments. For SO2, in contrast, over two thirds of the emissions occur in the country of production for both T-shirt and jacket. The difference in emission patterns between CO2 and SO2 is due to local electricity processes, justifying our emphasis on local energy infrastructure. The complexity of considering differences in location, product, and pollutant is rewarded by a much richer understanding of a global production–consumption chain. The inclusion of two different products in the LCI highlights the importance of the definition of a product's functional unit in the analysis and implications of results. Several use-phase scenarios demonstrate the importance of consumer behavior over equipment efficiency. The spatial emission patterns of the different pollutants allow us to understand the role of various energy infrastructure elements. The emission patterns furthermore inform the debate on the Environmental Kuznets Curve, which applies only to pollutants which can be easily filtered and does not take into account the effects of production displacement. We also discuss the appropriateness and limitations of applying the LCA methodology in a global context, especially in developing countries. Our spatial LCI method yields important insights in the quantity and pattern of emissions due to different product life cycle stages, dependent on the local technology, emphasizing the importance of consumer behavior. From a life cycle perspective, consumer education promoting air-drying and cool washing is more important than efficient appliances. Spatial LCI with country-specific data is a promising method, necessary for the challenges of globalized production–consumption chains. We recommend inventory reporting of final energy forms, such as electricity, and modular LCA databases, which would allow the easy modification of underlying energy infrastructure.

Impact of fly ash content and fly ash transportation distance on embodied greenhouse gas emissions and water consumption in concrete

Abstract: Fly ash, a by-product of coal-fired power stations, is substituted for Portland cement to improve the properties of concrete and reduce the embodied greenhouse gas (GHG) emissions. Much of the world’s fly ash is currently disposed of as a waste product. While replacing some Portland cement with fly ash can reduce production costs and the embodied emissions of concrete, the relationship between fly ash content and embodied GHG emissions in concrete has not been quantified. The impact of fly ash content on embodied water is also unknown. Furthermore, it is not known whether a global trade in fly ash for use in concrete is feasible from a carbon balance perspective, or if transport over long distances would eliminate any CO2 savings. This paper aims to quantify GHG emissions and water embodied in concrete (f′c = 32 MPa) as a function of fly ash content and to determine the critical fly ash transportation distance, beyond which use of fly ash in concrete increases embodied GHG emissions. This paper used previously published and reported data for GHG emissions and water usage in cement production, quarries, transportation and concrete batching to quantify the embodied GHG emissions (CO2-equivalent) and water in concrete and the critical transportation distance for fly ash. Fly ash content alone is not a good indicator of embodied emissions in concrete; increasing fly ash content only reduces embodied emissions when there is a corresponding reduction in the mass of Portland cement used. The total embodied GHG emissions in concrete (GHGconcrete, kg CO2-equivalent m−3) can be determined from the mass of Portland cement used (masscement, t m−3): GHGconcrete = 66 + 790.7 masscement. This equation can be used to determine the reduction in Portland cement required to meet specific GHG emissions targets for concrete, if the Portland cement is replaced by fly ash sourced within 100 km of a concrete batching plant. Fly ash content has little effect on embodied water, which was 2.7–4.1 m3 water per cubic metre of concrete. Fly ash can be transported more than 11,000 km by articulated truck, 47,000 km by rail and 54,000 km by sea and still result in a net reduction in GHG emissions if used to replace Portland cement in concrete. At least 70% of GHG emissions embodied in concrete were due to cement production, even for fly ash content as high as 40%. Aggregate production accounted for 17–25% of embodied GHG emissions. While transport of concrete from batching plant to site represented only 3–5% of GHG emissions, this distance is subject to wide variability and hence can be a source of variation in total embodied GHG emissions. Water used in quarrying aggregate is both the largest and the most variable quantity of water used in concrete production, and accounted for at least 89% of water consumption for all mix designs considered in this study. While this study used values applicable to Brisbane, Australia, results are presented in a generalised form for ready adaptation to other conditions, for example different distances to raw materials sources, transport emissions factors, etc. A global trade in fly ash has the potential to reduce GHG emissions embodied in concrete, if the fly ash is used to reduce the consumption of Portland cement per cubic metre of concrete. Increasing fly ash usage under these conditions will reduce both the volume of fly ash disposal and the GHG emissions from the concrete industry. Efforts to reduce water consumption in the concrete industry should focus on quarrying processes, and on finding replacement materials with lower embodied water, which may include recycled aggregate. While this study has quantified the GHG emissions and water embodied in concrete as a function of fly ash content, a full life cycle study of concrete is required to determine the full impact of substituting fly ash for Portland cement. Structural characteristics, life span and operational requirements of concrete should also be considered in any decision to alter cement and fly ash content.

Environmental impacts of forest production and supply of pulpwood: Spanish and Swedish case studies

Abstract: Background, aim and scope Forest operations use large amounts of energy, which must be considered when life cycle assessment (LCA) methodology is applied to forest products. Forest management practices differ considerably between countries and may also differ within a country. This paper aims to identify and compare the environmental burdens from forest operations in Sweden and Spain focused on pulpwood production and supply to pulp mills.

The role of seasonality in lettuce consumption: a case study of environmental and social aspects

Abstract: Considerable debate surrounds the assessment of the environmental impacts and the ethical justification for providing a year-round supply of fresh produce to consumers in the developed countries of northern Europe. Society is seeking environmentally sustainable supply chains which maintain the variety of fresh food on offer throughout the year. This paper compares the environmental impacts of different supply chains providing lettuce all year round to the UK and considers consumers' meanings of—and attitudes to—available options. Lettuce has been selected as a case study as its consumption has grown steadily during the last two decades and the supply chains through cold months are protected cropping in the UK and field cropping in Spain; during warm months, lettuce is sourced from field cropping in the UK. Data were collected from farms supplying each of these supply chains, and life cycle assessment methodology was used to analyse a range of impacts associated with producing (from plant propagation to harvesting and post-harvest cooling) and delivering 1 kg of lettuce to a UK Regional Distribution Centre (RDC). The downstream stages (i.e. retailing, consumption and waste management) are the same regardless of the origin of the product and were omitted from the comparison. The impacts considered included potential to induce global warming and acidification as well as three inventory indicators (primary energy use, land use and water use). Qualitative data were collected in order to assess the consumer considerations of purchasing lettuce also during winter. Importation of Spanish field-grown lettuce into the UK during winter produced fewer greenhouse gas (GHG) emissions than lettuce produced in UK-protected systems at that time (0.4–0.5 vs. 1.5–3.7 kg CO2-eq/kg lettuce in RDC). Refrigerated transport to the UK was an important element of the global warming potential associated with Spanish lettuce (42.5% of emissions), whilst energy for heating dominated the results in UK-protected cultivation (84.3% of emissions). Results for acidification were more variable and no overall trends are apparent. Results from qualitative social analysis revealed complex and multidimensional meanings of freshness and suggested that the most striking seasonal variation in vegetable/salad eating was a tendency to consume more salads in the summer and more cooked vegetables in the winter, thus suggesting that in-home consumption alone cannot explain the rise in winter imports of lettuce to the UK. UK field-grown lettuce had the lowest overall environmental impact; however, those lettuces are only available in summer, so consumers therefore need to either accept the environmental impacts associated with eating lettuce in the winter or to switch consumption to another food product in the winter. When lettuces were field-grown in Spain and then transported by road to the UK, the overall impacts were similar to the UK field lettuces. The variation within farms of the same country employing different cultivation regimes and practices was bigger than between farms of different countries. This paper has explored the environmental consequences of consuming lettuce year-round in the UK. Whilst recognising the small sample size, the comparative analysis of the different supply chains does suggest that seasonality can be an important variable when defining the best choice of lettuce from an environmental point of view. Further studies considering more production sites and product types are required to obtain conclusions whose general validity is clear and for different types of fresh produce. A clear distinction to be made in such studies is whether crops are produced in open fields or under protection. New characterisation methods are needed for environmental impacts derived from the use of key agricultural resources such as land and water. Social studies to investigate consumer preferences and the possibility of moving to more seasonal diets should be an integral part of these studies using samples composed of both urban and rural consumers and using a mixed methodology with both quantitative and qualitative components.

Environmental assessment of German electricity generation from coal-fired power plants with amine-based carbon capture

Abstract: One of the most important sources of global carbon dioxide emissions is the combustion of fossil fuels for power generation. Power plants contribute more than 40% of the worldwide anthropogenic CO2 emissions. Therefore, the increased requirements for climate protection are a great challenge for the power producers. In this context a significant increase in power plant efficiency will contribute to reduce specific CO2 emissions. Additionally, CO2 capture and storage (CCS) is receiving considerable attention as a greenhouse gas (GHG) mitigation option. CCS allows continued use of fossil fuels with no or little CO2 emissions given to the atmosphere. This could approve a moderate transition to a low-carbon energy generation over the next decades. Currently, R&D activities in the field of CCS are mainly concentrated on the development of capture techniques, the geological assessment of CO2 storage reservoirs, and on economic aspects. Although first studies on material and energy flows caused by CCS are available, a broader environmental analysis is necessary to show the overall environmental impacts of CCS. The objectives in this paper are coal-based power plants with and without CO2 capture via mono-ethanolamine (MEA) and the comparison of their environmental effects based on life cycle assessment methodology (LCA). This LCA study examines the environmental and human health effects of power generation of five coal-based steam power plants, which differ in the year of installation (2005, 2010, 2020), the conversion efficiency, and in the ability and efficiency to capture CO2. For the removal of CO2 from combustion and gasification processes in power plants, three main technology concepts exist: (1) pre-combustion technology, (2) oxyfuel combustion systems, and (3) post-combustion separation. As post-combustion technology shows the highest level of maturity, this study concentrates on this route, focusing on capture using mono-ethanolamine (MEA). The analysis regards the post-combustion retrofit of coal power plants with MEA to be a general option in 2020. Material and energy flows are balanced on the level of single processes as well as for the whole process chains. The life cycle inventory clearly shows decreasing inputs and outputs according to the efficiency increase from 43% to 49% in case of the power plants without CO2 capture. In case of the MEA plants, all inputs and emissions raise, according to the additional energy consumption, except CO2 and sulphur dioxide. The strong decrease of SO2 partly results from the necessary improvement of desulphurisation if MEA wash is used. The influence of up and downstream activities on the results is determined. For the MEA plants, a considerable effect of up and downstream activities on the overall results is observed. Finally, the inventory results are assigned to selected impact categories. Global warming (GWP), human toxicity (HTP), acidification (AP), photo-oxidant formation (POCP), eutrophication (EP), and primary energy demand are adopted as impact categories. The impact assessment indicates decreasing impacts for all categories with increasing combustion efficiency for the coal plants without carbon capture. As expected, the GWP for the MEA plants is much lower than for the power plants without CO2 capture. In contrast to this, the HTP and the EP are much higher (up to three times) for the MEA plants. Sensitivity analysis reveals that the origin of coal and the corresponding transport distances have a significant impact on the overall results. Furthermore, it is concluded from the sensitivity analysis that for CCS systems the length of CO2 pipeline has a negligible effect in comparison with the effect of capture efficiency. The LCA is completed by a normalisation of the environmental impact categories. The development of combustion efficiency in case of the power plants without CO2 capture has the main influence on the decreasing mass flows at the input side. The energy penalty of the MEA plants affects the use of the inputs into the opposite direction. Although the power producer’s focus is on the power plant, the sense of a life cycle assessment is an integrated environmental assessment of the full life cycle of a product (here 1 kWh) including up and downstream processes. Therefore, the inventory results are presented without and with up and downstream processes. The inventory analysis clearly shows the significant influence of the up and downstream processes on the overall emissions. This influence is higher for the MEA plants than for the power plants without capture. In case of CO2 emissions, the significance of up and downstream processes is especially considerable (approx. 30%). Sensitivity analysis reveals that the origin of coal and the corresponding transport distances have a significant impact on the overall results. The results point out that the reduction of carbon dioxide emissions into the atmosphere is achieved at the expense of increasing other emissions and corresponding environmental impacts. In most cases the influence of up and downstream processes is significant. Therefore, life cycle approaches are necessary to get a holistic evaluation. It also shows that the implementation of new techniques can change the environmental assessment of the process chain and, thus, positive and negative effects have to be compared and weighed up against each other. As there exist several possible technical options for CO2 capture, further studies are necessary to compare the overall environmental effects of competing capture concepts such as pre-combustion and oxyfuel technology. Additionally, gas separating membranes should be part of further studies as they have the potential to contribute to all three main capture technology routes. Further studies with more detail and reliable inventories for CO2 compression and liquefaction as well as for gas conditioning as an interface between CO2 capture and transport are needed. Furthermore, the environmental effects including long-term CO2 emission from the storage sites are recommended.

Environmental performance assessment of hardboard manufacture

Abstract: The forest-based and related industries comprise one of the most important industry sectors in the European Union, representing some 10% of the EU's manufacturing industries. Their activities are based on renewable raw material resources and efficient recycling. The forest-based industries can be broken down into the following sectors: forestry, woodworking, pulp and paper manufacturing, paper and board converting and printing and furniture. The woodworking sector includes many sub-sectors; one of the most important is that of wood panels accounting for 9% of total industry production. Wood panels are used as intermediate products in a wide variety of applications in the furniture and building industries. There are different kinds of panels: particleboard, fibreboard, veneer, plywood and blockboard. The main goal of this study was to assess the environmental impacts during the life cycle of wet-process fibreboard (hardboard) manufacturing to identify the processes with the largest environmental impacts. The study covers the life cycle of hardboard production from a cradle-to-gate perspective. A hardboard plant was analysed in detail, dividing the process chain into three subsystems: wood preparation, board forming and board finishing. Ancillary activities such as chemicals, wood chips, thermal energy and electricity production and transport were included within the system boundaries. Inventory data came from interviews and surveys (on-site measurements). When necessary, the data were complemented with bibliographic resources. The life cycle assessment procedure followed the ISO14040 series. The life cycle inventory (LCI) and impact assessment database for this study were constructed using SimaPro Version 7.0 software. Abiotic depletion (AD), global warming (GW), ozone layer depletion (OLD), human toxicity (HT), ecotoxicity, photochemical oxidant formation (PO), acidification (AC) and eutrophication (EP) were the impact categories analysed in this study. The wood preparation subsystem contributed more than 50% to all impact categories, followed by board forming and board finishing, which is mainly due to chemicals consumption in the wood preparation subsystem. In addition, thermal energy requirements (for all subsystems) were fulfilled by on-site wood waste burning and, accordingly, biomass energy converters were considered. Several processes were identified as hot spots in this study: phenol-formaldehyde resin production (with large contribution to HT, fresh water aquatic ecotoxicity and PO), electricity production (main contributor to marine aquatic ecotoxicity), wood chips production (AD and OLD) and finally, biomass burning for heat production (identified as the largest contributor to AC and EP due to NO X emissions). In addition, uncontrolled formaldehyde emissions from manufacturing processes at the plant such as fibre drying should be controlled due to relevant contributions to terrestrial ecotoxicity and PO. A sensitivity analysis of electricity profile generation (strong geographic dependence) was carried out and several European profiles were analysed. Novel binding agents for the wood panel industry as a substitute for the currently used formaldehyde-based binders have been extensively investigated. Reductions of toxic emissions during drying, mat forming and binder production are desirable. The improved method would considerably reduce the contributions to all impact categories. The results obtained in this work allow forecasting the importance of the wood preparation subsystem for the environmental burdens associated with hardboard manufacture. Special attention was paid to the inventory analysis stage for each subsystem. It is possible to improve the environmental performance of the hardboard manufacturing process if some alternatives are implemented regarding the use of chemicals, electricity profile and emission sources in the production processes located inside the plant. This study provides useful information for forest-based industries related to panel manufacture with the aim of increasing their sustainability. Our research continues to assess the use phase and final disposal of panels to complete the life cycle assessment. Future work will focus on analysing the environmental aspects associated with plywood, another type of commonly used wood panel.

A greenhouse gas indicator for bioenergy: some theoretical issues with practical implications.

Abstract: Background, aim, and scope The expectations with respect to biomass as a resource for sustainable energy are sky-high. Many industrialized countries have adopted ambitious policy targets and have introduced financial measures to stimulate the production or use of bioenergy. Meanwhile, the side-effects and associated risks have been pointed out as well. To be able to make a well-informed decision, the Dutch government has expressed the intention to include sustainability criteria into relevant policy instruments.

Uncertainty of global warming potential for milk production on a New Zealand farm and implications for decision making

Abstract: As a food exporting nation, New Zealand recognises that the Global Warming Potential (GWP) impact of agriculture has become important to food customers. Food production policy and industry analysts make GWP decisions based on greenhouse gas inventory and life cycle assessment (LCA) results. For decision making, the level of confidence associated with information is important. However, treatment of uncertainty has been problematic in LCA, especially in agricultural systems. In this paper, the GWP of 1 kg of milk was used as a case study to test the feasibility of quantifying uncertainties by Monte Carlo simulation in an LCA applied to an agriculture product. The study also contributes to the development of good practice and has implications for the incorporation of uncertainties into decision making. We distinguished between three sources of variation. First, there is variability amongst basic units such as dairy cattle, soils and farm characteristics which may be quantified by the standard deviation (SD). Second, there is uncertainty about true population means, which is typically provided by a sample and can be measured by the standard error of the mean (SEM). Third, choices, such as the time horizon for computing GWP, can strongly affect the LCA outcomes. The first two sources were analysed by compiling input variable statistics and undertaking Monte Carlo numerical simulations. The third source of variation was quantified by sensitivity analysis. Up to the farm-gate stage, the mean GWP of 1 kg of milk (computed over 100 years) was 0.96 kg CO2-eq. The associated SD was 38% of the mean when using the SD of input variables (and called “variability”) and 7% when using the SEM (and called “uncertainty”). The GWP was most sensitive to uncertainty of pasture dry matter intake by grazing cattle. The second and third key input variables were the cattle excreta nitrous oxide emission factor and the enteric fermentation methane emission factor, respectively. Changing the GWP from a 100-year computation to one of 20 years corresponded to GWP increasing by 92%, while for a change from 100 to 500 years GWP declined by 54%. Data compilation for the uncertainty analyses was challenging because the measurements available were made over smaller time and space scales than ideal, so observations had to be generalised and data gaps filled by expert judgement. Uncertainty analysis using the SEM of input variables was considered most adapted in LCA, so it is recommended as best practice. Identification of the key parameters responsible for uncertainty in the LCA revealed knowledge gaps where research should be directed, such as for methane digestion and nitrous oxide emissions from N excreted by ruminants. Moreover, richer information for those key parameters could be used to build a typology of more meaningful simulations instead of a single, virtual average for analysing environmental impacts of the agricultural system. The use of Monte Carlo simulations for uncertainty and sensitivity analyses of LCA estimates for an agricultural product was feasible and recommendations were made. Developing a typology of realistic simulations based on the key parameters identified in the sensitivity analysis could provide decision makers with more information. Furthermore, in comparative LCA studies, a probabilistic framework provides further information including the statistical significance of differences between technological options. This would represent considerable progress for the decision-making process. We recommend that uncertainty information such as SEM, when available, be part of inventory data for agriculture systems in public reports and databases including assessment of its statistical meaning and consistency.

Environmental impact of two aerobic composting technologies using life cycle assessment

Abstract: Composting is a viable technology to treat the organic fraction of municipal solid waste (OFMSW) because it stabilizes biodegradable organic matter and contributes to reduce the quantity of municipal solid waste to be incinerated or land-filled. However, the composting process generates environmental impacts such as atmospheric emissions and resources consumption that should be studied. This work presents the inventory data and the study of the environmental impact of two real composting plants using different technologies, tunnels (CT) and confined windrows (CCW). Inventory data of the two composting facilities studied were obtained from field measurements and from plant managers. Next, life cycle assessment (LCA) methodology was used to calculate the environmental impacts. Composting facilities were located in Catalonia (Spain) and were evaluated during 2007. Both studied plants treat source separated organic fraction of municipal solid waste. In both installations the analysis includes environmental impact from fuel, water, and electricity consumption and the main gaseous emissions from the composting process itself (ammonia and volatile organic compounds). Inventory analysis permitted the calculation of different ratios corresponding to resources consumption or plant performance and process yield with respect to 1 t of OFMSW. Among them, it can be highlighted that in both studied plants total energy consumption necessary to treat the OFMSW and transform it into compost was between 130 and 160 kWh/t OFMSW. Environmental impact was evaluated in terms of global warming potential (around 60 kg CO2/t OFMSW for both plants), acidification potential (7.13 and 3.69 kg SO2 eq/t OFMSW for CT and CCW plant respectively), photochemical oxidation potential (0.1 and 3.11 kg C2H4 eq/t OFMSW for CT and CCW plant, respectively), eutrophication (1.51 and 0.77 kg $$ {\text{PO}}_4^{3-} $$ /t OFMSW for CT and CCW plant, respectively), human toxicity (around 15 kg 1,4-DB eq/t OFMSW for both plants) and ozone layer depletion (1.66 × 10−5 and 2.77 × 10−5 kg CFC−11 eq/t OFMSW for CT and CCW plant, respectively). This work reflects that the life cycle perspective is a useful tool to analyze a composting process since it permits the comparison among different technologies. According to our results total energy consumption required for composting OFMSW is dependent on the technology used (ranging from 130 to 160 kWh/t OFMSW) as water consumption is (from 0.02 to 0.33 m3 of water/t OFMSW). Gaseous emissions from the composting process represent the main contribution to eutrophication, acidification and photochemical oxidation potentials, while those contributions related to energy consumption are the principal responsible for global warming. This work provides the evaluation of environmental impacts of two composting technologies that can be useful for its application to composting plants with similar characteristics. In addition, this study can also be part of future works to compare composting with other OFMSW treatments from a LCA perspective. Likewise, the results can be used for the elaboration of a greenhouse gasses emissions inventory in Catalonia and Spain.

The role of flexible packaging in the life cycle of coffee and butter

Abstract: The evaluation of packaging’s environmental performance usually concentrates on a comparison of different packaging materials or designs. Another important aspect in life cycle assessment (LCA) studies on packaging is the recycling or treatment of packaging wastes. LCA studies of packed food include the packaging with specific focus on the contribution of the packaging to the total results. The consumption behaviour is often assessed only roughly. Packaging is facilitating the distribution of goods to the society. Broader approaches, which focus on the life cycle of packed goods, including the entire supply system and the consumption of goods, are necessary to get an environmental footprint of the system with respect to sustainable production and consumption. A full LCA study has been conducted for two food products: coffee and butter packed in flexible packaging systems. The aim was to investigate the environmental performance of packaging with respect to its function within the life cycle of goods. The study looks at the environmental relevance of stages and interdependencies within the life cycle of goods whilst taking consumers’ behaviour and portion sizes into consideration. The impact assessment is based on the following impact categories: non-renewable cumulative energy demand (CED), climate change, ozone layer depletion (ODP), acidification, and eutrophication. The study shows that the most relevant environmental aspects for a cup of coffee are brewing (i.e. the heating of water) and coffee production. Transport and retail packaging are of minor importance. Brewing and coffee production have an impact share between 40% (ODP, white instant coffee) and 99% (eutrophication, black coffee). Milk added for white coffee is relevant for this type of preparation. The instant coffee in the one-portion stick-pack needs more packaging material per cup of coffee and is prepared by a kettle with lower energy demand, such as a coffee machine, thus leading to higher shares of the retail packaging in all indicators. A one-portion stick-pack can prevent wastage and resources related to coffee production can be saved. The most relevant aspect regarding the life cycle of butter is butter production, dominated by the provision of milk. Over 80% of the burdens in butter production stem from the provision of milk for all indicators discussed. Regarding climate change, methane and dinitrogen monoxide, emissions of milk cows and fodder production are most relevant. Fertilisation during livestock husbandry is responsible for most burdens regarding acidification and eutrophication. The distribution and selling stage influences the indicators CED and ODP distinctly. The reasons are, on the one hand, the relatively energy-intensive storage in supermarkets and, on the other hand, the use of refrigerants for chilled storage and transportation. The storage of butter in a refrigerator for 30 days is responsible for about 10% of the CED. Several aspects have been modelled in a sensitivity analysis. The influence of coffee packaging disposal is very small due to the general low influence of packaging. In contrast, the brewing behaviour is highly relevant for the environmental impact of a cup of coffee. That applies similarly to the type of heating device—i.e. using a kettle or an automatic coffee machine. Wastage leads to a significant increase of all indicators. Under the wastage scenario, the coffee from one-portion stick-packs has a considerable better environmental performance concerning all indicators because, in case of instant coffee wastage of hot water and in case of ground coffee wastage of prepared coffee, has been predicted. Regardless of urban or countryside distances, grocery shopping has a low impact. The storage time of butter is relevant for the results in the indicator non-renewable CED. This is mainly the case when butter is stored as stock in the freezer. The end of life treatment of the packaging system has practically no influence on the results. Grocery shopping is of limited importance no matter which means of transport are used or which distances are regarded. Spoilage or wastage is of great importance: a spoilage/wastage of one third results in about 49% increased impacts compared to the standard case for all indicators calculated. The most important factors concerning the environmental impact from the whole supply chain of a cup of coffee are the brewing of coffee, its cultivation and production and the milk production in case of white coffee. The study highlights consumer behaviour- and packaging-related measures to reduce the environmental impact of a cup of coffee. The most relevant measures reducing the environmental impacts of butter consumption are the optimisation of the milk and butter production. Another important factor is the consumers’ behaviour, i.e. the reduction of leftovers. The consumer can influence impacts of domestic storage using efficient and size-adequate appliances. The impacts of packaging in the life cycle of butter are not of primary importance. This study shows that, in the case of packaging industry, a reduction of relevant environmental impacts can only be achieved if aspects indirectly influenced by the packaging are also taken into account. Thus, the packaging industry should not only aim to improve the production process of their packages, but also provide packages whose functionality helps to reduce other more relevant environmental impacts in the life cycle such as, for example, losses. Depending on the product, tailor-made packaging may also help to increase overall resource efficiency.

Quantifying system uncertainty of life cycle assessment based on Monte Carlo simulation

Abstract: Many studies evaluate the results of applying different life cycle impact assessment (LCIA) methods to the same life cycle inventory (LCI) data and demonstrate that the assessment results would be different with different LICA methods used. Although the importance of uncertainty is recognized, most studies focus on individual stages of LCA, such as LCI and normalization and weighting stages of LCIA. However, an important question has not been answered in previous studies: Which part of the LCA processes will lead to the primary uncertainty? The understanding of the uncertainty contributions of each of the LCA components will facilitate the improvement of the credibility of LCA. A methodology is proposed to systematically analyze the uncertainties involved in the entire procedure of LCA. The Monte Carlo simulation is used to analyze the uncertainties associated with LCI, LCIA, and the normalization and weighting processes. Five LCIA methods are considered in this study, i.e., Eco-indicator 99, EDIP, EPS, IMPACT 2002+, and LIME. The uncertainty of the environmental performance for individual impact categories (e.g., global warming, ecotoxicity, acidification, eutrophication, photochemical smog, human health) is also calculated and compared. The LCA of municipal solid waste management strategies in Taiwan is used as a case study to illustrate the proposed methodology. The primary uncertainty source in the case study is the LCI stage under a given LCIA method. In comparison with various LCIA methods, EDIP has the highest uncertainty and Eco-indicator 99 the lowest uncertainty. Setting aside the uncertainty caused by LCI, the weighting step has higher uncertainty than the normalization step when Eco-indicator 99 is used. Comparing the uncertainty of various impact categories, the lowest is global warming, followed by eutrophication. Ecotoxicity, human health, and photochemical smog have higher uncertainty. In this case study of municipal waste management, it is confirmed that different LCIA methods would generate different assessment results. In other words, selection of LCIA methods is an important source of uncertainty. In this study, the impacts of human health, ecotoxicity, and photochemical smog can vary a lot when the uncertainties of LCI and LCIA procedures are considered. For the purpose of reducing the errors of impact estimation because of geographic differences, it is important to determine whether and which modifications of assessment of impact categories based on local conditions are necessary. This study develops a methodology of systematically evaluating the uncertainties involved in the entire LCA procedure to identify the contributions of different assessment stages to the overall uncertainty. Which modifications of the assessment of impact categories are needed can be determined based on the comparison of uncertainty of impact categories. Such an assessment of the system uncertainty of LCA will facilitate the improvement of LCA. If the main source of uncertainty is the LCI stage, the researchers should focus on the data quality of the LCI data. If the primary source of uncertainty is the LCIA stage, direct application of LCIA to non-LCIA software developing nations should be avoided.

Regional variations in greenhouse gas emissions of biobased products in the United States—corn-based ethanol and soybean oil

Abstract: Regional variations in the environmental impacts of plant biomass production are significant, and the environmental impacts associated with feedstock supply also contribute substantially to the environmental performance of biobased products Thus, the regional variations in the environmental performance of biobased products are also significant This study scrutinizes greenhouse gas (GHG) emissions associated with two biobased products (ie, ethanol and soybean oil) whose feedstocks (ie, corn and soybean) are produced in different farming locations We chose 40 counties in Corn Belt States in the United States as biorefinery locations (ie, corn dry milling, soybean crushing) and farming sites, and estimated cradle-to-gate GHG emissions of ethanol and of soybean oil, respectively The estimates are based on 1 kg of each biobased product (ie, ethanol or soybean oil) The system boundary includes biomass production, the biorefinery, and upstream processes Effects of direct land use change are included in the greenhouse gas analysis and measured as changes in soil organic carbon level, while the effects of indirect land use change are not considered in the baseline calculations Those indirect effects however are scrutinized in a sensitivity analysis GHG emissions of corn-based ethanol range from 11 to 20 kg of CO2 equivalent per kilogram of ethanol, while GHG emissions of soybean oil are 04–25 kg of CO2 equivalent per kilogram of soybean oil Thus, the regional variations due to farming locations are significant (by factors of 2–7) The largest GHG emission sources in ethanol production are N2O emissions from soil during corn cultivation and carbon dioxide from burning the natural gas used in corn dry milling The second largest GHG emission source groups in the ethanol production system are nitrogen fertilizer (8–12%), carbon sequestration by soil (−15–2%), and electricity used in corn dry milling (7–16%) The largest GHG emission sources in soybean oil production are N2O emissions from soil during soybean cultivation (13–57%) and carbon dioxide from burning the natural gas used in soybean crushing (21–47%) The second largest GHG emission source groups in soybean oil production are carbon sequestration by soil (−29–24%), diesel used in soybean cultivation (4–24%), and electricity used in the soybean crushing process (10–21%) The indirect land use changes increase GHG emissions of ethanol by 7–38%, depending on the fraction of forest converted when newly converted croplands maintain crop cultivation for 100 years Farming sites with higher biomass yields, lower nitrogen fertilizer application rates, and less tillage are favorable to future biorefinery locations in terms of global warming For existing biorefineries, farmers are encouraged to apply a site-specific optimal nitrogen fertilizer application rate, to convert to no-tillage practices and also to adopt winter cover practices whenever possible to reduce the GHG emissions of their biobased products Current practices for estimating the effects of indirect land use changes suffer from large uncertainties More research and consensus about system boundaries and allocation issues are needed to reduce uncertainties related to the effects of indirect land use changes

Enzymes for pharmaceutical applications—a cradle-to-gate life cycle assessment

Abstract: During the last decade, the interest in estimating environmental life cycle impacts of bioprocesses has markedly risen. To adequately quantify these impacts, accurate life cycle inventories of materials, such as agricultural substrates and enzymes, are required. The goals of this life cycle assessment were (1) to estimate the life cycle inventories (LCIs) and impacts of three supported enzymes produced in-house for pharmaceutical applications (A, B, and C) and (2) to determine the suitability of applying modular life cycle inventory estimation techniques to enzymes when individual enzyme LCIs are not readily available. The scope of this LCA was cradle to gate, covering the production and purification of the enzymes, energy generation, raw material production, waste treatment, and transportation of the raw materials. Three immobilized enzymes (A, B, and C) produced industrially for application in pharmaceutical products were studied. Enzyme production information was obtained from internal process descriptions. LCI information was obtained from GlaxoSmithKline’s in-house LCA database FLASC™, from LCA commercial databases, and literature. The LCI for the enzyme support was estimated using its material flows. Mass allocations were applied to multi-output processes in the upstream processes. The life cycle impacts considered were nonrenewable energy consumption, global warming, acidification, eutrophication, and photochemical smog formation. Life cycle impacts of the immobilized enzymes A, B, and C were estimated. For instance, nonrenewable energy use is between 117 to 207 MJ/kg of immobilized enzyme and the global warming potential ranges from 16 to 25 kg CO2 eq/kg immobilized enzyme. Contributions of different subprocesses were also estimated. For example, support production accounts for about 31% to 67% of the energy consumption and soybean protein and yeast extract account for about 64% to 72% of the total photochemical smog formation. Uncertainty and sensitivity analysis were performed using Monte Carlo simulation and showed that a standard deviation of the environmental impact is less than 7% of the mean in all the environmental impacts considered. “What if” analysis shows that using biobased glycerin instead of petroleum-based glycerin could reduce global warming impacts between 11% and 44%. The production of immobilized enzyme is, in general, energy intensive. Enzyme A has larger environmental impacts than the other enzymes evaluated because of larger energy intensity and lower enzyme production yield. The media preparation inputs (soybean protein, yeast extract) and immobilization subprocesses are the two major contributors to acidification, eutrophication, and photochemical smog formation. Immobilization is the major contributor for global warming potential. “What if” analysis estimated changes on life cycle impacts for biobased vs. synthetic substrates. The results of this LCA are, in general, comparable with results previously reported in the literature (Nielsen et al., Int J Life Cycle Assess 12(6):432–438, 2007). Therefore, using this technique to estimate LCI of enzymes appears to be suitable for future life cycle assessments of biocatalyzed processes. The results of this study will be integrated into GlaxoSmithKline’s FLASC™ to improve the accuracy of life cycle assessment for biocatalyzed processes and enzymes produced in-house.

Comparative life cycle assessments of incineration and non-incineration treatments for medical waste

Abstract: Background, aim, and scope Management of the medical waste produced in hospitals or health care facilities has raised concerns relating to public health, occupational safety, and the environment Life cycle assessment (LCA) is a decision-supporting tool in waste management practice; but relatively little research has been done on the evaluation of medical waste treatment from a life cycle perspective Our study compares the environmental performances of two dominant technologies, hazardous waste incineration (HWI) as a type of incineration technology and steam autoclave sterilization with sanitary landfill (AL) as a type of non-incineration technology, for specific medical waste of average composition The results of this study could support the medical waste hierarchy

Integrating life cycle costs and environmental impacts of composite rail car-bodies for a Korean train

Abstract: A coupled Life Cycle Costing and life cycle assessment has been performed for car-bodies of the Korean Tilting Train eXpress (TTX) project using European and Korean databases, with the objective of assessing environmental and cost performance to aid materials and process selection. More specifically, the potential of polymer composite car-body structures for the Korean Tilting Train eXpress (TTX) has been investigated. This assessment includes the cost of both carriage manufacturing and use phases, coupled with the life cycle environmental impacts of all stages from raw material production, through carriage manufacture and use, to end-of-life scenarios. Metallic carriages were compared with two composite options: hybrid steel-composite and full-composite carriages. The total planned production for this regional Korean train was 440 cars, with an annual production volume of 80 cars. The coupled analyses were used to generate plots of cost versus energy consumption and environmental impacts. The results show that the raw material and manufacturing phase costs are approximately half of the total life cycle costs, whilst their environmental impact is relatively insignificant (3–8%). The use phase of the car-body has the largest environmental impact for all scenarios, with near negligible contributions from the other phases. Since steel rail carriages weigh more (27–51%), the use phase cost is correspondingly higher, resulting in both the greatest environmental impact and the highest life cycle cost. Compared to the steel scenario, the hybrid composite variant has a lower life cycle cost (16%) and a lower environmental impact (26%). Though the full composite rail carriage may have the highest manufacturing cost, it results in the lowest total life cycle costs and lowest environmental impacts. This coupled cost and life cycle assessment showed that the full composite variant was the optimum solution. This case study showed that coupling of technical cost models with life cycle assessment offers an efficient route to accurately evaluate economic and environmental performance in a consistent way.

Life cycle assessment of composite materials made of recycled thermoplastics combined with rice husks and cotton linters

Abstract: Background, aim, and scope The goal of this study is to analyze the environmental impact of new composite materials obtained from the combination of recycled thermoplastics (polypropylene [PP] and high-density polyethylene [HDPE]) and biodegradable waste of little economic value, namely, rice husks and recycled cotton. The environmental impact of these materials is compared to the impact of virgin PP and HDPE using life cycle assessment.

Life cycle assessment of Australian automotive door skins

Abstract: Policy initiatives, such as the EU End of Life Vehicle (ELV) Directive for only 5% landfilling by 2015, are increasing the pressure for higher material recyclability rates. This is stimulating research into material alternatives and end-of-life strategies for automotive components. This study presents a Life Cycle Assessment (LCA) on an Australian automotive component, namely an exterior door skin. The functional unit for this study is one door skin set (4 exterior skins). The material alternatives are steel, which is currently used by Australian manufacturers, aluminium and glass-fiber reinforced polypropylene composite. Only the inputs and outputs relative to the door skin production, use and end-of-life phases were considered within the system boundary. Landfill, energy recovery and mechanical recycling were the end-of-life phases considered. The aim of the study is to highlight the most environmentally attractive material and end-of-life option. The LCA was performed according to the ISO 14040 standard series. All information considered in this study (use of fossil and non fossil based energy resources, water, chemicals etc.) were taken up in in-depth data. The data for the production, use and end-of-life phases of the door skin set was based upon softwares such as SimaPro and GEMIS which helped in the development of the inventory for the different end-of-life scenarios. In other cases, the inventory was developed using derivations obtained from published journals. Some data was obtained from GM-Holden and the Co-operative research Centre for Advanced Automotive Technology (AutoCRC), in Australia. In cases where data from the Australian economy was unavailable, such as the data relating to energy recovery methods, a generic data set based on European recycling companies was employed. The characterization factors used for normalization of data were taken from (Saling et. al. Int J Life Cycle Assess 7(4):203–218 2002) which detailed the method of carrying out an LCA. The production phase results in maximum raw material consumption for all materials, and it is higher for metals than for the composite. Energy consumption is greatest in the use phase, with maximum consumption for steel. Aluminium consumes most energy in the production phase. Global Warming Potential (GWP) also follows a trend similar to that of energy consumption. Photo Oxidants Creation Potential (POCP) is the highest for the landfill scenario for the composite, followed by steel and aluminium. Acidification Potential (AP) is the highest for all the end-of-life scenarios of the composite. Ozone Depletion Potential (ODP) is the highest for the metals. The net water emissions are also higher for composite in comparison to metals despite high pollution in the production phases of metallic door skins. Solid wastes are higher for the metallic door skins. The composite door skin has the lowest energy consumption in the production phase, due to the low energy requirements during the manufacturing of E-glass and its fusion with polypropylene to form sheet molding compounds. In general, the air emissions during the use phase are strongly dependent on the mass of the skins, with higher emissions for the metals than for the composite. Material recovery through recycling is the highest in metals due to efficient separation techniques, while mechanical recycling is the most efficient for the composite. The heavy steel skins produce the maximum solid wastes primarily due to higher fuel consumption. Water pollution reduction benefit is highest in case of metals, again due to the high efficiency of magnetic separation technique in the case of steel and eddy current separation technique in the case of aluminium. Material recovery in these metals reduces the amount of water needed to produce a new door skin set (water employed mainly in the ingot casting stage). Moreover, the use of heavy metals, inorganic salts and other chemicals is minimized by efficient material recovery. The use of the studied type of steel for the door skins is a poor environmental option in every impact category. Aluminium and composite materials should be considered to develop a more sustainable and energy efficient automobile. In particular, this LCA study shows that glass-fiber composite skins with mechanical recycling or energy recovery method could be environmentally desirable, compared to aluminium and steel skins. However, the current limit on the efficiency of recycling is the prime barrier to increasing the sustainability of composite skins. The study is successful in developing a detailed LCA for the three different types of door skin materials and their respective recycling or end-of-life scenarios. The results obtained could be used for future work on an eco-efficiency portfolio for the entire car. However, there is a need for a detailed assessment of toxicity and risk potentials arising from each of the four different types of door skin sets. This will require greater communication between academia and the automotive industry to improve the quality of the LCA data. Sensitivity analysis needs to be performed such as the assessment of the impact of varying substitution factors on the life cycle of a door skin. Incorporation of door skin sets made of new biomaterials need to be accounted for as another functional unit in future LCA studies.

A hybrid life cycle assessment model for comparison with conventional methodologies in Australia

Abstract: Background, aim, and scope One barrier to the further implementation of LCA as a quantitative decision-support tool is the uncertainty created by the diversity of available analytical approaches. This paper compares conventional (‘process analysis’) and alternative (‘input–output analysis’) approaches to LCA, and presents a hybrid LCA model for Australia that overcomes the methodological limitations of process and input–output analysis and enables a comparison between the results achieved using each method. A case study from the water industry illustrates this comparison.