Exploring the Use of Ecological Footprint in Life Cycle Impact Assessment

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

Life Cycle Assessment Software: Selection Can Impact Results

When software is used to facilitate life cycle assessments (LCAs), the implicit assumption is that the results obtained are not a function of the choice of software used. LCAs were done in both SimaPro and GaBi for simplified systems of creation and disposal of 1 kilogram each of four basic materials (aluminum, corrugated board, glass, and polyethylene terephthalate) to determine whether there were significant differences in the results. Data files and impact assessment methodologies (Impact 2002, ReCiPe, and TRACI 2) were ostensibly identical (although there were minor variations in the available ReCiPe version between the programs that were investigated). Differences in reported impacts of greater than 20% for at least one of the four materials were found for 9 of the 15 categories in Impact 2002+, 7 of the 18 categories in ReCiPe, and four of the nine categories in TRACI. In some cases, these differences resulted in changes in the relative rankings of the four materials. The causes of the differences for 14 combinations of materials and impact categories were examined by tracing the results back to the life cycle inventory data and the characterization factors in the life cycle impact assessment (LCIA) methods. In all cases examined, a difference in the characterization factors used by the two programs was the cause of the differing results. As a result, when these software programs are used to inform choices, the result can be different conclusions about relative environmental preference that are functions purely of the software implementation of LCIA methods, rather than of the underlying data.     

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

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

From Life Cycle Assessment to Life Cycle Management

Life cycle assessment (LCA) is a widely accepted methodology to support decision‐making processes in which one compares alternatives, and that helps prevent shifting of environmental burdens along the value chain or among impact categories. According to regulation in the European Union (EU), the movement of waste needs to be reduced and, if unavoidable, the environmental gain from a specific waste treatment option requiring transport must be larger than the losses arising from transport. The EU explicitly recommends the use of LCA or life cycle thinking for the formulation of new waste management plans. In the last two revisions of the Industrial Waste Management Programme of Catalonia (PROGRIC), the use of a life cycle thinking approach to waste policy was mandated. In this article we explain the process developed to arrive at practical life cycle management (LCM) from what started as an LCA project. LCM principles we have labeled the “3/3” principle or the “good enough is best” principle were found to be essential to obtain simplified models that are easy to understand for legislators and industries, useful in waste management regulation, and, ultimately, feasible. In this article, we present the four models of options for the management of waste solvent to be addressed under Catalan industrial waste management regulation. All involved actors concluded that the models are sufficiently robust, are easy to apply, and accomplish the aim of limiting the transport of waste outside Catalonia, according to the principles of proximity and sufficiency.     

Final Energy Requirements of Steam for Use in Environmental Life Cycle Assessment

Steam is an important utility that is required in nearly all industrial process chains and hence needs to be modeled in life cycle assessment studies. Industrial steam systems are often very complex, with different steam flows varying in pressure and temperature and being transported over different distances. This should be accounted for when calculating the energy requirements related to steam supply. In this article, we constructed a generic model that allows estimating final energy requirements (i.e., gate‐to‐gate energy required to generate the steam) of various types of single‐fuel steam systems without turbines (i.e., open and closed cycles) with or without flash steam and expressed per tonne (t) of steam supplied to a process (before heat exchange) or per gigajoule (GJ) heat delivered within the process (after heat exchange, i.e., as useful energy). The model focuses on steam provided for covering process heat requirements and hence excludes cogeneration schemes with steam turbines. Based on the final energy requirements estimated with our generic model, primary energy requirements and environmental impacts can be calculated for various circumstances. Depending on the conditions chosen, final energy requirements for natural gas–fueled systems, as estimated in this study, are 2.71 to 3.44 GJ/t produced steam or 1.33 to 1.78 GJ/GJ delivered heat.     

Implementing a Dynamic Life Cycle Assessment Methodology with a Case Study on Domestic Hot Water Production

This work contributes to the development of a dynamic life cycle assessment (DLCA) methodology by providing a methodological framework to link a dynamic system modeling method with a time‐dependent impact assessment method. This three‐step methodology starts by modeling systems where flows are described by temporal distributions. Then, a temporally differentiated life cycle inventory (TDLCI) is calculated to present the environmental exchanges through time. Finally, time‐dependent characterization factors are applied to the TDLCI to evaluate climate‐change impacts through time. The implementation of this new framework is illustrated by comparing systems producing domestic hot water (DHW) over an 80‐year period. Electricity is used to heat water in the first system, whereas the second system uses a combination of solar energy and gas to heat an equivalent amount of DHW at the same temperature. This comparison shows that using a different temporal precision (i.e., monthly vs. annual) to describe process flows can reverse conclusions regarding which case has the best environmental performance. Results also show that considering the timing of greenhouse gas (GHG) emissions reduces the absolute values of carbon footprint in the short‐term when compared with results from the static life cycle assessment. This pragmatic framework for the implementation of time in DLCA studies is proposed to help in the development of the methodology. It is not yet a fully operational scheme, and efforts are still required before DLCA can become state of practice.     

Analyzing the Practice of Life Cycle Assessment

Life cycle assessment (LCA) is a quantitative tool used to evaluate the environmental impacts of products or processes. With respect to buildings, LCA can be used to evaluate the environmental impacts of an entire building's life cycle. Currently LCA in the building area is used in a limited capacity, primarily to select building products. In order to determine the causality for the lack of whole‐building LCAs, focus groups with members of the architecture, engineering, and construction (AEC) communities were held. This article investigates the current level of knowledge of LCA in the AEC community and then discusses the benefits and barriers to the practice of LCA. In summary, the goal of the research was to identify why LCA is not used to its fullest potential in a whole‐building LCA. In an open forum and moderated setting, focus group participants were asked individually to self‐identify their experience with LCA, a brief education session on LCA was held, and then benefits and barriers to LCA were discussed. The focus group sessions were transcribed and systematically coded by social researchers in order to analyze the results. Hybrid flow and radar charts were developed. From the focus group results, the most important benefit to LCA was “provides information about environmental impacts.” The results did not identify a prominent barrier; however, building‐related metrics were ascertained to be one of the more crucial barriers. The benefits and barriers classified by this analysis will be utilized to develop a subsequent online survey to further understand the LCA and AEC community.     

Applying Leontief's Price Model to Estimate Missing Elements in Hybrid Life Cycle Inventories

This article presents an approach to estimate missing elements in hybrid life cycle inventories. Its development is motivated by a desire to rationalize inventory compilation while maintaining the quality of the data. The approach builds on a hybrid framework, that is, a combination of process‐ and input–output‐based life cycle assessment (LCA) methodology. The application of Leontief's price model is central in the proposed procedure. Through the application of this approach, an inventory with no cutoff with respect to costs can be obtained. The formal framework is presented and discussed. A numerical example is provided in Supplementary Appendix S1 on the Web.     

Consequential Life Cycle Assessment of Pasture‐based Milk Production: A Case Study in the Waikato Region,New Zealand

Farm intensification options in pasture‐based dairy systems are generally associated with increased stocking rates coupled with the increased use of off‐farm inputs to support the additional feed demand of animals. However, as well as increasing milk production per hectare, intensification can also exacerbate adverse impacts on the environment. The objective of the present study was to investigate environmental trade‐offs associated with potential intensification methods for pasture‐based dairy farming systems in the Waikato region, New Zealand. The intensification scenarios selected were (1) increased pasture utilization efficiency (PUE scenario), (2) increased use of nitrogen (N) fertilizer to boost on‐farm pasture production (N fertilizer scenario), and (3) increased use of brought‐in feed as maize silage (MS) (MS scenario). Twelve impact categories were assessed. The PUE scenario was the environmentally preferred intensification method, and the preferred choice between the N fertilizer and MS scenarios depended upon trade‐offs between different environmental impacts. Sensitivity analysis was carried out to test the effects of choice associated with: (1) the approaches used to account for indirect land‐use change (ILUC) and (2) the competing product systems (conventional beef systems) used to handle the co‐product dairy meat for the climate change (CC) indicator. Results showed that the magnitude of the CC indicator results was influenced by the ILUC accounting approaches and the choice associated with a global marginal beef mix, but the relative CC indicator results for the three intensification scenarios remained unchanged.     

Life Cycle Greenhouse Gas Emissions of Electricity Generated from Conventionally Produced Natural Gas

This research provides a systematic review and harmonization of the life cycle assessment (LCA) literature of electricity generated from conventionally produced natural gas. We focus on estimates of greenhouse gases (GHGs) emitted in the life cycle of electricity generation from natural gas‐fired combustion turbine (NGCT) and combined‐cycle (NGCC) systems. The smaller set of LCAs of liquefied natural gas power systems and natural gas plants with carbon capture and storage were also collected, but analyzed to a lesser extent. A meta‐analytical process we term “harmonization” was employed to align several system boundaries and technical performance parameters to better allow for cross‐study comparisons, with the aim of clarifying central tendency and reducing variability in estimates of life cycle GHG emissions. Of over 250 references identified, 42 passed screens for technological relevance and study quality, providing a total of 69 estimates for NGCT and NGCC. Harmonization increased the median estimates in each category as a result of several factors not typically considered in the previous research, including the regular clearing of liquids from a well, and consolidated the interquartile range for NGCC to 420 to 480 grams of carbon dioxide equivalent per kilowatt‐hour (g CO₂‐eq/kWh) and for NGCT to 570 to 750 g CO₂‐eq/kWh, with medians of 450 and 670 CO₂‐eq/kWh, respectively. Harmonization of thermal efficiency had the largest effect in reducing variability; methane leakage rate is likely similarly influential, but was unharmonized in this assessment as a result of the significant current uncertainties in its estimation, an area that is justifiably receiving significant research attention.     

Evaluation of Life Cycle Assessment Recycling Allocation Methods

Life cycle assessment practitioners struggle to accurately allocate environmental burdens of metals recycling, including the temporal dimension of environmental impacts. We analyze four approaches for calculating aluminum greenhouse gas emissions: the recycled content (RC) or cut‐off approach, which assumes that demand for recycled content displaces primary production; end‐of‐life recycling (EOLR), which assumes that postuse recycling displaces primary production; market‐based (MB) approaches, which estimate changes in supply and demand using price elasticities; and value‐corrected substitution (VCS), which allocates impact based on price differences between primary and recycled material. Our analysis suggests that applications of the VCS approach do not adequately account for the changing scrap to virgin material price ratio over time, whereas MB approaches do not address stock accumulation and depletion. The EOLR and RC approaches were analyzed using two case studies: U.S. aluminum beverage cans and vehicle engine blocks. These approaches produced similar results for beverage cans, which have a closed material loop system and a short product life. With longer product lifetimes, as noted with the engine blocks, the magnitude and timing of the emissions differs greatly between the RC and EOLR approaches. The EOLR approach indicates increased impacts at the time of production, offset by negative impacts in future years, whereas the RC approach assumes benefits to increased recycled content at the time of production. For vehicle engine blocks, emissions using EOLR are 140% higher than with RC. Results are highly sensitive to recycled content and future recycling rates, and the choice of allocation methods can have significant implications for life cycle studies.     

Life Cycle Assessment of ICT

The use of information and communication technology (ICT) is growing throughout society, and new products and solutions are developed at an increasing rate. To enable environmental assessment of specific ICT products and other products that rely on ICT in some way, a more complete, detailed, and up‐to‐date study based on real measurements is needed. To date, similar studies have not been readily available or fully comprehensive. This study assessed the overall operational electricity use and life‐cycle–based carbon footprint (CF) relating to ICT in Sweden, including activities not commonly addressed previously, such as shared data transport networks and data centers and manufacturing of network infrastructure. Specific, detailed inventory data are presented and used for assessment of the Internet Protocol core network, data transmission, operator activities, and access network. These specific data, in combination with secondary, more generic data for end‐user equipment, allow a comprehensive overall assessment. The majority of the ICT network CF is the result of end‐user equipment, mainly personal computers, followed by third‐party enterprise networks and data centers and then access networks. The parts closest to the user proved to be clearly responsible for the majority of the impact. The results are presented for Swedish ICT networks and for ICT networks in general based on a global average electricity mix.     

On the Complexity of Life Cycle Inventory Networks: Role of Life Cycle Processes with Network Analysis

Determining the relevance and importance of a technosphere process or a cluster of processes in relation to the rest of the industrial network can provide insights into the sustainability of supply chains: those that need to be optimized or controlled/safeguarded. Network analysis (NA) can offer a broad framework of indicators to tackle this problem. In this article, we present a detailed analysis of a life cycle inventory (LCI) model from an NA perspective. Specifically, the network is represented as a directed graph and the “emergy” numeraire is used as the weight associated with the arcs of the network. The case study of a technological system for drinking water production is presented. We investigate the topological and structural characteristics of the network representation of this system and compare properties of its weighted and unweighted network, as well as the importance of nodes (i.e., life cycle unit processes). By identifying a number of advantages and limitations linked to the modeling complexity of such emergy‐LCI networks, we classify the LCI technosphere network of our case study as a complex network belonging to the scale‐free network family. The salient feature of this network family is represented by the presence of “hubs”: nodes that connect with many other nodes. Hub failures may imply relevant changes, decreases, or even breaks in the connectedness with other smaller hubs and nodes of the network. Hence, by identifying node centralities, we can rank and interpret the relevance of each node for its special role in the life cycle network.     

The Design of a Sustainability Assessment Standard Using Life Cycle Information

Sustainability assessment standards are currently being developed for a range of building products. This activity has been stimulated through the considerable success of the U.S. Green Building Council's (USGBC) LEED? standard. Transparent life cycle–based standards can guide manufacturers to design products that have reduced environmental impact. The use of a sustainability standard can certify performance and avoid green washing. In this article we present a logical framework for designing a sustainability assessment standard through the creation of tables that award points in the standard to be consistent with life cycle information. Certain minimum principles of consistency are articulated. In the case that the life cycle impact assessment method maps the life cycle inventory to impact through a linear weighting, two design approaches—impact category and activity substitution—are constructed to be consistent with these principles. The approach is illustrated in a case study of a partial redesign of a carpet sustainability assessment standard (NSF/ANSI‐140).     

Comparing Three Life Cycle Impact Assessment Methods from an Endpoint Perspective

The impact assessment methods Eco‐Indicator 99 (H), Stepwise2006, and ReCiPe2008 (H) are compared with respect to the relative and absolute importance that they assign to the different mid‐point impact categories. The comparison is done by a common monetary valuation of the three endpoints that are common to the three methods: human well‐being, nature, and resources. Land use, global warming, and respiratory inorganic pollutants together make up between 86% and 97% of the overall impacts compared in all three methods. The overall monetarized impacts amount to 30%, 28%, and 165% of the gross domestic product (GDP), respectively. Resource depletion, land use, and global warming explain 99.5% of the positive deviation of ReCiPe2008, relative to the other two methods. The main causes for these differences are investigated and discussed, pointing to possibly questionable calculations and assumptions, for example, regarding the nonsubstitutability of resources and the very long relaxation time for transformed forestland in the relatively new ReCiPe2008 method, which leads us to recommend users to be cautious and critical when interpreting the results. Sensitivity analysis is made for other cultural perspectives and normalization references.     

Life Cycle Inventory Analysis of the Wood Pallet Repair Process in the United States

This study developed gate‐to‐gate life cycle inventory (LCI) data for the repair of 48 by 40 inch (1,219 by 1,016 millimeter [mm]) stringer‐class wood pallets in the United States. Data were collected from seven wood pallet repair facilities. Approximately 1.98 FBM (foot, board measure) (4.67E‐03 cubic meters) of lumber were used for repairing each 48 by 40 inch (1,219 by 1,016 mm) stringer‐class wood pallet, the majority (97%) recovered from damaged pallets received by the pallet repair facilities. Repair equipment powered by electricity made the largest contribution to greenhouse gas (GHG) emissions. Steel nails used for the pallet repair had the largest contribution to GHG emissions among the material inputs, while use of recovered lumber yielded the largest GHG emissions credits. Overall, the repair process for a 48 by 40 inch (1,219 by 1,016 mm) stringer‐class wood pallet had GHG credits rather than a positive GHG emission due to the GHG offsets from co‐products.     

Life Cycle Assessment of Biomass‐based Combined Heat and Power Plants

Norway, like many countries, has realized the need to extensively plan its renewable energy future sooner rather than later. Combined heat and power (CHP) through gasification of forest residues is one technology that is expected to aid Norway in achieving a desired doubling of bioenergy production by 2020. To assess the environmental impacts to determine the most suitable CHP size, we performed a unit process‐based attributional life cycle assessment (LCA), in which we compared three scales of CHP over ten environmental impact categories—micro (0.1 megawatts electricity [MWe]), small (1 MWe), and medium (50 MWe) scale. The functional units used were 1 megajoule (MJ) of electricity and 1 MJ of district heating delivered to the end user (two functional units), and therefore, the environmental impacts from distribution of electricity and hot water to the consumer were also considered. This study focuses on a regional perspective situated in middle‐Norway's Nord‐ and Sør‐Trøndelag counties. Overall, the unit‐based environmental impacts between the scales of CHP were quite mixed and within the same magnitude. The results indicated that energy distribution from CHP plant to end user creates from less than 1% to nearly 90% of the total system impacts, depending on impact category and energy product. Also, an optimal small‐scale CHP plant may be the best environmental option. The CHP systems had a global warming potential ranging from 2.4 to 2.8 grams of carbon dioxide equivalent per megajoule of thermal (g CO₂‐eq/MJ_th) district heating and from 8.8 to 10.5 grams carbon dioxide equivalent per megajoule of electricity (g CO₂‐eq/MJ_el) to the end user.     

Impact Assessment of Biodiversity and Carbon Pools from Land Use and Land Use Changes in Life Cycle Assessment,Exemplified with Forestry Operations in Norway

There is a strong need for methods within life cycle assessment (LCA) that enable the inclusion of all complex aspects related to land use and land use change (LULUC). This article presents a case study of the use of one hectare (ha) of forest managed for the production of wood for bioenergy production. Both permanent and temporary changes in above‐ground biomass are assessed together with the impact on biodiversity caused by LULUC as a result of forestry activities. The impact is measured as a product of time and area requirements, as well as by changes in carbon pools and impacts on biodiversity as a consequence of different management options. To elaborate the usefulness of the method as well as its dependency on assumptions, a range of scenarios are introduced in the study. The results show that the impact on climate change from LULUC dominates the results, compared to the impact from forestry operations. This clearly demonstrates the need to include LULUC in an LCA of forestry products. For impacts both on climate change and biodiversity, the results show large variability based on what assumptions are made; and impacts can be either positive or negative. Consequently, a mere measure of land used does not provide any meaning in LCA, as it is not possible to know whether this contributes a positive or negative impact.     

Confronting Uncertainty in Life Cycle Assessment Used for Decision Support

The aim of this article is to help confront uncertainty in life cycle assessments (LCAs) used for decision support. LCAs offer a quantitative approach to assess environmental effects of products, technologies, and services and are conducted by an LCA practitioner or analyst (AN) to support the decision maker (DM) in making the best possible choice for the environment. At present, some DMs do not trust the LCA to be a reliable decision‐support tool—often because DMs consider the uncertainty of an LCA to be too large. The standard evaluation of uncertainty in LCAs is an ex‐post approach that can be described as a variance simulation based on individual data points used in an LCA. This article develops and proposes a taxonomy for LCAs based on extensive research in the LCA, management, and economic literature. This taxonomy can be used ex ante to support planning and communication between an AN and DM regarding which type of LCA study to employ for the decision context at hand. This taxonomy enables the derivation of an LCA classification matrix to clearly identify and communicate the type of a given LCA. By relating the LCA classification matrix to statistical principles, we can also rank the different types of LCA on an expected inherent uncertainty scale that can be used to confront and address potential uncertainty. However, this article does not attempt to offer a quantitative approach for assessing uncertainty in LCAs used for decision support.