Life Cycle Assessment System Boundary Research Articles

Enhancing life cycle assessment for circular economy measurement of different case scenarios of modular steel slab

Life cycle assessment (LCA) has emerged as an essential method to evaluate materials' environmental impact. However, using LCA for assessing other dimensions of circular economy (CE), such as the technical, social, system, and functional dimensions, is fraught with several challenges. In this study, the LCA system boundary was extended to cradle-to-cradle and combined with the predictive building systemic circularity indicator to determine the environmental, technical, functional, and system dimensions of different case scenarios of the product system of a modular steel slab of a residential building in China. It was identified that the base scenario of the case slab could lead to about 50.4% of the mass of the slab being recyclable at EoL. In comparison, 0%, 70.8%, and 38.8% of the mass of the slab being recyclable were recorded for case scenarios one to three, respectively. The environmental impact of the scenarios showed that the base scenario would induce 38.64 kg CO2/m2 in global warming potential, while 68.2, 28.2, and 44.95 kg CO2/m2 were noted for case scenarios one to three, respectively. The simple additive weighting method was used to select the optimal scenario for the product system of the case slab. Adopting the optimal scenario for the case slab should lead to positive impacts and high recoverability at EoL. Implementing this iterative integrative method for assessing product systems enables considering the environmental, technical, systems, and functional dimensions of CE in assessments, which should lead to inclusive, sustainable decision-making.

A comparison and methodological proposal for hybrid approaches to quantify environmental impacts: A case study for renewable energies

The transition towards a more sustainable and decarbonised energy system is mandatory for achieving global climate objectives, and counting on proper tools to evaluate sustainability is essential. Among sustainability assessment methodologies, hybrid approaches integrating Input-Output analysis (IOA) and Life Cycle Assessment (LCA) are often proposed to overcome limitations and take advantage of strengths of both methodologies. In this paper we propose a new hybrid tiered approach, named Identification and Subtraction Method (ISM). Through a case study of Concentrated Solar Power (CSP) technology, we test the proposed method assessing seven environmental indicators and compare the results obtained by different methodological approaches: Environmental Extended Multiregional Input-Output (EMRIO), LCA and two hybrid approaches.Results showed that, in general, LCA and EMRIO provide the lowest and uppest impact values, respectively. The ISM method expands the LCA boundaries by including indirect impacts, avoiding double-counting and retaining the technological detail and representativeness of the LCA. The main advantage is the ability to establish with high accuracy the impact coming from the LCA system boundaries. Furthermore, ISM is easy to undertake for LCA practitioners, is a low time-consuming hybrid approach once the LCA and EMRIO models are run, and it does not require the alteration of the IO matrix as other hybrid methods. However, the need to perform the EMRIO and LCA analysis could imply high detailed data needs. An additional limitation of the model is that it is not be able to include partial contributions from EMRIO sectors. The highest differences between results obtained by the different methods are found in the assessment of local impacts and the resources depletion, while the methods tend to agree more on global and regional impacts quantification. However, there are limitations to the implementation of the impact characterization methods that should be borne in mind when comparing the results of the different methods.

Whole-building life-cycle analysis with a new GREET® tool: Embodied greenhouse gas emissions and payback period of a LEED-Certified library

Embodied greenhouse gas (GHG) emissions of building components and buildings operations need to be quantified to holistically address building sustainability. To evaluate embodied GHG emissions of buildings and to provide insights on building materials and building design decisions toward decarbonization, we have recently created a building life-cycle assessment (LCA) module in the widely used Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET®) LCA model. We applied the GREET building LCA module to examine embodied GHG impacts and the payback period of a LEED (Leadership in Energy and Environmental Design)-certified public library in Chicago, USA. We developed localized, detailed life-cycle inventories to address individual building materials used in the library. We expanded the LCA system boundary to include the mechanical, electrical, and plumbing system, as well as refrigerant impacts, which are often ignored in previous studies. Results show that the total embodied GHG emissions are approximately 817 metric tons, or approximately 538 kg/m2. Sensitivity analysis highlights the positive role of increasing the use of recycled materials for reducing embodied GHG emissions. Sensitivity analysis on embodied GHG emissions payback periods shows the need to benchmark the embodied and operational carbon performance of buildings for comparison to alternative building designs and sustainability practices. This analysis demonstrates that building LCA models, such as the GREET building LCA module, which addresses embodied and operational GHG emission impacts of whole buildings holistically, could empower building architects, technology developers, manufacturers, and general contractors to address embodied and operational impacts holistically for building sustainability.

Statistical variation in the embodied carbon of concrete mixtures

This study presents a refined calculation of the embodied carbon of concrete mixtures via life cycle assessment (LCA) with an explicit focus on three innovations. First, probability distributions that represent process-related variability in the embodied carbon of concrete are calculated using a variety of life cycle inventory data sources. Second, the traditional concrete LCA system boundary (i.e., cradle-to-gate) is expanded to incorporate and analyze estimates of in situ carbon sequestration via concrete carbonation. Third, we analyze the impact of different transportation scenarios on the utility of using fly ash to reduce the embodied carbon of concrete. We use these data to heuristically determine the breakeven transportation distance for fly ash via trucking to be 2655 km for domestic sources of fly ash. However, when fly ash is imported from international sources, reductions to embodied carbon attributed to fly ash replacement can be negligible. The calculated breakeven maritime shipping distance for fly ash equals 15,110 km—beyond which, the anticipated embodied carbon reductions due to fly ash use in concrete are compromised due to transportation. The advancements described herein enable improved scenario-based decision-making for understanding, quantifying, and reducing the embodied carbon of concrete mixtures. In addition, the results highlight the importance of accounting for international transportation of fly ash in LCAs, especially given that domestic sources of quality fly ash are expected to continue to decline and imports are expected to increase in many parts of the world over the next few decades.

Alternative POME Treatment Technology in the Implementation of Roundtable on Sustainable Palm Oil, Indonesian Sustainable Palm Oil (ISPO), and Malaysian Sustainable Palm Oil (MSPO) Standards Using LCA and AHP Methods

Palm oil mill effluent (POME) is a major concern as open lagoon technology is not environment-friendly. Therefore, the palm oil industry refers to a roundtable on sustainable palm oil (RSPO), Indonesian sustainable palm oil (ISPO), and Malaysian sustainable palm oil (MSPO) standards for POME treatment to reduce greenhouse gas emissions. An alternative POME treatment technology is the combination of open lagoon technology (COLT) with composting, biogas technology plus composting, biogas technology plus membrane, and biogas technology plus land application. The objective of this study is to analyze the life cycle assessment (LCA) result using a multi-criteria decision approach and to determine the implementation of POME treatment in the RSPO, ISPO, and MSPO standards. The LCA system boundary was considered from gate-to-gate and unit per ton of fresh fruit bunch as a functional unit. SimaPro® was used as the LCA analysis tool; Expert Choice® and Super Decision Software® were used to perform the analytic hierarchy process and analytic network process, respectively. In this study, COLT–Biogas plus composting technology had the maximum priority weight (0.470), according to the opinion of experts. The results could help palm oil mill decision-makers in choosing environment-friendly POME treatment technology.

Potential Reductions in Greenhouse Gas and Fine Particulate Matter Emissions Using Corn Stover for Ethanol Production in China

Corn stover is an abundant raw material that can be used to produce ethanol and reduce air pollution. This paper studied the potential reductions in greenhouse gas (GHG) and fine particulate matter (PM2.5) emissions across China if corn stover was used for ethanol production. Field surveys in nine provincial regions were conducted. Life-cycle assessment (LCA) was used to assess the GHG and PM2.5 emissions from a corn stover based ethanol system. The LCA system boundaries included several process stages from corn planting to ethanol fuel used in vehicles. Corn stover geographical distributions and emission reduction factors were combined. Results showed that the total surplus quantity of corn stover in China was 86.2 million metric tons (Mt) in 2015. It was sufficient to reach the ethanol production target set by the Chinese government. In the scenario that 38.5 Mt or 44.6% of corn stover surplus were used for ethanol production, the total potential emission reductions were 36.5 Mt CO2-eq GHG and 450.9 kt PM2.5. Among the 31 provincial regions in China, the reduction potentials varied from 0.001 to 8.9 Mt CO2-eq for GHG and from 0.013 to 109.7 kt for PM2.5. This study provided useful information to policy makers, researchers and industry managers who work on environmental control and corn stover management.

Environmental evaluation of Waste to Energy plant coupled with concentrated solar energy

Life Cycle Assessment (LCA) was applied to evaluate the environmental impact of a hybrid energy system based on the integration of a Waste to Energy plant with concentrated solar energy plant. In the Waste to Energy (WtE) section only saturated steam is produced, while the superheating takes place in an external superheater fed by the concentrated solar energy or, when this is not enough, by a natural gas backup boiler. Different couples of pressure and temperature, for the superheated steam (51 bar, 440 °C; 60 bar, 480 °C; 70 bar, 520 °C), different values for the solar multiple (1.5, 2.0 and 2.5) and different values for the thermal storage capacity (6 h, 10 h and 14 h) were considered, leading to 27 possible cases. Construction, operation and end-of-life phases were included in the LCA system boundary. Calculated global warming indicator, in kg of equivalent CO2 per MJ of produced electricity, slightly decreases for increasing steam parameter cases and for increasing storage hour cases, while a more relevant reduction was observed for increasing solar multiple values. The main contribution to global warming derives from the operation phase of the WtE part (67-86% of the operation), while the remaining part (14-33%) is given by the solar section, for which, in turn, the main contribution is the impact deriving from the natural gas combustion in the backup boiler.

Life cycle greenhouse gas emission reduction potential of battery electric vehicle

Abstract Purpose This study uses the life cycle assessment (LCA) method to calculate and compare the life cycle greenhouse gas (GHG) emissions from battery electric vehicles (BEVs) and conventional gasoline internal combustion engine vehicles (ICEVs) in 2010, 2014 and 2020 under different scenarios, including different electricity mixes, electricity generation technologies and combined heat and power (CHP) scales, as well as discusses the GHG emission reduction potential of BEVs throughout their life cycle. Methods The LCA system boundaries, including the vehicle cycle and the fuel cycle, are examined in accordance with the ISO 14040/14044 standards. The China Automotive Life Cycle Database (CALCD), which is the first and primary life cycle database of the China automotive industry, was used. The compositional data for the vehicle components and the battery material were obtained from the GREET2 2017 model. Results and discussion As the electricity mix is optimized, the electricity generation technology is advanced, and the CHP scale is increased from 2010 to 2020, the total life cycle GHG reduction potential of BEVs will gradually improve, reaching 13.4% in 2020, relative to ICEVs. Conclusions The sensitivity analysis shows that the GHG emissions from electricity, the percentage of fossil fuel in the electricity mix and the electricity consumption of the BEV during use are important parameters influencing the GHG emission reduction potential of BEVs. By adjusting the electricity mix, advancing electricity generation technologies and increasing the CHP scale, the GHG emission reduction potential of BEVs can be improved.

Life-cycle impact assessment of organic and non-organic grass-fed beef production in Japan

Beef production, especially when based on the calves from suckler cows, typically has the greatest environmental impacts among various livestock production systems. Conventional beef production in Japan uses a large amount of imported concentrate feed, which results in substantial environmental impacts. Yakumo Farm, located in northern Japan, produces grass-fed beef using only farm-grown feed. Pesticides and chemical fertilizer were used in the past, but organic management was introduced at the farm more recently. We assessed the environmental impacts of grass-fed beef production at Yakumo Farm before and after the introduction of organic management (hereafter, non-organic and organic, respectively), and a conventional Japanese (hereafter, conventional) system using life-cycle assessment (LCA). We constructed the LCA models based on data collected at Yakumo Farm, from the literature and from LCA databases. The LCA system boundaries included feed production, transportation, processing, animal management, enteric fermentation, and manure and its management. The functional unit was defined as 1 kg of cold carcass weight of beef steers. The impact of each system was determined regarding its potential contribution to global warming, acidification, and eutrophication, as well as its energy consumption. Both the organic and non-organic systems had much smaller impacts on acidification, eutrophication, and energy consumption than the conventional system. The impact on global warming associated with the organic system was equivalent to the conventional system, whereas for the non-organic system it was greater than for the conventional system. Generally, the exclusion of the process of feed transportation reduced the environmental impacts. The use of chemical fertilizer increased the global warming-related impact in the non-organic system. Therefore, we concluded that introducing organic management to Yakumo Farm mitigated its environmental impacts. Our results provide implications for mitigating the environmental impacts caused by beef or other livestock production not only in Japan, but also in other countries depending upon imported feed.

Environmental comparison of alternative treatments for sewage sludge: An Italian case study

A Life Cycle Assessment (LCA) was applied to compare different alternatives for sewage sludge treatment: such as land spreading, composting, incineration, landfill and wet oxidation. The LCA system boundaries include mechanical dewatering, the alternative treatment, transport, and final disposal/recovery of residues. Cases of recovered materials produced as outputs from the systems, were resolved by expanding the system boundaries to include avoided primary productions. The impact assessment was calculated using the CML-IA baseline method. Results showed that the incineration of sewage sludge with electricity production and solid residues recovery collects the lowest impact indicator values in the categories human toxicity, fresh water aquatic ecotoxicity, acidification and eutrophication, while it has the highest values for the categories global warming and ozone layer depletion. Land spreading has the lowest values for the categories abiotic depletion, fossil fuel depletion, global warming, ozone layer depletion and photochemical oxidation, while it collects the highest values for terrestrial ecotoxicity and eutrophication. Wet oxidation has just one of the best indicators (terrestrial ecotoxicity) and three of the worst ones (abiotic depletion, human toxicity and fresh water aquatic ecotoxicity). Composting process shows intermediate results. Landfill has the worst performances in global warming, photochemical oxidation and acidification. Results indicate that if the aim is to reduce the effect of the common practice of sludge land spreading on human and ecosystem toxicity, on acidification and on eutrophication, incineration with energy recovery would clearly improve the environmental performance of those indicators, but an increase in resource depletion and global warming is unavoidable. However, these conclusions are strictly linked to the effective recovery of solid residues from incineration, as the results are shown to be very sensitive with respect to this assumption. Similarly, the quality of the wet oxidation process residues plays an important role in defining the impact of this treatment.

Life Cyle Assessment Based Environmental Performance Comparison of Batch and Continuous Processing: A Case of 4-d-Erythronolactone Synthesis

Continuous processing, as a form of process intensification, is one of the keys of green engineering research and development in the pharmaceutical industry. It has the potential to reduce solvent use and cost of production as well as increase production quality and operational safety. In light of the increased research interest surrounding continuous processing, the goal of this work is to compare the environmental performances of batch (BP) and continuous (CP) processing of 4-d-erythronolactone (4-DEL) at pilot plant scale as case study. The processing systems are evaluated using green chemistry metrics and a cradle-to-gate life cycle assessment (LCA). The processing serves as the case study for this article’s goal. The LCA system boundary includes raw material extraction, transportation, synthesis of 4-DEL (as part of primary pharmaceutical manufacturing), equipment cleaning, plant utilities, and off-site waste management. In order to obtain life cycle inventories to support the LCA study of the BP and...

Life-Cycle Assessment of Biodiesel Produced from Grease Trap Waste.

Grease trap waste (GTW) is a low-quality waste material with variable lipid content that is an untapped resource for producing biodiesel. Compared to conventional biodiesel feedstocks, GTW requires different and additional processing steps for biodiesel production due to its heterogeneous composition, high acidity, and high sulfur content. Life-cycle assessment (LCA) is used to quantify greenhouse gas emissions, fossil energy demand, and criteria air pollutant emissions for the GTW-biodiesel process, in which the sensitivity to lipid concentration in GTW is analyzed using Monte Carlo simulation. The life-cycle environmental performance of GTW-biodiesel is compared to that of current GTW disposal, the soybean-biodiesel process, and low-sulfur diesel (LSD). The disposal of the water and solid wastes produced from separating lipids from GTW has a high contribution to the environmental impacts; however, the impacts of these processed wastes are part of the current disposal practice for GTW and could be excluded with consequential LCA system boundaries. At lipid concentrations greater than 10%, most of the environmental metrics studied are lower than those of LSD and comparable to soybean biodiesel.

Environmental impacts of extensive and intensive beef production systems in Thailand evaluated by life cycle assessment

Beef production is rapidly increasing and is accordingly becoming intensified in Southeast Asia, and the changes in beef production systems could contribute to large changes in the environmental impacts, taking into account the emission intensity of beef production. Here we assessed and compared the environmental impacts of extensive and intensive beef production systems in northeastern Thailand, using life cycle assessment (LCA). The extensive system was based on grazing and forage from grassland, and the intensive system houses cattle in the fattening phase and uses purchased concentrate feed as well as home-grown forage. An LCA model was developed based on data collected by site investigations of beef farms as well as literature and LCA databases. The processes associated with the beef-farming life cycle, i.e., animal management including biological activities of the cattle, grassland management, purchased feed production, and waste treatment were included within the LCA system boundary. The functional unit was defined as 1 kg of liveweight of marketed beef cattle. The environmental impacts of the extensive and intensive beef production systems were 14.0 and 10.6 kg CO2 equivalents for climate change, 3.5 and 11.3 MJ for energy consumption, 47.4 and 61.8 g SO2 equivalents for acidification, and 30.4 and 33.9 g PO43− equivalents for eutrophication, respectively. These impacts except for eutrophication were significantly different (P < 0.05) between the two systems. The enteric CH4 emissions were the largest sources for climate change, and the manure-related emissions were the largest sources for acidification and eutrophication. In the intensive system, the purchased feed contributed a great deal to energy consumption and to some extent to other impact categories. Our results suggested that the ongoing intensification of beef production in Thailand reduces GHG emissions while increasing impacts on energy consumption and acidification. These results provide helpful information to develop a strategy to balance the increasing productivity with the environmental sustainability of beef production in developing countries.

Attributional and Consequential Life-cycle Assessment in Biofuels: a Review of Recent Literature in the Context of System Boundaries

At the core of the debate over life-cycle assessment (LCA) modeling of the environmental impacts of biofuels is doubt that biofuels can mitigate climate change. Two types of LCA, attributional and consequential, have been applied to answer this question with competing results. These results turn on system boundary design, including feedstock considerations and assumptions of indirect land-use impacts. The broadening of the system boundary to include large scale land-use change of biofuel production has challenged the viability of biofuels to meet climate change goals. This paper reviews some of the latest literature in biofuels LCA exemplary of this debate and discusses the distinctions between attributional and consequential models in biofuels. We also present a generalized boundary map that can be used to convey LCA system boundaries clearly and succinctly within both attributional and consequential LCA.

A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices

The application of in-place recycling techniques has emerged as a practical and effective way to enhance the sustainability of agency pavement management decisions for asphalt-surfaced pavements. However, the potential environmental benefits resulting from applying in-place recycling techniques have not been fully documented in the literature. This paper presents a comprehensive pavement life cycle assessment (LCA) model that extends the typical pavement LCA's system boundaries to include the environmental impacts resulting from the usage phase and the production of the energy sources. The results of the application of the pavement LCA model to a specific highway rehabilitation project in the state of Virginia showed that in-place recycling practices and an effective control of the pavement roughness can improve significantly the life cycle environmental performance of a pavement system.

Analyzing instability of industrial clustering techniques

The process life-cycle assessment (LCA) method has a crucial problem such that the LCA system boundary is freely decided by LCA practitioners, which consequently leads to truncation error and underestimation of life-cycle emission. This paper focuses on clustering methods (eigenvalue decomposition of the normalized Laplacian matrix and nonnegative matrix factorization of the normalized affinity matrix) which are useful in determining the LCA system boundary and investigates the instability of the clustering methods. The results indicate that, in cases involving a relatively small number of K-means repetitions (approximately 10), choosing the nonnegative matrix factorization method over the eigenvalue decomposition method yields smaller values of “normalized cut” value N cut (an indicator showing the goodness of network partitions), the benchmark indicating optimal cluster assignment. On the other hand, for a larger number of K-means repetitions (100 or more), neither method is universally superior to the other.

Energy decision making in a pulp and paper mill: selection of LCA system boundary

Background, aim, and scope North American pulp and paper mills are facing tremendous challenges, which may necessitate major mill modernizations. An example is process modification to reduce dependency on purchased power, which is an expensive resource. Such modifications may have environmental implications at the mills’ sites, on their product life cycle, and on other interconnected systems, and therefore, systematic tools such as life cycle assessment (LCA) need to be applied. Different LCA system boundary approaches can be used for such process design applications, and these approaches need to be compared to determine their respective benefits and limitations in this context. This study compares setting the system boundary according to a cradle-to-gate approach [attributional LCA (ALCA)] and a system expansion [consequential LCA (CLCA)] approach using a case study, which deals with implementing cogeneration and increased de-inked pulp production at an integrated newsprint mill.