End-of-life modelling in life cycle assessment—material or product-centred perspective?

Purpose

End-of-life (EoL) modelling in life cycle assessment has already been broadly discussed within several studies. However, no consensus has been achieved on how to model recycling in LCA, even though several approaches have been developed. Within this paper, results arising from the application of two new EoL formulas, the product environmental footprint (PEF) and the multi-recycling-approach (MRA) ones, are compared and discussed. Both formulas consider multiple EoL scenarios such as recycling, incineration and landfill.

Methods

The PEF formula has been developed within the PEF programme whose intent is to define a harmonized methodology to evaluate the environmental performance of products. The formula is based on a 50:50 allocation approach, as burdens and benefits associated with recycling are accounted for a 50% rate. The MRA formula has been developed to change focus from products to materials. Recycling cycles and material losses over time are considered with reference to material pools. Allocation between systems is no longer needed, as the actual number of potential life cycles for a certain material is included in the calculation. Both the approaches have been tested within two case studies.

Results and discussion

Methodological differences could thereof be determined, as well as applicability concerns, due to the type of data required for each formula. As far as the environmental performance is concerned, impacts delivered by MRA are lower than those delivered by PEF for aluminium, while the opposite happens for plastic and rubber due to the higher share of energy recovery accounted in PEF formula. Stainless steel impacts are almost the same.

Conclusions and recommendations

The application of the two formulas provides some inputs for the EoL dilemma in LCA. The use of a wider perspective, better reflecting material properties all over the material life cycle, is of substantial importance to properly represent recycling situations. In MRA, such properties are treated and less data are required compared to the PEF formula. On the contrary, the PEF model better accommodates the modelling of products whose materials, at end of life, can undertake the route of recycling or recovery (or landfill), depending on country-specific EoL management practices. However, its application requires more data.

     

Development of a social impact assessment methodology for recycling systems in low-income countries

Purpose

Informal recycling is one of the most significant activities within waste management systems in low-income countries. The main aspect of a number of recently implemented waste management systems has been to organise the informal recycling sector. The implementation of formalisation is expected to eliminate social problems related to the informal sector, but this has not been precisely measured and evaluated. A lack of methodology to assess social impacts persists, as does the comparison of different formalisation approaches. The goal of this work is to develop a methodological procedure for assessing the contribution of formalised recycling systems in low-income countries in terms of social impacts, in comparison with informal systems.

Methods

Some existing social assessment approaches were evaluated by a review of literature. This investigation focuses on the development of the social life cycle assessment approach, the analysed social aspects, proposed indicators and characterisation models within this framework.

Results and discussion

This study proposes an approach for the social assessment of recycling systems based on formalisation approaches in low-income countries oriented towards the social life cycle assessment methodology (sLCA). The approach developed considers 3 social impact categories, 9 social subcategories and 26 semi-quantitative indicators for the assessment of the social impacts on formalised recyclers. It includes a characterisation procedure that takes into consideration the application of a score system and the calculation of average scores at both the indicator and subcategory levels.

Conclusions

This research shows that it would be feasible to apply a sLCA-based methodology to evaluate recycling systems based on formalisation of the informal sector. The impact categories and subcategories identified represent the social problems of informal recyclers. The 26 semi-quantitative indicators and the proposed characterisation approach attempt to measure the social impacts that currently are only qualitatively assumed. The applicability and validation of the indicators and characterisation procedure will be determined by further research. The methodology developed will be tested using data from three recycling systems in Peruvian cities.     

Comparative LCA of treatment options for US scrap tires: material recycling and tire-derived fuel combustion

Purpose

This life cycle assessment (LCA) study compares two prevalent end-of-life (EOL) treatment methods for scrap tires: material recycling and energy recovery. The primary intended use of the study results is to inform stakeholders of the relative environmental burdens and trade-offs associated with these two EOL vehicle tire treatment methods. The study supports prioritization of the waste treatment hierarchy for this material stream in the US.

Methods

This LCA compares (1) material recycling through ambient-temperature mechanical processing and (2) energy recovery through co-incineration of both whole and preprocessed scrap tires at a cement kiln. The avoided burden recycling methodology reflects the substitution of virgin synthetic rubber used in asphalt modification with the ground tire rubber from material recycling and the substitution of conventional kiln fuels with the tire-derived fuel (TDF). Both attributional (ALCA) and consequential (CLCA) methodologies are used: the ALCA assesses the environmental profiles of the treatment methods and the CLCA examines the potential effects of shifting more scrap tires to material recycling. The attributional portion of the LCA study was conducted in accordance with ISO standards 14044 series.

Results

The results in both methodological approaches indicate that the material recycling scenario provides greater impact reductions than the energy recovery scenario in terms of the examined environmental impact potentials: energy demand, iron ore consumption, global warming potential, acidification, eutrophication, smog formation, and respiratory effects. The additional impact reductions from material recycling are significant, and the establishment of new infrastructure required for a shift to material recycling incurs relatively insignificant burdens. Sensitivity analyses indicate that this conclusion does not change for (1) a range of TDF heating values, (2) a decrease in the mixed scrap tire rubber-to-steel composition ratio, (3) two alternative electricity grid fuel mixes with higher and lower carbon dioxide emission rankings than that of the baseline scenario, or (4) a comparison of material recycling to energy recovery when TDF is used in pulp and paper mills instead of cement kilns.

Conclusions

These results provide a basis for more informed decision-making when prioritizing scrap tire waste treatment hierarchy.     

Consequential life cycle assessment: a review

Purpose  

Over the past two decades, consequential life cycle assessment (CLCA) has emerged as a modeling approach for capturing environmental impacts of product systems beyond physical relationships accounted for in attributional LCA (ALCA). Put simply, CLCA represents the convergence of LCA and economic modeling approaches.     

REACH and LCA—methodological approaches and challenges

Purpose  

This paper discusses issues associated with the research question: What are the similarities and differences between the REACH and life cycle assessment (LCA) approaches, and how can synergies between these two approaches be exploited to achieve environmental improvements in a holistic perspective?     

Life cycle assessment of construction materials: the influence of assumptions in end-of-life modelling

Purpose

The nature of end-of-life (EoL) processes is highly uncertain for constructions built today. This uncertainty is often neglected in life cycle assessments (LCAs) of construction materials. This paper tests how EoL assumptions influence LCA comparisons of two alternative roof construction elements: glue-laminated wooden beams and steel frames. The assumptions tested include the type of technology and the use of attributional or consequential modelling approaches.

Methods

The study covers impact categories often considered in the construction industry: total and non-renewable primary energy demand, water depletion, global warming, eutrophication and photo-chemical oxidant creation. The following elements of the EoL processes are tested: energy source used in demolition, fuel type used for transportation to the disposal site, means of disposal and method for handling allocation problems of the EoL modelling. Two assumptions regarding technology development are tested: no development from today’s technologies and that today’s low-impact technologies have become representative for the average future technologies. For allocating environmental impacts of the waste handling to by-products (heat or recycled material), an attributional cut-off approach is compared with a consequential substitution approach. A scenario excluding all EoL processes is also considered.

Results and discussion

In all comparable scenarios, glulam beams have clear environmental benefits compared to steel frames, except for in a scenario in which steel frames are recycled and today’s average steel production is substituted, in which impacts are similar. The choice of methodological approach (attributional, consequential or fully disregarding EoL processes) does not seem to influence the relative performance of the compared construction elements. In absolute terms, four factors are shown to be critical for the results: whether EoL phases are considered at all, whether recycling or incineration is assumed in the disposal of glulam beams, whether a consequential or attributional approach is used in modelling the disposal processes and whether today’s average technology or a low-impact technology is assumed for the substituted technology.

Conclusions

The results suggest that EoL assumptions can be highly important for LCA comparisons of construction materials, particularly in absolute terms. Therefore, we recommend that EoL uncertainties are taken into consideration in any LCA of long-lived products. For the studied product type, LCA practitioners should particularly consider EoL assumptions regarding the means of disposal, the expected technology development of disposal processes and any substituted technology and the choice between attributional and consequential approaches.     

The influence of durability and recycling on life cycle impacts of window frame assemblies

Purpose

A set of comparative life cycle assessment case studies were undertaken to explore key issues relating to the environmental impacts of building materials. The case studies explore modeling practice for long-life components by investigating (1) recycled content and end-of-life recycling scenarios and (2) service life and maintenance scenarios. The study uses a window unit frames as the object of comparison, allowing for exploration of multiple materials and assembly techniques.

Methods

Four window frame types were compared: aluminum, wood, aluminum-clad wood, and unplasticized PVC (PVCu). These used existing product life cycle inventory data which included primary frame material, coatings, weather stripping sealants, but not glazing. The functional unit was a window frame required to produce 1 m² of visible glazing, with similar thermal performance over a building lifespan of 80 years. The frames were compared using both the end-of-life and recycled content methods for end-of-life scenarios. The models were also tested using custom-use scenarios.

Results and discussion

Well-maintained aluminum window frames proved to be the least impactful option across all categories, in large part due to the credits delivered from recycling and expectations of long-life. Wood window frames had the least variability associated with maintenance and durability. The global warming potential (GWP) of a moderately maintained aluminum assembly was found to be 68 % less than PVCu and 50 % less than aluminum-clad wood. Using a long-life scenario, wood windows were found to have a 7 % lower GWP than the long-life scenario for aluminum-clad woods. Moderately and well-maintained aluminum windows require less energy to be produced and maintained over their lifetime than any of the wood scenarios. Expectations of service life proved to be the most important factor in considering environmental impact of frame materials.

Conclusions

The research shows significant gaps in available data—such as average realized life expectancies of common building components—while further underscoring that recycling rates are a driving factor in the environmental impact of aluminum building products. A modeling shift from the recycled content method to the end-of-life recycling method should promote goals of material recovery over pursuit of material with high recycled content. Hybrid methods, such as the use of Module D, may bridge the divide between these two approaches by providing due credit for use of recycled material, while supporting a design for recycling ethos. Further research is needed on how design and construction decisions affect collection and recovery rates in practice.

     

Life cycle assessment of carbon fiber-reinforced polymer composites

Purpose  

The use of carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles; however energy intensity and cost remain major barriers to the wide-scale adoption of this material for automotive applications. This study determines the relative life cycle benefits of two precursor types (conventional textile-type acrylic fibers and renewable-based lignin), part manufacturing technologies (conventional SMC and P4), and a fiber recycling technology.     

Application of a methodology for the social life cycle assessment of recycling systems in low income countries: three Peruvian case studies

Purpose

In a previous phase of this work, a methodology oriented towards social Life Cycle Assessment (sLCA) was developed to assess the social impact of formalised recycling systems in low income countries. To support this, a literature review of social impact assessment methodologies was carried out incorporating the social issues of both the informal and the implemented, formal recycling approaches. The goal of this study is to determine the feasibility of applying this methodology by assessing the current social impacts of three Peruvian recycling systems based on two formalisation approaches. A further goal is to identify and measure the social impacts of the formalisation procedures, thereby confirming or rebutting the expectations and forecasts of organisations (NGOs, Local Authorities, Ministries & Business) involved in the implementation.

Methods

The methodology developed was applied to three Peruvian recycling systems which had been formalised using two different approaches. One approach utilizes cooperation with recyclers’ associations and the second one, operated by the municipality uses formalised recyclers as employees. Interviews were conducted with local recycling system stakeholders in order to collect data to assess fulfilment of the social criteria. Three impact categories and 9 subcategories were analysed using 26 indicators. To transform the qualitative information into numerical values, a score system 1 or 0 for the fulfilment or non-fulfilment of social criteria was applied. After obtaining the indicators’ average scores, further characterisation by social impact subcategory was effected. The final scores for the subcategories show the fulfilment or otherwise of all social criteria related to the subcategory.

Results and discussion

The assessment substantiates similar negative impacts of both formalisation approaches for the social subcategories discrimination, recognised employment relationships and fulfilment of social benefit, physical working conditions and education. The formalisation based on cooperation with recyclers’ associations reveals a positive social impact for freedom of association and collective bargaining, psychological working conditions and social acceptance whereas the method operated by the municipality scores better for working time and minimum, fair incomes. Regarding the methodology, no difficulties were detected in applying the indicators.

Conclusions

It can be concluded that although sLCA was originally used to analyse products and production processes, it is feasible to adapt it for the social assessment of recycling systems based on formalisation of the informal sector in low income countries. A comparison of current social impacts between different formalisation approaches using this methodology is also viable. A further conclusion is that it is feasible to measure the social impacts of formalisation approaches using the selected indicators and characterisation procedure. Social issues such as anti-discrimination policies, employment terms, payment of social benefits, preventive policies, occupational and health training and adult education can be improved following the evaluation.     

The search for an appropriate end-of-life formula for the purpose of the European Commission Environmental Footprint initiative

Purpose

This paper explains in details the rationale behind the choice of the end-of-life allocation approach in the European Commission Product Environmental Footprint (PEF) and Organisational Environmental Footprint (OEF) methods. The end-of-life allocation formula in the PEF/OEF methods aims at enabling the assessment of all end-of-life scenarios possible, including recycling, reuse, incineration (with heat recovery) and disposal for both open- and closed-loop systems in a consistent and reproducible way. It presents how the formula builds on existing standards and how and why it deviates from them.

Methods

Various end-of-life allocation approaches and formulas, mainly taken not only from/based on existing environmental impact assessment methods and/or standards but also one original linearly degressive approach, were analysed against a predetermined set of criteria, reflecting the overall aim of the PEF/OEF methods. This set of criteria is physical realism, distribution of burdens and benefits in a product cascade system and applicability. Besides the qualitative analysis, the various formulas were implemented for several products and for different scenarios regarding recycled content and recyclability to check the robustness of the outcomes, exemplary expressed for the Global Warming Potential impact category.

Results and discussion

As reaching physical realism was impossible at both the product and overall product cascade system level by any of the end-of-life approaches analysed, one of both had to be prioritised. The paper explains in details why a product level approach was preferred in the context of the PEF/OEF methods. In consequence, allocation of the end-of-life processes which are related to more than one product in a product cascade system is needed and should be carefully considered as it has a major influence on the results and decision taking.

Conclusions

A formula taking into account the number of recycling cycles of a material was identified as preferred to reach physical realism and to allocate burdens and benefits of repeatedly recycling of a material over the different products in a product cascade system. However, this approach was not selected for the PEF/OEF methods as data on the number of recycling cycles was insufficiently available (for the time being) for all products on the market and hence fails the criterion of “applicability”. This explains why, instead, a formula based on the 50:50 approach—allocating shared end-of-life processes equally between the previous and subsequent product—was selected for the PEF/OEF methods.

     

Life cycle assessment of a steam thermolysis process to recover carbon fibers from carbon fiber-reinforced polymer waste

Purpose

Carbon fibers have been widely used in composite materials, such as carbon fiber-reinforced polymer (CFRP). Therefore, a considerable amount of CFRP waste has been generated. Different recycling technologies have been proposed to treat the CFRP waste and recover carbon fibers for reuse in other applications. This study aims to perform a life cycle assessment (LCA) to evaluate the environmental impacts of recycling carbon fibers from CFRP waste by steam thermolysis, which is a recycling process developed in France.

Methods

The LCA is performed by comparing a scenario where the CFRP waste is recycled by steam-thermolysis with other where the CFRP waste is directly disposed in landfill and incineration. The functional unit set for this study is 2 kg of composite. The inventory analysis is established for the different phases of the two scenarios considered in the study, such as the manufacturing phase, the recycling phase, and the end-of-life phase. The input and output flows associated with each elementary process are standardized to the functional unit. The life cycle impact assessment (LCIA) is performed using the SimaPro software and the Ecoinvent 3 database by the implementation of the CML-IA baseline LCIA method and the ILCD 2011 midpoint LCIA method.

Results and discussion

Despite that the addition of recycling phase produces non-negligible environmental impacts, the impact assessment shows that, overall, the scenario with recycling is less impactful on the environment than the scenario without recycling. The recycling of CFRP waste reduces between 25 and 30% of the impacts and requires about 25% less energy. The two LCIA methods used, CML-IA baseline and ILCD 2011 midpoint, lead to similar results, allowing the verification of the robustness and reliability of the LCIA results.

Conclusions

The recycling of composite materials with recovery of carbon fibers brings evident advantages from an environmental point of view. Although this study presents some limitations, the LCA conducted allows the evaluation of potential environmental impacts of steam thermolysis recycling process in comparison with a scenario where the composites are directly sent to final disposal. The proposed approach can be scaled up to be used in other life cycle assessments, such as in industrial scales, and furthermore to compare the steam thermolysis to other recycling processes.

     

Prospective CO<Subscript>2</Subscript> emissions from energy supplying systems: photovoltaic systems and conventional grid within Spanish frame conditions

Background, aim, and scope  

In order to assess the environmental sustainability of a novel wastewater treatment process based on power an electrochemical reactor by photovoltaic solar modules (photovoltaic solar electrochemical oxidation), a life cycle approach was considered to quantify the CO₂ equivalent (CO₂-eq.) emissions coming from the two supplying power systems to the electrochemical process: conventional grid power or photovoltaic solar power under Spain frame conditions.     

Are we still keeping it “real”? Proposing a revised paradigm for recycling credits in attributional life cycle assessment

Purpose

End-of-life (EoL) recycling poses a challenge to many practitioners today due to the availability of different calculation approaches and the lack of scientific consensus, which is fueled by academic research and vested industry interests alike. One of the main challenges in EoL modeling is the credible calculation of the appropriate recycling credit in open-loop and closed-loop situations.

Methods

We believe that part of the challenge is caused by a lack of understanding of the underlying recycling paradigm, which refers to the meaning that is assigned to the recycling credit. Referred to as “system expansion through substitution” and “future displacement of primary production,” the two predominant paradigms are delineated from each other followed by a discussion of their remaining challenges.

Results and discussion

Based on these considerations, we propose a revised paradigm based on embodied burdens that is able to alleviate many of the most pressing issues associated with material recycling in attributional life cycle assessment.

Conclusions

With this discussion paper, we look forward to a productive and lively debate on the matter.

     

Metals recycling maps and allocation procedures in life cycle assessment

Goal, scope, and background  

The aim of this work is to present guidance on the application of ISO 14044 to allocation procedures for metal recycling. As such, graphical patterns of metal recycling and generic “rules” for metal recycling maps are presented. The results are intended to be useful in assessing and validating the suitability of allocation procedures for metal recycling in the context of life cycle assessment (LCA) and assist in the understanding of metals flow patterns in product systems. LCA uses a product-focus; therefore, the perspective here is on recycling metals in post-consumer products. The discussions, analysis, and illustrations in this paper emphasize old (post-consumer) scrap and do not detail flows of new (post-manufacturing, pre-consumer) or prompt (internal) scrap. The work included participation and review from International Council on Mining and Metals, the Nickel Institute, the International Copper Association, the International Zinc Association, worldsteel (formerly International Iron and Steel Institute), and the International Aluminium Institute.     

Steel’s recyclability: demonstrating the benefits of recycling steel to achieve a circular economy

Purpose

In a world where the population is expected to peak at around 9 billion people in the next 30 to 40 years, carefully managing our finite natural resources is becoming critical. We must abandon the outdated ‘take, make, consume and dispose’ mentality and move toward a circular economy model for optimal resource efficiency. Products must be designed for reuse and remanufacturing, which would reduce significant costs in terms of energy and natural resources.

Methods

To measure progress in achieving a circular economy, we need a life cycle approach that measures the social, economic and environmental impact of a product throughout its full life cycle—from raw material extraction to end-of-life (EoL) recycling or disposal. Life cycle thinking must become a key requirement for all manufacturing decisions, ensuring that the most appropriate material is chosen for the specific application, considering all aspects of a products’ life. The steel industry has been developing LCI data for 20 years. This is used to assess a product’s environmental performance from steel production to steel recycling at end-of-life. The steel industry has developed a methodology to show the benefits of using recycled steel to make new products. Using recycled materials also carries an embodied burden that should be considered when undertaking a full LCA.

Results and discussion

The recycling methodology is in accordance with ISO 14040/44:2006 and considers the environmental burden of using steel scrap and the benefit of scrap recycling from end-of-life products. It considers the recycling of scrap into new steel as closed material loop recycling, and thus, recycling steel scrap avoids the production of primary steel. The methodology developed shows that for every 1 kg of steel scrap that is recycled at the end of the products life, a saving of 1.5 kg CO₂-e emissions, 13.4 MJ primary energy and 1.4 kg iron ore can be achieved. This equates to 73, 64 and 90 %, respectively, when compared to 100 % primary production.

Conclusions

Incorporating this recycling methodology into a full LCA demonstrates how the steel industry is an integral part of the circular economy model which promotes zero waste; a reduction in the amount of materials used and encourages the reuse and recycling of materials.

     

GEM System: automatic prototyping of cell-wide metabolic pathway models from genomes

Background  

Successful realization of a "systems biology" approach to analyzing cells is a grand challenge for our understanding of life. However, current modeling approaches to cell simulation are labor-intensive, manual affairs, and therefore constitute a major bottleneck in the evolution of computational cell biology.     

INCITE: A randomised trial comparing constraint induced movement therapy and bimanual training in children with congenital hemiplegia

Background  

Congenital hemiplegia is the most common form of cerebral palsy (CP) accounting for 1 in 1300 live births. These children have limitations in capacity to use the impaired upper limb and bimanual coordination deficits which impact on daily activities and participation in home, school and community life. There are currently two diverse intensive therapy approaches. Traditional therapy has adopted a bimanual approach (BIM training) and recently, constraint induced movement therapy (CIMT) has emerged as a promising unimanual approach. Uncertainty remains about the efficacy of these interventions and characteristics of best responders. This study aims to compare the efficacy of CIMT to BIM training to improve outcomes across the ICF for school children with congenital hemiplegia.     

Design of recycling system for poly(methyl methacrylate) (PMMA). Part 1: recycling scenario analysis

Introduction

In this series of papers, we present a poly(methyl methacrylate) (PMMA) recycling system design based on environmental impacts, chemical hazards, and resource availability. We evaluated the recycling system by life cycle assessment, environment, health, and safety method, and material flow analysis.

Purpose

Previous recycling systems have not focused on highly functional plastics such as PMMA, partly because of lower available volumes of waste PMMA compared with other commodity plastics such as polyethylene or polypropylene. However, with the popularization of PMMA-containing products such as liquid crystal displays, the use of PMMA is increasing and this will result in an increase in waste PMMA in the future. The design and testing of recycling systems and technologies for treating waste PMMA is therefore a high research priority. In this study, we analyze recycling of PMMA monomers under a range of scenarios.

Methods

Based on the differences between PMMA grades and their life cycles, we developed a life cycle model and designed a range of scenarios for PMMA recycling. We obtained monomer recycling process inventory data based on the operational results of a pilot plant. Using this process inventory data, we quantified life cycle greenhouse gas (LC-GHG) emissions and fossil resource consumption, and we calculated the LIME single index.

Results and discussion

PMMA produces more than twice the amount of GHG emissions than other commodity resins. Through scenario and sensitivity analyses, we demonstrated that monomer recycling is more effective than mechanical recycling. Operational modifications in the monomer recycling process can potentially decrease LC-GHG emissions.

Conclusions

Highly functional plastics should be recycled while maintaining their key functions, such as the high transparency of PMMA. Monomer recycling has the potential to achieve a closed-loop recycling of PMMA.     

Broadly sampled multigene trees of eukaryotes

Background  

Our understanding of the eukaryotic tree of life and the tremendous diversity of microbial eukaryotes is in flux as additional genes and diverse taxa are sampled for molecular analyses. Despite instability in many analyses, there is an increasing trend to classify eukaryotic diversity into six major supergroups: the 'Amoebozoa', 'Chromalveolata', 'Excavata', 'Opisthokonta', 'Plantae', and 'Rhizaria'. Previous molecular analyses have often suffered from either a broad taxon sampling using only single-gene data or have used multigene data with a limited sample of taxa. This study has two major aims: (1) to place taxa represented by 72 sequences, 61 of which have not been characterized previously, onto a well-sampled multigene genealogy, and (2) to evaluate the support for the six putative supergroups using two taxon-rich data sets and a variety of phylogenetic approaches.     

LCA of the timber sector in Ghana: preliminary life cycle impact assessment (LCIA)

Purpose  

Most life cycle impact assessment (LCIA) approaches in life cycle assessment (LCA) are developed for western countries. Their LCIA approaches and characterization methodologies for different impact categories may not be necessarily relevant to African environmental conditions and particularly not for the timber sector in Ghana. This study reviews the relevance of existing impact categories and LCIA approaches, and uses the most relevant for the timber sector of Ghana.