A new hybrid method for reducing the gap between WTW and LCA in the carbon footprint assessment of electric vehicles

Purpose

The well-to-wheel (WTW) methodology is widely used for policy support in road transport. It can be seen as a simplified life cycle assessment (LCA) that focuses on the energy consumption and CO₂ emissions only for the fuel being consumed, ignoring other stages of a vehicle’s life cycle. WTW results are therefore different from LCA results. In order to close this gap, the authors propose a hybrid WTW+LCA methodology useful to assess the greenhouse gas (GHG) profiles of road vehicles.

Methods

The proposed method (hybrid WTW+LCA) keeps the main hypotheses of the WTW methodology, but integrates them with LCA data restricted to the global warming potential (GWP) occurring during the manufacturing of the battery pack. WTW data are used for the GHG intensity of the EU electric mix, after a consistency check with the main life cycle impact (LCI) sources available in literature.

Results and discussion

A numerical example is provided, comparing GHG emissions due to the use of a battery electric vehicle (BEV) with emissions from an internal combustion engine vehicle. This comparison is done both according to the WTW approach (namely the JEC WTW version 4) and the proposed hybrid WTW+LCA method. The GHG savings due to the use of BEVs calculated with the WTW-4 range between 44 and 56 %, while according to the hybrid method the savings are lower (31–46 %). This difference is due to the GWP which arises as a result of the manufacturing of the battery pack for the electric vehicles.

Conclusions

The WTW methodology used in policy support to quantify energy content and GHG emissions of fuels and powertrains can produce results closer to the LCA methodology by adopting a hybrid WTW+LCA approach. While evaluating GHG savings due to the use of BEVs, it is important that this method considers the GWP due to the manufacturing of the battery pack.

     

Potential emission savings from refrigeration and air conditioning systems by using low GWP refrigerants

Purpose

Refrigeration and air conditioning systems have high, negative environmental impacts due to refrigerant charge leaks from the system and their corresponding high global warming potential. Thus, many efforts are in progress to obtain suitable low GWP alternative refrigerants and more environmentally friendly systems for the future. The system’s life cycle climate performance (LCCP) is a widespread metric proposed for the evaluation of the system’s environmental impact.

Methods

In this paper, the potential emission reductions in the commercial refrigeration and residential air conditioning systems, made possible by shifting towards more environmentally friendly refrigerants in the US, are presented. First, the current LCCP of the most common commercial refrigeration and residential air conditioning systems is calculated. Then, the LCCP of the baseline systems, when using the potential low GWP alternative refrigerants, is presented. This helps to determine the systems which have the highest potential for emission reductions.

Results and discussion

By shifting from the baseline refrigerants, R-404A and R-410A, to the suggested low GWP refrigerants, N-40 and L-41a, in the commercial refrigeration and residential HVAC systems, respectively, a combined drop of 30.43 % in the total emissions (i.e., total equivalent mass of emissions in kg CO_2eq) is obtained. This results from a 50.5 and 28.01 % drop in total emissions from supermarket refrigeration systems and residential air conditioning, respectively.

Conclusions

Shifting to lower GWP refrigerants in the refrigeration and air conditioning systems helps to reduce the total emissions and negative environmental impacts of these systems. Shifting to a secondary circuit commercial refrigeration system using N-40/L-40 and residential air conditioning and heat pump systems using L-41a helps in reducing the total emissions.

     

Methane oxidation,biogenic carbon,and the IPCC’s emission metrics. Proposal for a consistent greenhouse-gas accounting

Purpose

The fifth assessment report by the IPCC includes methane oxidation as an additional indirect effect in the global warming potential (GWP) and global temperature potential (GTP) values for methane. An analysis of the figures provided by the IPCC reveals they lead to different outcomes measured in CO₂-eq., depending on whether or not biogenic CO₂ emissions are considered neutral. In this article, we discuss this inconsistency and propose a correction.

Methods

We propose a simple framework to account for methane oxidation in GWP and GTP in a way that is independent on the accounting rules for biogenic carbon. An equation with three components is provided to calculate metric values, and its application is tested, together with the original IPCC figures, in a hypothetical example focusing on GWP100.

Results and discussion

The hypothetical example shows that the only set of GWP100 values consistently leading to the same outcome, regardless of how we account for biogenic carbon, is the one proposed in this article. Using the methane GWP100 values from the IPCC report results in conflicting net GHG emissions, thus pointing to an inconsistency.

Conclusions

In order to consistently discriminate between biogenic and fossil methane sources, a difference of 2.75 kg CO₂-eq. is needed, which corresponds to the ratio of the molecular weights of CO₂ and methane (44/16). We propose to correct the GWP and GTP values for methane accordingly.

     

Shale gas: a life-cycle perspective for UK production

Purpose

Following the boom of shale gas production in the USA and the decrease in the US gas prices, increasing interest in shale gas is developing in many countries holding shale reserves and exploration is already taking place in some EU countries, including the UK. Any commercial development of shale gas in Europe requires a broad environmental assessment, recognizing the different European conditions and legislations.

Methods

This study focuses on the UK situation and estimates the environmental impacts of shale gas using life-cycle assessment (LCA); the burdens of shale gas production in the UK are compared with the burdens of the current UK natural gas mix. The main focus is on the analysis of water impacts, but a broad range of other impact categories are also considered. A sensitivity analysis is performed on the most environmentally criticized operations in shale gas production, including flowback disposal and emission control, by considering a range of possible process options.

Results and discussion

Improper waste water management and direct disposal or spills of waste water to river can lead to high water and human ecotoxicity. Mining of the sand and withdrawal of the water used in fracking fluids determine the main impacts on water use and degradation. However, the water degradation of the conventional natural gas supply to the UK is shown to be even higher than that of shale gas. For the global warming potential (GWP), the handling methods of the emissions associated with the hydraulic fracturing influence the results only when emissions are vented. Finally, the estimated ultimate recovery of the well has the greatest impact on the results as well as the flowback ratio and flowback disposal method.

Conclusions

This paper provides insights to better understand the future development of shale gas in the UK. Adequate waste water management and emission handling significantly reduce the environmental impacts of shale gas production. Policy makers should consider that shale gas at the same time increases the water consumption and decreases the water degradation when compared with the gas mix supply. Furthermore, the environmental impacts of shale gas should be considered according to the low productivity that force the drilling and exploitation of a high number of wells.

     

Estimating the global warming emissions of the LCAXVII conference: connecting flights matter

Purpose

Conferences are an important element of scientific activity but can also be a major cause of environmental burden. With this in mind, we analysed the global warming emissions of the 2017 annual conference of the American Center for Life Cycle Assessment (ACLCA), in order to estimate the carbon footprint and identify potential ways to reduce it.

Methods

We used survey data from participants as well as literature sources to complete an attributional assessment of the greenhouse gas emissions per participant. A method to calculate the ‘ideal’ location is proposed, which can be used to identify ‘unreasonably’ distant conference locations.

Results and discussion

The average emissions per participant were found to be 952 kg CO_2eq, but with a large variability due to differences in travelled distance. Connecting flights were found to increase emissions up to 32% compared to direct flights, due to the increased number of take-offs and landings.

Conclusions

Results indicate that future studies should use distance-dependent flight emissions to increase the accuracy of the assessment. Some measures, such as meat-free menus, had a relatively minor contribution to emission reductions, but could be important as scientists advocating for the reduction of environmental burden should lead by example.

     

Life cycle assessment-based selection of a sustainable lightweight automotive engine hood design

Purpose

This study presents a life cycle assessment (LCA)-based sustainable and lightweight automotive engine hood design and compares the life cycle energy consumption and potential environmental impacts of a steel (baseline) automotive engine hood with three types of lightweight design: advanced high strength steel (AHSS), aluminum, and carbon fiber.

Methods

A “cradle-to-grave” LCA including the production, use, and end-of-life stages is conducted in accordance with the ISO 14040/14044 standards. Onsite data collected by Chinese automotive companies in 2015 are used in the assessment. The Cumulative Energy Demand v1.09 method is applied to evaluate cumulative energy demand (CED), and the International Panel on Climate Change 2013 100a method is used to estimate global warming potential (GWP 100a).

Results and discussion

Among the different lightweight designs for the engine hood, the aluminum design is the most sustainable and has the lowest CED and GWP (100a) from a life cycle perspective, which is based on a lifetime driving distance of approximately 150,000 km. In addition, the AHSS design is also sustainable and lightweight. The carbon fiber design results in higher CED and GWP (100a) values than the steel (baseline) design during the life cycle but results in the largest CED and GWP (100a) savings through waste material recycling. The AHSS design exhibits the best break-even distance based on CED and GWP (100a) within 150,000 km.

Conclusions

Sensitivity analysis results show that the lifetime driving distance and material recycling rate have the largest impacts on the overall CEDs and GWPs of the three lightweight designs.

     

Analysis of greenhouse gas emissions related to aluminium transport applications

Background, aim and scope

Climate change is a subject of growing global concern. Based on International Energy Agency (IEA 2004) research, about 19% of the greenhouse gas emissions from fuel combustion are generated by the transportation sector, and its share is likely to grow. Significant increases in the vehicles fleets are expected in particular in China, India, the Middle East and Latin America. As a result, reducing vehicle fuel consumption is most essential for the future. The reduction of the vehicle weight, the introduction of improved engine technologies, lower air friction, better lubricants, etc. are established methods of improving fuel efficiency, reducing energy consumption and greenhouse gas emissions. Continued progress will be required along all these fronts with light-weighting being one of the most promising options for the global transport sector. This paper quantifies greenhouse gas savings realised from light-weighting cars with aluminium based on life cycle assessment methodology. The study uses a pragmatic approach to assess mass reduction by comparing specific examples of components meeting identical performance criteria. The four examples presented in this analysis come from practical applications of aluminium. For each case study, the vehicle manufacturer has supplied the respective masses of the aluminium and the alternative component.

Material and methods

A full life cycle assessment with regards to greenhouse gas emissions and savings has been carried out for different aluminium applications in cars as compared to the same applications in steel or cast iron. The case studies reference real cases, where aluminium is actually used in series production. The studies are based on a greenhouse gas lifecycle model, which has been developed following the ISO standard 14040 framework. For each component, sensitivity analysis is applied to determine the impact of lifetime driving distance, driving characteristics (impact of air friction) and recycling rate.

Results

Life cycle results show that in automotive applications, each kilogram of aluminium replacing mild steel, cast iron or high strength steel saves, depending on the specific case (bumper and motor block of a compact car, front hood of a large family car, body-in white of a luxury car), between 13 and 20 kg of greenhouse gas emissions.

Discussion

The performed sensitivity analysis finds that even with ‘worst case’ scenarios savings are still significant.

Conclusions

The results not only demonstrate significant benefits of aluminium with regard to greenhouse gas savings but also show that these are very sensitive to variations of the recycling rate, the life-time driving distance and the driving behaviour.

Recommendations and perspectives

Good care is needed to gather life-cycle data and to make informed estimates, where no data are available. Furthermore, greenhouse gas savings for additional components should be calculated using this life cycle model to sustain the findings.

     

Comparative LCA of recycled and conventional concrete for structural applications

Purpose

Construction and demolition (C&D) waste recycling has been considered to be a valuable option not only for minimising C&D waste streams to landfills but also for mitigating primary mineral resource depletion. However, the potentially higher cement demand due to the larger surface of the coarse recycled aggregates challenges the environmental benefits of recycling concrete. Furthermore, it is unclear how the environmental impacts depend on concrete mixture, cement type, aggregates composition and transport distances.

Methods

We therefore analysed the life cycle impacts of 12 recycled concrete (RC) mixtures with two different cement types and compared it with corresponding conventional concretes (CC) for three structural applications. The RC mixtures were selected according to laws, standards and construction practice in Switzerland. We compared the environmental impacts of ready-for-use concrete on the construction site, assuming equal lifetimes for recycled and conventional concrete in a full life cycle assessment. System expansion and substitution are considered to achieve the same functionality for all systems.

Results and discussion

The results show clear (～30 %) environmental benefits for all RC options at endpoint level (ecoindicator 99 and ecological scarcity). The difference is mainly due to the avoided burdens associated to reinforcing steel recycling and avoided disposal of C&D waste. Regarding global warming potential (GWP), the results are more balanced and primarily depend on the additional amount of cement needed for RC. Above 22 to 40 kg additional cement per cubic metre of concrete, RC exhibits a GWP comparable to CC. Additional transport distances above 15 km for the RC options do result in environmental impacts higher than those for CC.

Conclusions

In summary, the current market mixtures of recycled concrete in Switzerland show significant environmental benefits compared to conventional concrete and cause similar GWP, if additional cement and transport for RC are limited.

     

Life cycle assessment of European anchovy (<Emphasis Type="Italic">Engraulis encrasicolus</Emphasis>) landed by purse seine vessels in northern Spain

Purpose

The main purpose of this article is to assess the environmental impacts associated with the fishing operations related to European anchovy fishing in Cantabria (northern Spain) under a life cycle approach.

Methods

The life cycle assessment (LCA) methodology was applied for this case study including construction, maintenance, use, and end of life of the vessels. The functional unit used was 1 kg of landed round anchovy at port. Inventory data were collected for the main inputs and outputs of 32 vessels, representing a majority of vessels in the fleet.

Results and discussion

Results indicated, in a similar line to what is reported in the literature, that the production, transportation, and use of diesel were the main environmental hot spots in conventional impact categories. Moreover, in this case, the production and transportation of seine nets was also relevant. Impacts linked to greenhouse gas (GHG) emissions suggest that emissions were in the upper range for fishing species captured with seine nets and the value of global warming potential (GWP) was 1.44 kg CO₂ eq per functional unit. The ecotoxicity impacts were mainly due to the emissions of antifouling substances to the ocean. Regarding fishery-specific categories, many were discarded given the lack of detailed stock assessments for this fishery. Hence, only the biotic resource use category was computed, demonstrating that the ecosystems’ effort to sustain the fishery is relatively low.

Conclusions

The use of the LCA methodology allowed identifying the main environmental hot spots of the purse seining fleet targeting European anchovy in Cantabria. Individualized results per port or per vessel suggested that there are significant differences in GHG emissions between groups. In addition, fuel use is high when compared to similar fisheries. Therefore, research needs to be undertaken to identify why fuel use is so high, particularly if it is related to biomass and fisheries management or if skipper decisions could play a role.

     

Mapping the impacts of farmed Scottish salmon from a life cycle perspective

Purpose

The European Union relies on seafood imports to supply growing demand that European production has failed to meet. Politically motivated media reports have denigrated competing imports in favour of local production. While life cycle assessment (LCA) measures global impact of value chains, it often fails to contextualise them. Using LCA, this article takes farmed Scottish Atlantic salmon as a case study of “local” production to identify and map the contributions to global environmental impact.

Methods

Data on the Scottish salmon value chain were collected by structured survey from a large international feed mill, six farms and a major processor. Secondary data were collected from available literature on feed ingredients and background data from EcoInvent2.2. A mid-point CML2001 approach was adopted focussing on global warming potential (GWP), acidification potential (AP), eutrophication potential, ozone depletion potential, photo-chemical oxidation potential, consumptive water use and land use. Results were displayed as contribution analyses of materials and processes and mapped geographically using area plots.

Results and discussion

Far from being a “locally” produced commodity, nearly 50% of the feed ingredients were sourced from South America and less than 25% originated in the UK. It was found that over 90% of the impact to farm-gate was embodied in feed, apart from eutrophication potential which was high at the farm from direct nitrogenous emissions into the marine environment. The majority of impacts do not occur in Scotland, particularly for land and water use, which occur at a more geographically significant level than GWP or AP, which are more global or regional impacts, respectively. High GWP emissions from vegetable-based ingredients were related to soil management and energy intensive processes such as wet milling to produce gluten from wheat and maize, sunflower and rapeseed oil processing.

Conclusions

The results show that in an age of globalised commodity trading, concerns around “local” production are often misleading. As consumers try to make more responsible purchase choices, they may be misled over the global impacts their choices are having. There are clearly trade-offs between different feed ingredients, especially regarding substitution of marine ingredients with those of vegetable origin. While marine ingredients perform comparatively well, they are highly limited, and biodiversity impacts of different ingredients are less clear and difficult to compare.

     

Life cycle assessment of biodiesel production from beef tallow in Brazil

Purpose

Renewable energy sources, particularly biofuels, are being promoted as possible solutions to address global warming and the depletion of petroleum resources. In this context, biodiesel is a solution to the growing demand for renewable fuels. Beef tallow is the second leading raw material after soybean oil used in biodiesel production in Brazil. Evaluating and addressing the environmental impacts of beef tallow biodiesel are of great importance for its life cycle impact assessment (LCIA).

Methods

Inventory data on tallow and biodiesel production were collected from the literature and from a primary data source provided by a Brazilian biodiesel plant. The modeled system represents the Brazilian reality for the 2005–2015 decade. Subsequently, the environmental impacts of beef tallow biodiesel production were characterized for a selection of environmental impact indicators: global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), and water footprint (assessed based on blue water use (BWU) and blue water consumption (BWC) indicators). From the characterization of these environmental burdens, the main sources of environmental impact were evaluated. Sensitivity analysis was conducted to verify the influence of key parameters (emission factor, energy consumption, and prices) on changes in the environmental load of beef tallow biodiesel.

Results and discussion

Carbon flux results indicate that beef tallow biodiesel production acts as a carbon source. Namely, pasture carbon uptake (91% of all carbon input) is lower than combined biogenic and fossil CO₂ emissions, which are controlled by cattle enteric fermentation as methane (72%) and by thermal energy processes (25%). Otherwise, thermal energy production accounts for 80% of total AP emissions, and cattle urine and manure are responsible for 70% of total EP emissions. The BWC and BWU water footprints of the whole process are controlled by electricity usage, which was greater than 90% for each indicator due to the high proportion of total energy (70%) derived from hydropower in Brazil. The environmental burden from transportation is minimal compared to other processes. Tallow biodiesel GWP can be improved if the carbon uptake potential from grass and low fertilizer utilization are accurately considered, as observed in the sensitivity analysis. For each MJ of beef tallow biodiesel produced, 4.6 g of CO₂ is released to the atmosphere.

Conclusions

Methane emissions, mainly due to cattle enteric fermentation, and thermal energy processes at the industrial units were the main sources of environmental GWP, AP, and EP impacts. Otherwise, water footprint indicators were associated with the high proportion of total energy derived from hydropower in Brazil.

     

Metabolomic profiling of maternal hair suggests rapid development of intrahepatic cholestasis of pregnancy

Introduction

Intrahepatic cholestasis of pregnancy (ICP) is a common maternal liver disease; development can result in devastating consequences, including sudden fetal death and stillbirth. Currently, recognition of ICP only occurs following onset of clinical symptoms.

Objective

Investigate the maternal hair metabolome for predictive biomarkers of ICP.

Methods

The maternal hair metabolome (gestational age of sampling between 17 and 41 weeks) of 38 Chinese women with ICP and 46 pregnant controls was analysed using gas chromatography–mass spectrometry.

Results

Of 105 metabolites detected in hair, none were significantly associated with ICP.

Conclusion

Hair samples represent accumulative environmental exposure over time. Samples collected at the onset of ICP did not reveal any metabolic shifts, suggesting rapid development of the disease.

     

Do green wooden composites using lignin-based binder have environmentally benign alternatives? A preliminary LCA case study in China

Purpose

Nowadays, formaldehyde emissions from petroleum-based adhesives contribute considerably to environmental problems and are a constraint to the development of forest-based industries. Although many efforts are being made to develop new lignin-based adhesives for panels, very few studies were carried out via life cycle assessment (LCA). This study aims to assess the life cycle of green wooden composites by using hybrid-modified ammonium lignosulfonate (HMAL) as the binder and investigate the possibility of lignin-based binder to be a good alternative.

Methods

This study is a step further of the previous work conducted on HMAL as an alternative binder for medium-density fiberboard (MDF) or, in other words, the wooden composite made from HMAL and wood fiber (WF). LCA was carried out to assess the environmental impacts during the life cycle of the new manufacturing process of HMAL/WF production using ReCiPe 1.08 Endpoint and IPCC global warming potential (GWP) method built into the GaBi version 6.0 software. The production system involved two subsystems: raw material supply and board manufacture. Meanwhile, a comparative LCA of conventional MDF, with three main damage categories and GWP, was also carried out.

Results and discussion

The hydrogen peroxide (H₂O₂) production, electricity, and the HMAL/WF manufacturing stages had the greatest environmental impact. The comparative results pointed out that HMAL/WF production is environmentally superior to conventional MDF in general. Due to the environmental impacts associated with the HMAL binder, a sensitivity analysis was carried out. Suggestions were made for a cleaner production, in which the H₂O₂ dose was reduced to 24 wt%.

Conclusions

H₂O₂ use, energy, and electricity consumption are main contributors to most impact categories, which help us to find the potential improvements of sustainability, choose the appropriate HMAL technology, and optimize the HMAL/WF system. Feasible production processes and life cycle costs are factors that still need to be studied.

     

Role of e-reader adoption in life cycle greenhouse gas emissions of book reading activities

Purpose

The purpose of this research is to identify at what extent e-book reading reduces global warming potential (GWP) of book reading activities relative to that of reading only paper books. Past studies assume e-books and paper books are interchangeable during consumption, but adopting e-book reading can alter reading patterns in reality. This research comparatively assessed the GWP of reading only paper books and that of reading pattern of after e-reader adoption of consumer segments.

Methods

We computed GWP of book reading activities of consumer segments that include a life cycle of paper book, e-book, and e-book reading device. Two e-book devices were considered: a designated e-book device (e-reader) and a tablet. The functional units are book reading activities per person and per person-book, which account the number of books purchased or acquired and the reading hours per person. We collected data through a web survey in the USA. Consumer segmentation was performed by analyzing the level of importance in the aspects of book reading activities as a measurement variable. To observe the changes in reading patterns upon e-reader adoption within the same population, we conducted a 3-month social experiment involving e-readers in the USA.

Results and discussion

Adopting e-readers was discovered to reduce both the GWP per person and the GWP per person-book of book reading activities. The GWP of e-books read with an e-reader and the GWP of paper books were found to break even at 4.7 books per year, provided consumers read less than 11 h a day. According to the web survey, e-reader users purchase more than seven e-books annually on average, which resulted in a smaller GWP per person-book relative to that of one paper book. Furthermore, the GWP per person in the social experiment was smaller for e-reader adopters than those who only read paper books because they substituted e-books for paper books. The overall book reading volume remains unchanged upon e-reader adoption.

Conclusions

Adoption of e-readers reduces the GWP from book reading activities with only paper books, provided more than 4.7 paper books are substituted by e-books annually, and provided consumers’ total consumption volume remain unchanged. E-reader adopters read sufficient number of e-books to break even with paper books. However, most e-reader adopters are yet to fully abandon paper books for e-books. Analyzing the differences in the reading experience between e-books and paper books is a future task.

     

Evaluating the carbon footprint of the cork sector with a dynamic approach including biogenic carbon flows

Purpose

The aim of the present study is to assess the influence of two different attributional life cycle assessment (LCA) approaches, namely static LCA (sLCA) and dynamic LCA (dLCA), through their application to the calculation of the carbon footprint (CF) of the entire cork sector in Portugal. The effect of including biogenic carbon sequestration and emissions is considered as well.

Methods

sLCA is often described as a static tool since all the emissions are accounted for as if occurring at the same time which may not be the case in reality for greenhouse gases. In contrast, dLCA aims to evaluate the impact of life cycle greenhouse gas emissions on radiative forcing considering the specific moment when these emissions occur.

Results and discussion

The results show that the total CF of the cork sector differs depending on the approach and time horizon chosen. However, the greater it is the time horizon chosen, the smaller the difference between the CF results of the two approaches. Additionally, the inclusion of biogenic carbon sequestration and emissions also influences significantly the CF result. The cork sector is considered a net carbon source when biogenic carbon is excluded from the calculations and a net carbon sink when biogenic carbon is included in the calculations since more carbon is sequestered than emitted along the sector.

Conclusions

dLCA allows an overview of greenhouse gas emissions along the time. This is an advantage as it allows to identify and plan different management approaches for the cork sector. Even though dLCA is a more realistic approach, it is a more time-consuming and complex approach for long life cycles. The choice of time horizon was found to be another important aspect for CF assessment.

     

Why going beyond standard LCI databases is important: lessons from a meta-analysis of potable water supply system LCAs

Purpose

Our aim is to assess the comparability and generic applicability of harmonized published lifecycle assessment (LCA) studies on water supply systems. In the absence of localized life cycle inventories for water systems, generic or country specific databases may be inadequate if applied elsewhere. The objectives of this paper are to calculate the potential magnitude of errors introduced by this practice and recommend ways to better account for sources of impact variability.

Methods

In this study, harmonization has been carried out rigorously, utilizing a systematic differentiation of the subsystems, functional units, and system boundaries referenced in over 100 candidate studies, resulting in a comparable subset of 34 LCA studies. Statistical techniques (cluster analysis and Welch’s analysis of variance) were used to isolate and validate the main sources of variation in impact scores and identify the sub-systems in which these are most pronounced. The significance of technology-specific contribution to the impacts was compared to the significance of electricity as a contributing factor to the global warming potential (GWP) by applying statistical correlation analysis.

Results and discussion

Our review revealed that most of the published LCAs analyzed water systems in well-developed countries. Large variation was found in the impacts of water supply systems (e.g., GWP between 0.16 and 3.4 kg CO2-eq/m³ of supplied water), with mean value of 0.84 kg CO2-eq/m3 and median of 0.57 kg CO2-eq/m3. The main contributor to GWP is water production and desalination in particular, making water production the most important differentiating factor. Cluster analysis also showed that production technology is the most important differentiating factor with respect to terrestrial acidification, ozone depletion, eutrophication, and abiotic depletion impacts of water production systems. There is a weak correlation between impact scores of electricity mixes and entire water supply systems.

Conclusions

An LCA of water-intensive products drawing from a standard life cycle inventory databases could be substantially inaccurate, especially in a region with desalination. More accurate results can be achieved by taking local water production technology into account. Meta-analysis is a useful tool to explore the sources of variance in the impacts of water systems. Applying harmonized results is a cost-effective way for obtaining more accurate LCA results as compared to applying generic databases only.

     

Road transport: new life cycle inventories for fossil-fuelled passenger cars and non-exhaust emissions in ecoinvent v3

Purpose

The paper presents new and updated datasets for the operation of fossil-fuelled passenger cars. These are intended to be used either as background processes or in the comparative assessment of transport options. Central goals were to achieve a high level of consistency, transparency and flexibility for a representative range of current vehicle sizes, emission standards and fuel types, and to make a clear definition between exhaust and non-exhaust emissions. The latter is an important contribution to studies focusing on hybrid and electric vehicles.

Methods

The datasets are the direct development of those available in ecoinvent v2 and are largely based on updated versions of the same sources. The datasets address petrol, diesel and natural gas vehicle fuels. The number of datasets was increased to cover small, medium and large vehicles. Other data sources were used in order to fill data gaps and to balance inconsistencies, particularly for the natural gas vehicles. Parameterisation was incorporated via the ecoeditor tool. This allows the datasets to be adapted for use as foreground processes and also increases transparency. An important method used was to observe the trends in fuel consumption and emissions across all sizes and emission standards simultaneously so that consistency would be achieved across the whole range of vehicles. Non-exhaust emissions were made dependent on vehicle weight and thereby independent of vehicle type.

Results and discussion

Some significant changes in individual emission factors between the v2 and v3 datasets was shown. This can be explained by a combination of corrections, updates based on more recent versions of the data sources, and attempts to make the datasets consistent to each other. This has also meant that the non-exhaust emissions are readily definable in terms of brake, tyre and road wear as a factor of vehicle weight, with the intention that this data can be applied to passenger vehicles of all technologies.

Conclusions

Fuel consumption, emission factors and infrastructure demand have been improved, extended and updated for petrol, diesel and natural gas vehicles adhering to the Euro 3, 4 and 5 emissions standards. Using the ecoeditor tool, significant parameterisation was included which has made the datasets far more flexible, consistent and transparent. The clear definition of non-exhaust emissions means that these can easily be applied to studies on hybrid and electric vehicles.

     

Optimization of fecal sample preparation for untargeted LC-HRMS based metabolomics

Introduction

Collecting feces is easy. It offers direct outcome to endogenous and microbial metabolites.

Objectives

In a context of lack of consensus about fecal sample preparation, especially in animal species, we developed a robust protocol allowing untargeted LC-HRMS fingerprinting.

Methods

The conditions of extraction (quantity, preparation, solvents, dilutions) were investigated in bovine feces.

Results

A rapid and simple protocol involving feces extraction with methanol (1/3, M/V) followed by centrifugation and a step filtration (10 kDa) was developed.

Conclusion

The workflow generated repeatable and informative fingerprints for robust metabolome characterization.

     

Well-to-wheel GHG emissions and mitigation potential from light-duty vehicles in Macau

Purpose

The rapid growth of vehicle sales and usage has highlighted the need for greenhouse gas (GHG) emission reduction in Macau, a special administrative region (SAR) of China. As the most primary vehicle type, light-duty vehicles (LDV, including light-duty gasoline vehicles (LDGVs) and light-duty diesel vehicles (LDDVs)) play a key role in promoting the GHG reduction and development of green transportation system in Macau.

Methods

This study, on the basis of real-world tested and statistical data, firstly performed a streamlined life-cycle assessment (SLCA) on LDVs, to evaluate the potential GHG emissions and reduction through shifting to hybrid electric vehicles (HEVs) and electric vehicles (EVs).

Results and discussion

The results show that the mean GHG emissions from the LDGVs, LDDVs, and HEVs per 100 km were 25.16, 20.30, and 15.00 kg CO₂ eq, respectively. Under the current electricity mix in Macau, EVs with the emissions of 12.39 kg CO₂ eq/100 km can achieve a significant GHG emission reduction of LDVs in Macau. The total GHG emissions from LDVs increased from 124.99 to 247.82 thousand metric tons over the periods 2001–2014, with a 5.42% annual growth rate. A scenario analysis indicated that the development of HEVs and EVs—especially EVs—has the potential to control the GHG emissions from LDVs. Under the electricity mix of natural gas (NG) and solar energy (SE), the GHG emissions from EVs would drop by about 22 and 28%, respectively, by 2030.

Conclusions

This study develops a useful approach to evaluate the potential GHG emissions and its reduction strategies in Macau. All the obtained results could be useful for decision makers, providing robust support for drawing up an appropriate plan for improving green transportation systems in Macau.

     

Electric passenger car transport and passenger car life cycle inventories in ecoinvent version 3

Purpose

Due to the large environmental challenges posed by the transport sector, reliable and state-of-the art data for its life cycle assessment is essential for enabling a successful transition towards more sustainable systems. In this paper, the new electric passenger car transport and vehicle datasets, which have been developed for ecoinvent version 3, are presented.

Methods

The new datasets have been developed with a strong modular approach, defining a hierarchy of datasets corresponding to various technical components in the vehicle. A vehicle is therefore modelled by linking together the various component datasets. Also, parameters and mathematical formulas have been introduced in order to define the amount of exchanges in the datasets through common transport and vehicle characteristics. This supports users in the choice of the amount of exchanges and enhances the transparency of the dataset.

Results

The new transport dataset describes the transport over 1 km with a battery electric passenger car taking into account the vehicle production and end of life, the energy consumption due to the use phase, non-exhaust emissions, maintenance and road infrastructure. The dataset has been developed and is suitable for a compact class vehicle.

Conclusions

A new electric passenger car transport dataset has been developed for version 3 of the ecoinvent database which exploits modularisation and parameters with the aim of facilitating users in adapting the data to their specific needs. Apart from the direct use of the transport dataset for background data, the various datasets for the different components can also be used as building blocks for virtual vehicles.