Life Cycle Global Warming Impact Research Articles

Life Cycle Global Warming Impact of Long-Distance Liquid Hydrogen Transport from Africa to Germany

The global interest in hydrogen as an energy carrier is steadily increasing. In this study, multiple scenarios of liquid hydrogen exports from Africa to Germany are analyzed by life cycle assessment (LCA) to quantify the global warming potential (GWP) of 1 kg hydrogen. The investigation is driven by the promise that hydrogen can be sustainably and economically produced by photovoltaic (PV)-powered electrolysis in Africa, benefiting from the geographical location near the equator and, consequently, higher solar irradiation levels. Given the absence of a pipeline network, shipping hydrogen emerges as the most efficient short-term transportation option to Germany. In this paper, supply locations—Morocco, Senegal, and Nigeria—are evaluated by means of an LCA and compared to hydrogen supply from Germany. Results show that emissions from hydrogen production and transportation by ship from Morocco range from 3.32 to 3.41 kgCO2-eq/kgH2. From Senegal, the range is 3.88 to 3.99 kgCO2eq/kgH2, and from Nigeria, it falls between 4.38 and 4.27 kgCO2-eq/kgH2. These emission levels are influenced by factors such as the GWP of PV electricity, the efficiency of the electrolyzer, and the transportation distance. Interestingly, the analysis reveals that PV-powered electrolysis of hydrogen in Germany, including 300 km distribution, causes, in most scenarios, a lower GWP in the range of 3.48 to 3.61 kgCO2-eq/kgH2 than hydrogen from the analyzed African regions. Opting for grid electricity instead of PV (with a value of 0.420 kgCO2-eq/kWh) for hydrogen production in Germany yields a GWP ranging from 24.35 to 25.42 kgCO2-eq/kgH2. Hence, we can conclude that in any event, PV-powered hydrogen electrolysis has a low environmental impact not only within Africa but also in Germany. However, it is crucial to carefully consider the balance of the GWP of production versus transportation given the distance between a hydrogen production site and the location of consumption.

Life-cycle global warming impact of hydrogen transport through pipelines from Africa to Germany

A unique life cycle assessment highlights the potential of photovoltaics to limit the global warming potential of hydrogen imports, using Germany's domestic supply as a reference.

Review and Harmonization of the Life-Cycle Global Warming Impact of PV-Powered Hydrogen Production by Electrolysis

This work presents a review of life-cycle assessment (LCA) studies of hydrogen electrolysis using power from photovoltaic (PV) systems. The paper discusses the assumptions, strengths and weaknesses of 13 LCA studies and identifies the causes of the environmental impact. Differences in assumptions of system boundaries, system sizes, evaluation methods, and functional units make it challenging to directly compare the Global Warming Potential (GWP) resulting from different studies. To simplify this process, 13 selected LCA studies on PV-powered hydrogen production have been harmonized following a consistent framework described by this paper. The harmonized GWP values vary from 0.7 to 6.6 kg CO2-eq/kg H2 which can be considered a wide range. The maximum absolute difference between the original and harmonized GWP results of a study is 1.5 kg CO2-eq/kg H2. Yet even the highest GWP of this study is over four times lower than the GWP of grid-powered electrolysis in Germany. Due to the lack of transparency of most LCAs included in this review, full identification of the sources of discrepancies (methods applied, assumed production conditions) is not possible. Overall it can be concluded that the environmental impact of the electrolytic hydrogen production process is mainly caused by the GWP of the electricity supply. For future environmental impact studies on hydrogen production systems, it is highly recommended to 1) divide the whole system into well-defined subsystems using compression as the final stage of the LCA and 2) to provide energy inputs/GWP results for the different subsystems.

Challenges in using soil carbon modelling in LCA of agricultural products\u2014the devil is in the detail

PurposeCurrently, there is no consensus on how the impacts of land use on the soil organic carbon (SOC) stocks would be best quantified within life cycle assessments (LCA) of agricultural products. The impacts of different decisions were tested within a model-based assessment of soil carbon changes on the life cycle global warming impact for spring wheat produced in two example regions in Finland (Southwest Finland and Northern Savonia) on mineral fields.MethodsGlobal warming impact for spring wheat was assessed, including CO2 emissions due to the SOC change. The SOC change assessment was made with the soil carbon model Yasso07. The effects of assumptions on land use history were tested, i.e. the initialisation of the model and time horizon of the analysis (20 or 100 years) on the SOC change estimates. Other greenhouse gas emissions contributing to the global warming impact of spring wheat production were assessed using general LCA methodology taking into account the greenhouse gas emissions caused by the production of input materials and fuels, as well as direct and indirect N2O emissions from the soil due to fertilising and the decomposition of crop residues and organic matter, nitrogen leaching and volatilisation and lime application.Results and discussionThe selection of the model initialisation method and timeframe remarkably affected the SOC change estimates. The global warming impact of wheat production, without accounting for SOC changes, was 0.68 and 0.89 kg CO2-eq/kg yield in Southwest Finland and Northern Savonia, respectively. The impact of SOC stock changes on the total global warming impact varied from –4 to 5% in Southwest Finland and from 5 to 21% in Northern Savonia, depending on the assumptions used to initialise the model or the timeframe applied in the analysis. Adding a cover crop as a means to increase the SOC stock removed between –67 and –26% of the total global warming impact in both regions.ConclusionsIt is essential that all the decisions made in the analysis are transparently reported and communicated. The choice of assumptions regarding the reference state, model initialisation and time horizon of the assessment period should be made based on the scope and goal definition of the LCA study.

A dynamic approach for life cycle global warming impact assessment of machine tool considering time effect

PurposeMachine tools are the equipment used for the cutting and shaping of materials, like metals, which generate greenhouse gas (GHG) emissions across their life cycles due to material use and energy consumption. The life cycle emissions of machine tools are distributed over time and may vary with technology advancement. This paper aims to incorporate these temporal factors into the global warming impact (GWI) assessment of machine tools and further reveal their influences on the results.MethodIncorporating emission time into the GWI assessment of machine tools is based on the following dynamic life cycle assessment (LCA) framework. First, compute temporally differentiated GHGs of machine tools based on the activity-based modeling. And then, use time-dependent characterization factors (CFs), which are developed based on the radiative forcing concept, to assess their GWI. By using this framework, a dynamic life cycle GWI assessment of machine tool is conducted using two gear hobbing machines. Both the emission time and the potential changes of life cycle emissions due to the improvement of electricity mix and the variation of machine tool use modes are considered.Results and discussionThe results demonstrated that when the emission time was considered, both machines offered 3% of reduction of GWI, compared with their static results, respectively. Further reductions were found for the two machines, when the electricity improvement and the changes of the machine tool use modes were considered. All the differences between the static and the dynamic environmental impact results become smaller with the extension of the time horizons (THs) that accounted for the evaluation.Conclusions and recommendationsThe conventional static LCA has the potential to overestimate the real GWI of machine tools. It is more important to account for the emission time in GWI assessment at shorter THs or for a longer lifetime of machine tools. This work offers a method to dynamically assess the real GWI of machine tools. The proposed method helps to make robust decision-making for environmentally friendly machine tool selection and support sustainable production.

Dynamic global warming impact assessment integrating temporal variables: Application to a residential building in China

Climate warming is a global concern, and buildings have been recognized as a major contributor because the carbon emissions during their entire life cycles constitute a large share of the total value (almost 40% globally). Many life cycle assessments of buildings have been conducted to quantify the associated global warming impacts. However, few studies have considered the potential temporal variation over the long lifetimes of buildings. In this study, various temporal variables were combined to evaluate the dynamic life cycle global warming impact of a residential building in China. First, annual material and energy consumption data throughout the entire life cycle were acquired from questionnaire survey, statistical reports and literatures. Five dynamic variables (household size, usage behavior, replacement and improvement of components, waste treatment, and energy mix) and their effects on consumption levels were considered. Second, a dynamic inventory analysis tool (DyPLCA) was used to transform the temporal consumption data into dynamic greenhouse gas quantities. The global warming effects of these emissions were quantified using a dynamic characterization tool (DynCO2). Finally, emission reduction targets for future decades were used to weight the severities of the impacts at different times. The dynamic instantaneous and cumulative global warming impacts of the building were calculated. Dynamic and static assessment results were compared. We also analyzed the contribution of each dynamic variable to the final results and found that the dynamic variables had very different effects (ranging from −42.00% to 45.34%). This study provided an operable dynamic assessment model and available dynamic data for the global warming impact assessment of buildings in China.

Greenhouse gas emissions and energy assessment of modified diesohol using cashew nut shell liquid and biodiesel as additives

The development of sustainable biofuel production has been promoted in many countries to reduce the use of fossil fuel. This work analyses the life cycle global warming impact, net energy and fossil energy ratios for two alternatives diesohol (diesel/bioethanol) fuels and a new modified diesohol using distilled cashew nut shell liquid/biodiesel. Owing to the molecular structure, biodiesel and distilled cashew nut shell liquid can be used as emulsifier to stabilise the diesohol as well as to slightly reduce the portion of diesel in the blend. The uncertainty analysis, land use change impact, and cost performance comparison in the life cycle assessment were also considered. The well-to-wheel analysis of the biofuel life cycle was used as a system boundary. The results indicated that the global warming impact and the energy performance were not significantly different among the three diesohol alternatives. The global warming impact of all studied alternative fuels was estimated as 68.22–75.69 kg CO2 equivalent/1000 MJ, which was 18–26% lower than that of conventional diesel. This was due to the environmental benefits obtained from biodiesel, bioethanol, and distilled cashew nut shell liquid, avoiding CO2 emissions from combustion in fuel blends because they are of biogenic origin. The substitution of diesel by fuel blends resulted in the net energy ratios (1.01–1.08) and fossil energy ratios (0.96–1.04) of the three alternatives diesohol fuels that were 14–19% and 9–16% higher than that of the conventional diesel. The fossil energy ratios of fuel blends were slightly lower than the net energy ratios by 3.70–4.95%. The LCIA result showed that, according to the uncertainty analysis, the global warming impact from well-to-wheel analysis of the modified diesohol fuel with 85 vol.% diesel, 15 vol.% bioethanol and 20 vol.% (based on the combined volume of diesel and bioethanol) biodiesel was, with 100% probability, less than that of other disohol alternatives studied. The results indicated that alternative diesohol fuel in the case of 15% bioethanol was an environmental and economic superior choice of all studied alternatives fuels because of its lowest global warming impact (with and without LUC), while providing the highest energy efficiency with the net energy ratio and fossil energy ratio of 1.08 and 1.04, respectively. To improve the performance in terms of environmental and eonomic perspectives, the integration of fossil fuels and biofuels would improve the sustainable choices and promote the value-added domestic materials from renewable resources for transportation fuels in Thailand.

Life cycle global warming impact of CO2 capture by in-situ gasification chemical looping combustion using ilmenite oxygen carriers

In-situ gasification chemical looping combustion (iG-CLC), which has been tested on pilot plant level, is regarded as an advanced carbon capture and storage (CCS) technology for reducing CO2 emissions. A life cycle global warming impact (GWI) analysis is performed to consider the lifetime emissions of the low-carbon iG-CLC technology. Herein, the capacity is considered to be 610 MWe using natural ilmenite as oxygen carrier and steam as gasification agent. At the condition of operational pressure of 15 atm and air reactor temperature of 1050 °C, the net power efficiency of 37.7% for achieving 93.5% inherent CO2 capture is obtained in simulations with thermodynamically optimum condition. The life cycle GWI is calculated equal to be 160.3 kg CO2-equivalent/MW h. The effects of several essential parameters, including steam to carbon ratio (S/C), oxygen carrier to fuel ratio (ф), different oxygen carriers and lifetime of oxygen carriers, on the lifecycle GWI have been analyzed and discussed to meet the potential possibility for further reducing greenhouse gas (GHG) emissions. To obtain sufficient carbon capture efficiency, the S/C ratio and ф are suggested to be 1.3 and 1.2 in this study, respectively. The life cycle GWI is heavily dependent on lifetime of ferrum (Fe) when it is less than 2000 h, beyond that range, the GWI is decreasing, but very slowly.

Indirect environmental benefits of a variable set-point for HCl emission in waste-to-energy flue gas cleaning

Hydrogen chloride (HCl) is a typical contaminant generated in waste combustion, whose emission is strictly regulated. In order to cope with severe limits issued by local authorities on the annual mass flow of HCl emitted, several European waste-to-energy plants perform at least a two-stage abatement of the pollutant and operate with a set-point for HCl concentration at stack well below the hourly emission limit imposed by the Industrial Emissions Directive. Even though the operating conditions in a WtE facility are highly variable (both in terms of HCl release from the burnt waste and of operating temperature of the HCl removal system), it is common industrial practice to keep both the set-point for HCl concentration at stack and the set-point for HCl concentration between the two abatement stages at a constant value. However, this might force the abatement system to operate far from its design conditions and from the optimal reactivity window of the adopted HCl removal agent, thus increasing the consumption rate of reactant and the consequent generation rate of process residues. Both the supply chain of reactants and the management of residues generate environmental impacts. The present work demonstrates that the adoption of variable values for both set-points can provide cost savings and indirect environmental benefits, thanks to the reduction of reactant consumption and residue generation. By considering as case study a WtE plant equipped with a two-stage dry HCl removal system, a year of operation of the plant was analysed. The operating costs and life cycle impacts generated by the actual operation of the HCl treatment system with constant set-points were compared with those generated if the plant had operated with variable set-points, simulated with a semi-empirical model for HCl removal tuned on historical process data from the plant. A 13 % reduction of the life cycle global warming impact and an 8 % reduction of the life cycle acidification impact, in addition to 10 % cost savings, were associated to the utilisation of variable set-points.

Estimation of Greenhouse Gas Emissions and Mitigation Methods in Electrical Power Sector of Dire Dawa City from 2015 to 2025

This manuscript reviews and compares the results of recent greenhouse gas (GHG) emission life-cycle analyses. Specific attention is paid to fossil energy technologies and renewable energy technologies (RETs). It is therefore desirable for GHG emissions under national, regional and international mitigation policies to be accounted for over its entire life-cycle. The results presented here indicate that the most significant GHG avoidance (in absolute terms) can be made from technology substitution. The introduction of advanced fossil fuel technologies can also lead to improvements in life-cycle GHG emissions. Overall, hydro, nuclear, solar and wind energy technologies can produce electricity with the least life-cycle global warming impact. The advantage of using renewable resources for energy production from conventional resources scarcity and power system reliability point of view is too much. Using renewable resources specially wind and solar are becoming common in developing countries for electrifying the remote and rural areas where grid electrification is economically infeasible. This research work shows an investigation that uses a combination of solar and wind energy as hybrid system (HPS) for electrical generation in Dire Dawa. The generated electricity has been utilized for different purposes. The system has also integrated a diesel generator to be more reliable. This system is not linked with conventional energy. The total energy consumption of each household is 29.44 kWh/day. Measurements included the solar radiation intensity, the ambient temperature and the wind speed was collected from national meteorology agency which was collected for 15 years. To simulate the hybrid power system (HPS) HOMER was used. Emissions and renewable energy generation fraction (RF) of total energy consumption are calculated as the main environmental indicator. The net present cost (NPC) and cost of energy (COE) are calculated for economic evaluation. It is found that, for Dire Dawa climates, the optimum results of HPS show a 93.73% reduction of emissions with 99% of renewable energy fraction.

Harmonising the cumulative energy demand of renewable hydrogen for robust comparative life-cycle studies

A significant number of case studies evaluating hydrogen through the Life Cycle Assessment (LCA) methodology are available in the scientific literature. However, inconsistencies in their methodological frameworks lead to potential misinterpretation concerns when it comes to comparing LCA results. In order to mitigate this risk, harmonisation protocols for life-cycle indicators arise as helpful tools. In this regard, a harmonisation protocol for the life-cycle global warming impact (GWP) of hydrogen has been recently developed. Taking this protocol as a starting point, this article expands the list of harmonised sustainability indicators of hydrogen by formulating a new protocol for the cumulative non-renewable energy demand (CEDnr) indicator. Furthermore, the protocol is applied to a sample of case studies of renewable hydrogen (harmonised CEDnr ranging from 3 to 184 MJ kg−1 H2) as well as to a reference case study of conventional hydrogen produced via steam methane reforming (harmonised CEDnr of 201 MJ kg−1 H2). The resultant library of harmonised CEDnr consistently complements that of harmonised carbon footprints of hydrogen, showing a high correlation between GWP and CEDnr (R2 = 0.91). Overall, LCA harmonisation initiatives are found to mitigate misinterpretation concerns when comparing and ranking hydrogen energy systems both within the same technological category and between different technological categories (thermochemical, electrochemical, and biological).

Harmonised life-cycle global warming impact of renewable hydrogen

An increasing number of studies addressing the Life Cycle Assessment (LCA) of hydrogen energy systems is found in the scientific literature. Most of these studies are comparative and show significant differences in terms of methodological choices. These differences significantly affect the results of the LCA studies and hamper their robust interpretation, especially when comparing results from different studies. Hence, harmonisation of the results under a consistent methodological framework is needed. This article defines a protocol for the harmonisation of the life-cycle global warming impact of hydrogen. Furthermore, the protocol is applied to renewable hydrogen based on a thorough literature survey of relevant LCA case studies classified by hydrogen-production technological category: thermochemical, electrochemical, and biological. In this sense, the two main outcomes of the study are the harmonisation protocol and the initial library of harmonised carbon footprints of renewable hydrogen for 71 case studies. Key methodological choices subject to harmonisation include (i) attributional approach, (ii) functional unit, (iii) system boundaries, and (iv) multifunctionality approach. Harmonisation is found to affect more significantly the thermochemical and biological categories than the electrochemical one. Nevertheless, risk of misinterpretation is found and exemplified in every technological category. The sources of potential misinterpretation are found to be usually linked to inconsistencies in terms of system boundaries (e.g., hydrogen compression) and, when applicable, multifunctionality approaches. Future LCA practitioners are highly recommended to use the proposed protocol to provide, along with their own results, the harmonised global warming impact of hydrogen in order to enhance current and future result interpretation when comparisons are made.

Global warming impact assessment of a crop residue gasification project—A dynamic LCA perspective

Bioenergy from crop residues is one of the prevailing sustainable energy sources owing to the abundant reserves worldwide. Amongst a wide variety of energy conversion technologies, crop residue gasification has been regarded as promising owing to its higher energy efficiency than that of direct combustion. However, prior to large-scale application of crop residue gasification, the lifetime environmental performance should be investigated to shed light on sustainable strategies. As traditional static life cycle assessment (LCA) does not include temporal information for dynamic processes, we proposed a dynamic life cycle assessment approach, which improves the static LCA approach by considering time-varying factors, e.g., greenhouse gas characterization factors and energy intensity. As the gasification project can reduce greenhouse gas (GHG) discharge compared with traditional direct fuel combustion, trade-offs between the benefits of global warming mitigation and the impact on global warming of crop residue gasification should be considered. Therefore, indicators of net global warming mitigation benefit and global warming impact mitigation period are put forward to justify the feasibility of the crop residue gasification project. The proposed dynamic LCA and indicators were then applied to estimate the life cycle global warming impact of a crop residue gasification system in China. Results show that the crop residue gasification project has high net global warming mitigation benefit and a short global warming impact mitigation period, indicating its prominent potential in alleviating global warming impact. During the lifetime of the project, the largest emitters of the crop residue gasification project are the operation and construction stages, attributed mainly to the consumption of crop residue, electricity and steel. In addition, the comparison of the results obtained with both traditional and dynamic LCA approaches indicates that there is an exaggeration of the global warming impact reduction potential of crop residue gasification projects. This dynamic LCA can also make the decision maker acknowledge the real-time GHG performance during the lifetime of a production process, and thus make timely decisions to minimize the lifetime GHG emissions.

GREEN-MAC-LCCP: A Tool for Assessing the Life Cycle Climate Performance of MAC Systems

In 2008, 95% of the vehicle fleet in the developed countries and 80% of fleet in the developing countries were equipped with mobile air conditioning systems (MACs). Greenhouse gases (GHGs) are emitted due to refrigerant leakage (direct emissions) and due to the energy consumed by MACs operation (indirect emissions). In response to reducing the global warming impact of MACs, policy makers and the industry are investigating alternative refrigerant systems that use low global warming potential (GWP) refrigerants. The GREEN-MAC-LCCP model assesses the direct and indirect CO(2) equivalent emissions related to MACs usage, as well as those associated with the production, use and disposal of alternative refrigerants and MACs components. This model provides a platform for simple data input and provides an output summary as well as details that can be analyzed in a custom fashion by the user. It provides engineers and policy makers a state-of-the-art tool, based on sound engineering data and methods, in order to facilitate the process of evaluating alternate refrigerants with low lifecycle global warming impact as well as providing the total impact of any MACs on the environment. It has been recognized as the standard of the MACs industry.

LCAを用いたインターネット環境にあるパソコンの温暖化分析

Objective. A Life Cycle Assessment (LCA) of a personal computer (PC) connected to Internet is required because it is concerned that environmental load will increase by worldwide glowing Internet population. This study was performed as a case study to evaluate the life cycle global warming impact of a PC under internet condition by LCA (with Process Analysis method). Results and Discussion. The subject PC system was composed of a desktop PC coupled with a 15” liquid crystal display (LCD) and a router. During this study, several key data were obtained such as the foreground data of LSI manufacturing stage, the amount of power consumption of PC during use stage, and some components like CD-ROM, hard disk, keyboard, and so on. By this study it became clear that LSI emitted several hundred times amount green house gas (GHG) of its own weight during production stage, and also that the global warming impact by electrical parts were much higher than materials such as iron and resins. On the other hand, this study revealed the deficiency of the background data of electrical parts like that resistor, transformer, connector and circuit board and so on. Conclusion. The foreground data of LSI and the data of the components of PC obtained in this study may be very useful for the analyses of many other electric devices. However, the deficiency of the background data of many electric parts was revealed. The background data of the electric parts should be collected more and more.

A guide to life-cycle greenhouse gas (GHG) emissions from electric supply technologies

This manuscript reviews and compares the results of recent greenhouse gas (GHG) emission life-cycle analyses. Specific attention is paid to fossil energy technologies, nuclear and renewable energy technologies (RETs), as well as carbon capture and storage (CCS) and energy storage systems. Analysing up- and downstream processes and their associated GHG emissions, which arise upstream and downstream of the power plant (i.e., electricity generation stage), is important; otherwise, the GHG emissions resulting from electricity generation of the various fuel options are underestimated. For fossil fuel technology options upstream GHG emission rates can be up to 25% of the direct emissions from the power plant, whereas for most RETs and nuclear power upstream and downstream GHG emissions can account for way over 90% of cumulative emissions. In economies where carbon is being priced or GHG emissions constrained, this may provide an advantage to technologies with trans-boundary upstream emissions over technologies without significant life-cycle emissions arising outside the legislative boundaries of GHG mitigation policies. It is therefore desirable for GHG emissions under national, regional and international mitigation policies to be accounted for over its entire life-cycle. The results presented here indicate that the most significant GHG avoidance (in absolute terms) can be made from technology substitution. The introduction of advanced fossil fuel technologies can also lead to improvements in life-cycle GHG emissions. Overall, hydro, nuclear and wind energy technologies can produce electricity with the least life-cycle global warming impact.