Life Cycle GHG Emissions Research Articles

EU building stock characterization for whole life cycle assessment: Data challenges and key insights

Abstract The building sector plays an important role in achieving the climate objectives of the EU Green Deal. While prioritizing measures to reduce operational energy and GHG emissions has proven beneficial, it has shifted burdens by increasing embodied emissions. Quantifying and regulating emissions throughout the entire building life cycle is therefore crucial. An ongoing DG GROW project is investigating strategies to reduce life cycle GHG emissions within the EU. Various steps are being carried out to achieve the research goals: identification of data needs and sources, baseline analysis of the existing whole life carbon emissions of the EU building stock, modelling of future scenarios. This paper elaborates on the building stock characterization, demonstrating innovation through its level of granularity. Firstly, key data sources are chosen to provide the desired granularity. Secondly, archetypes are defined based on the data sources. Thirdly, attributes are chosen to describe the building stock in terms of geometry, building element composition, energy use, etc. The paper concludes by discussing challenges related to collecting attribute information and managing data gaps. The insights derived offer valuable recommendations for establishing a future data repository dedicated to environmental LCA of the EU building stock.

Cost, innovation, and emissions leakage from overlapping climate policy

Jurisdictions have implemented a variety of policy instruments to mitigate greenhouse gas emissions. However, interactions between overlapping climate policies can lead to unintended impacts. This study demonstrates how interactions between an incomplete emissions cap and additional climate policy can result in higher emissions and higher average abatement costs relative to an emissions cap alone. This sectoral policy emissions displacement effect is then quantified through simulations using a computable general equilibrium model for the case of California's low-carbon fuel standard (LCFS) and cap-and-trade program. Emissions increase as a result of the LCFS incentivizing greater production of alternative transportation fuels with emissions not covered by the emissions cap. Emissions leakage can be mitigated by incorporating elements of a fixed-price instrument (i.e. carbon tax) to improve policy complementarity or requiring an obligation for the lifecycle GHG emissions of fuels under the emissions cap.

Thermo-economic and environmental analyses of supercritical carbon dioxide Brayton cycle for high temperature gas-cooled reactor

The supercritical carbon dioxide (sCO2) Brayton cycle demonstrates special advantages for the high temperature gas-cooled reactor (HTGR) delivered into commercial operation recently in China, with its high efficiency, compactness, flexibility, and safety compared to the conventional steam Rankine cycle. However, the large temperature rise of 500 °C for the HTGR brings new challenges for the design of sCO2 cycle. Here, we present the first study on the thermodynamic, economic, and environmental performance of the HTGR-sCO2 system using the energy, exergy, economic, and environmental (4E) evaluation method. The cascaded sCO2 cycle made up of two independent sCO2 cycles is proposed, which are arranged in series on the cold side of reactor heat exchanger. We show that the cascaded sCO2 cycle can utilize the heat absorption from HTGR effectively by optimizing the cycle configurations of top and bottom sub-cycles. The improved cascaded sCO2 cycle minimizes the exergy loss, and increases the thermal efficiency to 43.2% when compared to the steam Rankine cycle of HTGR demonstration power plant and the single recompression cycle. By balancing the fixed-capital investment cost with the net power, the levelized cost of electricity can be reduced to 0.0283$/kWh. The life-cycle GHG emission intensity of HTGR-sCO2 systems is about 6.5gCO2,eq/kWh, which is much smaller than that of coal-fired power plants, suggesting a great potential for decarbonization of the HTGR-sCO2 system. Our study may find implications for the advancement of the sCO2 Brayton cycle in next-generation nuclear power plant.

Comparative assessment of global warming potential of gasoline, battery, and hybrid vehicles in India

This study reports a comparative analysis of life cycle greenhouse gas (GHG, CO2-eq.) emissions of three fuel-type vehicles, viz. internal combustion engine (ICEVs), battery electric (BEVs), and hybrid electric vehicles (HEVs), from an Indian perspective. Vehicles in hatchback and compact sports utility vehicles (SUVs) categories were analyzed. GHG emissions in fuel life cycle (well-to-tank and tank-to-wheel) and vehicle life cycle were estimated using data from websites of OEMs and ministries of Government of India, and the GREET software. The vehicle life cycle constitutes a smaller fraction (15–20 %) of total life cycle GHG emissions for ICEVs and HEVs compared to BEVs (∼35 %). The vehicle cycle emissions of BEVs are higher than ICEV and HEV in both categories (52–63 % for hatchback and approx. 45 % for compact SUV). The fuel cycle emissions of BEVs are smaller than ICEV and HEV in both categories (29–34 % for hatchback and 32–40 % for compact SUV). The total life cycle GHG emissions of BEVs were lower than ICEV and HEV (15–17 % in hatchback and 17–25 % in compact SUV category) for the 2023 energy mix in India with a significant share of thermal route. With anticipated doubling of renewable energy sources in India by 2030, the total life cycle GHG emission of BEV will decrease by approximately 20 %. However, sensitivity analysis revealed that BEVs produce higher GHG emissions than ICEVs and HEVs until a minimum lifetime travel distance. Thermal power plant efficiency and battery lifespan also influence BEVs lifetime GHG emissions.

A comparative life cycle assessment of fifth-generation district heating and cooling systems

With the growing global demand for cooling, there is a critical need for sustainable solutions that efficiently provide both heating and cooling. Fifth-generation district heating and cooling (5GDHC) systems present a promising option, integrating renewable energy and enabling energy sharing. Despite their potential, the environmental performance of 5GDHC systems has not been comprehensively studied until now. This study addresses this critical gap by conducting the first comprehensive cradle-to-grave life cycle assessment of 5GDHC systems, uniquely incorporating hybrid environmental flow coefficients. This approach significantly enhances the coverage and accuracy of the analysis compared to traditional assessment methods. Using the University of Melbourne’s proposed Fishermans Bend campus as a case study, we compare different 5GDHC configurations with a state-of-the-art traditional system. Our findings reveal that 5GDHC systems can reduce total life cycle GHG emissions by up to 52%, particularly when suitable heat sources and sinks are available. This study underscores the importance of considering life cycle impacts in the early planning stages of energy systems, positioning 5GDHC as a viable solution for the energy transition.

Plug-in charging or electric roads? Powering U.S. long-haul heavy-duty trucks in 2050

Abstract Pervasive plug-in fast chargers and/or electrified roadways (eRoads) might address the limited range, long recharging times, and reliance on greenhouse gas (GHG)-intensive, costly, and heavy batteries associated with electrifying long-haul heavy-duty trucks (HDTs). While these large-scale interventions shift environmental and cost burdens onto infrastructure, there is a lack of studies investigating how eRoads affect system-level GHG emissions, costs, material use, and peak electric grid power demands. We compare these aspects for the case of electrifying U.S long-haul HDTs (Class 8) in 2050 powered by combinations of plug-in fast chargers and eRoads. Our model accounts for battery downsizing, energy consumption, and truck operation patterns in quantifying life cycle impacts of batteries, plug-in chargers, eRoads, and hourly truck electricity demand. We find that plug-in fast chargers and eRoads reduce annualized 2050 HDT life cycle GHG emissions by 8% to 14% compared to using long-range batteries, which in turn have at least 50% lower emissions than diesel trucks. Conductive rails, overhead lines, and wireless eRoads (amortized across light- and heavy-duty vehicles) have lower system-wide costs than long-range batteries, plug-in fast chargers, or diesel trucks. Cost savings from smaller batteries, lower energy use and avoided recharging time offset high eRoads capital costs. While eRoads can reduce both system-level GHG and costs compared to diesel trucks, these reductions are sensitive to eRoads capital costs and losses from wireless power transfer and air resistance. eRoads require less lithium (87%) and copper (67%) than long-range batteries but increase regional peak power demands by up to 32%. Efficient wireless power transfer and aerodynamic pantographs enhance eRoads’ GHG and cost advantages, which may diminish if future batteries are more energy-dense, cheaper, or less GHG intensive. If successfully deployed, eRoads present opportunities for tighter integration between the transportation and electricity infrastructure systems, enabling optimized charging strategies to lower GHG emissions and costs.

Life-cycle GHG emissions of standard houses in Thailand

Life-cycle GHG emissions of standard houses in Thailand

Process optimization, exergy analysis, and GHG emissions of ammonia production systems by gasification of high-sulfur petroleum coke with CO2 capture

High-sulfur petroleum coke is commonly used as a fuel because of its high carbon content and calorific value. Direct combustion of high-sulfur petroleum coke has the problem of emitting a lot of CO2 and sulfide. Gasification is an environmentally friendly way to utilize high-sulfur petroleum coke. Therefore, this study first established hydrogen production systems with CO2 capture through high-sulfur petroleum coke gasification. The hydrogen is then reacted with nitrogen from air separation unit for producing ammonia, which is easy to transport and store. After optimizing and analyzing the key parameters of the established models, exergy and life cycle GHG emissions analysis are carried out to evaluate the technical performance and environmental impact. In the system with an 85 % gasification conversion rate of petroleum coke, the ammonia production capacity, exergy efficiency, and GHG emissions are 2300 kmol/h, 45.39 %, and 1468 kg CO2-eq/t NH3. When the conversion rate is elevated by ten percentage points, the ammonia production and exergy efficiency are increased to 2664 kmol/h and 51.95 %, while the GHG emissions are only reduced by 85 kg CO2-eq/t NH3 since most of the CO2 produced by the system is captured. Improving the petroleum coke conversion rate can significantly increase the exergy efficiency of ammonia production system, but has little impact on reducing GHG emissions during the process.

Aqueous-phase product treatment and monetization options of wet waste hydrothermal liquefaction: Comprehensive techno-economic and life-cycle GHG emission assessment unveiling research opportunities

While wet waste hydrothermal liquefaction technology has a high biofuel yield, a significant amount of the carbon and nitrogen in the feedstock reports to the aqueous-phase product. Pretreatment of this stream before sending to a conventional wastewater plant is essential or at the very least, advisable. In this work, techno-economic and life-cycle assessments were conducted for the state-of-technology baseline and four aqueous-phase product treatment and monetization options based on experimental data. These options can cut minimum fuel selling prices by up to 13 % and life-cycle greenhouse gas emissions by up to 39 % compared to the baseline. These findings highlight the substantial influence of aqueous produce treatment strategies on the entire wet waste hydrothermal liquefaction process, demonstrating the potential for optimizing economic viability and environmental impact through further research and development of milder treatment methods and diversified by-product valorization pathways.

Sailing towards sustainability: offshore wind's green hydrogen potential for decarbonization in coastal USA

A systems optimization framework and life cycle assessment to evaluate economic and environmental implications of green hydrogen produced offshore predicts a delivered cost of $2.50–$7.00 per kg H2 and life cycle GHG emissions below the 4 kg CO2e per kg H2 benchmark.

Life cycle energy-carbon-water footprint assessment of an existing coal power plant retrofitted with calcium looping (CaL) based CCS system

The current study uses a detailed process based LCA model to evaluate the life cycle energy, carbon and water footprint of an existing 660 MWe supercritical coal powerplant in India retrofitted with the calcium looping based CCS system. LCA of the base case is followed by a sensitivity analysis to analyze effect of variation of different input parameters on the output performance metrics such as life cycle energy input, EROI, life cycle GHG emissions and life cycle blue water consumption. Further, the performance of calcium looping is compared with other mature CCS technologies such as MEA and oxycombustion, which are also retrofitted to the same existing coal power plant. Results show that, as compared to the base power plant, the life cycle energy input and life cycle blue water consumption of the integrated system using calcium looping increases by around 31 and 36% respectively, whereas EROI and life cycle GHG emissions decrease by 33–45% and 79–83% respectively. Sensitivity analysis results show that EROI has the largest variation range and change in rail transportation distance of coal leads to maximum variation in life cycle energy input, EROI and life cycle GHG emissions. Comparison of the three CCS technologies clearly shows that the integrated system using calcium looping has the lowest increase in life cycle energy input and life cycle blue water consumption and the lowest decrease in EROI. Thus, in addition to efficiently reducing CO2 emissions and enhancing power generation capacity of existing coal powerplants, use of calcium looping is also favourable from a life cycle sustainability perspective.

Reuse practices in building construction: proposition of a life cycle assessment methodology and application to a case study in Switzerland

This paper presents a life cycle assessment (LCA) methodology for evaluating the environmental impacts of reuse in building projects and apply it to a case study in Switzerland with 11% of reused components in its total mass. The results show that the life cycle GHG emissions on the construction domain that includes modules A1 to A4, B4, and C1-C4, are 487 kg CO2-eq./m2. In the other hand, the indirect effect of reuse lead to avoided GHG emissions of 76 kg CO2-eq./m2. At the level of a product’s supply chain, the analysis demonstrates a significant reduction in the embodied impacts of the reused components compared to newly manufactured ones. The potential benefits from avoided manufacturing and waste management depend on the type of material that is reused.

Stepwise renovation of buildings: what to refurbish first to minimize life-cycle carbon emissions?

To tackle the upcoming renovation wave, this work evaluates renovation strategies with a life cycle GHG emissions perspective and includes time and sequencing in the decision-making process. A case study is used to conduct a full life cycle assessment of renovation strategies in line with the Swiss normative context. Improvements in the operational energy consumption are evaluated with an energy model using the software Lesosai and considering the normative limits from the SIA 380/1. GHG emissions are calculated using the Swiss KBOB data inventory and in line with the SIA 2032 methodology. The renovation measures are then examined individually with the carbon payback time indicator and strategies with cumulative emissions over time in contrast to carbon budgets. Results show that the sequence of the refurbishment steps can increase or decrease cumulative GHG emissions of ca. 30% over the lifetime of the building. Changing a fossil-fuel based heating system is the most impactful measure and must happen as soon as possible. Switching to decarbonized heating systems reduces the carbon effectiveness of subsequent renovation measures but poses the question of energy availability. Fully renovating a building but delaying the change of heating system by only 7 years can compromise the achievement of the carbon targets.

Sustainable aviation fuel production using in-situ hydrogen supply via aqueous phase reforming: A techno-economic and life-cycle greenhouse gas emissions assessment

Sustainable aviation fuel (SAF) production is one of the strategies to guarantee an environmental-friendly development of the aviation sector. This work evaluates the technical, economic and environmental feasibility of obtaining SAFs by hydrogenation of vegetable oils thanks to in-situ hydrogen production via aqueous phase reforming (APR) of glycerol by-product. The novel implementation of APR would avoid the environmental burden of conventional fossil-derived hydrogen production, as well as intermittency and storage issues related to the use of RES-based (renewable energy sources) electrolysers. The conceptual design of a conventional and advanced (APR-aided) biorefinery was performed, considering a standard plant capacity equal to 180 ktonne/y of palm oil. For the advanced scenario, the feed underwent hydrolysis into glycerol and fatty acids; hence, the former was subjected to APR to provide hydrogen, which was further used in the hydrotreatment reactor where the fatty acids were deoxygenated. The techno-economic results showed that APR implementation led to a slight increase of the fixed capital investment by 6.6% compared to the conventional one, while direct manufacturing costs decreased by 22%. In order to get a 10% internal rate of return, the minimum fuel selling price was found equal to 1.84 $/kg, which is 17% lower than the one derived from conventional configurations (2.20 $/kg). The life-cycle GHG emission assessment showed that the carbon footprint of the advanced scenario was equal to ca. 12 g CO2/MJSAF, i.e., 54% lower than the conventional one (considering an energy-based allocation). The sensitivity analysis pointed out that the cost of the feedstock, SAF yield and the chosen plant size are keys parameters for the marketability of this biorefinery, while the energy price has a negligible impact; moreover, the source of hydrogen has significant consequences on the environmental footprint of the plant. Finally, possible uncertainties for both scenarios were undertaken via Monte Carlo simulations.

Technical and life cycle performance comparison between petroleum coke chemical looping combustion and oxy-combustion combining with advanced steam cycles for power generation processes

Inferior petroleum coke is attractive to be used in power generation industry since it has the advantage of high calorific value. To address the environmental problem of petroleum coke combustion for power generation, this paper establishes a process model of petroleum coke chemical looping combustion (CLC) and compares its performance with that of a petroleum coke oxy-combustion (OCB). The results show that CO2 capture rate of the CLC and OCB both reach about 100%. Under the petroleum coke conversion rate of 70%, the net electrical efficiencies of the petroleum coke CLC and OCB are 28.61% and 24.68%. The life cycle energy consumption and GHG emission of the CLC and OCB are 12.08/12.76 GJ/MWh and 338.03/397.91 kg CO2 eq/MWh, respectively. Compared with the sub-critical steam cycle in the above base case, the net electrical efficiencies of the CLC integrated with supercritical and ultra-supercritical cycles are increased by 0.93 and 1.53 percentages points, while their life cycle energy consumption and GHG emission are decreased by 0.31/0.49 GJ/MWh and 5.85/10.34 kg CO2 eq/MWh. When the conversion rate increases from 70% to 95%, the net electrical efficiencies of the CLC process are increased to 39.71/40.97/41.84%, and their life cycle results are decreased to 9.32/9.09/8.95 GJ/MWh and 300.85/296.20/292.07 kg CO2 eq/MWh. Therefore, improving conversion rate of the CLC and its coupling with advanced steam cycles for power generation are important for clean and efficient utilization of inferior petroleum coke.

A framework for determining the life cycle GHG emissions of fossil marine fuels in countries reliant on imported energy through maritime transportation: A case study of South Korea

This research was motivated to address limitations in the current lifecycle assessment frameworks with the absence of proper guidelines for developing default lifecycle values of energies in consideration of supply chain activities and maritime transportation. Given this, it aims to evaluate the level of life cycle GHG emissions of heavy fuel oil, LNG, LPG and methanol as marine fuels produced and supplied in energy import-dependent countries, using South Korea as a case study. The analysis clearly shows that the impact of international shipping on Well-to-Tank (WtT) GHG emissions for energy carriers would be subject to several factors: propulsion system types, the quantify of energy transported, and the routes and distances of voyages. For instance, transportation emissions from LNG carriers for LNG fuel vary significantly depending on the country of import, ranging from 2.26 g CO2 eq./MJ (representing 12.2 % of Well-to-Tank (WtT) emissions for Malaysia) to 5.97 g CO2 eq./MJ (representing 33.3 % of WtT emissions for Qatar). As a preliminary study, an enhancement on the quality of the input/inventory data is imperative for obtaining a reliability of results. Nevertheless, the comparative analysis of different fuels and life stages provides valuable insights for stakeholders to develop effective policies and energy refueling plans for reducing life cycle GHG emissions from marine fuels. These findings could also enhance the current regulatory framework and provide meaningful lifecycle carbon footprints of marine fuels for energy importing countries. The study results also strongly suggest that default values of GHG emission for different countries relying on energy imports via international maritime transport should be further developed in consideration of the impact of regional differences, such as distance, from the importing country for successful arrival of LCA application on marine industry.

Estimation of life cycle greenhouse gas emissions of asphaltene-based carbon fibers derived from oil sands bitumen

Bitumen-derived asphaltenes have emerged as a potential precursor for carbon fiber production. The technology to make it possible is in the early stages of research and development and so there are no studies on the GHG emissions from the process, which are critical to compare its carbon footprint with that of polyacrylonitrile (PAN), the standard precursor for carbon fiber production. The asphaltene-based carbon fiber (ACF) life cycle stages are bitumen production, asphaltene separation, precursor manufacturing, and carbon fiber production. In this study, we developed data-intensive models to estimate the life cycle GHG emissions of ACF. Sensitivity and uncertainty analyses were also performed to determine the inputs that have the largest effect on the GHG emissions of ACF. The results show that the life cycle GHG emissions of ACF are 16.2 kg CO2eq/kg CF. This value represents a reduction of 68.7% compared to PAN-based carbon fiber. The carbon fiber production stage is the most emission-intensive, mainly because of the high consumption of electricity. When uncertainty is considered, the life cycle GHG emissions of ACF range from 10.4 to 21.8 kg CO2eq/kg CF. The outcome of this study confirms the potential of asphaltenes as a low-carbon intense raw material for carbon fiber production.

Mitigating lifecycle GHG emissions of building sector through prefabricated light-steel buildings in comparison with traditional cast-in-place buildings

Prefabricated light-steel buildings (PLB), as a typical prefabricated building, are regarded as a potential solution in the sustainable building process. However, few researches have systematically identified the GHG emissions and reduction potential of PLBs from the whole lifecycle perspective. Thus, taking two low-rise buildings with similar building scales as the research objects, this study is designed to understand the lifecycle GHG emissions and reduction potential of PLB and traditional cast-in-place building (TCB) using Life Cycle Assessment method. The results show that the life-cycle GHG emissions of PLB and TCB are 2848.58 and 3055.11 kg CO2 eq. /m2, respectively, implying a 6.76% reduction potential of PLB. The use and operation phase of PLB (85.76%) and TCB (83.57%) accounts for the majority of GHG emissions. Compared with TCB, the GHG emissions in the construction phase of PLB are reduced by 12.45%, and its environment benefit in the end-of-life (EoL) phase is 170.05% higher. Aside from the use and operation phase, the reduction potential of PLB GHG emissions, compared with TCB, is 59.58%, in the construction and EoL phases together. Overall, this study evaluates PLB and TCB' GHG emissions, and finds sustainable buildings and effective reduction emission measures, which will promote the green development of construction industry in China.

The development of life cycle greenhouse gas emission footprints of novel pathways for the solvent-assisted and solvent-electromagnetic heating oil sands extraction processes

Steam-based oil sands extraction methods are emissions-intensive. Solvent-assisted and solvent-electromagnetic heating are alternative methods with the potential to lower greenhouse gas emissions (GHG). However, identifying an energy-efficient process pathway for these technologies remains a major concern. This is a gap in the research. In this study, we developed simulation models to assess the performance of solvent-assisted, solvent-electromagnetic heating, and steam-assisted oil sands extraction central processing facilities. Three central processing facilities (pathways) were developed for solvent-assisted and solvent-electromagnetic heating processes to recover bitumen and solvent from emulsions. Pathways I and III use a low-temperature and a high-temperature distillation system, respectively, to purify the solvent. Pathway II uses a high-pressure separator to lower the amount of non-condensable gases in the solvent. Each pathway was applied to a deep and a shallow reservoir. Sensitivity and uncertainty analyses were conducted to present the GHG emission results. The results show that pathways I and III produce satisfactory solvent purity and minimize solvent losses in the central processing facility, and pathway II does not. Pathway II can be applied when a high degree of purity is not required. The life cycle GHG emissions from pathways I and II may not be favorable to the solvent-assisted process if the electricity emission factor and solvent-to-oil ratio are high. The lowest GHG emissions are from pathway III. The life cycle GHG emissions of the solvent-electromagnetic heating extraction in pathway III range from 34.4 to 61.7 and 23.3 to 43.9 kgCO2e/b-e for the deep and shallow reservoirs, respectively, while solvent-assisted emissions range from 26.6 to 48.2 and 20.2 to 40.0 kgCO2e/b-e for the deep and shallow reservoirs, respectively. Steam-assisted gravity drainage emissions range from 72.7 to 111.6 kgCO2e/b. The results show that solvent-assisted and solvent-electromagnetic heating processes can provide better performance than steam-assisted gravity drainage when a high-temperature distillation is installed in the central processing facility to recycle the solvent.

Developing Supportive Bioeconomy Policies

Developing Supportive Bioeconomy Policies