Life Cycle CO2 Emissions Research Articles

Influence of Natural Fiber Content on the Frictional Material of Brake Pads—A Review

Research into the use of eco-friendly materials, such as natural fibers, in brake pads has gained momentum in the last few decades. This can be attributed to the potential of natural fibers to replace traditional materials in tribological applications such as braking pads. The harmful impact of the commonly-used brake pad materials, such as metal and mineral fibers, on human health and the environment necessitates the development of eco-friendly alternatives. Natural fibers, such as banana peels, palm kernels, and palm slag, have been shown to be a viable replacement for traditional brake pad materials. This article reviews the literature on the use of different natural fibers in brake pads and their impact on the physical, mechanical, and tribological properties. Trends for density, porosity, hardness, coefficient of friction (COF), and wear rate are observed. The recommended formulations to yield the optimum properties, according to the perspective of several studies, are showcased. In addition, the effect of asbestos material and natural fibers on life-cycle assessment and CO2 emission is highlighted. This article is an attempt to provide a foundation for future researchers in the field of natural fiber-reinforced composites for brake pad applications.

Performance Investigation of Life Cycle Cost and CO2 Emissions of the Solar PV System

Abstract: With depletion of fossil fuel resources, the world is moving towards the use of non-conventional energy resources; among which the solar energy is pollution free and inexhaustible option. In this study, energy based analysis of photovoltaic (PV) system is analyzed for the climate of Madhav Institute of Technology and science, Gwalior, India and carbon credit is earned and calculated for the same. This analysis of PV system is done based on monthly performance of the system and life of 30 years. Embodied energy and Energy Payback (EPB) is also analyzed for calculation of reduction in CO2 emission while generating of electrical energy.

CO2 emission reduction effect of photovoltaic industry through 2060 in China

In the coming four-decade, China will face serious challenge while shifting to carbon neutral. Photovoltaic (PV) power, as one of the most promising clean energies, is seen as an important focus for decarbonization of the power sector in China. The novelty of this study is to use life cycle assessment (LCA) methods to analyze the CO2 emission reduction of the PV generation industry before 2060 base on the amount of energy and resources consumed and PV generation's CO2 reduction benefits during the whole industrial chain. This paper aims to examine CO2 emission reduction contribution, we firstly compute the historical emissions and predict future PV waste and new power capacity from 2010 to 2060. Then, considering the change of industrial structure and technological evolution, the yearly life cycle CO2 emission from producing stage to recycling stage is calculated. The key results show that the unit CO2 emission of PV system producing will reduce 88.07% from 2010 to 2060. PV generation industry's total CO2 emission has reached its neutrality between 2014 and 2015, and will reduce 33.03 Giga tons CO2-eq till 2060. The findings can offer relevant insights to low-carbon development of China's PV industry and will provide suggestions for policy-making.

Application of Alkali-Activated Sustainable Materials: A Step towards Net Zero Binder

Economic growth and rapid urbanization have resulted in the increase in demand for infrastructure development. To meet this ever increasing demand, conventional construction materials such as concrete are used, which requires an energy intensive process that in turn impacts the environment adversely. Ordinary Portland Cement, being the dominant binder in the industry, contributes around 8% of worldwide annual carbon emissions, and this is expected to reach around 20% by 2050. Population growth has resulted in the significant increase in agro-industrial waste generation during recent years. Inadequate waste management raises a number of environmental concerns. With the growing economy and rising living standards, global raw material consumption is expected to double by 2060. The reutilization of waste materials will aid in their management, while conserving the available resources. Alkali-activated materials (AAM) have recently been introduced as an eco-friendly alternative to conventional binders with fewer environmental impacts. AAM reduce the need for Ordinary Portland Cement (OPC) by substituting it with supplementary cementitious materials (SCM), and therefore, reducing the amount of subsequent carbon emissions. Alkali activation is a complex chemical process between the precursors (alumino-silicate materials) and their dissolution in the activators. Different materials react to alkali activators in different ways depending on their properties. The current study aims to provide a critical review of potential agro-industrial wastes on the fresh and hardened properties of alkali-activated concrete (AAC). To understand the design and development of AAC, influencing the parameters such as the molarity of NaOH, alkali activators, and the ratio of the activators have been discussed in detail. The curing regime and its effect on the behavior of alkali-activated concrete are mentioned. The different admixtures used to regulate the properties of AAC are highlighted. AAC exhibited optimized embodied energy, operational energy, life cycle cost, CO2 emission, and raw material consumption rates than the conventional concrete did. However, these results varied based on the precursors used in them. This paper focuses on the design and development of AAC, and it should be viewed as an important contribution towards the adoption of AAC in practical applications. The study presents the potential of AAM as a net zero binder in the making of sustainable concrete with enhanced properties.

An Analysis of the Potential and Cost of the U.S. Refinery Sector Decarbonization.

In 2019, U.S. petroleum refineries emitted 196 million metric tons (MT) of CO2, while the well-to-gate and the full life cycle CO2 emissions were significantly higher, reaching 419 and 2843 million MT of CO2, respectively. This analysis examines decarbonization opportunities for U.S. refineries and the cost to achieve both refinery-level and complete life-cycle CO2 emission reductions. We used 2019 life-cycle CO2 emissions from U.S. refineries as a baseline and identified three categories of decarbonization opportunity: (1) switching refinery energy inputs from fossil to renewable sources (e.g., switch hydrogen source); (2) carbon capture and storage of CO2 from various refining units; and (3) changing the feedstock from petroleum crude to biocrude using various blending levels. While all three options can reduce CO2 emissions from refineries, only the third can reduce emissions throughout the life cycle of refinery products, including the combustion of fuels (e.g., gasoline and diesel) during end use applications. A decarbonization approach that combines strategies 1, 2, and 3 can achieve negative life-cycle CO2 emissions, with an average CO2 avoidance cost of $113-$477/MT CO2, or $54-$227/bbl of processed crude; these costs are driven primarily by the high cost of biocrude feedstock.

New modelling approach for the optimal sizing of an islanded microgrid considering economic and environmental challenges

The goal of this study is to optimize the sizing of PV/Batteries/Diesel generator/Electrical load Microgrid (MG) through targeting the minimization of cost and CO2 life cycle emissions of all the MG components. In order to reach these objectives, an Energy Management System (EMS) is designed. A Mixed Integer Linear Programming (MILP) generates the power flow distribution while minimizing CO2 life cycle emissions. The power flow computed by the MILP does not operate on real-time basis. The MILP algorithm takes into consideration the future usage cost of batteries and provides the EMS by ensuring that the storage system returns back to initial conditions at the end of every representative day. An economic function computes the capital expenditure (CAPEX) and the operation expenditure (OPEX) costs using both the power flow calculated by the MILP function and the sizing parameters generated from Genetic Algorithm (GA). The GA algorithm finds a set of sizing solutions that minimize life cycle CO2 emissions and CAPEX and OPEX of the microgrid. A new modelling strategy based on hourly allocation of costs and emissions is presented in this study. It allows taking sizing decisions on hourly basis while avoiding to specify MG elements replacement time and costs. A sensitivity analysis is conducted in this paper to show the robustness of the optimal sizing towards economic and emission parameters’ variation.

Estimating mortality cost and social cost of CO2 emitted by items, applied to passenger vehicles

Over 60% of carbon emissions are from residential consumption. People in developed nations need to reduce their carbon footprints six-fold to stabilize CO2 levels in the atmosphere. This research develops a method of estimating and monetizing mortality costs of items. Mortality Cost of Carbon Rate (MCCR) is the fraction of a climate change related death that would probably occur over 80 yr with a specified temperature trajectory, from the emission of 1 tCO2e. MCCRs are allocated to items on an exponential curve generated from two researched MCCRs corresponding to temperature trajectories. MCC of an item (MCCI) is its MCCR multiplied by its life cycle CO2e emissions. The method was applied to the 2020 Australian passenger vehicle fleet and 6 vehicle types. MCCI was compared to mortalities from crashes and exhaust pollution. Total fleet mortality was estimated at around 62,000/ year. Mortality from 2020 CO2 emissions will probably be around 56,000 - 75 times higher than crash deaths - with uncertainty range 28,000 to 106,000, compared to toxic exhaust emissions 5,600 and crashes 750. A Sustainable Personal CO2 Footprint' of 1.5 t CO2/ person/ year was set as a benchmark for sustainable consumption. Electric buses, E-bicycles/ scooters and micro-EVs are sustainable and if universally adopted, would reduce mortality by 96%. Social Cost of Carbon Mortality Rate (SCCMR) monetizes MCCR using a global Value of a Statistical Life Year. SCCM of items (SCCMI) is calculated as for MCCI. Research estimates of MCCR and SCCMR vary according to assumed causes of mortality, temperature trajectories and discount rates; many are underestimated as they exclude some mortality damage sectors. Toxic exhaust emission and crash mortalities were monetized using the Australian Value of a Statistical Life. Total social mortality cost of a large 4 wd ICE diesel SUV was approximately $6300, current fleet average $4800, and micro-EV $400.

Environmental and energy impacts of battery electric and conventional vehicles: A study in Sweden under recycling scenarios

Electromobility is the future main system for Swedish road transport that encourage sustainable urban transportation. However, emission impacts of applying electric vehicles (EVs) are currently controversial. This study evaluates and compares internal combustion engine vehicles (ICEVs) refer to both petrol and diesel-based engines and BEVs, focusing on environmental and energy impacts. The entire life cycle of vehicles production, fuel production and fuel use are considered and life cycle emissions impacts due to various electricity generation alternatives will be studied. LCA of BEV is also conducted under different recycling scenarios to determine what extent CO2 can be further reduced owing to car and battery recycling. The results show that BEVs charged by natural-gas, and renewable electricity produce less emissions of CO2, SO2, PM, VOCs, NOX and Sb than ICEVs but higher PO4 emissions and need more energy. The largest fraction of CO2 emissions for BEVs charged via renewable electricity is due to vehicle production (61-78% of BEV's life cycle CO2 emissions). CO2 emissions regarding to vehicle production for BEVs is 14.6 ton (60.8 gCO2/km) which is 132% and 123% of that for petrol and diesel ICEVs, respectively. Human toxicity and eutrophication impacts highlight as potentially important categories for transition from ICEVs to BEVs due to high toxicity and PO4 emissions in BEV production. By applying high scenario for car and battery recycling, CO2 emissions in BEVs lifespan charged by renewable electricity can be reduced 50% (83 gCO2/km); total PO4 emissions can be also decreased 56% with production of 79 mgPO4/km.

Thermal and optical performance analysis of triangular solar air collectors and regional applicability in China

Improving the applicability of solar air collectors in different climatic regions is important for its popularization. In this study, a novel triangular solar air collector (TSAC) was proposed. The insulation material (TSAC_1), transparent cover plate (TSAC_2) or double transparent cover plate (TSAC_3) could be fitted on the side of TSAC to adapt to different climates. The optical model and heat transfer model of the TSACs were established and verified. Two optical efficiencies were defined and the optical properties of three TSACs were compared. The effect of environment temperature, global solar radiation, solar azimuth angle and insulation material absorption on the thermal performance of TSACs were analyzed. Based on meteorological parameters of eight cities in different climate and solar energy distribution regions, the applicability of TSACs was compared, and their life-cycle economics and CO2 emission reduction capacity were assessed. Results indicate that the TSAC_2 has the highest optical efficiency, and 15.2 % higher than that of TSAC_1. Three TSACs are suitable for different climatic regions, the average thermal efficiency of the optimal TSAC applied to the eight cities is 47.3 % during the heating period, which is 5.6 % higher than that of the single TSAC_1. TSACs have good economics in all climate regions, and the average net CO2 emission reduction of whole life cycle is 3230.3 kg.

Fuel cell integrated carbon negative power generation from biomass

Combining biomass-fuelled power plant with carbon capture and storage allows CO2 to be removed from the atmosphere, considering biomass a carbon–neutral fuel. In the present study, a biomass-based CO2 negative system has been proposed, which combines a biomass steam gasification facility with a solid oxide fuel cell, a post-combustion carbon capture facility with a molten carbonate fuel cell (MCFC), and waste heat recovery using the organic Rankine cycle. A techno-economic analysis of two scenarios, namely a) with MCFC-based CO2 capture and b) without CO2 capture, was conducted. Integration of MCFC and carbon capture system was able to capture 99.2% of CO2. It was found that the energy efficiency of the system was decreased by 9.43%, with the incorporation of CO2 capture facilities. Furthermore, exergy efficiencies for the configuration with CO2 capture and without CO2 capture are calculated as 62% and 70.22%, respectively. The economic analysis reveals that the levelized cost of electricity (LCOE) for the configuration with CO2 capture and without CO2 capture is estimated to be 0.062 $/kWh and 0.052 $/kWh, respectively. Finally, life cycle CO2 emissions for both the scenarios have been performed, and the analysis reveals that the proposed CO2 negative system is able to capture 1100 tonnes of CO2 per year.

Evaluation of carbon footprint and energy input of internal combustion engine vehicles in China

AbstractLarge amounts of carbon dioxide (CO2) are discharged into air by combustion of gasoline and energy is input in a passenger internal combustion engine vehicle (ICEV) system through lifecycle phases. Thus, this study aims to evaluate the lifecycle carbon emissions and primary energy input of passenger ICEVs. With the life cycle assessment method, the calculations of carbon emission intensity and energy input intensity of materials used in lifecycle phases were made. The results show that the total lifecycle gasoline consumption of a vehicle was estimated to be 33,000 kg and the lifecycle CO2 emissions reached 81,311 kg per vehicle. Lifecycle CO2 emissions in use period occupied 89.43%, mainly attributed to the combustion of petrol. The average lifecycle CO2 emission intensity of the materials used was 2.33 kg/kg. The lifecycle carbon footprint of the passenger ICEVs was 163 g/km. The total CO2 emissions of ICEVs in Beijing were largest of all cities due to the maximum owning amount. The ratio of total lifecycle CO2 emissions of ICEVs in 13 large cities studied in this work to those of nationwide ICEVs was 0.179. Thus, more new energy vehicles will be given the prioritized choice in the future.

Targeted Use of Sustainable Aviation Fuel to Maximize Climate Benefits.

Sustainable aviation fuel (SAF) can reduce aviation's CO2 and non-CO2 impacts. We quantify the change in contrail properties and climate forcing in the North Atlantic resulting from different blending ratios of SAF and demonstrate that intelligently allocating the limited SAF supply could multiply its overall climate benefit by factors of 9-15. A fleetwide adoption of 100% SAF increases contrail occurrence (+5%), but lower nonvolatile particle emissions (-52%) reduce the annual mean contrail net radiative forcing (-44%), adding to climate gains from reduced life cycle CO2 emissions. However, in the short term, SAF supply will be constrained. SAF blended at a 1% ratio and uniformly distributed to all transatlantic flights would reduce both the annual contrail energy forcing (EFcontrail) and the total energy forcing (EFtotal, contrails + change in CO2 life cycle emissions) by ∼0.6%. Instead, targeting the same quantity of SAF at a 50% blend ratio to ∼2% of flights responsible for the most highly warming contrails reduces EFcontrail and EFtotal by ∼10 and ∼6%, respectively. Acknowledging forecasting uncertainties, SAF blended at lower ratios (10%) and distributed to more flights (∼9%) still reduces EFcontrail (∼5%) and EFtotal (∼3%). Both strategies deploy SAF on flights with engine particle emissions exceeding 1012 m-1, at night-time, and in winter.

Life Cycle Analysis of Thin-Film Photovoltaic Thermal Systems for Different Tropical Regions

Different energy solutions are required to satisfy the energy demand of the world’s ever-growing population. Photovoltaic Thermal systems (PVT) could propose resolutions to tackle real-time issues regarding power generation. Life Cycle Analysis (LCA) is performed to compare the environmental impact and measure the energy across different PVT modules consisting of a-Si, CdTe, and CIS thin-film solar cells. The authors performed LCA to calculate the energy payback time (EPBT) and life-cycle CO2 emissions of residential rooftop and open-field PVT systems. The primary energy needed to produce thin-film PVT modules of 1 m2 cell area was considered in the present life cycle analysis studies operated using water as the working fluid. The annual net electrical energy savings at various Indian weather conditions, such as New Delhi, Jodhpur, and Ladakh, have been calculated. For the thin-film PVT systems, the calculated values of annual energy yield for three locations with average solar radiation levels and peak sun hours in the range of 600–1000 W/m2 and 6–8 h were reported. Results show that the CO2 emissions for rooftop installation of CdTe and CIS are around 200 and 156 kg/annually, which is lower than the open field installation of the same, where CO2 emissions were found to be 295 and 250 kg/year.

Life cycle impacts of concentrated solar power generation on land resources and soil carbon losses in the United States

Endpoint impacts related to the transformation of land—including that related to energy infrastructure—have yet to be fully quantified and understood in life cycle assessment (LCA). Concentrated solar power (CSP) which generates electricity by using mirrors to concentrate incoming shortwave radiation onto a receiver, may serve as an alternate source of reliable baseload power in the coming years. As of 2019 (baseline year of the study), the United States (U.S.) had 1.7 GW of installed capacity across a total of eight CSP sites. In this study, we (1) develop an empirical, spatially explicit methodology to categorize physical elements embodied in energy infrastructure using a LCA approach and manual image annotation, (2) use this categorization scheme to quantify land- and ecosystem service-related endpoint impacts, notably potential losses in soil carbon, owing to energy infrastructure development and as a function of electricity generated (i.e., megawatt-hour, MWh); and (3) validate and apply this method to CSP power plants within the U.S. In the Western U.S., CSP projects are sited in Arizona, California, and Nevada. Project infrastructure can be disaggregated into the following physical elements: mirrors (“heliostats”), generators, internal roads, external roads, substations, and water bodies. Of these elements, results reveal that mirrors are the most land intensive element of CSP infrastructure (>90%). Median land transformation and capacity-based land-use efficiency are 0.4 (range of 0.3–6.8) m2/MWh and 40 (range of 11–48) W/m2, respectively. Soil grading and other site preparation disturbances may result in the release of both organic and inorganic carbon—the latter representing the majority stocks in deeper caliche layers—thus leading to potentially significant losses of stored carbon. We estimate three scenarios of soil carbon loss into the atmosphere across 30 years, based on land transformation in m2per megawatt-hour (m2/MWh) and carbon stock in kilograms of carbon per megawatt-hour (kg C/MWh). Results reveal that potential belowground CO2released may range from 7 to 137% of total life cycle CO2emissions. While this study takes a simplistic approach to estimating loss of carbon, the broad methodology provides a valuable baseline for improving comparative analyses of land-related endpoint impacts across energy technologies and other product systems.

Techno-economic assessment of vehicle electrification in the six largest global automotive markets

Recently, many countries have set the target for the automakers to sell only vehicles with zero tailpipe emissions in the future, like in Europe, the United Kingdom, as well as the United States of America, promoting a major shift towards electric vehicles globally. But the electric vehicles do have emissions during their entire life cycle, these emissions vary from country to country, depending mainly on their electricity generation mix. Moreover, considering the cost aspect, an Electric Vehicle with a driving range of 500 km costs way higher than an Internal Combustion Engine Vehicle offering twice the range. Hence, in this study, a numerical evaluation is done for conventional diesel, hybrid and electric sports utility vehicles, on real drive cycles in the six largest automotive markets, namely, China, United States of America, Europe, Japan, India and Brazil, to assess the degree of electrification suitable for lowest life cycle emissions and total cost of ownership in each country. The global results for diesel, hybrid and electric vehicles of life cycle CO2 emissions are 0.21–0.29 kg/km, 0.13–0.20 kg/km and 0.08–0.20 kg/km while for total cost of ownership are 0.21–0.33 €/km, 0.23–0.34 €/km and 0.37–0.47 €/km, respectively. Thus, although the long-range Electric Vehicles can be emitting lowest in few markets, its total cost of ownership will still be the highest.

An eco-technoeconomic analysis of hydrogen production using solid oxide electrolysis cells that accounts for long-term degradation

This paper presents an eco-technoeconomic analysis (eTEA) of hydrogen production via solid oxide electrolysis cells (SOECs) aimed at identifying the economically optimal size and operating trajectories for these cells. Notably, degradation effects were accounted by employing a data-driven degradation-based model previously developed by our group for the analysis of SOECs. This model enabled the identification of the optimal trajectories under which SOECs can be economically operated over extended periods of time, with reduced degradation rate. The findings indicated that the levelized cost of hydrogen (LCOH) produced by SOECs (ranging from 2.78 to 11.67 $/kg H2) is higher compared to gray hydrogen generated via steam methane reforming (SMR) (varying from 1.03 to 2.16 $ per kg H2), which is currently the dominant commercial process for large-scale hydrogen production. Additionally, SOECs generally had lower life cycle CO2 emissions per kilogram of produced hydrogen (from 1.62 to 3.6 kg CO2 per kg H2) compared to SMR (10.72–15.86 kg CO2 per kg H2). However, SOEC life cycle CO2 emissions are highly dependent on the CO2 emissions produced by its power source, as SOECs powered by high-CO2-emission sources can produce as much as 32.22 kg CO2 per kg H2. Finally, the findings of a sensitivity analysis indicated that the price of electricity has a greater influence on the LCOH than the capital cost.

Sustainable Public Procurement in the Building Construction Sector

Considering that in the E.U. public procurement in the construction sector is highly represented, the Directive 2014/24/EU is implemented for harmonizing procurement processes across European countries. The Directive is transposed in Italy, through the Sustainable Public Procurement (SPP) national action plan, for supporting public procurement and public–private partnership (PPP) interventions. SPP is founded on two pillars: according to an economic viewpoint, the financial efficiency is the key aspect to verify, and, according to a sustainability viewpoint, externalities are a key element in the environmental evaluation, despite the fact that their monetary quantification into the global cost calculation is quite complex. Thus, this work aims to explore a methodology for the joint evaluation of economic–environmental sustainability of project options, in the tender evaluation phase of the SPP. The methodology is based on the life cycle costing (LCC) and CO2 emissions joint assessment, including criteria weighting and uncertainty components. Two alternative technologies—a timber and an aluminum window frame—are assumed as a case for a simulation, implemented with the software “Smart SPP LCC-CO2 Tool” (developed through the research “Smart SPP—Innovation through sustainable procurement”, supported by Intelligent Energy Europe). The simulation demonstrates that the methodology is a fast and effective modality for selecting alternative options, introducing sustainability in the decision-making process. The work is a contribution to the growing literature on the topic, and for giving support to subjects (public authorities and private operators) involved in public procurement processes/PPP interventions.

Unsteady Flamelet modeling study on OMEx-type fuels under Engine Combustion Network Spray A conditions

Poly-Oxymethylene Dimethyl Ethers OMEx are synthetic and potentially-renewable fuels that lead to a notable reduction of the lifecycle CO2 emissions while promoting lower soot emissions than conventional Diesel fuel. In the present contribution, a computational study with a single component OME1 and a multicomponent OMEx fuel has been carried out under reference Spray A conditions from the Engine Combustion Network (ECN), which mimic in-cylinder conditions representative of Diesel engines. For both fuels, three ambient temperature conditions have been swept at constant ambient density. Calculations have been carried out using an Unsteady Flamelet Progress Variable (UFPV) combustion model and detailed chemical mechanisms. For both OMEx-type fuels, low temperature ignition in flamelet configurations start in lean mixtures, which shifts towards the fuel-rich zone and eventually leads to high temperature ignition, similar to typical hydrocarbons. In agreement with corresponding fuel cetane numbers, ignition of OMEx occurs at timings similar to those of n-dodecane, which is the reference fuel for ECN studies, while a delayed ignition is obtained for OME1. However, the actual difference in ignition timing between OMEx and n-dodecane depends on diffusion in the mixture fraction space. Moreover, ignition in spray calculations seems to occur fully on the lean side, especially for OME1, as well as for the low temperature cases. This difference in ignitable mixture range between the canonical flamelet configuration and the spray calculations results from the finite residence time for relevant mixtures in the latter case, compared to an infinite residence time in flamelets. Comparison with experiments show that the modeling approach predicts most combustion metrics for both fuels and temperature values. The combination of ambient temperature and fuel-related reactivity has enabled a transition from a short ignition lifted diffusion flame structure (OMEx at 1000–900 K) towards long ignition cases, where lift-off length may eventually be longer than the maximum length of the stoichiometric surface. This results in a reaction front stabilization at very lean conditions, i.e. a type of lean mixing-controlled flame.

Digital Twin Aided Sustainability Assessment of Modern Light Rail Infrastructures

This study aims to evaluate the whole life cycle performance of Precast Advanced Track (PCAT) light rail systems in a digital twin environment, which is time-saving, flexible, and highly accurate. Two sustainability aspects of the system are addressed: environmental and economic impacts. In the life cycle assessment (LCA), energy consumption and CO2 emissions are calculated, whereas costs at each stage were calculated and converted to present values in the life cycle costing assessment (LCC). Revit is used for assessment. It enables the bill of quantities in the models to provide quantitative data for sustainability assessments. In the PCAT light rail systems, all structures and components have been considered, including subbase, concrete slab, rail fastening, rails, bituminous layer, rubber pad, and grease lubrication. Results exhibit that concrete slabs for street and off-street systems have a minor contribution to minimizing energy consumption, CO2 emissions, and costs. Rail fastenings and rails can be recycled, but the energy consumption is relatively enormous. Unrecyclable materials such as bitumen and grout account for a large portion of lifecycle CO2 emissions and costs. Surprisingly, these two materials are quite sensitive to parametric change. Accordingly, the digital twin confirms that PCAT concrete slabs demonstrate a good performance throughout the whole life cycle. However, there is still room for improvements, for example, re-designing a concrete slab with less grout while showing good waterproof performance. These structural modifications can be updated on the digital twin to enact positive changes for the sustainable development of light rail systems.

Towards lower CO2 emissions in iron and steel production: Life cycle energy demand-LEAP based multi-stage and multi-technique simulation

The energy-related CO2 emissions in all techniques used in the life cycle of iron and steel production (ISP) and mitigation measures need to be investigated. We combine life cycle energy demand and long-range energy alternatives planning to develop an integrated model. This model is firstly applied to measure the energy-related CO2 emissions in the life cycle of ISP including the stages of raw material acquisition, material processing, manufacturing and recycling in Jilin Province during 2020–2030. The model is also used to quantify the emission reduction potentials in three scenarios with different application levels of mitigation measures. Material processing induces over 80% of the life cycle CO2 emissions in all scenarios. A 13.90% reduction of CO2 emissions in 2030 is achieved in the low carbon scenario (LCS). 100% equipment large-scaling, application of hydrogen reduction ironmaking technology (HRIT) with a share of 30%, and increasing 15% of electric arc furnace (EAF) route contribute 29.67%, 19.55%, and 14.74% of total emission reduction in LCS, respectively. Achieving future low carbon development of ISP will depend heavily on the further increase in the proportions of HRIT, EAF route, and low carbon electricity. The findings are expected to provide government with references to formulating mitigation policies for ISP in China and other countries.