Well-to-wheel Greenhouse Gas Research Articles

Well‐to‐wheels analysis of greenhouse gas emissions for passenger vehicles in Middle East and North Africa

AbstractBattery electric vehicles (BEVs) are widely considered a pathway to achieve low carbon mobility. BEVs emit zero emissions from the tailpipe, but their life cycle carbon reduction compared to gasoline vehicles varies based on primary energy sources, electricity generation, and use efficiency. The Middle East and North Africa (MENA) region is an area rich in fossil fuels, meriting a detailed comparison between the emissions from BEV and other powertrains. We developed a MENA‐specific life cycle model that estimates well‐to‐wheel (WTW) greenhouse gas (GHG) emissions from passenger transport with internal combustion engine vehicles (ICEVs), hybrid electric vehicles (HEVs), plug‐in hybrid electric vehicles, and BEVs. MENA's average WTW GHG emissions for all supply chain steps including combustion emissions from vehicle operation are 767 g/kWh and 84 g CO2eq/MJ for electricity and gasoline, respectively, but are highly variable due to heterogeneity in upstream supply chains. The use of hybrid gasoline ICEVs provides the largest emission reduction opportunity for existing vehicle fleets in 9 of the 16 MENA countries. For these nine countries, replacing gasoline ICEVs with HEVs could, on average, reduce country‐level life cycle GHG emissions by 47%. There is a similar emission reduction opportunity for 14 of the 16 MENA countries when normalizing vehicle efficiencies irrespective of the powertrain shares and other trends in existing vehicle fleets. Future scenario analysis shows that BEVs would have the lowest WTW GHG emissions among all powertrains in most MENA countries only if significantly reduced electricity transmission losses and cleaner grid mix are realized, although a high cost of infrastructure developments is expected.

Fuel Selections for Electrified Vehicles: A Well-to-Wheel Analysis

Electrified vehicles (xEV), especially the battery electric vehicle (BEV), are burgeoning and growing fast in China, aimed at building a sustainable, carbon-neutral future. This work presents an overview and quantitative comparison of the carbon-neutral vehicles fuel options based on the well-to-wheel (WTW) analysis. A more intuitionistic figure demonstrates the fuel options for greenhouse gas (GHG) emissions and describes the sustainability. Electricity and hydrogen shift the tailpipe emissions to the upstream process, forming larger WTW emissions from a fuel cycle view. The electricity WTW GHG emission reaches as much as twice that of gasoline. However, the high efficiency of the electric drive system improves the WTW emission performance from a vehicle view, making the lowest WTW emission of BEV. The fuel options’ technical and environmental perspectives are presented. Finally, long-term carbon-neutral vehicle development is discussed.

Performance of Anisole and Isobutanol as Gasoline Bio-Blendstocks for Spark Ignition Engines

Several countries have set ambitious targets for the transport sector that mandate a gradual increase in advanced biofuel content in the coming years. The current work addresses this transition and indicates two promising gasoline bio-blendstocks: Anisole and isobutanol. The whole value chains of these bio-components were considered, focusing on end-use performance, but also analyzing feedstock and its conversion, well-to wheel (WTW) greenhouse gas (GHG) emissions and costs. Three alternative fuels, namely a ternary blend (15% anisole, 15% isobutanol, 70% fossil gasoline on an energy basis) and two binary blends (15% anisole with fossil gasoline and 30% isobutanol with fossil gasoline), were tested, focusing on their drop-in applicability in spark ignition (SI) engines. The formulated liquid fuels performed well and showed the potential to increase brake thermal efficiency (BTE) by 1.4% on average. Measured unburned hydrocarbons (HC) and carbon monoxide (CO) emissions were increased on average by 12–29% and 17–51%, respectively. However, HC and CO concentrations and exhaust temperatures were at acceptable levels for proper catalyst operation. The studied blends were estimated to bring 11–22% of WTW GHG emission reductions compared to base gasoline. Additionally, the fleet performance and benefits of flexi-fuel vehicles (FFV) were modeled for ternary blends.

Life cycle assessment of LPG and diesel vehicles in Korea

With LPG automobile deregulation in 2019, the demand for LPG automobiles has increased in Korea; therefore, a comparison of the eco-friendliness of LPG and other petroleum-based vehicles has become necessary. We conducted a well-to-wheels (WTW) analysis of diesel and LPG fuel in Korea. GREET, PRELIM, and GHGenius models were utilized to calculate and appropriately allocate the energy use and greenhouse gas (GHG) emission in the life cycle process of diesel and LPG fuel. In the well-to-tank (WTT) step, the GHG emissions of LPG were lower than that of diesel because of the lower energy consumption of LPG in fuel production. For the WTW comparison, we selected four automobiles currently sold in Korea and a 1,500kg curb weight model. The WTW GHG emissions of the LPG automobiles were lower than those of the diesel SUV and the 1 ton truck. On the other hand, the WTW GHG emissions of diesel automobiles were lower in the sedans and in the 1,500 kg model. Finally, it was verified that LPG automobiles were advantageous in terms of GHG emission in the SUV and one-ton truck, although the GHG emissions of diesel and LPG vehicles can vary depending on the fuel economy of the vehicles.

Statistically enhanced model of oil sands operations: Well-to-wheel comparison of in situ oil sands pathways

Abstract Although the life cycle greenhouse gas (GHG) emissions associated with Canadian oil sands have been investigated in recent years, questions remain regarding the source and impact of variability in emissions in this industry over time. This study combines publicly-available data from the fifteen largest operating in situ extraction projects, i.e., cyclic steam stimulation (CSS) and steam assisted gravity drainage (SAGD) with a statistically-enhanced life cycle model to investigate variability in well-to-wheel (WTW) GHG emissions. We estimate that the WTW GHG emissions from CSS-derived gasoline range from 99 to 114 g CO2eq/MJ (80% confidence interval), 6–22% higher than the RFS2 baseline. The corresponding range for SAGD-derived gasoline is 98–133 g CO2eq/MJ, 5–42% higher than the RFS2 baseline. SAGD-derived gasoline has more variability as some operators “upgrade” their crudes, emitting GHGs, whereas no CSS operator employs upgrading. Without upgrading, the 90th percentile for SAGD emissions would be 114 g CO2eq/MJ. Upstream variability in GHG emissions drives the positively skewed WTW GHG distributions. This demonstrates the importance of understanding the nature and magnitude of variability and uncertainty in decision making.

Well-to-wheel greenhouse gas implications of mid-level ethanol blend deployment in Canada's light-duty fleet

Replacing conventional gasoline with mid-level ethanol blends (15–30% ethanol by volume) can reduce fossil fuel use and greenhouse gas (GHG) emissions but require vehicle compatibility. This study quantifies the changes in fuel volumes and well-to-wheel (WTW) GHG emissions associated with potential mid-level ethanol blend deployment in Canada's light-duty vehicle fleet from 2018 to 2030. We develop a Canadian fleet model that projects the number of vehicles by vehicle technology and production year from 2015 to 2030, their fuel blend compatibilities, and their annual fuel use, considering the potential effects of ethanol blend level on vehicle fuel consumption and associated GHG emissions. The results show that the deployment of low and mid-level ethanol blends, such as E10, E15 or E25, could reduce petroleum gasoline use by 12% in 2030, while tripling ethanol use, from 2.6 to 7.2 billion liters annually. Incorporating emission factors from the GHGenius model suggests that mid-level blends can reduce fleet WTW GHG emissions in 2030 by 7.2% assuming the use of corn and wheat ethanol, and by up to 13.4% assuming cellulosic ethanol. The octane enhancing effect of ethanol is responsible for up to 30% of the reductions. Achieving the above reductions would require coordination among vehicle manufacturers, refiners and policymakers. Overall, mid-level blends can materially reduce GHG emissions of the Canadian light-duty fleet, but represent less than 1/5 of the reductions required for the light-duty fleet to achieve emissions that are 30% below 2005 levels (Canada's pledge under the Paris Agreement).

Multiobjective component sizing of a hybrid ethanol-electric vehicle propulsion system

Concerns over energy efficiency and greenhouse gas (GHG) emissions are driving research investments into advanced propulsion technologies. Plug-in hybrid electric vehicles (PHEVs) can provide a bridge that connects transport electrification to renewable bioenergy sources such as ethanol. However, it remains unclear how this pathway can simultaneously address economic, energy and environmental goals. To tackle this challenge, the present study explores, for the first time, the multiobjective optimal sizing of PHEVs powered by low-carbon sources of electricity and ethanol-gasoline blend. The empirical ethanol-gasoline blend model is incorporated into the PHEV simulation whose relevant parameters are validated using laboratory data from the European Commission – Joint Research Centre. We develop a full picture of the use-phase well-to-wheel (WTW) GHG emissions from ethanol, gasoline and grid electricity and their energy consumptions. Consequently, market-oriented PHEV sizing solutions are provided as per the power utility generation portfolio and automobile fuel properties of the target region. The results indicate that better performances of the PHEV, regarding GHG emissions and energy consumption, are associated with larger battery size and smaller engine displacement but result in a higher cost-to-power ratio. Specifically, for E25-fuelled PHEVs in markets with world average electricity carbon intensity, every 1.0 USD/kW increase in cost-to-power ratio leads to savings of 1.6 MJ energy consumption and 1.7 g CO2-eq/km WTW GHG emissions. Moreover, a clear benefit of using E25 in the hybrid propulsion system is identified, where the energy consumption and GHG emissions can be reduced by 5.9% and 12.3%, respectively.

Greenhouse gas emissions of conventional and alternative vehicles: Predictions based on energy policy analysis in South Korea

This paper compares the well-to-wheel (WTW) greenhouse gas (GHG) emissions of representative vehicle types–internal combustion engine vehicle (ICEV), hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV), battery electric vehicle (BEV), and fuel cell electric vehicle (FCEV)–in the future (2030) based on a WTW analysis for the present (2017) and an analysis of various energy policies that could affect future emissions. South Korea was selected as the target region because it has detailed energy policies related to alternative vehicles. The WTW analysis for the present was performed based on three sets of subordinate analyses: (1) life cycle analyses of eight base fuels; (2) life cycle analyses of electricity and hydrogen; and (3) analyses of the fuel economies of seven vehicle types. From the WTW analysis for the present, the national average WTW GHG emissions of ICEV-gasoline, ICEV-diesel, ICEV-liquefied petroleum gas, HEV, PHEV, BEV, and FCEV were calculated as 225, 233, 201, 159, 133, 109, and 55 g-CO2-eq./km, respectively. For calculating the WTW GHG emissions in the future, two policies regarding electricity production and three policies regarding hydrogen production were analysed. Three cases with varying the degrees of improvements in fuel economies were considered. Six future scenarios were constructed, and each scenario represented the case in which each energy policy is enacted. In the reference scenario, for compact car, the WTW GHG emissions of ICEVs-gasoline, HEV, PHEV, BEV-200 mile, FCEV were analysed as 161, 110, 97, 86, and 91 g-CO2-eq./km, respectively. The differences between ICEV/HEV and BEV were predicted to decrease in the future mainly due to larger improvements of ICEV/HEV in fuel economies compared to that of BEV. The future life cycle GHG emissions of electricity and hydrogen were calculated according to energy policy. Both two policies regarding power generation were confirmed to increase the benefits of utilizing BEVs, but current energy policy regarding hydrogen production were confirmed to decrease the benefits of utilizing FCEVs. Based on the comprehensive results of this study, a framework was proposed to evaluate the impacts of an energy policy regarding electricity and hydrogen production on the benefits of using BEVs and FCEVs compared to using HEVs and ICEVs. This framework can also be utilized in other countries when they assess and establish their energy policies.

Quantifying variability in well-to-wheel greenhouse gas emission intensities of transportation fuels derived from Canadian oil sands mining operations

How oil sands bitumen is produced (through mining or in situ methods) and how the crude is processed (either upgraded to synthetic crude oil, SCO, or diluted to produce dilbit) result in a range of crude properties with distinct downstream emissions. Previous life cycle studies of the greenhouse gas (GHG) intensities of transportation fuels derived from oil sands bitumen have not accounted for this downstream variability. We quantify, on a project basis as well as across the industry, variability in well-to-wheel (WTW) GHG intensities of transportation fuels from mined oil sands bitumen using detailed upstream, crude transport, and refinery models. Across projects, the mining project producing dilbit has lower median WTW GHG intensity per MJ (low heating value basis) gasoline (median: 96; 80% confidence interval: 93–101 g CO2eq/MJ gasoline) versus SCO projects (median: 108–114; 80% confidence interval across all SCO projects: 106–123 g CO2eq/MJ gasoline) but is strongly influenced by assumptions regarding refinery configuration and allocation to refinery products. Intraproject variability exceeds interproject variability, with 80% confidence intervals for individual projects varying up to 16 g CO2eq/MJ, and is driven in approximately equal proportions by the upstream and refining stages, although their relative contributions vary across projects. Compared to the U.S. EPA baselines, the mining project producing dilbit has a WTW GHG intensities that range from 1% (lower) to 8% (higher) and 2% (lower) to 6% (higher) for gasoline and diesel, respectively (80% confidence intervals). Across mining projects producing SCO, WTW GHG intensities range from 10 to 32% higher and 2–25% higher than the U.S. EPA baselines for gasoline and diesel, respectively. We show how downstream modeling decisions (e.g., allocation of refinery emissions to products such as gasoline) influence WTW GHG intensity distributions, compare mining and in situ bitumen production methods’ GHG intensities, and discuss implications for meeting intensity-based targets.

Environmental and economic analysis of liquefied natural gas (LNG) for heavy goods vehicles in the UK: A Well-to-Wheel and total cost of ownership evaluation

This paper evaluates the environmental and economic performance of liquefied natural gas (LNG) as a transition fuel to replace diesel in heavy goods vehicles (HGVs). A Well-to-Wheel (WTW) assessment based on real-world HGV drive cycles is performed to determine the life-cycle greenhouse gas (GHG) emissions associated with LNG relative to diesel. The analysis is complemented with a probabilistic approach to determine the total cost of ownership (TCO) across a range of scenarios. The methodologies are validated via a case study of vehicles operating in the UK, using data provided by a large food retailer. The spark-ignited LNG vehicles under study were observed to be 18% less energy efficient than their diesel counterparts, leading to a 7% increase in WTW GHG emissions. However, a reduction of up to 13% is feasible if LNG vehicles reach parity efficiency with diesel. Refuelling at publicly available stations enabled a 7% TCO saving in the nominal case, while development of private infrastructure incurred net costs. The findings of this study highlight that GHG emission reductions from LNG HGVs will only be realised if there are vehicle efficiency improvements, while the financial case for operators is positive only if a publicly accessible refuelling network is available.

Well-to-wheels greenhouse gas and air pollutant emissions from battery electric vehicles in China

Electric vehicles (EVs) play a crucial role in addressing climate change and urban air quality concerns. China has emerged as the global largest EV market with 1.2 million EVs sold in 2018. This study established a novel life cycle energy use and emission inventory collecting up-to-date data including the electricity generation mix, emission controls in the power and industrial sectors, and the energy use in the fuel transport to estimate the well-to-wheels (WTW) greenhouse gas (GHG), and air pollutant emissions for battery electric vehicles (BEVs) and gasoline passenger vehicles in China. The results show that an average BEV has 35% lower WTW GHG emissions than an average gasoline car. BEVs reduce volatile organic compounds (VOCs) and nitrogen oxides (NOX) emissions by 98% and 34%, respectively, but have comparable or slightly higher primary fine particulate matter (PM2.5) and sulfur dioxide (SO2) emissions. Compact and small-size vehicles generally have lower GHG and air pollutant emissions than mid- and large-size vehicles. Class A vehicles contribute the most in the absolute amount of GHG and air pollutant emissions and therefore have the biggest potential for emission reduction. Our results suggest that global policymakers should continue to promote the transition to clean power sources, emission control, and fuel economy regulations, which are critical to enhancing emission mitigation benefits of BEVs. We also suggest EV development strategies should be formulated targeting vehicle class with the biggest emission mitigation potentials.

China Electricity Generation Greenhouse Gas Emission Intensity in 2030: Implications for Electric Vehicles.

Electrification of transportation offers clear national energy security benefits but unclear climate benefits. With the current heterogeneity of grid electricity mix in China, greenhouse gas (GHG) benefits of battery electric vehicles (BEVs) vary dramatically with location. Currently, compared to baseline conventional gasoline vehicles, BEVs in north and northeastern Chinese provinces have very modest (∼10-20%) well-to-wheel (WTW) GHG benefits, whereas BEVs in southern provinces have substantial benefits (∼50%). With the expected transition to a more renewable electricity mix documented here, regional effects will largely disappear and the benefits of BEVs will be substantial (∼60-70% lower than current internal combustion engine vehicles (ICEVs) and ∼10-40% lower than 2030 advanced hybrid electric vehicles (HEVs)) across the whole of China by 2030. GHG emissions from BEVs in Chinese cities (Beijing, Shanghai, Chongqing, and Pearl River Delta) and United States cities and regions (New York; Washington, DC; Chicago; New England; Texas; and California) in 2015 and 2030 are evaluated and compared. BEVs in Chinese cities will still have substantially higher WTW GHG emissions than those in New York, New England, and California in 2030.

Life cycle (well-to-wheel) energy and environmental assessment of natural gas as transportation fuel in Pakistan

Consumers and organizations worldwide are searching for low-carbon alternatives to conventional gasoline and diesel vehicles to reduce greenhouse gas (GHG) emissions and their impact on the environment. Natural gas as an alternative transportation fuel has made significant inroads in the light and heavy duty vehicles market over the last fifteen years. In a sustainable development view, both vehicle emissions and energy supply chain analysis from well-to-wheel must be addressed. The aim of this research is to provide a Well-to-Wheel (WtW) assessment of energy consumptions and GHG emissions for 25 combinations of automotive fuel and matching powertrain systems, with a special focus on the natural gas pathways. Although several well-to-wheel studies available in literature are comprehensive in relation to developed countries’ conditions, it is problematic to apply the results to developing countries fuel markets, since the local fuel conditions and respective vehicle powertrain technologies are considerably different. This study deal with a comparative well-to-wheel analysis of natural gas, diesel and gasoline fuels looking at the Pakistanis situation but the models and approaches for this study can be applied to other countries having similar characteristics, as long as all the assumptions are well defined and modified to find a substitute automotive energy source and establish an energy policy in a specific region. The well-to-tank step was made using the GREET model, developed by the U.S. Argonne National Laboratory while tank-to-wheel analysis was performed using AVL Cruise, a commercially-available backward vehicle simulator. Later both stages were integrated in a well-to-wheel stage where relevant indexes were proposed and discussed. The results indicate that natural gas vehicles are 5–17% and 23–36% less fuel efficient, depending on the engine technology employed as compared to gasoline and diesel powertrain, respectively. Natural gas appears as an environmental efficient pathway regarding GHG emissions, especially compared to gasoline. In addition, using 20-year GWPs instead of 100-year GWPs increases WtW GHG emissions by 19–26% for natural gas pathways.

Well-to-wheel greenhouse gas emissions of battery electric vehicles in countries dependent on the import of fuels through maritime transportation: A South Korean case study

Well-to-wheel (WTW) analysis of battery electric vehicles (BEVs) has been mainly performed in the U.S., China, and Europe, which are countries that can produce sizable amounts of fuels or import additionally required fuels through land transportation. However, the situation characterizing these countries is far different from that of countries dependent on the import of fuels through maritime transportation, such as Japan, South Korea, and Taiwan, because the dependence on fuel imports through maritime transportation affects not only the energy mix but also the complexity and results of WTW analysis. In addition, determining the WTW greenhouse gas (GHG) emissions of driving BEVs in these countries is very important since these countries have large amounts of GHG emissions and strong interests in the widespread adoption of BEVs. Therefore, unlike previous studies, this study evaluates the WTW GHG emissions of BEVs in South Korea as an example of such countries. To perform WTW analysis of BEVs, comprehensive life cycle analyses of five power generation fuels (coal, natural gas, petroleum-based fuel, uranium, and bio heavy oil) are conducted. In addition, ten different power generation technologies and two different electric grids (mainland and the Jeju Island) in South Korea are analysed. The fuel economies of BEVs and conventional vehicles are also considered for evaluating the WTW GHG emissions. The result of this study shows that import processes commonly increase the life cycle GHG emissions of power generation fuels. The GHG emissions of natural gas from the upstream process are ∼40% higher than those of the U.S due to the liquefaction and regasification required for importing natural gas. However, although natural gas produces large amounts of GHG emissions from the upstream process, the electricity generated from natural gas still produces the lowest GHG emissions among the fossil fuels like other countries due to the high efficiency of combined cycle systems. The life cycle GHG emissions of electricity of the Korean mainland and Jeju are calculated to be 578 g CO2 eq/kWh and 544 g CO2 eq/kWh, respectively, which are higher than that of the EU and lower than that of the U.S. and China. Driving BEVs in South Korea was found to have advantages of 90–110 g CO2 eq/km and 50–60 g CO2 eq/km on average over driving internal combustion engine vehicles (ICEVs) and hybrid electric vehicles (HEVs), respectively, not only on the Korean mainland but also on Jeju Island. Because the GHG emissions from the upstream process of major power generation fuels and the life cycle GHG emissions of the electricity from major power generation technologies are determined in this study, these results are expected to be informative for other countries, which may have different detailed generation mixes, in similar situations.

Scenario Analysis of Urban Road Transportation Energy Demand and GHG Emissions in China—A Case Study for Chongqing

This study, using Chongqing City of China as an example, predicts the future motor vehicle population using the Gompertz Model and the motorcycle population using the piecewise regression model, and predicts and analyzes fuel consumption and greenhouse gas (GHG) emissions of motor vehicles from 2016 to 2035 based on the bottom-up method under different scenarios of improving the fuel economy of conventional vehicles, promoting alternative fuel vehicles, and the mixed policy of the above two policy options. The results indicate that the total population of motor vehicles in Chongqing will increase from 4.61 million in 2015 to 10.15 million in 2035. In the business-as-usual scenario, the road-transportation energy demand in Chongqing will keep increasing from 2015 and will peak in 2030, before it begins to decline by 2035. The trends for the tank to wheel (TTW) and well to wheel (WTW) GHG emissions are similar to that of energy demand. The WTW GHG emissions will increase from 24.9 Mt CO2e in 2016 to 50.5 Mt CO2e in 2030 and will then gradually decline to 48.9 Mt CO2e in 2035. Under the policy scenarios of improving fuel economy of conventional fuel passenger cars, promoting alternative fuel vehicles, and their mixed policy, direct energy consumption and TTW and WTW GHG emissions from 2016 to 2035 will be reduced to different levels. It is also found that the two types of policies have a hedging effect on the direct energy-consumption saving, TTW, and WTW GHG emission reductions. Sensitivity analysis of key parameters and policy settings is conducted to investigate the impact of their changes on the vehicle population projection, direct energy demand, and WTW GHG emissions. Some policy implications are suggested to provide reference for the formulation and adjustment of Chongqing’s, or even China’s, low-carbon road transportation policies in the future based on the analysis results.

Engine Thermal Efficiency Gain and Well-to-Wheel Greenhouse Gas Savings When Using Bioethanol as a Gasoline-Blending Component in Future Spark-Ignition Engines: A China Case Study

In 2017, the Chinese government issued a strategic policy of nationwide use of bioethanol as a gasoline-blending component by 2020 for the consideration of reducing smog and greenhouse gas (GHG) emissions. It is highly relevant to estimate the benefits of well-to-wheel (WTW) GHG emission savings using future engine technologies. However, literature about the WTW GHG emissions for ethanol blends did not cover the engine efficiency gains in engines with future technologies. In a previous publication from the authors’ group, an empirical model was developed to predict the anti-knock property and engine thermal efficiency gains of ethanol blends in spark-ignition (SI) engines. This paper is a follow-up study, looking at not only the potential engine thermal efficiency gains but also WTW GHG emissions in future engine technologies. More specifically, a case study of adding bioethanol to two representative E10 fuels (main- and premium-octane-grade fuels) from China was conducted. It is assumed that future engin...

Well-to-Wheel analysis of fossil energy use and greenhouse gas emissions for conventional, hybrid-electric and plug-in hybrid-electric city buses in the BRT system in Curitiba, Brazil

This study estimates Well-to-Wheel (WTW) fossil energy use and greenhouse gas (GHG) emissions for six types of city buses with conventional, hybrid-electric and plug-in hybrid-electric powertrains, including two-axle, articulated and bi-articulated chassis in the BRT (Bus Rapid Transit) system in Curitiba, Brazil. Particular emphasis is put on the operation phase (Tank-to-Wheel, TTW) of the city buses using the Advanced Vehicle Simulator (ADVISOR). The simulations are based on real-world driving patterns collected from Curitiba, comprising 42 driving cycles that represent city bus operation on seven BRT routes with six operation times for each.Hybrid-electric and plug-in hybrid-electric two-axle city buses use 30% and 75% less WTW fossil energy per distance compared to a conventional two-axle city bus (19.46MJfossil,WTW/km). This gives an absolute reduction of 1115gCO2e,WTW/km in WTW GHG emissions when operating a plug-in hybrid-electric city bus instead of a conventional two-axle city bus (1539gCO2e,WTW/km). However, a conventional bi-articulated city bus can be environment-friendlier than hybrid-electric city buses in terms of WTW fossil energy use and WTW GHG emissions per passenger-distance, if its passenger capacity is sufficiently utilised. Nonetheless, the plug-in hybrid-electric city bus remains the most energy-efficient and less polluting option. Hybrid-electric and plug-in hybrid-electric powertrains offer the possibility to achieve much higher levels of decarbonisation in the BRT system in Curitiba than the blending mandate of 7%vol biodiesel into diesel implemented in Brazil in 2016. In addition, the simulations show that TTW energy use can considerably vary by up to 77% between different operation times, BRT routes and types of city buses.In conclusion, advanced powertrains and large passenger capacity utilisation can promote sustainability in Curitiba’s BRT system. The results of this analysis provide important insights for decision makers both in Curitiba and other cities with similar conditions.

Life-cycle greenhouse gas emission and energy use of bioethanol produced from corn stover in China: Current perspectives and future prospectives

In this study, a life cycle analysis (LCA) of bioethanol production from corn stover is carried out under Chinese context. Three scenarios were developed and assessed based on current and future technology levels of the ethanol conversion process. Well-to-pump (WTP) and well-to-wheels (WTW) results are presented in this paper via functional units of 1 MJ of ethanol produced, 1 MJ of E100 produced and used, and 1 km of distance driven by a light-duty vehicle on E10 fuel, respectively. It was calculated that for 1 MJ of E100, the WTW Greenhouse gas (GHG) emission reduction relative to gasoline reaches 52%–55%, and the savings of fossil fuel and petroleum fuel reach 72%–76% and 74%–85%, respectively. For 1 MJ of ethanol produced, GHG emissions occurred in ethanol conversion process account for 51%–55%, and the contribution of chemical inputs reaches 36%–37% of the total life cycle GHG emissions. Furthermore, the life cycle results were found to be highly sensitive to allocation methods.

Well-to-wheel life cycle assessment of transportation fuels derived from different North American conventional crudes

Abstract A life cycle assessment (LCA) is an extremely useful tool to assess the greenhouse gas (GHG) emissions associated with all the stages of a crude oil’s life from well-to-wheel (WTW). All of the WTW life cycle stages of crude oil consume energy and produce significant amounts of GHG emissions. The present study attempts to quantify the WTW life cycle GHG emissions for transportation fuels derived from five North American conventional crudes through the development of an LCA model called FUNNEL-GHG-CCO (FUNdamental Engineering PrinciplEs-based ModeL for Estimation of GreenHouse Gases in Conventional Crude Oils). This model estimates GHG emissions from all the life cycle stages from recovery of crude to the combustion of transportation fuels in vehicle engines. The contribution of recovery emissions in the total WTW GHG emissions ranges from 3.12% for Mars crude to 24.25% for California’s Kern County heavy oil. The transportation of crude oil and refined fuel contributes only 0.44–1.73% of the total WTW life cycle GHG emissions, depending on the transportation methods and total distance transported. The GHG emissions for refining were calculated from the amount of energy use in the refining of crude oil to produce transportation fuels. All the upstream GHG emissions were allocated to gasoline, diesel, and jet fuel. Refining GHG emissions vary from 13.66–18.70 g-CO2eq/MJ-gasoline, 9.71–15.33 g-CO2eq/MJ-diesel, and 6.38–9.92 g-CO2eq/MJ-jet fuel derived from Alaska North Slope and California’s Kern County heavy oil, respectively. The total WTW life cycle GHG emissions range from 97.55 g-CO2eq/MJ-gasoline derived from Mars crude to 127.74 g-CO2eq/MJ-gasoline derived from California’s Kern County heavy oil.

Life cycle assessment of greenhouse gas emissions from Canada's oil sands-derived transportation fuels

A comprehensive LCA (life cycle assessment) for transportation fuels (gasoline, diesel, and jet fuel) derived from Canada's oil sands was conducted, and all the current possible pathways from bitumen extraction to use in vehicles were explored. Authors, in earlier studies, have presented the energy consumption and GHG (greenhouse gas) emission results for individual unit operations-recovery, extraction, upgrading and refining. The LC (life cycle) inventory data for the current LCA study were obtained from theoretical model named FUNNEL-GHG-OS (FUNdamental ENgineering PrinciplEs- based ModeL for Estimation of GreenHouse Gases in the Oil Sands), developed from fundamental engineering principles. The impact of the cogeneration of electricity in oil sands recovery, extraction, and upgrading on the LC GHG emissions of gasoline was explored. LC WTW (well-to-wheel) GHG emissions range from 106.8 to 116 g-CO2equivalent/MJ of gasoline, 100.5 to 115.2 g-CO2equivalent/MJ of diesel, and 96.4 to 109.2 g-CO2equivalent/MJ of jet fuel, depending on the pathway. Combustion emissions (64.7%–70.3%) are the largest constituent of WTW emissions for gasoline production; recovery (through surface mining and steam assisted gravity drainage) forms 7.2%–16% depending on the LC production process of gasoline.