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Biomass fast pyrolysis followed by electrocatalytic hydrogenation (Py-ECH) with renewable electricity outperforms cellulosic ethanol in three environmental impact categories.

Coupling renewable electricity with corn stover biomass using electrocatalytic hydrogenation of pyrolysis bio-oil is potentially economically competitive vs. cellulosic ethanol.

A comprehensive experimental study of the atmospheric chemistry of (Z)- and (E)-CHClCHCl. The compounds have short atmospheric lifetimes, low photochemical ozone creation potentials, and show a substantial Cl-elimination pathway for the OH-adduct.

Correction for ‘Atmospheric chemistry of (Z)- and (E)-1,2-dichloroethene: kinetics and mechanisms of the reactions with Cl atoms, OH radicals, and O3’ by Mads P. Sulbaek Andersen et al., Phys. Chem. Chem. Phys., 2022, 24, 7356–7373, https://doi.org/10.1039/D1CP04877E.

This short article discusses the units of rate constants as used in chemical kinetics and, in particular, the aspect of non-integral powers of base units, which some might find unusual for units in the SI system. In many ways the fact that the units of the rate constants as usually defined convey information about the order of the reaction or reactions involved is very useful, but in other ways having the same (or at least very similar) quantity that has different units under different conditions is not so desirable. Furthermore, just as with chemical equilibrium constants, taking functions of the rate constant (such as the logarithm when representing the Arrhenius equation in the form ln k vs. 1/T) needs special attention. Here we examine a possible alternative definition of rate constants in terms of an explicit ratio to the concentration standard state and although we acknowledge that this approach unlikely to be adopted by the community, it serves as a basis to discuss the meaning of rate constants., Accreditation and Quality Assurance, 28 (3), ISSN:0949-1775, ISSN:1432-0517

The COVID-19 pandemic has accelerated the growth of e-commerce and automated warehouses, vehicles, and robots and has created new options for grocery supply chains. We report and compare the greenhouse gas (GHG) emissions for a 36-item grocery basket transported along 72 unique paths from a centralized warehouse to the customer, including impacts of micro-fulfillment centers, refrigeration, vehicle automation, and last-mile transportation. Our base case is in-store shopping with last-mile transportation using an internal combustion engine (ICE) SUV (6.0 kg CO

Modern automobiles are composed of more than 2000 different compounds comprising 76 different elements. Identifying supply risks across this palette of materials is important to ensure a smooth transition to more sustainable transportation technologies. This paper provides insight into how electrification is changing vehicle composition and how that change drives supply risk vulnerability by providing the first comprehensive, high-resolution (elemental and compound level) snapshot of material use in both conventional and hybrid electric vehicles (HEVs) using a consistent methodology. To make these contributions, we analyze part-level data of material use for seven current year models, ranging from internal combustion engine vehicles (ICEV) to plug-in hybrid vehicles (PHEVs). With this data set, we apply a novel machine learning algorithm to estimate missing or unreported composition data. We propose and apply a metric of vulnerability, referred to as exposure, which captures economic importance and susceptibility to price changes. We find that exposure increases from $874 per vehicle for ICEV passenger vehicles to $2344 per vehicle for SUV PHEVs. The shift to a PHEV fleet would double automaker exposure adding approximately $1 billion per year of supply risk to a hypothetical fleet of a million vehicles. The increase in exposure is largely not only due to the increased use of battery elements like cobalt, graphite, and nickel but also some more commonly used materials, most notably copper.

The introduction of automated, electrified, and ridesourcing mobility options will likely revolutionize mobility over the coming decades. Adoption of these new mobility technologies will be shaped by their economic competitiveness. Economic assessments typically focus on fixed and variable out-of-pocket monetary costs such as vehicle purchase, fuel, maintenance, parking, and insurance cost. Non-monetary costs, while difficult to quantify, are also important in determining the relative attractiveness of competing mobility options. Travel time cost (TTC) is an important non-monetary hedonic cost. Vehicle automation and shared mobility enable more productive use of travel time and have a large impact on TTC. We build on our recent monetary cost (MC) analysis by adding TTC for driving a personal vehicle, riding as a passenger, waiting for pickup, searching for parking, and walking to and from vehicles and destination points. We show that TTCs can be of major importance and are sometimes greater in value than the MCs for competing choices. The sum of MC and TTC which we define as “generalized cost” varies with trip type, travel time, and the traveler's value of time which is a function of their income. In our circa 2020 scenarios driving a personal car is the lowest cost mode for all income levels and trip lengths. Pooled ridesourcing is typically lower cost than solo ridesourcing. In marked contrast to the situation in circa 2020, in our hypothetical future automated scenario in 2030–2035 ridesourcing becomes cost competitive with private vehicles; pooled ridesourcing is generally the least attractive option for short trips. Finally, we review road pricing programs around the world. We find that even those systems with the highest fees per mile do not change the relative costs of private and ridesourced trip options significantly, with the exception of congestion area fees (such as London's). These can substantially disfavor the use of private vehicles especially for short trips.

Electrofuels, fuels produced from electricity, water, and carbon or nitrogen, are of interest as substitutes for fossil fuels in all energy and chemical sectors. This paper focuses on electrofuels for transportation, where some can be used in existing vehicle/vessel/aircraft fleets and fueling infrastructure. The aim of this study is to review publications on electrofuels and summarize costs and environmental performance. A special case, denoted as bio-electrofuels, involves hydrogen supplementing existing biomethane production (e.g. anaerobic digestion) to generate additional or different fuels. We use costs, identified in the literature, to calculate harmonized production costs for a range of electrofuels and bio-electrofuels. Results from the harmonized calculations show that bio-electrofuels generally have lower costs than electrofuels produced using captured carbon. Lowest costs are found for liquefied bio-electro-methane, bio-electro-methanol, and bio-electro-dimethyl ether. The highest cost is for electro-jet fuel. All analyzed fuels have the potential for long-term production costs in the range 90–160 € MWh−1. Dominant factors impacting production costs are electrolyzer and electricity costs, the latter connected to capacity factors (CFs) and cost for hydrogen storage. Electrofuel production costs also depend on regional conditions for renewable electricity generation, which are analyzed in sensitivity analyses using corresponding CFs in four European regions. Results show a production cost range for electro-methanol of 76–118 € MWh−1 depending on scenario and region assuming an electrolyzer CAPEX of 300–450 € kWelec −1 and CFs of 45%–65%. Lowest production costs are found in regions with good conditions for renewable electricity, such as Ireland and western Spain. The choice of system boundary has a large impact on the environmental assessments. The literature is not consistent regarding the environmental impact from different CO2 sources. The literature, however, points to the fact that renewable energy sources are required to achieve low global warming impact over the electrofuel life cycle.

This article, the eighth in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers the gas-phase thermal and photochemical reactions of organic species with four, or more, carbon atoms (≥ C4) available on the IUPAC website in 2021, including thermal reactions of closed-shell organic species with HO and NO3 radicals and their photolysis. The present work is a continuation of volume II (Atkinson et al., 2006), with new reactions and updated data sheets for reactions of HO (77 reactions) and NO3 (36 reactions) with ≥ C4 organics, including alkanes, alkenes, dienes, aromatics, oxygenated, organic nitrates and nitro compounds in addition to photochemical processes for nine species. The article consists of a summary table (Table 1), containing the recommended kinetic parameters for the evaluated reactions, and a supplement containing the data sheets, which provide information upon which recommendations are made.

Recognition of the adverse impacts of climate change has led to interest in a transition to renewable, carbon-neutral energy and fuels. Ammonia has been proposed as a renewable transportation fuel, a medium for local energy storage, and a means for long-distance renewable energy transportation. We provide a perspective on the future use of ammonia as a transportation fuel. Ammonia poses health and safety concerns and ensuring safety for widespread distribution and consumer use would be challenging. Ammonia has a low energy content and is difficult to ignite, making it a relatively poor fuel in internal combustion engines. Engine unburnt ammonia emissions reported in the literature are approximately two to three orders of magnitude greater than Euro IV tailpipe limits and point to severe challenges in meeting emission regulations. Ammonia can be used in solid oxide fuel cells, but these operate at high temperatures (700–800 °C) and are not well suited for road vehicles. Proton exchange membrane and direct ammonia alkaline membrane fuel cell systems operate near room temperature and can use ammonia directly or indirectly (after conversion to H2) however poisoning and durability is problematic. Therefore, the expected use of ammonia as fuel for road transportation is very limited. With its low energy content, ammonia is not a viable aviation fuel. Substantial use of ammonia in rail applications seems unlikely given the advanced state of electrification and challenges associated with ammonia noted for road transport, many of which would also apply to rail. In contrast, the future use of ammonia as fuel in ocean-going ships seems feasible. Many large ports are already equipped to handle ammonia, storage volume and weight are not pressing issues for large ships, safety issues would be addressed with trained crews, and emission standards are less stringent. Ammonia might also find use as an energy carrier for transport of renewable energy between regions which would be a synergy with its use as a marine fuel.

We argue that there is a need for a more precise of PFAS in a way that avoids including compounds with single CF3-, -CF2-, or CF- groups and excludes TFA and compounds that degrade to just give TFA. An example that meets this need is the definition by the U.S. Environmental Protection Agency of PFAS as "per- and polyfluorinated substances that structurally contain the unit R-(CF2)-C(F)(R1)R2. Both the CF2 and CF moieties are saturated carbons and none of the R groups (R, R1, or R2) can be hydrogen". Adoption of this definition, or one like it, would place future technical and regulatory discussions of the environmental impacts of organo-fluorine compounds on a sounder technical footing by focusing PFAS discussions and regulation on long-chain perfluoroalkyl sulfonic acids and perfluoroalkyl carboxylic acids.

Asia Pacific (AP) is the largest regional vehicle market and accounted for 48% of global sales in 2019. Air quality is a pressing issue in many AP countries and together with increased vehicle sales has led to intense scrutiny of vehicle emissions. The heterogeneity of socio-economic features and transportation patterns in AP countries has resulted in different emission levels and control policies. We present an assessment of the historical and future emissions of on-road transportation and strategies to tackle emission challenges. First, we collected historical country-level population, economic development, vehicle ownership, and transportation policy data from 1900 to 2020, and forecast future development of on-road transportation activity (both passenger and freight) based on its historical relationship with socio-economic development through 2050. We considered major countries (China, India, Japan, South Korea, Australia) individually and other AP countries as a group. Second, we generated a series of emission control scenarios with various stringency levels after a comprehensive review of vehicle control measures implemented in AP countries. The control packages included transportation mode shifts, pollutant emission standards, fuel consumption standards, fuel and powertrain diversification, improvement in fuel quality, and economic and transportation policies. Localized emission factors for greenhouse gases (GHGs) and criteria air pollutants (carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM)) were collected and estimated in line with the emission control measures. Third, we estimated historical and future emissions of AP on-road transportation from 1900 to 2050. The results showed that major air pollutants (NOx, CO, and PM2.5) from on-road vehicles peaked in 2000–2010 and are now declining despite increasing vehicle population. Control of GHGs is more challenging than for criteria air pollutants. In our reference scenario where existing policies and emission standards are implemented and new technologies are adopted according to national plans, road transportation GHG emissions in AP peak in approximately 2040.

Smog chambers interfaced with

The development of mobile Internet, smartphones, and location-based services has enabled ridesourcing, which pools vehicles and drivers to provide on-demand travel services. As an alternative transportation option, ridesourcing has significant impacts on urban travel. However, the unique mobility pattern of ridesourcing and its impact on vehicle electrification have not been well studied. To address this gap, this paper presents a comparative, big-data-driven framework to characterize the ridesourcing mobility pattern, and evaluate the acceptance potential of electric vehicles for ridesourcing in comparison with other types of vehicle use. Multi-temporal resolution ridesourcing trips are extracted from raw GPS trajectories. The patterns of three urban travel (household, ridesourcing, and taxis) are extracted from GPS trajectories in Beijing, and compared. The electrification potentials of these types of travel under different charging levels are then evaluated. The results demonstrate that mobility patterns of household, ridesourcing, and taxi drivers are similar when a single trip is considered but differ significantly when total vehicle travel is considered. We show that potential acceptance of electric vehicles decreases significantly from household to ridesourcing and taxi vehicle use. These findings provide useful insights into of the role vehicle electrification can play in sustainability of urban personal transportation across a range of drivers.

Ethanol blending into gasoline yields a wide range of octane rating responses, most frequently synergistic (i.e., greater than expected by linear blending), but also linear or antagonistic. A new a...

Smog chamber/FTIR techniques were used to investigate the kinetics and mechanism of the Cl atom and OH radical initiated oxidation of 2,2-dichloroethanol at (296 ± 1) K. Relative rate methods were used to measure k(Cl + CHCl2CH2OH) = (5.87 ± 0.96) × 10-12 and k(OH + CHCl2CH2OH) = (5.54 ± 1.94) × 10-13 cm3 molecule-1 s-1. Chlorine atom initiated oxidation of CHCl2CH2OH in one atmosphere of air gives HCOCl, CHCl2CHO, and COCl2 in yields of (62 ± 5)%, (39 ± 10)%, and (8 ± 2)%, respectively. The rate constant k(Cl + CHCl2CHO) = (8.3 ± 16) × 10-12 cm3 molecule-1 s-1 was determined and the IR spectra of CHCl2CHO is reported for the first time. The atmospheric lifetime for CHCl2CH2OH is estimated as 21 days. The experimental results are discussed in the context of the atmospheric chemistry of chlorinated alcohols.

Revolutions in shared mobility services, vehicle electrification, and automated vehicle technology will affect urban traffic patterns, energy use and CO2 emissions, the automotive industry, public transportation, and more. This paper examines the monetary costs of these innovations for users in the near-term (approximately 2020) and how they may evolve in the long-term (approximately 2030–2035). We estimate traveler costs for light duty vehicle trips on a per-mile basis, and investigate their sensitivity to vehicle powertrain, vehicle size, travel mode and intensity of vehicle use, and DC charging assumptions. To highlight differences between human and automated driving, we consider only autonomous vehicle scenarios in the long-term. We document three main findings. First, as battery costs continue to drop over the next decade, private battery electric vehicles will become more cost-competitive with internal combustion vehicles; and in high-mileage ridesourcing applications, electric vehicles will be much more cost-competitive. Second, near-term ridesourcing trips will likely remain about 4–5 times the per-mile cost of driving one's own car, while pooled trips cut this factor to around 3. Third, in the long-term automated vehicles may make ridesourcing cheaper than driving one's own vehicle. Even if the manufacturing cost of automated vehicles remains high, this cost will be minor when amortized over a service life of 400,000 miles. These findings are unchanged even with significant variations in assumed future battery and automation costs, electricity (charging) cost, vehicle insurance and maintenance cost, and ridesourcing providers' overhead rates.

Henry’s law states that the abundance of a volatile solute dissolved in a liquid is proportional to its abundance in the gas phase. It applies at equilibrium and in the limit of infinite dilution of the solute. For historical reasons, numerous different definitions, names, and symbols are used in the literature to express the proportionality coefficient, denoted the “Henry’s law constant”. Here, a consistent set of recommendations is presented. An important distinction is made between two new recommended reciprocal quantities: “Henry’s law solubility constant” (H s) and “Henry’s law volatility constant” (H v). Eight recommended variants of H s and H v are described and relations among them presented.

To meet climate targets the emissions of greenhouse gases from transport need to be reduced considerably. Electrofuels (e-fuels) produced from low-CO2 electricity, water, and carbon (or nitrogen) are potential low-climate-impact transportation fuels. The purpose of this review is to provide a technoeconomic assessment of the feasibility and potential of e-fuels for road, ocean, and air transport. The assessment is based on a review of publications discussing e-fuels for one or more transport modes. For each transport mode, (a) e-fuel options are mapped, (b) cost per transport unit (e.g. vehicle km) and carbon abatement costs are estimated and compared to conventional options, (c) prospects and challenges are highlighted, and (d) policy context is described. Carbon abatement costs for e-fuels (considering vehicle cost, fuel production and distribution cost) are estimated to be in the range 110–1250 € tonne−1 CO2 with e-gasoline and e-diesel at the high end of the range. The investigated combined biofuel and e-fuels production pathways (based on forest residues and waste) are more cost-competitive than the stand-alone e-fuel production pathways, but the global availability of sustainable biomass is limited making these pathways more constrained. While the potential for e-fuels to decarbonize the transport sector has been discussed extensively in the literature, many uncertainties in terms of production costs, vehicle costs and environmental performance remain. It is too early to rule out or strongly promote particular e-fuels for different transport modes. For e-fuels to play a significant role in transportation, their attractiveness relative to other transport options needs to be improved. Incentives will be needed for e-fuels to be cost-effective and increased clarity on how e-fuels are linked to existing policies is needed.

Increased E-commerce and demand for contactless delivery during the COVID-19 pandemic have fueled interest in robotic package delivery. We evaluate life cycle greenhouse gas (GHG) emissions for automated suburban ground delivery systems consisting of a vehicle (last-mile) and a robot (final-50-feet). Small and large cargo vans (125 and 350 cubic feet; V125 and V350) with an internal combustion engine (ICEV) and battery electric (BEV) powertrains were assessed for three delivery scenarios: (i) conventional, human-driven vehicle with human delivery; (ii) partially automated, human-driven vehicle with robot delivery; and (iii) fully automated, connected automated vehicle (CAV) with robot delivery. The robot's contribution to life cycle GHG emissions is small (2-6%). Compared to the conventional scenario, full automation results in similar GHG emissions for the V350-ICEV but 10% higher for the V125-BEV. Conventional delivery with a V125-BEV provides the lowest GHG emissions, 167 g CO2e/package, while partially automated delivery with a V350-ICEV generates the most at 486 g CO2e/package. Fuel economy and delivery density are key parameters, and electrification of the vehicle and carbon intensity of the electricity have a large impact. CAV power requirements and efficiency benefits largely offset each other, and automation has a moderate impact on life cycle GHG emissions.

Although recent studies of autonomous taxis (ATs) have begun to explore potential environmental implications of fleet deployment, little is known about their impacts over the long term. We present a life-cycle assessment framework that incorporates both direct and indirect effects of ATs at the subsystem, vehicle, and mobility-system levels. Eco-driving and intersection connectivity are the direct effects analyzed along with indirect effects that include empty kilometers, parking, charging infrastructure, powertrain rightsizing, electric vehicle adoption, ride-sharing, and fleet-turnover rates. A case study of an AT fleet in Austin, Texas from 2020 to 2050 with constant travel demand indicates the strategic deployment of an electrified AT fleet can reduce cumulative energy and greenhouse gas (GHG) emissions by 60% in the base case, with a majority of this benefit resulting from electrified powertrains. Further reductions up to 87% can be achieved with accelerated electrical grid decarbonization, dynamic ride-share, longer vehicle lifetime, more energy efficient computer systems, and faster fuel efficiency improvements for new vehicles. We highlight the major opportunities for maximizing the environmental performance of AT fleets over the long term.

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.

Interest and investment in electric vertical takeoff and landing aircraft (VTOLs), commonly known as flying cars, have grown significantly. However, their sustainability implications are unclear. We report a physics-based analysis of primary energy and greenhouse gas (GHG) emissions of VTOLs vs. ground-based cars. Tilt-rotor/duct/wing VTOLs are efficient when cruising but consume substantial energy for takeoff and climb; hence, their burdens depend critically on trip distance. For our base case, traveling 100 km (point-to-point) with one pilot in a VTOL results in well-to-wing/wheel GHG emissions that are 35% lower but 28% higher than a one-occupant internal combustion engine vehicle (ICEV) and battery electric vehicle (BEV), respectively. Comparing fully loaded VTOLs (three passengers) with ground-based cars with an average occupancy of 1.54, VTOL GHG emissions per passenger-kilometer are 52% lower than ICEVs and 6% lower than BEVs. VTOLs offer fast, predictable transportation and could have a niche role in sustainable mobility., Vertical takeoff and landing aircraft (VTOLs), or “flying cars” can shorten commute time and could play a niche role in sustainable mobility. The authors estimate that over long distances, fully-loaded electric VTOL taxis could result in fewer GHG emissions than average occupancy ground-based cars.

Substituting conventional materials with lightweight materials is an effective way to reduce the life cycle greenhouse gas (GHG) emissions from light-duty vehicles. However, estimated GHG emission reductions of lightweighting depend on multiple factors including the vehicle powertrain technology and efficiency, lightweight material employed, and end-of-life material recovery. We developed a fleet-based life cycle model to estimate the GHG emission changes due to lightweighting the U.S. light-duty fleet from 2016 to 2050, using either high strength steel or aluminum as the lightweight material. Our model estimates that implementation of an aggressive lightweighting scenario using aluminum reduces 2016 through 2050 cumulative life cycle GHG emissions from the fleet by 2.9 Gt CO

While e-fuels offer a path towards large scale use of renewable electricity in transportation and improved energy security their economic effectiveness is unclear. To address this gap, an economic and environmental analysis of e-fuel production in Germany using renewable wind energy, different electrolysis technologies, and Fischer-Tropsch synthesis in 2015 and 2030 was performed. For current alkaline electrolysis and future solid oxide co-electrolysis using wind energy for electrolysis, e-fuel production costs and life cycle emissions were estimated to be 4.97 €/leq diesel and 64.07 gCO2-eq/MJ in 2015, and 3.24 €/leq diesel and 6.63 gCO2-eq/MJ in 2030. The critical parameters determining e-fuel cost are electricity cost, carbon dioxide (CO2) cost, electrolysis investment cost, and capacity utilization. Using optimistic estimates for all these parameters gives a production cost of 1.17 €/leq diesel (3.12 € ct/MJ). Abatement costs in the range 544–6424 €/tCO2-eq were estimated for e-fuels; much higher than those for competing vehicle-fuel technology options. While e-fuels are currently not a cost-effective method to reduce CO2 emissions they could be in the future if investment cost, capacity utilization, CO2 cost, and wind electricity cost can be improved by further research and development, or if fossil fuel prices increase substantially.

The reaction of perfluorooctanoic acid with the smallest carbonyl oxide Criegee intermediate, CH2OO, has been measured and is very rapid, with a rate coefficient of (4.9 ± 0.8) × 10-10 cm3 s-1, similar to that for reactions of Criegee intermediates with other organic acids. Evidence is shown for the formation of hydroperoxymethyl perfluorooctanoate as a product. With such a large rate coefficient, reaction with Criegee intermediates can be a substantial contributor to atmospheric removal of perfluorocarboxylic acids. However, the atmospheric fates of the ester product largely regenerate the initial acid reactant. Wet deposition regenerates the perfluorocarboxylic acid via condensed-phase hydrolysis. Gas-phase reaction with OH is expected principally to result in formation of the acid anhydride, which also hydrolyzes to regenerate the acid, although a minor channel could lead to destruction of the perfluorinated backbone.

The term open-air factor (OAF) was coined following microbiological research in the 1960s and 1970s which established that rural air had powerful germicidal properties and attributed this to Criegee intermediates formed in the reaction of ozone with alkenes. We have re-evaluated those early experiments applying the current state of knowledge of ozone–alkene reactions. Contrary to previous speculation, neither Criegee intermediates nor the HO radicals formed in their decomposition are directly responsible for the germicidal activity attributed to the OAF. We identify other potential candidates, which are formed in ozone–alkene reactions and have known (and likely) germicidal properties, but the compounds responsible for the OAF remain a mystery. There has been very little research into the OAF since the 1970s, and this effect seems to have been largely forgotten. In this opinion piece we remind the community of the germicidal open-air factor. Given the current global pandemic spread by an airborne pathogen, understanding the natural germicidal effects of ambient air, solving the mystery of the open-air factor and determining how this effect can be used to improve human welfare should be a high priority for the atmospheric science community.

Expanded use of novel oil extraction technologies has increased the variability of petroleum resources and diversified the carbon footprint of the global oil supply1. Past life-cycle assessment (LCA) studies overlooked upstream emission heterogeneity by assuming that a decline in oil demand will displace average crude oil2. We explore the life-cycle greenhouse gas emissions impacts of marginal crude sources, identifying the upstream carbon intensity (CI) of the producers most sensitive to an oil demand decline (for example, due to a shift to alternative vehicles). We link econometric models of production profitability of 1,933 oilfields (~90% of the 2015 world supply) with their production CI. Then, we examine their response to a decline in demand under three oil market structures. According to our estimates, small demand shocks have different upstream CI implications than large shocks. Irrespective of the market structure, small shocks (−2.5% demand) displace mostly heavy crudes with ~25–54% higher CI than that of the global average. However, this imbalance diminishes as the shocks become bigger and if producers with market power coordinate their response to a demand decline. The carbon emissions benefits of reduction in oil demand are systematically dependent on the magnitude of demand drop and the global oil market structure. Here the non-linear relationship is revealed between carbon emissions reductions and oil demand reductions, which depends on the magnitude of demand drop and the global oil market structure.

Oil production choices are influenced by the interaction of oilfield production costs and the global price of oil. What are the characteristics of less economic oilfields, fields whose profitably is at the margin? These oilfields may differ from average fields in terms of geographical location, crude type, production practices, and carbon intensity (CI). Because these economically-marginal fields are the ones likely to respond to drop in demand (e.g., due to 2020 COVID-19 pandemic, or a rapid shift to alternatives), they represent the likely sources of oil that would be displaced. The present paper links the field-by-field costs of 1933 oilfields (representing ~ 90% of 2015 worldwide crude production) with their production environmental footprint. We show that many marginal fields also have high CI. We estimate that the fields at margin due to the 2020 COVID-19 pandemic demand reduction have upstream CI and marginal cost of production ~ 35% and 3 times higher than global average, respectively. The production termination of these fields could result in 181 Mtonne CO2Eq. annual reduction in upstream emissions in the short-term. The marginal producers in a generic small demand shock (5% or ~ 3.6 mmbbl/d drop) have an upstream CI 26% higher than average global oil producers, and at our larger generic demand shock (20% or ~ 14.3 mmbbl/d drop) have CI that is 5% higher than average. Heavy oilfields have the highest volume share in marginal crudes in all scenarios. These results further suggest that life cycle benefits of alternative fuels or vehicles or regulations that lead to reduced oil consumption are systematically larger than those typically estimated when displaced emissions are modeled using average crudes. The results only cover the upstream production CI and do not include synergistic impacts of differences in refining CI of different types of crudes, and thus could underestimate the total life cycle differences between marginal and average crudes.

Expanded use of novel oil extraction technologies has increased the variability of petroleum resources and diversified the carbon footprint of the global oil supply