Greenhouse Gas Benefits Research Articles

Regional Emissions Analysis of Light-Duty Battery Electric Vehicles

Light-duty battery electric vehicles (BEVs) can reduce both greenhouse gas (GHG) and criteria air pollutant (CAPs) emissions, when compared to gasoline vehicles. However, research has found that while today’s BEVs typically reduce GHGs, they can increase certain CAPs, though with significant regional variability based on the electric grid mix. In addition, the environmental performance of electric and gasoline vehicles is not static, as key factors driving emissions have undergone significant changes recently and are expected to continue to evolve. In this study, we perform a cradle-to-grave life cycle analysis using state-level generation mix and vehicle operation emission data. We generated state-level emission factors using a projection from 2020 to 2050 for three light-duty vehicle types. We found that BEVs currently provide GHG benefits in nearly every state, with the median state’s benefit being between approximately 50% to 60% lower than gasoline counterparts. However, gasoline vehicles currently have lower total NOx, urban NOx, total PM2.5, and urban PM2.5 in 33%; 15%; 70%; and 10% of states, respectively. BEV emissions will decrease in 2050 due to a cleaner grid, but the relative benefits when compared to gasoline vehicles do not change significantly, as gasoline vehicles are also improving over this time.

Supporting data for Implementation of greenhouse gas benefit quantification for diverse forest management activities in a statewide program

Supporting data for Implementation of greenhouse gas benefit quantification for diverse forest management activities in a statewide program

Perspectives on Bioenergy Feedstock Development in Pakistan: Challenges and Opportunities

Pakistan faces challenges in both food and energy security. Indeed, extensive literature suggests that food and energy security are interdependent. While acknowledging that food security is still a primary concern for Pakistan, energy security is also a major issue. It is crucial to develop sustainable energy sources for energy production. Among sustainable sources, biomass is a promising source that can be effectively used for environmentally friendly energy production. This article addresses the energy issues and potential solutions using crop residues, non-edible energy crops, and animal and municipal solid wastes in Pakistan. The current research challenges, relevant industries, opportunities, and the future share of energy production derived from renewable and sustainable sources are emphasized with a focus on the potential of biomass energy. This article shows that Pakistan has considerable potential to develop bioenergy crops on marginal lands without compromising food security, with considerable greenhouse gas (GHG) benefits. Pakistan has vast biomass resources, including crop residues, animal waste, municipal solid waste, and forest residues, which collectively produce 230 billion tons of biomass annually. There are about 72 million bovines (cows and buffaloes), 81 million tons per year of crop biomass, and about 785 million birds in poultry farms across the country. Land that is currently non-productive could be used for energy crops, and this has the potential to produce 2500–3000 MW of energy. The utilization of waste cooking oil and fats is the most economically feasible option for obtaining biodiesel due to its easy and almost free availability in Pakistan. Systematic management is needed to collect this huge quantity of waste cooking oil and efficiently convert it to biodiesel. Similarly, molasses may be a promising source for bioethanol production. Furthermore, this study suggests that Pakistan’s energy policies need to be amended to ensure that the energy supply meets the demand. In the future, massive energy projects on biomass-based bioenergy need to be implemented in Pakistan. To achieve its bioenergy potential, Pakistan needs to develop incentive-based bioenergy technologies. Moreover, this objective can only be achieved in the country by initiating R&D projects to promote advanced biomass conversion technologies, such as biogas plants and combustion systems.

Life-Cycle Greenhouse Gas Emission Benefits of Natural Gas Vehicles

Abundant supply, low prices, and low carbon content may result in an increased use of natural gas (NG) as an alternative transportation fuel. Assessments of the associated climate benefits are sensitive to the climate metric and time horizon selected to equate methane to equivalent CO2 emissions and to the assumptions of methane emissions during NG production, distribution, and use. We report life-cycle greenhouse gas (GHG) emissions from cars, light-duty trucks (LDTs), and heavy-duty trucks (HDTs) that are powered directly or indirectly using NG as a function of methane emission rates. We show that whether internal combustion engine vehicles (ICEVs) powered by fossil compressed natural gas (CNG) have GHG benefits over their gasoline and diesel counterparts depends on a value judgment of using either an integrated or end-point climate metric (e.g., global warming potential [GWP] or global temperature change potential [GTP]) and a short or long time horizon (e.g., 20 or 100 years). Conversion of NG into electricity or hydrogen for use in battery electric vehicles (BEVs) or fuel-cell vehicles (FCVs) has clear GHG benefits for cars and LDTs. Benefits are less clear for HDTs where heavy batteries and CNG tanks lead to a relatively poor GHG performance of BEVs and CNG_ICEVs compared to the incumbent diesel technology.

An anticipatory life cycle assessment of the use of biochar from sugarcane residues as a greenhouse gas removal technology

Greenhouse gas removal technologies are needed to reach the targets of the UNFCCC Paris Agreement. Among existing technologies, the use of biochar is considered promising, particularly biochar derived from the large quantities of sugarcane residues available in South America and elsewhere. However, the net greenhouse gas removal potential of sugarcane biochar has not been assessed hitherto. We use a scenario-based anticipatory life cycle assessment to investigate the emissions associated with a change from the combustion of sugarcane residues in a combined heat and power plant to the pyrolysis of these residues for biochar production and field application in São Paulo State, Brazil. We define scenarios based on different mean marginal electricity production and biochar production share. The results indicate that emissions from covering the electricity deficit generated by partial combustion of biomass during biochar production is the main emitting process. Overall, the processes associated with biochar production lower the net greenhouse gas benefits of the biochar by around 25%. Our analysis suggests that allocating 100% of the available sugarcane residues to biochar production could sequester 6.3 ± 0.5 t CO2eq ha−1 yr−1 of sugarcane in São Paulo State. Scaled up to the entire State, the practice could lead to the removal of 23% of the total amount of GHGs emitted by the State in 2016.

Blending blue hydrogen with natural gas for direct consumption: Examining the effect of hydrogen concentration on transportation and well-to-combustion greenhouse gas emissions

Jurisdictions are looking into mixing hydrogen into the natural gas (NG) system to reduce greenhouse gas (GHG) emissions. Earlier studies have focused on well-to-wheel analysis of H2 fuel cell vehicles, using high-level estimates for transportation-based emissions. There is limited research on transportation emissions of hythane, a blend of H2 and NG used for combustion. An in-depth analysis of the pipeline transportation system was performed for hythane and includes sensitivity and uncertainty analyses. When hythane with 15% H2 is used, transportation GHG emissions (gCO2eq/GJ) increase by 8%, combustion GHG emissions (gCO2eq/GJ) decrease by 5%, and pipeline energy capacity (GJ/hr) decreases by 11% for 50–100 million m3/d pipelines. Well-to-combustion (WTC) emissions increase by 2.0% without CCS, stay the same with a 41% CCS rate, decrease by 2.8% for the 100% CCS scenario, and decrease by 3.6% in the optimal CO2-free scenario. While hythane contains 15% H2 by volume only 5% of the gas’ energy comes from H2, limiting its GHG benefit.

Behavioral and technology implications of electromobility on household travel emissions

This paper investigates the share of household travel electrified or Utility Factor(UF) and well-to-wheel(WtW) greenhouse gas(GHG) emissions of battery electric vehicles(BEVs) in two-car households. We examine a multiyear travel data collected via GPS loggers from both vehicles(internal combustion engine vehicle-ICE and BEV) belonging to 73 California households:30 Nissan Leaf, 21 Chevy Bolt, and 22 Tesla ModelS.Results indicate that two distinct substitution patterns moderated by vehicle attributes effectuate diversified outcomes on UF and GHG. Energy efficiency losses due to technology and user preferences counteracts range enabled UF gains offsetting BEV’s GHG benefits. Fuel inefficient ICEs could aggravate emissions of longer-range BEV households. Conversely, energy efficiency improvements can augment GHG reduction, but UF decreases.Maximum UF of 75–80% can be achieved by upgrading to a longer-range BEV. Longer-range performance-oriented BEV upgrade does not improve UF but nullifies 15–30% of emission abatement potential realized by driving their existing BEV instead of ICE.

Life cycle energy and greenhouse gas emissions implications of using carbon fiber reinforced polymers in automotive components: Front subframe case study

Vehicle lightweighting benefits consumers through fuel savings, manufacturers through a more fuel-efficient vehicle portfolio, and the environment through reduced fossil fuel use and lower emissions. Vehicle components can be lightweighted by replacing conventional materials with alternatives such as aluminum or composites. However, lightweight materials come with their own set of environmental and economic challenges. Often, manufacturing of lightweight materials requires more energy than for conventional materials such as steel. Understanding the net energy and environmental benefits of lightweighting requires life cycle assessment with a large enough system boundary to prevent shifting of impacts and to ensure a fair comparison between different material options. Life cycle assessments of carbon fiber composite parts are hampered by substantial uncertainties in the energy needed for their production and recycling and the vehicle fuel consumption benefits. The present study addresses these deficiencies using a detailed vehicle fuel consumption model and industrially relevant carbon fiber production data and component design. The front subframe case study considered illustrates the challenges associated with achieving life cycle energy and greenhouse gas savings using carbon fiber. The base case with no powertrain resizing, secondary weight savings, or recycled carbon fiber and with 160,000 miles vehicle lifetime has no energy or emission benefits. When powertrain resizing, secondary weight savings, carbon fiber recycling, and increased vehicle lifetime travel were considered, energy and greenhouse gas benefits were found.

Valuing Density: An Evaluation of the Extent to which American, Australian, and Canadian Cities Account for the Climate Benefits of Density through Environmental Review

This study looks at the extent to which major cities in the United States, Australia, and Canada assess the climate impacts of densification through the environmental review process. Research indicates that greater urban density is associated with lower household greenhouse gas (GHG) emissions in high GDP countries. Yet there is reason to believe that cities may be taking a parochial approach to evaluating the climate impacts of rezonings in their environmental reviews that fails to consider the environmental costs of maintaining low density. In this study, we survey the legal and policy frameworks governing the environmental review in American, Australian, and Canadian cities to determine the extent to which they consider and analyze the GHG benefits of land use changes that increase urban density. We also analyze environmental review documents for proposals to increase residential density in cities to determine the extent to which policy makers have incorporated empirical knowledge regarding the relationship between density and GHGs emissions into their environmental reviews of proposed land use changes. We find that very few cities of those we surveyed use a formal environmental review process for analyzing the GHG impacts of land use changes. In addition, the small number of cities in our survey that analyze the GHG implications of land use changes do not appear to comprehensively consider the broader GHG benefits of densification. In fact, cities that assess the GHG impacts of zoning changes appear more likely to consider densification as causing climate harms rather than climate benefits.

Evaluation of best management practices with greenhouse gas benefits for salt-affected paddy soils in South Asia

Anthropogenic climate change has caused increased soil salinity in South Asia due to saltwater intrusion caused by sea level rise, input of fertilizers with high salt index, and irrigation malpractices, etc. Salinity has a multitude of impacts on plant and soil processes, leading to alterations in gas fluxes and rice productivity. The remedial measures adopted on salt-affected soils to reduce the salinity effect could enhance future climate change if they cause an increase in greenhouse gas (GHG) emissions. This study was conducted to find the best agricultural management practices (BMPs) for salt-affected soils in rice cropping systems (i.e. the major cropping system in Asia) in four South Asian countries (Sri Lanka, India, Bangladesh and Pakistan) considering net GHG emissions and other socioeconomic benefits associated with the adopted measures. The salinity-affected sites were selected based on available information (e.g. agricultural statistics and maps). Site-level measurements on soil parameters and GHG emissions were made in control- and managed plots and farmer surveys were conducted. Although organic amendments ameliorated salinity, it could cause a net increase in carbon dioxide or methane emissions depending on the soil conditions, particularly during the initial stages. This impact could be ameliorated by combining organic amendments with other management practices. In the Indo-Gangetic region, poor soil drainage causing anaerobic conditions favoured nitrous oxide emission under low to medium salinity. Yield losses and emissions in high salinity sites were controlled through organic amendment, irrigation and rice-fallow cropping sequence. The combination of transplanting of rice seedlings, the addition of organic matter, and intermittent irrigated water levels was identified as the BMP for Sri Lankan farmers. The outcome of this project will be used to raise awareness among farmers and policymakers.

Large Variations in N2O Fluxes from Bioenergy Crops According to Management Practices and Crop Type

Field N2O emissions are a key point in the evaluation of the greenhouse gas benefits of bioenergy crops. The aim of this study was to investigate N2O fluxes from perennial (miscanthus and switchgrass), semi-perennial (fescue and alfalfa) and annual (sorghum and triticale) bioenergy crops and to analyze the effect of the management of perennials (nitrogen fertilization and/or harvest date). Daily N2O emissions were measured quasi-continuously during at least two years in a long-term experiment, using automated chambers, with 2–5 treatments monitored simultaneously. Cumulative N2O emissions from perennials were strongly affected by management practices: fertilized miscanthus harvested early and unfertilized miscanthus harvested late had systematically much lower emissions than fertilized miscanthus harvested late (50, 160 and 1470 g N2O-N ha−1 year−1, respectively). Fertilized perennials often had similar or higher cumulative emissions than semi-perennial or annual crops. Fluxes from perennial and semi-perennial crops were characterized by long periods with low emissions interspersed with short periods with high emissions. Temperature, water-filled pore space and soil nitrates affected daily emissions but their influence varied between crop types. This study shows the complex interaction between crop type, crop management and climate, which results in large variations in N2O fluxes for a given site.

Predicting greenhouse gas benefits of improved nitrogen management in North American maize.

Farmers, food supply companies, and policymakers need practical yet scientifically robust methods to quantify how improved nitrogen (N) fertilizer management can reduce nitrous oxide (N2 O) emissions. To meet this need, we developed an empirical model based on published field data for predicting N2 O emission from rainfed maize (Zea mays L.) fields managed with inorganic N fertilizer in the United States and Canada. Nitrous oxide emissions ranged widely on an area basis (0.03-32.9kg N ha-1 yr-1 ) and a yield-scaled basis (0.006-4.8kg N Mg-1 grain yr-1 ). We evaluated multiple modeling approaches and variables using three metrics of model fit (Akaike information criteria corrected for small sample sizes [AICc], RMSE, and R2 ). Our model explains 32.8% of the total observed variation and 50% of observed site-level variation. Soil clay content was very important for predicting N2 O emission and predicting the change in N2 O emission due to a change in N balance, with the addition of a clay fixed effect explaining 37% of site-level variation. Sites with higher clay content showed greater reductions in N2 O emission for a given reduction in N balance. Therefore, high-clay sites are particularly important targets for reducing N2 O emissions. Our linear mixed model is more suitable for predicting the effect of improved N management on N2 O emission in maize fields than other published models because it (a) requires only input data readily available on working farms, (b) is derived from field observations, (c) correctly represents differences among sites using a mixed modeling approach, and (d) includes soil texture because it strongly influences N2 O emissions.

Life cycle greenhouse gas emissions of concrete containing supplementary cementitious materials: cut-off vs. substitution

Existing life cycle assessments of concrete containing supplementary cementitious materials (SCMs) hinge on methodological procedures that might skew the results towards the conclusion that increasing the use of SCMs in concrete always decreases greenhouse gas (GHG) emissions. These procedures relate to the treatment of co-products and selection of functional units. Co-production is typically addressed via cut-off procedures and by-products are always considered to be unconstrained resources, while functional units often do not account for exposure conditions and concrete properties such as strength and workability. To address this limitation, the aim of this study was to investigate the GHG benefits of using SCMs by (1) adopting different approaches to solve multifunctionality (cut-off vs. substitution) and (2) including strength, workability and exposure conditions of concrete in the functional unit. Ontario (Canada) was used as case study, and both SCMs currently used there (i.e., slag, silica fume and metakaolin) and a wide range of alternative cementitious materials used around the world (i.e., fly ash, oil shale ash, calcium carbide residue, volcanic ash, coal bottom ash and rice husk ash) were investigated. The new contribution of this study reveals that different conclusions can be drawn when different methodological procedures are adopted. If the market for SCM is constrained (i.e., by-products are already fully utilized) and the unconstrained alternative on the market is Portland cement, the benefits of using SCM are greatly reduced, or even reversed, if the substitution approach is adopted. In contrast, unconstrained SCMs result in considerable GHG savings unless they significantly reduce the water-to-binder ratio to reach a prescribed strength and require long distance transport.

Would environmental regulation improve the greenhouse gas benefits of natural gas use? A Chinese case study

Abstract Along with rapidly increasing natural gas consumption and carbon dioxide (CO2) levels and the gradually strengthening environmental regulation, further investigation of the emission-natural gas-environmental regulation nexus in China is particularly useful for mitigating the country's CO2 emissions. To empirically investigate whether environmental regulation improves the greenhouse gas benefits of natural gas use in China, this study investigates the causal relationships among CO2 emissions, natural gas consumption, and environmental regulation in China, based on panel data of China's 30 provinces covering 2005–2015. Fully considering the potential cross-sectional dependence, the system general method of moments (SYS-GMM) estimation method is utilized. The empirical results reveal that: (1) Environmental Kuznets curve (EKC) hypothesis for CO2 emissions is valid in China; (2) environmental regulation will not only directly affect CO2 emissions, but also indirectly affect CO2 emissions by influencing the energy consumption structure; (3) environmental regulation cannot significantly improve the greenhouse gas benefits of natural gas use, as environmental regulation in China can indirectly reduce CO2 emissions by decreasing coal consumption rather than increasing natural gas consumption; and (4) the causality analysis for three regions confirms the existence of significant regional differences. These findings offer several targeted policies for reducing CO2 emissions and promoting growth in the natural gas industry in China.

An integrated model for quantifying the impacts of pavement albedo and urban morphology on building energy demand

This contribution details a high-resolution approach to estimate the net greenhouse gas (GHG) impact of changing pavement albedo in urban areas by accounting for both changes in air temperature and building energy demand (BED) caused by the albedo change. The approach uses machine-learning-based meta-models that allow stakeholders to estimate the impact of pavement albedo modification for specific, detailed neighborhoods in a rapid, computationally efficient manner. This method is applied to a case study involving all buildings and the adjacent pavements in Boston, MA. Results from the case study indicate that increasing pavement albedo reduces average temperature and usually reduces carbon emissions from BED for densely-built and medium-density neighborhoods while results from low-density neighborhoods were mixed. Model results suggest that increasing pavement albedo would lead to BED GHG benefits in 88% of Boston neighborhoods. Increasing the albedo of the 1100 miles of roads in those communities would yield nearly 91,720 metric tons of reduced carbon emissions over the next fifty years.

Reducing methane losses across the gas value chain – Woodside journey to excellence

Woodside is the first, and, to date, only, Australian listed company to be a signatory to the Methane Guiding Principles, an industry, non-Government organisation and educational institution collaboration aimed at reducing methane emissions across the natural gas value chain. Woodside’s methane emissions are ~0.04% of our total hydrocarbon production, or 400 kt CO2-eq per annum (Woodside Energy 2019). This is a relatively small methane emission footprint in comparison with other industrial and oil and gas operators; however, to ensure the greenhouse gas and environmental benefits of LNG over coal and other greenhouse intensive fossil fuels remain legitimate and substantial, we recognise the important role of minimising methane losses through the natural gas value chain. The global-warming potential of methane is 86 times more potent over a 20-year time frame than that of carbon dioxide (IPCC 2014). By tackling methane emissions, significant inroads can be made in reducing the impacts of greenhouse gases in the atmosphere. Woodside became a signatory to the Methane Guiding Principles in April 2018 and has commenced a program of work to deliver on the five principles, which are to (1) continually reduce methane emissions, (2) advance strong performance across gas value chains, (3) improve accuracy of methane emissions data, (4) advocate sound policy and regulations on methane emissions and (5) increase transparency. This paper will focus on the journey we are on, namely, understanding our methane emission footprint within our operational boundaries and setting in place an action plan to reduce these emissions. But it is also a lot broader as we start to look beyond our gates to the transport and distribution networks, through to the end user turning on their gas stove at home. It is about cradle to grave custody of our product for it to be a viable long-term solution in a lower-carbon economy.

Climate Benefits of Increasing Plant Diversity in Perennial Bioenergy Crops

Bioenergy from perennial grasses mitigates climate change via displacing fossil fuels and storing atmospheric CO2 belowground as soil carbon. Here, we conduct a critical review to examine whether increasing plant diversity in bioenergy grassland systems can further increase their climate change mitigation potential. We find that compared with highly productive monocultures, diverse mixtures tend to produce as great or greater yields. In particular, there is strong evidence that legume addition improves yield, in some cases equivalent to mineral nitrogen fertilization at 33–150 kg per ha. Plant diversity can also promote soil carbon storage in the long term, reduce soil N2O emissions by 30%–40%, and suppress weed invasion, hence reducing herbicide use. These potential benefits of plant diversity translate to 50%–65% greater life-cycle greenhouse gas savings for biofuels from more diverse grassland biomass grown on degraded soils. In addition, there is growing evidence that plant diversity can accelerate land restoration.

Cradle-to-gate greenhouse gas (GHG) burdens for aluminum and steel production and cradle-to-grave GHG benefits of vehicle lightweighting in China

Greenhouse gas (GHG) burdens of steel and aluminum production and life cycle benefits of vehicle lightweighting in China were evaluated. Production of advanced high-strength steel (AHSS) and wrought aluminum (Al) have average cradle-to-gate GHG emissions of 3.9 and 17.5 kg CO2eq/kg. Lightweighting benefits for eleven passenger car models over five driving cycles (including real-world and regulatory cycles) were determined. Lightweighting using AHSS to replace conventional steel has cradle-to-grave GHG savings in all cases, mainly attributed to savings in material use. Wrought Al has a much higher GHG production burden than AHSS and requires greater fuel savings in the use phase to achieve net cradle-to-grave GHG savings. Maximum GHG savings occur with Al versus AHSS in cases where the powertrain is resized, travel is congested, or lifetime travel distance is long. A typical Beijing peak-hour driving cycle with low speed and frequent stop-and-go has higher fuel reduction values (FRVs) and GHG savings than other cycles. Congested travel conditions make lightweighting a particularly effective emissions reduction strategy in China.

Economic and Climate Benefits of Electric Vehicles in China, the United States, and Germany.

Mass adoption of electric vehicles (EVs) is widely viewed as essential to address climate change and requires a compelling case for ownership worldwide. While the manufacturing costs and technical capabilities of EVs are similar across regions, customer needs and economic contexts vary widely. Assessments of the all-electric-range required to cover day-to-day driving demand, and the climate and economic benefits of EVs, need to account for differences in regional characteristics and individual travel patterns. To meet this need travel profiles for 1681 light-duty passenger vehicles in China, the U.S., and Germany were used to make the first consistent multiregional comparison of customer and greenhouse gas (GHG) emission benefits of EVs. We show that despite differences in fuel prices, driving patterns, and subsidies, the economic benefits/challenges of EVs are generally similar across regions. Individuals who are economically most likely to adopt EVs have GHG benefits that are substantially greater than for average drivers. Such "priority" EV customers have large (32%-63%) reductions in cradle-to-grave GHG emissions. It is shown that low battery costs (below approximately $100/kWh) and a portfolio of EV offerings are required for mass adoption of electric vehicles.

An international dialogue about electric vehicle deployment to bring energy and greenhouse gas benefits through 2030 on a well-to-wheels basis

In this paper, we aim to assess the potential influence of increased adoption of electric vehicles (EVs) on a well-to-wheel (WTW) basis in the four countries with highest passenger car sales (Germany, the United States, China, and Japan), and Norway which represents a highly renewable energy market on greenhouse gas emissions. To characterize these emissions, we define critical parameters regarding fleet composition, activity, efficiency and fuel production in each country. Overall, with today’s technology at a national average level, on a per km driven basis, battery electric vehicles emit fewer greenhouse gases than conventional vehicles in all countries. Though vehicle energy consumption is similar in all countries, electricity production energy efficiency and greenhouse gas emissions per kWh electricity vary considerably, with Norway and China representing the low and high emitting endpoints, respectively. As electricity generation decarbonizes, EVs have the potential to be lower greenhouse-gas emitting than gasoline vehicles in all countries considered. The complexity of EV analysis across international boundaries, time periods, and environmental media complicates communication of EV benefits to stakeholders. Analysts must continue to address and clearly communicate the influence of EV and electricity production technology advancement into the future on EV impacts on all environmental media (air, water, land).