Greenhouse Gas Implications Research Articles

Shipping-specific ESG rating and reporting framework

ABSTRACT Strict regulatory requirements supporting environmental sustainability are consistently promoted for the shipping sector, including the IMO 2050 framework to reduce greenhouse gas implications by 50% and CO2 emissions by 70% compared to respective 2008 levels. These requirements bear critical implications for vital investment, financing, and operational decisions of shipping company management teams. Empirical evidence, furthermore, indicates growing investor preferences in favor of companies promoting ESG (environmental, social, governance) good practices. This study develops an innovative methodology to construct an integrated ESG Index tailormade to shipping idiosyncrasies. The ESG Index offers support to shipping company sustainable policies, standardizes and facilitates materially the ESG reporting process, and promotes the comparative evaluation of ESG rating between companies as well as market segments. ESG reporting and rating are constructed in a robust dynamic framework to deliver useful feedback to shipping company sustainability prospects, promoting informed managerial, stakeholder, financier, and regulatory decisions.

Greenhouse Gas Emissions and Potential for Electrifying Transportation Network Companies in Toronto

This study investigates the spatial and temporal patterns of greenhouse gas (GHG) emissions from transportation network companies (TNCs) in Toronto, Canada. TNC services primarily consist of short-distance trips in the central business district. Deadheading—driving without passengers—contributes 40% of TNC GHG emissions, and part-time drivers had a higher deadheading proportion than full-time drivers. Pooled TNC trips account for 10% of total trips, and just 27% of pooled trips resulted in multiple passengers sharing a vehicle on the same route. The GHG implications of pooled trips were compared with other TNC services and with a consumer driving their own private vehicle, through the estimation of median trip emission intensities of each TNC service in grams of CO2eq per passenger-km, while accounting for deadheading. Non-pooled internal combustion engine (ICE) ride-hailing trips have a median emission intensity 61% higher than that of a single-occupancy private vehicle. The median emission intensity for a pooled ICE ride-hailing trip is 20% higher than that of driving one’s own vehicle. Vehicle electrification provides a 91% daily GHG emission reduction for this fleet. This reduction is mainly achieved through full-time drivers, who, on average, achieve three times as much GHG savings per electrified vehicle compared with part-time drivers.

Complementary roles for mechanical and solvent-based recycling in low-carbon, circular polypropylene.

Plastic recycling presents a vexing challenge. Mechanical recycling offers substantial greenhouse gas emissions savings relative to virgin plastic production but suffers from degraded aesthetic and mechanical properties. Polypropylene, one of the most widely used and lowest-cost plastics, features methyl pendants along the polymer backbone, rendering it particularly susceptible to declining properties, performance, and aesthetics across a succession of mechanical recycles. Advanced processes, such as solvent-assisted recycling, promise near-virgin quality outputs at a greater energy and emissions footprint. Mechanical and advanced recycling are often presented as competing options, but real-world plastic waste streams are likely to require preprocessing regardless of whether they are routed to an advanced process. This study quantifies the life-cycle greenhouse gas implications of multiple recycling strategies and proposes a system in which mechanical and solvent-assisted recycling can be leveraged together to boost recycling rates and satisfy demand for a wider range of product applications. Polypropylene can be recovered from mixed-plastic bales produced at material recovery facilities and processed through mechanical recycling, with a varying fraction sent for further upgrading via solvent-assisted recycling to produce material approved for food packaging and other higher-quality applications. The resulting mechanically recycled rigid polypropylene reduces life-cycle greenhouse gas emissions by 80% relative to the same quantity of virgin material, while the upgraded higher-quality material achieves GHG savings of 30%.

Revisiting electric vehicle life cycle greenhouse gas emissions in China: A marginal emission perspective

The accurate estimation of electric vehicle (EV) life cycle greenhouse gas (GHG) emissions is critical for policymakers to predict and manage the reduction of GHG emissions due to transportation electrification. Most previous studies in the Chinese context evaluated the EV life cycle GHG based on the annual average emission factor (AAEF). However, the hourly marginal emission factor (HMEF), which is conceptually more appropriate than AAEF for evaluating the GHG implications of EV growth, has not been applied in China. This study fills this gap by estimating the EV life cycle GHG in China based on the HMEF and comparing it with AAEF-based estimates. It is found that the estimates based on the AAEF substantially underestimate the EV life cycle GHG in China. Moreover, the influences of the electricity marketization reform and changes in the EV charging mode on the EV life cycle GHG in China are analyzed.

Energy and greenhouse gas implications of shared automated electric vehicles

Automated vehicles can facilitate vehicle sharing within and between households, thus decreasing ownership rates, albeit increasing miles travelled. While electrification can achieve deep reductions in transportation-related greenhouse gas emissions, shared automated electric vehicles will have different charging needs considering their higher mileage. In this study, travel survey data collected in Toronto is used to optimize the charging needs of shared automated electric vehicles, with the objective of reducing greenhouse gas emissions from electricity generation by choosing charging times that are associated with lower marginal emission factors. Optimized charging schedules reduce greenhouse gas emissions by at least 50% relative to vehicles charging once they return home. Life cycle assessment of multiple sharing scenarios indicates that higher levels of sharing increase emissions. Indeed, empty mileage associated with vehicle relocation and higher deterioration lead to a higher fleet turnover. With vehicle sharing, there is a risk of increasing mileage and vehicle production emissions.

Greenhouse Gas Implications of Extending the Service Life of PEM Fuel Cells for Automotive Applications: A Life Cycle Assessment

A larger adoption of hydrogen fuel-cell electric vehicles (FCEVs) is typically included in the strategies to decarbonize the transportation sector. This inclusion is supported by life-cycle assessments (LCAs), which show the potential greenhouse gas (GHG) emission benefit of replacing internal combustion engine vehicles with their fuel cell counterpart. However, the literature review performed in this study shows that the effects of durability and performance losses of fuel cells on the life-cycle environmental impact of the vehicle have rarely been assessed. Most of the LCAs assume a constant fuel consumption (ranging from 0.58 to 1.15 kgH2/100 km) for the vehicles throughout their service life, which ranges in the assessments from 120,000 to 225,000 km. In this study, the effect of performance losses on the life-cycle GHG emissions of the vehicles was assessed based on laboratory experiments. Losses have the effect of increasing the life-cycle GHG emissions of the vehicle up to 13%. Moreover, this study attempted for the first time to investigate via laboratory analyses the GHG implications of replacing the hydrophobic polymer for the gas diffusion medium (GDM) of fuel cells to increase their durability. LCA showed that when the service life of the vehicle was fixed at 150,000 km, the GHG emission savings of using an FC with lower performance losses (i.e., FC coated with fluorinated ethylene propylene (FEP) instead of polytetrafluoroethylene (PTFE)) are negligible compared to the overall life-cycle impact of the vehicle. Both the GDM coating and the amount of hydrogen saved account for less than 2% of the GHG emissions arising during vehicle operation. On the other hand, when the service life of the vehicle depends on the operability of the fuel cell, the global warming potential per driven km of the FEP-based FCEV reduces by 7 to 32%. The range of results depends on several variables, such as the GHG emissions from hydrogen production and the initial fuel consumption of the vehicle. Higher GHG savings are expected from an FC vehicle with high consumption of hydrogen produced with fossil fuels. Based on the results, we recommend the inclusion of fuel-cell durability in future LCAs of FCEVs. We also advocate for more research on the real-life performance of fuel cells employing alternative materials.

Economic and greenhouse gas analysis of regional bioenergy-powered district energy systems in California

There is an urgent need for building energy services that are not only low-carbon but reliable. District energy systems (DES) have the potential to meet building power, heating and cooling needs efficiently and reliably, but further research is needed to understand their coupling with local renewable energy sources such as biomass. Here we assess the cost and greenhouse gas implications of using bioenergy from local organic waste to power DES in California communities. We describe a set of possible scenarios for bioenergy integration into DES, including fuel switching and retrofitting of existing systems and DES expansion through new projects. In all locations, DES have higher combined capital and operating expenses (ranging from $5–12 million) than conventional fossil fuel building thermal systems. However, the net amortized annual cost of DES can reach as low as 70% that of the conventional system from the sale of excess electricity. Bioenergy-powered DES can offer a cost of carbon abatement on par with distributed solar-powered building thermal systems (50% less to 34% more). Furthermore, upgrading existing DES from fossil to renewable natural gas represents an immediate economical path to decarbonize buildings.

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.

Understanding multifunctional Bay of Fundy dykelands and tidal wetlands using ecosystem services—a baseline

We review what is known about ecosystem service (ES) delivery from agricultural dykelands and tidal wetlands around the dynamic Bay of Fundy in the face of climate change and sea-level rise, at the outset of the national NSERC ResNet project. Agricultural dykelands are areas of drained tidal wetland that have been converted to agricultural lands and protected using dykes and aboiteaux (one-way drains or sluices), first introduced by early French settlers (Acadians). Today, Nova Scotia’s 242 km system of dykes protect 17,364 ha of increasingly diverse land uses—including residential, industrial, and commercial uses as well as significant tourism, recreational, and cultural amenities—and is undergoing system modernization and adaptation. Different ES are provided by drained and undrained landscapes such as agriculture from dykelands and regulating services from wetlands, but more complex dynamics exist when beneficiaries are differentiated. This review reveals many knowledge gaps about ES delivery and dynamics, including around net greenhouse gas implications, storm protection, water quality, fish stocks, pollination processes, sense of place, and aesthetics, some of which may reveal shared ES or synergies instead of trade-offs. We emphasize the need to be open to adapting ES concepts and categorizations to fully understand Indigenous implications of these land use decisions.

Air quality and greenhouse gas implications of autonomous vehicles in Vancouver, Canada

Abstract This study explores vehicle fleet emissions changes due to connected and autonomous vehicle (CAV) diffusion, over the years 2030 and 2040 in Metro Vancouver, using the US Environmental Protection Agency’s MOtor Vehicle Emission Simulator (MOVES). Impacts were assessed across scenarios with varying future vehicle kilometers traveled (VKT), transit use, fuel-type, and diffusion rate. In all models, greenhouse gas emissions (GHGs) were reduced due to increasing electric vehicles, though reductions varied. At best, CAVs decreased GHGs by 20% compared to no-CAV conditions in 2040. At worst, we model a 6% decrease in GHGs if autonomy provokes increased use of personal vehicles (Motor City scenario), even with 85% electric vehicles. An overall reduction in emissions is seen for other pollutants, with the exception of PM, ranging from emissions reductions of up to 20% (PM exhaust) to an increase in emissions by 30% (PM2.5 brakewear) in 2040. Increased VKT per CAV had the most significant impact.

Cost and Life-Cycle Greenhouse Gas Implications of Integrating Biogas Upgrading and Carbon Capture Technologies in Cellulosic Biorefineries.

Gaseous streams in biorefineries have been undervalued and underutilized. In cellulosic biorefineries, coproduced biogas is assumed to be combusted alongside lignin to generate process heat and electricity. Biogas can instead be upgraded to compressed biomethane and used as a transportation fuel. Capturing CO2-rich streams generated in biorefineries can also contribute to greenhouse gas (GHG) mitigation goals. We explore the economic and life-cycle GHG impacts of biogas upgrading and CO2 capture and storage (CCS) at ionic liquid-based cellulosic ethanol biorefineries using biomass sorghum. Without policy incentives, biorefineries with biogas upgrading systems can achieve a comparable minimum ethanol selling price (MESP) and reduced GHG footprint ($1.38/liter gasoline equivalent (LGE) and 12.9 gCO2e/MJ) relative to facilities that combust biogas onsite ($1.34/LGE and 24.3 gCO2e/MJ). Incorporating renewable identification number (RIN) values advantages facilities that upgrade biogas relative to other options (MESP of $0.72/LGE). Incorporating CCS increases the MESP but dramatically decreases the GHG footprint (-21.3 gCO2e/MJ for partial, -110.7 gCO2e/MJ for full CCS). The addition of CCS also decreases the cost of carbon mitigation to as low as $52-$78/t CO2, depending on the assumed fuel selling price, and is the lowest-cost option if both RIN and California's Low Carbon Fuel Standard credits are incorporated.

Life Cycle Greenhouse Gas Implications of Multi Jet Fusion Additive Manufacturing

This study fills a gap in additive manufacturing life cycle assessments to improve decision-making in plastic product manufacturing. This assessment investigated cradle-to-gate life cycle energy co...

Grid-Scale Life Cycle Greenhouse Gas Implications of Renewable, Storage, and Carbon Pricing Options.

Models that characterize life cycle greenhouse gases from electricity generation are limited in their capability to estimate emissions changes at scales that capture the grid-scale benefits of technologies and policies that enhance renewable systems integration. National assumptions about generation mixes are often applied at annual time steps, neglecting spatiotemporal resolutions that provide insights on impacts from time-variable emissions. Our grid-scale model incorporates details of transmission and generation planning that allows a geographically and temporally textured and more realistic assessment of the life cycle greenhouse gas emissions outcomes, using a case study of the Western Interconnection of North America. Results from a co-optimized model of generation, transmission, and operations-the Johns Hopkins Stochastic Multistage Integrated Network Expansion Model-provide a detailed characterization of twenty-one scenarios with different configurations of storage additions, new renewable capacity, and carbon prices. Life cycle results suggest that optimization models that focus on generation alone may underestimate emissions by 18-29% because only emissions from power generation are quantified (i.e., supply chain emissions are omitted) but also that carbon pricing is the predominant driver of reducing emissions in the scenarios we examine. Life cycle assessment of electricity generation should move beyond individual technologies toward capturing the influence of policies at the system level to better understand technology-policy dynamics for the grid.

Lifecycle greenhouse gas emissions for an ethanol production process based on genetically modified cyanobacteria: CO2 sourcing options

AbstractAlgal biofuel production requires CO2, electricity, and process heat. Previous studies assumed CO2 sourcing from nearby coal or natural gas power plants. This may not be viable at a large scale or for the long term. The diurnal algal growth cycle imposes additional system design challenges for CO2 delivery. For ethanol produced by cyanobacteria in photobioreactors, we design onsite systems that provide heat, power and CO2 (CHP‐CO2), fueled by natural gas or biomass. Meeting the CO2 requirement produces excess electricity, which can be sold back to the grid. The scale of the CHP‐CO2 can be reduced by night‐time capture and refrigerated storage of CO2. The lifecycle greenhouse gas (GHG) emissions for 1 MJ ethanol are about −19 g CO2e for biomass CHP‐CO2, and +31–35 CO2e g for natural gas CHP‐CO2 options, compared with +19 g CO2e for the direct use of coal flue gas, and 91.3 g CO2e for 1 MJ of conventional gasoline. This work evaluates the energy and GHG implications of onsite CHP‐CO2 for algal ethanol production and other CO2 sourcing options. Combined heat and power (CHP) facilities, fueled by natural gas or biomass, could be co‐located with algal ethanol production, capturing and utilizing carbon dioxide to make biofuel, and thus providing an essentially stand‐alone biofuel operation, free from the constraints of co‐location with anthropogenic sources. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd

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

Abstract 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).

Greenhouse gas implications of replacing fish protein with beef in the lower Mekong Basin

At least 88 new hydropower dams are planned between 2010 and 2030 in the lower Mekong River basin in Southeast Asia as a source of electricity with lower greenhouse gas emissions. Dams result in declines in fish populations that will need to be replaced with other sources of protein for food security. We make the first assessment of emissions should beef production substitute for lost fish in Cambodia and Laos. We assessed two sources of emissions. Replacing lost fish with beef would require as much as 12 million hectares of new pasture. Forest clearing for pastures in Cambodia and Lao PDR would initially emit between 0.859 and 3.015 giga‐tonnes of carbon dioxide equivalents (Gt CO2‐eq.). Methane emissions from additional cattle would add at least 0.0013 Gt CO2‐eq./year to Cambodia's total greenhouse gas emissions, equivalent to a 20% increase. In Laos at least 0.0005 Gt CO2‐eq./year would be released, a 4–12% increase in annual emissions. We demonstrate that activities displaced by hydropower developments could significantly increase emissions. It shows how enclosure of commons at local scales impacts upon other common pool resources at different scales, raising questions for sustainable and equitable transboundary governance.

Greenhouse gas implications of mobilizing agricultural biomass for energy: a reassessment of global potentials in 2050 under different food-system pathways

Global bioenergy potentials have been the subject of extensive research and continued controversy. Due to vast uncertainties regarding future yields, diets and other influencing parameters, estimates of future agricultural biomass potentials vary widely. Most scenarios compatible with ambitious climate targets foresee a large expansion of bioenergy, mainly from energy crops that needs to be kept consistent with projections of agriculture and food production. Using the global biomass balance model BioBaM, we here present an assessment of agricultural bioenergy potentials compatible with the Food and Agriculture Organization’s (2018) ‘Alternative pathways to 2050’ projections. Mobilizing biomass at larger scales may be associated with systemic feedbacks causing greenhouse gas (GHG) emissions, e.g. crop residue removal resulting in loss of soil carbon stocks and increased emissions from fertilization. To assess these effects, we derive ‘GHG cost supply-curves’, i.e. integrated representations of biomass potentials and their systemic GHG costs. Livestock manure is most favourable in terms of GHG costs, as anaerobic digestion yields reductions of GHG emissions from manure management. Global potentials from intensive livestock systems are about 5 EJ/yr. Crop residues can provide up to 20 EJ/yr at moderate GHG costs. For energy crops, we find that the medium range of literature estimates (∼40 to 90 EJ/yr) is only compatible with FAO yield and human diet projections if energy plantations expand into grazing areas (∼4–5 million km2) and grazing land is intensified globally. Direct carbon stock changes associated with perennial energy crops are beneficial for climate mitigation, yet there are—sometimes considerable—‘opportunity GHG costs’ if one accounts the foregone opportunity of afforestation. Our results indicate that the large potentials of energy crops foreseen in many energy scenarios are not freely and unconditionally available. Disregarding systemic effects in agriculture can result in misjudgement of GHG saving potentials and flawed climate mitigation strategies.

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.

Greenhouse gas implications of leucaena-based pastures. Can we develop an emissions reduction methodology for the beef industry?

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.The perennial legume leucaena (Leucaena leucocephala) is grown across the subtropics for a variety of purposes including livestock fodder. Livestock in Australia emit a significant proportion of the methane produced by the agriculture sector and there is increasing pressure to decrease emissions from beef cattle production systems. In addition to direct productivity gains for livestock, leucaena has been shown to lower enteric methane production, suggesting an opportunity for emissions mitigation and Commonwealth Emissions Reduction Fund (ERF) methodology development, where leucaena browse is adopted for high value beef production. Determining the proportion of leucaena in the diet may be one of the more challenging aspects in attributing mitigation. Current enteric emission relationships for cattle consuming mixed grass-leucaena diets are based on intensive respiration chamber work. Herd-scale methane flux has also been determined using open path laser methodologies and may be used to validate an on-farm herd-scale methodology for leucaena feeding systems. The methodology should also address increased potential for soil organic carbon storage by leucaena grazing systems, and changes in nitrous oxide production. This paper outlines the background, justification, eligibility requirements and potential gaps in research for an emissions quantification protocol that will lead to the adoption of a leucaena methodology by the Australian beef industry. Development of a methodology would be supported by research conducted in Australia.

Lifecycle Impacts of Structural Frame Materials for Multi-storey Building Systems

In this study the lifecycle primary energy and greenhouse gas (GHG) implications of multi-storeybuilding versions with different structural frame materials as well as construction systems are analysedconsidering flows from the production, operation and end-of-life phases and the full natural resourceschains. The analysed building versions include conventional and modern construction systems withlight-frame timber, reinforced concrete-frame, massive timber frame, beam-and-column timber frameor modular timber frame structural systems and are designed to the energy efficiency level of thepassive house criteria. The results show that the lifecycle primary energy use and GHG emissions forthe reinforced concrete building system are higher than those for the timber-based building systems,due primarily to the lower production primary energy use and GHG emissions as well as greater amountof biomass residues when using wood-based materials. The operation primary energy use and GHGemission for the buildings are lower when heated with cogenerated district heating compared to whenheated with electric-based heat pump, showing the significance of heat supply choice. The findingsemphasize the importance of structural frame material choice and system-wide lifecycle perspective inreducing primary energy use and GHG emissions in the built environment.