Search

This study investigates the life cycle GHG emissions of jet fuel produced via the hydroprocessed esters and fatty acids (HEFA) pathway from canola grown in western Canada, with a focus on characterizing regional influences on emissions. We examine the effects of geographic variations in soil type, agricultural inputs, farming practices, and direct land use changes on life cycle GHG emissions. We utilize GREET 2016 but replace default feedstock production inputs with geographically representative data for canola production across eight western Canadian regions (representing 99% of Canada's canola production) and replace the default conversion process with data from a novel process model previously developed in ASPEN in our research group wherein oil extraction is integrated with the HEFA‐based fuel production process. Although canola production inputs and yields vary across the regions, resulting life cycle GHG emissions are similar if effects of land use and land management changes (LMC) are not included; 44–48 g CO2e/MJ for the eight regions (45%–50% reduction compared to petroleum jet fuel). Results are considerably more variable, 16–58 g CO2e/MJ, when including effects of land use and LMC directly related to conversion of lands from other uses to canola production (34%–82% reduction compared to petroleum jet fuel). We establish the main sources of emissions in the life cycle of canola jet fuel (N‐fertilizer and related emissions, fuel production), identify that substantially higher emissions may occur when using feedstock sourced from regions where conversion of forested land to cropland had occurred, and identify benefits of less intense tillage practices and increased use of summerfallow land. The methods and findings are relevant in jurisdictions internationally that are incorporating GHG emissions reductions from aviation fuels in a low carbon fuel market or legislating carbon intensity reduction requirements. [ABSTRACT FROM AUTHOR]

Conventional cost-effectiveness calculations ignore the implications of greenhouse gas ( GHG) emissions timing and thus may not properly inform decision-makers in the efficient allocation of resources to mitigate climate change. To begin to address this disconnect with climate change science, we modify the conventional cost-effectiveness approach to account for emissions timing. GHG emissions flows occurring over time are translated into an 'Equivalent Present Emission' based on radiative forcing, enabling a comparison of system costs and emissions on a consistent present time basis. We apply this 'Present Cost-Effectiveness' method to case studies of biomass-based electricity generation (biomass co-firing with coal, biomass cogeneration) to evaluate implications of forest carbon trade-offs on the cost-effectiveness of emission reductions. Bioenergy production from forest biomass can reduce forest carbon stocks, an immediate emissions source that contributes to atmospheric greenhouse gases. Forest carbon impacts thereby lessen emission reductions in the near-term relative to the assumption of biomass 'carbon neutrality', resulting in higher costs of emission reductions when emissions timing is considered. In contrast, conventional cost-effectiveness approaches implicitly evaluate strategies over an infinite analytical time horizon, underestimating nearer term emissions reduction costs and failing to identify pathways that can most efficiently contribute to climate change mitigation objectives over shorter time spans (e.g. up to 100 years). While providing only a simple representation of the climate change implications of emissions timing, the Present Cost-Effectiveness method provides a straightforward approach to assessing the cost-effectiveness of emission reductions associated with any climate change mitigation strategy where future GHG reductions require significant initial capital investment or increase near-term emissions. Timing is a critical factor in determining the attractiveness of any investment; accounting for emissions timing can better inform decisions related to the merit of alternative resource uses to meet near-, mid-, and long-term climate change mitigation objectives. [ABSTRACT FROM AUTHOR]

• This study integrates LCA and energy simulation on a visual programming interface. • 16,128 envelope variants are studied exploring passive EEMs on walls, windows, and roofs. • This study considers projected future climate and GHG intensity of energy sources. • The application of energy efficiency measures may increase total GHG emissions. • Studying embodied emissions is critical when highly efficient HVAC systems are used. The building industry has been developing measures for reducing operational emissions in the fight against climate change. Some of these well-intentioned measures may result in higher embodied emissions, potentially more than offsetting reductions achieved during operation. This research evaluates the effectiveness of different levels of application of five passive energy efficiency measures to reduce life cycle greenhouse gas (GHG) emissions in high-rise residential buildings in Toronto, Canada, while considering projected future climate and GHG intensity of energy sources. Through combining and automating life cycle assessment and energy simulation on a visual programing interface, the study evaluates 16,128 envelope variants, examining 56 wall, 12 roof, 6 window assemblies and 4 window-to-wall ratios (WWRs). Decreasing the WWR is found to be the most effective measure to reduce total envelope related GHG emissions (by about 28%). Increasing wall and roof insulation with GHG intensive materials (e.g., extruded polystyrene [XPS]), and increasing spandrel wall insulation potentially augment total emissions, depending on the scenario. Higher trade-offs between embodied and operational emissions are found when highly efficient electric HVAC systems are implemented (e.g., heat pumps). Results demonstrate it is imperative to assess both embodied and operational emissions during the design process of building envelopes to effectively reduce GHG emissions. [ABSTRACT FROM AUTHOR]

Abstract: Over the last 30 years the use of light weight, inexpensive, and durable plastics in automobiles has nearly tripled on a per vehicle basis. Although this has created benefits such as increased fuel efficiency and associated lower CO2 emissions, the growing disposition of plastics from end-of-life vehicles has put increasing pressure on North American landfill capacity. Financial and life cycle assessment models were developed and applied to the current and proposed recycling business operations of AADCO Automotive Incorporated (AADCO), a leading Canadian automotive dismantling company. By applying both kinds of models, two key questions are addressed. First, how much is it expected to cost AADCO to participate in a start-up automotive plastics recycling network? and second, by estimating greenhouse gas emissions and energy requirements, is recycling automotive plastics actually better for the environment compared to manufacturing virgin plastic resin within the boundaries set forth in this case study? The present study concluded that the proposed recycling network would reduce greenhouse gas emissions and energy requirements by nearly 50% when compared to the current operations at AADCO (equating to a reduction of 1063tonnes of CO2(eq) and 18TJ, respectively). However, in spite of the environmental benefits, the magnitude of the added costs for AADCO to participate in the post-consumer automotive plastics recycling network resulted in an unprofitable value proposition for the company. [Copyright &y& Elsevier]

Canada's ratification of the Kyoto Protocol has focused attention on the importance of accurately estimating emissions of greenhouse gases (GHG) from all sectors. An inventory of emissions of greenhouse gases from Canadian municipal wastewater treatment plants was prepared using a life-cycle approach. Both on-site emissions at the treatment facility due to the biological processes used and fossil fuels consumed for energy and heat and upstream emissions related to off-site production and transmission of fuels and the off-site production of electricity for the plant were included. For the year 2000, the on-site methane (CH4) emission rate from Canadian municipal wastewater treatment facilities was estimated at 1600 Mg/year. The total on-site emission rate of carbon dioxide (CO2) was estimated at 669 100 Mg/year, but the estimated total CO2 equivalent emissions rose to 1 048 500 Mg/year once upstream emissions were included. Clear abatement strategies related to more efficient energy use and energy recovery can be identified once accurate GHG emissions inventories are in place. [ABSTRACT FROM AUTHOR]

To support more sustainable development of a region, decision support tools must consider local and global systems level impacts on the economy, environment, and society. Through the development and application of "economic input–output water resources" models for Beijing, China for the years 1985, 1990, and 1992, historical trends related to the economy structure and its water use are investigated. The study finds that the economy of Beijing and water use are highly concentrated in agriculture and heavy industry, but this intensive water use is indirectly reflected in the production of most other goods and services throughout the economy because of the interrelationships among various sectors of the economy. In spite of progress during the time period observed (e.g., between 1985 and 1990 the output of the economy doubled, but water consumption increased only 12% partly because of a significant increase in the price of water in 1988) and given the seriousness of water resources issues in the region, it is critical that future regional development make progress toward a more water-efficient economic system. [ABSTRACT FROM AUTHOR]

Highlights • The corn stover ethanol models from GREET and GHGenius were compared. • Life cycle greenhouse gas emissions from baseline models differed by 45 gCO 2 e MJ−1. • Key inputs and assumptions in the models were aligned and made identical. • Life cycle greenhouse gas emissions differed by 1.3 gCO 2 e MJ−1 after alignment. • Variations in emissions persisted for key inputs even after model alignment. Abstract This paper evaluates differences in life cycle greenhouse gas emissions of corn stover ethanol produced in the U.S. Midwest, as estimated by the life cycle-based software GHGenius 4.03a, GREET 2013, and GREET 2015. Life cycle assessments are not typically conducted using more than one software package, but comparisons such as the analysis in this paper provide a critical review of a fuel product system. In particular, differences in the data and assumptions become evident for life cycle stages of the same fuel product when compared between life cycle assessment software packages. Using default settings in the three software packages, life cycle greenhouse gas emissions predictions ranged from 2.75 to 47.8 gCO 2 equivalent per MJ of ethanol (gCO 2 e MJ−1), which presents a difference of as much as 45 gCO 2 e MJ−1. Assumptions regarding nitrogen fertilizer, land management, on/off-site enzyme production, and material/energy inputs included/excluded had substantial effects on life cycle greenhouse gas emissions. A consistent corn stover ethanol pathway using equivalent model assumptions and material/energy inputs was developed and implemented in each of the software packages, resulting in life cycle greenhouse gas emissions ranging from 40.7 to 42.0 gCO 2 e MJ−1. The difference in life cycle greenhouse gas emissions was considerably reduced to 1.3 gCO 2 e MJ−1 at most between software packages; however, individual emissions sources such as nitrogen fertilizer production, fertilizer application, corn steep liquor, glucose, sodium hydroxide, and biomass electricity still exhibit variation between software packages (e.g., up to 7.3 gCO 2 e MJ−1 E100 for equivalent glucose input), mainly due to different emissions factors data. Life cycle greenhouse gas emissions appeared consistent because emissions sources that vary between software packages offset each other. Differences in greenhouse gas emissions determined for corn stover ethanol point to the need to improve the life cycle modelling and replicability of life cycle studies on this biofuel pathway. Such inconsistencies are relevant in a carbon economy because the same product will have a different value in different jurisdictions as a result of differences in life cycle assessment software packages. [ABSTRACT FROM AUTHOR]

This paper evaluates the financial viability of renewable jet fuel production, from two oilseed crops Camelina sativa (camelina) and Brassica carinata (carinata) and used cooking oil (UCO), by the hydrodeoxygenation pathway. A Monte Carlo analysis is performed to examine the robustness of the financial performance by taking into consideration key uncertain parameters, including capital cost, oil content of seeds, and prices of feedstocks, gas, electricity, water, meal co-product, and crude oil (indicator of fuel product prices). The Monte Carlo analysis revealed that under the conditions analyzed, the probabilities that the net present value would be positive are 29% for camelina, 18% for carinata and 8% for UCO, indicating that the three projects are risky for investors. Sensitivity analysis determined that the projects’ financial performance is highly sensitive to prices of fuel products and feedstocks. The impacts of two different hypothetical biofuel economic incentives were assessed: Carbon trading and tradable credits similar to the Renewable Identification Number (RIN). Income earned in the form of a RIN would have a large positive impact on the projects’ viabilities. By assuming an incentive of $0.20/L of renewable fuel, the probabilities that the NPV would be positive are 85% for camelina, 75% for carinata and 58% for UCO. [ABSTRACT FROM AUTHOR]

Steam-treated pellets can help to address technical barriers that limit the uptake of pellets as a fuel for electricity generation, but there is limited understanding of the cost and environmental impacts of their production and use. This study investigates life cycle environmental (greenhouse gas (GHG) and air pollutant emissions) and financial implications of electricity generation from steam-treated pellets, including fuel cycle activities (biomass supply, pellet production, and combustion) and retrofit infrastructure to enable 100% pellet firing at a generating station that previously used coal. Models are informed by operating experience of pellet manufacturers and generating stations utilising coal, steam-treated and conventional pellets. Results are compared with conventional pellets and fossil fuels in a case study of electricity generation in northwestern Ontario, Canada. Steam-treated pellet production has similar GHG impacts to conventional pellets as their higher biomass feedstock requirement is balanced by reduced process electricity consumption. GHG reductions of more than 90% relative to coal and ∼85% relative to natural gas (excluding retrofit infrastructure) could be obtained with both pellet options. Pellets can also reduce fuel cycle air pollutant emissions relative to coal by 30% (NOx), 97% (SOx), and 75% (PM 10 ). Lesser retrofit requirements for steam-treated pellets more than compensate for marginally higher pellet production costs, resulting in lower electricity production cost compared to conventional pellets ($0.14/kW h vs. $0.16/kW h). Impacts of retrofit infrastructure become increasingly significant at lower generating station capacity factors, further favouring steam-treated pellets for both environmental and financial metrics. [ABSTRACT FROM AUTHOR]

Despite international efforts to increase the adoption of alternative fuel vehicles, global gasoline internal combustion engine vehicles (ICEV-Gs) sales are projected to remain strong for the coming decades, with electric vehicles (EV) sales remaining well below 50% under International Energy Agency projections for 2030. The current study analyzes the cumulative reduction of greenhouse gas emissions that can be obtained by 2050 from policies targeting these gasoline powered vehicles. The analysis is applied to the case of the U.S. light-duty vehicles (LDV) fleet, a representative country with a large LDV fleet and slow EV penetration; the work considers technological, decisional and behavioral solutions. Technological pathways include fuel economy improvements, vehicle lightweighting and a greater provision of ethanol blends. Decisional pathways include purchasing decisions related to vehicle size and relative (best-in-class) fuel economy among available models. Behavioral pathways include improvements in driving habits. This study demonstrates the transitional and complementary role to fleet electrification that ICEV-Gs can play to meet climate targets, starting from vehicle models in the market today. A scenario-based analysis confirms that effective and diverse mitigation pathways targeting ICEV-G decarbonisation may lessen the need for aggressive fleet electrification rates – reducing the required cumulative electric vehicle sales through 2050 by at least 10% and by as much as 98% under extreme scenarios in the U.S. The analysis also identifies the limit of the ICEV-G fleet decarbonisation at 40% of cumulative lifecycle emissions from 2021 to 2050 in a very optimistic scenario, suggesting that these measures can complement but not replace the need to develop alternative fuels and powertrains. • Examined GHG mitigation measures targeting gasoline vehicle (ICEV-G) technology • Higher efficiency, hybridization & downsizing help ICEV-Gs meet GHG targets • Such measures can reduce cumulative fleet GHG emissions through 2050 by 5 to 30% • Plausible ICEV-G measures can delay need for full electrification by 5–25 years • Effective policy requires both technological improvements and behavioral changes [ABSTRACT FROM AUTHOR]

Up to 500 litres of water may be consumed at the batching plant per cubic meter of ready mix concrete, if water for washing mixing trucks and equipment is included. Demand for concrete is growing almost everywhere, regardless of local availability of freshwater. The use of freshwater for concrete production exacerbates stress on natural water resources. In water-stressed coastal countries such as Israel, desalinated seawater (DSW) is often used in the production of concrete. However, the environmental impacts of this practice have not yet been assessed. In this study the effect of using DSW on the water and carbon footprints of concrete was investigated using life cycle assessment. Water footprint results highlight the benefits of using DSW rather than freshwater to produce concrete in Israel. In contrast, because desalination is an energy intensive process, using DSW increases the greenhouse gas intensity of concrete. Nevertheless, this increase (0.27 kg CO2e/m³ concrete) is small, if compared to the life cycle greenhouse gas emissions of concrete. Our results show that using untreated seawater in the mix (transported by truck from the coast) in place of DSW, would be beneficial in terms of water and carbon footprints if the batching plant were located less than 13 km from the withdrawal point. However, use of untreated seawater increases steel reinforcement corrosion, resulting in loss of structural integrity of the reinforced concrete composite. Sustainability of replacing steel with non-corrosive materials should be explored as a way to reduce both water and carbon footprints of concrete. [ABSTRACT FROM AUTHOR]

Abstract: An integrated modelling approach is adopted to estimate microscale urban traffic emissions. The modelling framework consists of a traffic microsimulation model developed in PARAMICS, a microscopic emissions model (Comprehensive Modal Emissions Model), and two dispersion models, AERMOD and the Quick Urban and Industrial Complex (QUIC). This framework is applied to a traffic network in downtown Toronto, Canada to evaluate summer time morning peak traffic emissions of carbon monoxide (CO) and nitrogen oxides (NO x ) during five weekdays at a traffic intersection. The model predicted results are validated against sensor observations with 100% of the AERMOD modelled CO concentrations and 97.5% of the QUIC modelled NO x concentrations within a factor of two of the corresponding observed concentrations. Availability of local estimates of ambient concentration is useful for accurate comparisons of predicted concentrations with observed concentrations. Predicted and sensor measured concentrations are significantly lower than the hourly threshold Maximum Acceptable Levels for CO (31 ppm, ∼90 times lower) and NO2 (0.4 mg/m3, ∼12 times lower), within the National Ambient Air Quality Objectives established by Environment Canada. [Copyright &y& Elsevier]

The potential supply of biomass feedstocks in the US and Canada is estimated using a static supply function approach. Estimated total biomass available at a price of $100 per metric ton is 568 million metric tons in the US and 123 million tons in Canada, which together can displace 23-45 billion gallons of gasoline. Sufficient biomass, mainly agricultural and mill residues, will be available at prices of around $50/ton to meet the advanced biofuel mandates of the US Energy Independence and Security Act of 2007. The estimates of agricultural residue supply are very sensitive to the assumed fraction of residues that can be sustainably removed from the field, and the potential of municipal solid waste as a feedstock depends on which components can be economically converted into liquid biofuels. [ABSTRACT FROM AUTHOR]

Municipal wastewater treatment may lead to the emission of greenhouse gases. The current Intergovernmental Panel on Climate Change (Geneva, Switzerland) approach attributes only methane emissions to wastewater treatment, but this approach may overestimate greenhouse gas emissions from the highly aerobic processes primarily used in North America. To better estimate greenhouse gas emissions, a procedure is developed that can be used either with plant-specific data or more general regional data. The procedure was evaluated using full-scale data from 16 Canadian wastewater treatment facilities and then applied to all 10 Canadian provinces. The principal greenhouse gas emitted from municipal wastewater treatment plants was estimated to be carbon dioxide (CO2), with very little methane expected. The emission rates ranged from 0.005 kg CO2-equivalent/m³ treated for primary treatment facilities to 0.26 kg CO2-equivalent/m³ for conventional activated sludge, with anaerobic sludge digestion to over 0.8 kg CO2-equivalent/m³ for extended aeration with aerobic digestion. Increasing the effectiveness of biogas generation and use will decrease the greenhouse gas emissions that may be assigned to the wastewater treatment plant. [ABSTRACT FROM AUTHOR]

Emerging oil sands technologies could influence industry-wide greenhouse gas emissions, however projecting future emissions is difficult due to limited public reporting of expected performance and deployment of emerging technologies. An expert elicitation was conducted to gauge how experts anticipate emerging in situ, surface mining and upgrading technologies will be deployed and perform compared to current technologies. All experts project the majority (60–98%) of in situ bitumen production in 2034 will be produced using current technologies or hybrid steam-solvent processes. Experts built boxplots to show how they project commercial projects employing emerging technologies would perform in 2034 compared to a current project employing steam-assisted gravity drainage. Across experts, the median reduction in steam-to-oil ratio for hybrid steam-solvent projects and current in situ projects employing process changes (e.g., better well placement) ranged from 3 to 30% and from 12 to 14%, respectively. Median projections from experts about the change in bitumen recovery rate compared to a current (2014) steam-assisted gravity drainage project ranged from 3 to 30% for hybrid steam-solvents and up to 15% for electro-thermal and in situ combustion projects. The responses show that a slight reduction in energy consumption from the adoption of hybrid steam-solvent processes is expected by experts. Experts projected that emerging in situ technologies, which have the largest potential for adoption, will be used primarily for accessing marginal resources and increasing overall production levels, rather than targeting greenhouse gas emissions reductions. Therefore, deployment of emerging technologies is not expected to contribute substantially to meeting greenhouse gas emissions reduction targets for the industry by 2034 under the regulatory conditions at the time of the elicitation, a key insight for policy makers. [ABSTRACT FROM AUTHOR]

Lignocellulosic ethanol has potential for lower life cycle greenhouse gas emissions compared to gasoline and conventional grain-based ethanol. Ethanol production ‘pathways’ need to meet economic and environmental goals. Numerous life cycle assessments of lignocellulosic ethanol have been published over the last 15 years, but gaps remain in understanding life cycle performance due to insufficient data, and model and methodological issues. We highlight key aspects of these issues, drawing on literature and a case study of corn stover ethanol. Challenges include the complexity of feedstock/ecosystems and market-mediated aspects and the short history of commercial lignocellulosic ethanol facilities, which collectively have led to uncertainty in GHG emissions estimates, and to debates on LCA methods and the role of uncertainty in decision making. [ABSTRACT FROM AUTHOR]

Forest bioenergy can contribute to climate change mitigation by reducing greenhouse gas ( GHG) emissions associated with energy production. We assessed changes in GHG emissions resulting from displacement of coal with wood pellets for the Atikokan Generating Station located in Northwestern Ontario, Canada. Two contrasting biomass sources were considered for continuous wood pellet production: harvest residue from current harvest operations (residue scenario) and fibre from expanded harvest of standing live trees (stemwood scenario). For the stemwood scenario, two metrics were used to assess the effects of displacing coal with forest biomass on GHG emissions: (i) time to carbon sequestration parity, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in regenerating forest equalled the amount of forest carbon without harvest for energy production; and (ii) time to carbon debt repayment, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in the regenerating forest equalled forest carbon at the time of harvest. Only time to carbon sequestration parity was used for the residue scenario. In the residue scenario, carbon sequestration parity was achieved within 1 year. In the stemwood scenario, times to carbon sequestration parity and carbon debt repayment were 91 and 112 years, respectively. Sensitivity analysis showed that estimates were robust when parameter values were varied. Modelling experiments showed that increasing growth rates for regenerating stands in the stemwood scenario could substantially reduce time to carbon sequestration parity. We discuss the use of the two metrics (time to carbon sequestration parity and time to carbon debt repayment) for assessing the effects of forest bioenergy projects on GHG emissions and make recommendations on terminology and methodologies for forest bioenergy studies. [ABSTRACT FROM AUTHOR]

Life cycle environmental performance of lignocellulosic ethanol produced through different production pathways and having different co-products has rarely been reported in the literature, with most studies focusing on a single pre-treatment and single co-product (electricity). The aim of this paper is to understand the life cycle energy use and greenhouse gas (GHG) emissions implications of alternative pre-treatment technologies (dilute acid hydrolysis, ammonia fiber expansion and autohydrolysis) and co-products (electricity, pellet, protein and xylitol) through developing a consistent life cycle framework for ethanol production from corn stover. Results show that the choices of pre-treatment technology and co-product(s) can impact ethanol yield, life cycle energy use and GHG emissions. Dilute acid pathways generally exhibit higher ethanol yields (20-25%) and lower net total energy use (15-25%) than the autohydrolysis and ammonia fiber expansion pathways. Similar GHG emissions are found for the pre-treatment technologies when producing the same co-product. Xylitol co-production diverts xylose from ethanol production and results in the lowest ethanol yield (200 L per dry t of stover). Compared to producing only electricity as a co-product, the co-production of pellets and xylitol decreases life cycle GHG emissions associated with the ethanol, while protein production increases emissions. The life cycle GHG emissions of blended ethanol fuel (85% denatured ethanol by volume) range from -38.5-37.2 g CO2 eq/MJ of fuel produced, reducing emissions by 61-141% relative to gasoline. All ethanol pathways result in major reductions of fossil energy use relative to gasoline, at least by 47%. [ABSTRACT FROM AUTHOR]

Replacement of fossil fuels with sustainably produced biomass crops for energy purposes has the potential to make progress in addressing climate change concerns, nonrenewable resource use, and energy security. The perennial grass Miscanthus is a dedicated energy crop candidate being field tested in Ontario, Canada, and elsewhere. Miscanthus could potentially be grown in areas of the province that differ substantially in terms of agricultural land class, environmental factors and current land use. These differences could significantly affect Miscanthus yields, input requirements, production practices, and the types of crops being displaced by Miscanthus establishment. This study assesses implications on life cycle greenhouse gas ( GHG) emissions of these differences through evaluating five Miscanthus production scenarios within the Ontario context. Emissions associated with electricity generation with Miscanthus pellets in a hypothetically retrofitted coal generating station are examined. Indirect land use change impacts are not quantified but are discussed. The net life cycle emissions for Miscanthus production varied greatly among scenarios (−90-170 kg CO2eq per oven dry tonne of Miscanthus bales at the farm gate). In some cases, the carbon stock dynamics of the agricultural system offset the combined emissions of all other life cycle stages (i.e., production, harvest, transport, and processing of biomass). Yield and soil C of the displaced agricultural systems are key parameters affecting emissions. The systems with the highest potential to provide reductions in GHG emissions are those with high yields, or systems established on land with low soil carbon. All scenarios have substantially lower life cycle emissions (−20-190 g CO2eq kWh−1) compared with coal-generated electricity (1130 g CO2eq kWh−1). Policy development should consider the implication of land class, environmental factors, and current land use on Miscanthus production. [ABSTRACT FROM AUTHOR]

Abstract: Increased use of ethanol as a vehicle fuel worldwide warrants the need to understand air quality impacts of replacing gasoline with ethanol. This study evaluates the impacts of dedicated E85 (85% ethanol/15% gasoline) light-duty vehicles on emissions, ozone and particulate matter (PM) concentrations in the United States for a future year (2022) using a 3-D photochemical model, detailed emissions inventories that account for changes in all sectors studied, and winter and summer meteorology that occurred in 2002. Use of E85 introduces new emissions from ethanol production and distribution, reduces petrochemical industry emissions due to lower gasoline consumption, changes on-road vehicle emissions and alters biogenic emissions due to land use changes. Three scenarios with increased ethanol production for dedicated E85 light-duty vehicles were compared to a base case without increased ethanol production. Increased use of E85 caused both increases and decreases in ozone and PM, driven mainly by changes in NO x emissions related to biogenic and upstream petrochemical industry sources. In all states modeled, adoption of dedicated E85 vehicles caused negligible change in average higher ozone and PM concentrations of importance for air quality management strategies. Ozone and PM changes are relatively insensitive to how land area is allocated for switchgrass production. The findings are subject to various uncertainties, especially those in vehicle technology and emissions from cellulosic ethanol production. [Copyright &y& Elsevier]

The environmental and human health impacts of engineering activities have reshaped the way engineers make decisions. Increasingly, engineering decision-making is taking into consideration the full life cycle implications of engineering activities. This paper details the development and application of a national economic input–output-based life cycle assessment model, a tool for guiding engineering decision-making, for the Canadian economy. The model consists of 61 industries and 103 commodities and incorporates economic and environmental–resource data, including marginal resource consumption, energy use, releases of National Pollutant Release Inventory compounds, and emissions of greenhouse gases. The model is useful for evaluating various development strategies and analyzing the potential direct and indirect impacts of alternative public policies on the Canadian economy and environment. The model is applied to various sectors of the Canadian economy, and the life-cycle implications of demands for different commodities are determined, including demand for electricity and construction materials for highway design. [ABSTRACT FROM AUTHOR]

Life cycle assessments can help inform decision-making about greenhouse gas (GHG) emission reduction opportunities but are often not embraced by stakeholders associated with industries where study results are highly scrutinized and often contentious. This project was motivated by stakeholder interest in understanding open source life cycle models (the Oil Production Greenhouse Gas Emissions Estimator, OPGEE, and the Petroleum Refinery Life Cycle Inventory Model, PRELIM) and how accurately they can estimate emissions for existing oil sands projects and emerging technologies. We evaluate the robustness of these models and improve them using data from three existing oil sands projects (mining + upgrading, mining + dilution, and steam assisted gravity drainage, SAGD, + dilution). The models are then applied to estimate the GHG emissions reduction potential for two emerging in situ oil sands technologies. We find that, when boundaries are aligned, OPGEE can generate upstream GHG emissions estimates for the projects modeled within 1-4% of company reported GHG emissions data. Extending the boundary to include indirect (life cycle) emissions can lead to a doubling in upstream GHG emissions intensity. The two emerging technologies evaluated in the study can reduce upstream emissions by 14-19% compared to a SAGD project operating at the same reservoir, or 1.4-1.9% on a well-to-wheel basis. This work contributes a revised process of conducting LCAs that includes stakeholder input throughout and results in more robust and transparent estimates of emissions from deploying existing and emerging technologies. • New method to engage stakeholders in life cycle assessment of oil sands projects. • Open source models estimate emissions within 1–4% of reported upstream emissions. • New technologies reduce upstream emissions 14–19% relative to current technology. • Well-to-wheel emissions decrease 1.6–1.9% with adoption of new technologies. • Adopting regional factors in open source models reduces upstream emissions 14–35%. [ABSTRACT FROM AUTHOR]

The refurbished Don Valley Brick Works' Kiln Building, in Toronto, Canada, now the TD Future Cities Centre, is designed to have net zero carbon emissions. This is to be achieved through the reuse of existing materials and structures, selection of lower-carbon materials purchased from local sources, installation of renewable energy systems, natural lighting and improved thermal insulation of the building's envelope, as well as developing a carbon offset strategy. The heritage designation of the building imposed restrictions on the design of the project (e.g., preventing insulation of exterior walls). In collaboration with the owner and constructor, the project team completed a life cycle assessment (LCA) consisting of an assessment of embodied emissions of the building's restoration from cradle to grave, accompanied by a scoping estimate of greenhouse gas emissions associated with its future operational energy use. Primary construction data for the newly-added materials, transport, and construction activities were used. Life cycle inventory analysis and impact assessment were implemented in the One Click LCA software. Use phase carbon intensity was estimated using design and literature data. In addition to the 'core and shell' LCA scope typically applied to buildings, the team also tracked materials and processes that are often not included in building LCA studies such as HVAC, plumbing, and renewable energy systems. Embodied carbon for the restoration project, assuming a 60-year lifetime, is calculated as 1250 tonnes carbon dioxide equivalent (tCO 2 e). Sixty-nine percent of the carbon comes from the materials (extraction to manufacturing) used in construction, 20% is due to replacement of materials during the building's service life, and most of the remaining 11% is from on-site construction energy (5%) and waste disposal at end-of-life (4%). The main building elements contributing to the embodied carbon are the renewable energy systems (31%) and the raised concrete floor (26%). Building envelope and foundation play minor roles, as they are mostly pre-existing. The embodied carbon added to the building through the restoration project is forecast to be balanced by savings in operational energy related to heating, cooling and lighting, within 3–13 years, depending on whether natural gas or electricity use are avoided, respectively. Uncertainties in the analysis arise from partial or missing data, modeling assumptions and future scenario unknowns. The model is sensitive to the useable lifetime of the building, local or non-local sourcing of building materials, modeling of certain components used in large quantities, and changes in the recycled content of steel. This study of a net zero carbon refurbishment project of a heritage building provides insights for assessments of future projects as such refurbishments become more commonplace. The methods and recommendations regarding data sources, data collection, and approach to uncertainty evaluation will be useful for LCA of any construction project. • A brick kiln building was refurbished as an event space targeting net zero carbon. • Existing structures were upgraded and a geo-solar exchange system installed. • Total project embodied carbon is estimated at 255 kgCO 2 e/m2, given a 60-year lifetime. • 69% of estimated GHG emissions are embodied in materials purchased during construction. • Results are sensitive to building lifetime, datapoint modeling and other parameters. [ABSTRACT FROM AUTHOR]

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. • Market constraints of SCMs should be included in LCA studies of concrete. • Concrete properties and exposure conditions must be included in the functional unit. • If the SCM is constrained, overall GHG benefits of using it are greatly reduced. • Increasing SCMs in concrete does not always decrease its GHG emissions. • The use of alternative unconstrained SCMs should be further explored and promoted. [ABSTRACT FROM AUTHOR]

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

This paper presents three scenarios of urban growth, energy use and greenhouse gas (GHG) emissions in Dar es Salaam using narratives that are consistent with the Shared Socio-Economic Pathways (SSPs). We estimate residential energy demand and GHG emissions from 2015 to 2050 for household activities (including upstream electricity generation) and passenger (road) transport (Scopes 1 and 2). We project that by 2050, Dar es Salaam's total residential emissions would increase from 1,400 ktCO 2 e (in 2015) up to 25,000–33,000 ktCO 2 e (SSP1); 11,000–19,000 ktCO 2 e (SSP2); and 5,700–11,000 ktCO 2 e (SSP3), with ranges corresponding to different assumptions about household size. This correlates with an increase in per capita emissions from 0.2 tCO 2 e in 2015 to 1.5–2 tCO 2 e (SSP1); 0.7–1.3 tCO 2 e (SSP2); and 0.5–0.9 tCO 2 e (SSP3). Higher emissions in SSP1 (the sustainability scenario) are driven by a higher urban population in 2050 and increased energy access and electricity consumption. Through aggressive GHG mitigation policies focused on decarbonization of the electricity sector and road transport, total emissions under SSP1 can be reduced by ∼66% in 2050. Study insights aim to inform policies that identify and capture synergies between low-GHG investments and broader socio-economic development goals in Sub-Saharan African cities. • Provides the first projection of residential energy use and GHG emissions in Dar es Salaam and demonstrates the use of the SSPs at the city scale. • Analyzes the key drivers of residential energy use and GHG emissions in a large SSA city, Dar es Salaam, offering new insights for the region. • Demonstrates a method for projecting emissions in a data-poor environment. • Shows the wide uncertainty in these future projections, while also demonstrating the order of magnitude jump in emissions that can be expected in Dar es Salaam to 2050. [ABSTRACT FROM AUTHOR]