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• Important variabilities exist in material intensities of single-family dwellings within and between locations. • The choice of functional unit changes the perception of which location has more efficient building material use. • House size is a strong predictor of overall material use. • Foundations and exterior walls consume the most materials in houses but in different ratios across geographical locations. This study examines variability in material use in single-family dwellings within and between three different locations (Toronto, Perth, and Luzon). It investigates how the use of different functional units changes the perception of what buildings are more materially efficient and which location has the more materially efficient home building norms. Material intensities for 80 single- family dwellings in the three locations form the foundational data for the paper. Important variabilities exist in the material intensities of the single-family dwellings and change with the functional unit selected (e.g., 7–23% for 1 m2 functional unit). Toronto single-family dwellings appear to be one of the least material intensive when presented per 1 m2 floor area but become the most material intensive when presented per 1 building and 1 bedroom with the opposite for Luzon. Housing size is the most effective explainer of overall material use with foundations and walls consuming the most materials but in different ratios across the three locations. [ABSTRACT FROM AUTHOR]

While bioenergy plays a key role in strategies for increasing renewable energy deployment, studies assessing greenhouse gas (GHG) emissions from forest bioenergy systems have identified a potential trade-off of the system with forest carbon stocks. Of particular importance to national GHG inventories is how trade-offs between forest carbon stocks and bioenergy production are accounted for within the Agriculture, Forestry and Other Land Use (AFOLU) sector under current and future international climate change mitigation agreements. Through a case study of electricity produced using wood pellets from harvested forest stands in Ontario, Canada, this study assesses the implications of forest carbon accounting approaches on net emissions attributable to pellets produced for domestic use or export. Particular emphasis is placed on the forest management reference level (FMRL) method, as it will be employed by most Annex I nations in the next Kyoto Protocol Commitment Period. While bioenergy production is found to reduce forest carbon sequestration, under the FMRL approach this trade-off may not be accounted for and thus not incur an accountable AFOLU-related emission, provided that total forest harvest remains at or below that defined under the FMRL baseline. In contrast, accounting for forest carbon trade-offs associated with harvest for bioenergy results in an increase in net GHG emissions (AFOLU and life cycle emissions) lasting 37 or 90 years (if displacing coal or natural gas combined cycle generation, respectively). AFOLU emissions calculated using the Gross-Net approach are dominated by legacy effects of past management and natural disturbance, indicating near-term net forest carbon increase but longer-term reduction in forest carbon stocks. Export of wood pellets to EU markets does not greatly affect the total life cycle GHG emissions of wood pellets. However, pellet exporting countries risk creating a considerable GHG emissions burden, as they are responsible for AFOLU and bioenergy production emissions but do not receive credit for pellets displacing fossil fuel-related GHG emissions. Countries producing bioenergy from forest biomass, whether for domestic use or for export, should carefully consider potential implications of alternate forest carbon accounting methods to ensure that potential bioenergy pathways can contribute to GHG emissions reduction targets. [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]

Battery-electric trucks (BET) are an alternative to diesel trucks and have the potential for lower life cycle greenhouse gas (GHG) emissions and total lifetime costs (TCO). This study compares a Class 6 medium-duty BET with a Class 6 medium-duty diesel truck. Vehicle fuel consumption is simulated for Toronto driving conditions, based on different drive cycles, operating temperatures and payloads. The base case results show the BET has lower life cycle GHG emissions and higher lifetime TCO than the diesel truck, but this does not hold across all conditions. GHG emissions of the BET are higher than those of the diesel truck under 100% payload in driving conditions with infrequent stops, while the results are less sensitive to operating temperature. The lifetime cost of the BET can be lower than that of the diesel truck in situations that have driving with frequent stops/starts and with low payloads and low battery and charging station costs. These variables also affect estimated GHG abatement costs, which are highly relevant as carbon pricing is being introduced in the province. [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]

This paper examines impacts of regional factors affecting biomass and process input supply chains and ongoing technology development on the life cycle greenhouse gas (GHG) emissions of ethanol production from corn stover in the U.S. Corn stover supply results in GHG emissions from −6 gCO 2 eq./MJ ethanol (Macon County, Missouri) to 13 gCO 2 eq./MJ ethanol (Hardin County, Iowa), reflecting location-specific soil carbon and N 2 O emissions responses to stover removal. Biorefinery emissions based on the 2011 National Renewable Energy Laboratory (NREL) process model are the single greatest emissions source (18 gCO 2 eq./MJ ethanol) and are approximately double those assessed for the 2002 NREL design model, due primarily to the inclusion of GHG-intensive inputs (caustic, ammonia, glucose). Energy demands of on-site enzyme production included in the 2011 design contribute to reducing the electricity co-product and associated emissions credit, which is also dependent on the GHG-intensity of regional electricity supply. Life cycle emissions vary between 1.5 and 22 gCO 2 eq./MJ ethanol (2011 design) depending on production location (98%–77% reduction vs. gasoline). Using system expansion for co-product allocation, ethanol production in studied locations meet the Energy Independence and Security Act emissions requirements for cellulosic biofuels; however, regional factors and on-going technology developments significantly influence these results. [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]