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Large scale, low cost, and low carbon intensity hydrogen production is needed to reduce emissions in the energy and transportation sectors. We present a techno-economic analysis and life cycle assessment of natural gas pyrolysis technologies for hydrogen production, with carbon black (CB) as a co-product. Four designs were considered based on the source of heat to the pyrolysis system, the combustion medium, and use of carbon capture (CC) technology. The oxygen-fired-CB design with CC is the most attractive from financial and environmental perspectives, superior to a conventional steam methane reformer (SMR) process with CC. The estimated pre-tax minimum hydrogen selling prices for the pyrolysis technologies range between $1.08/kg and $2.43/kg when natural gas (NG) costs $3.76/GJ. Key advantages include near-zero onsite GHG emissions of the oxygen-fired-CB design with CC and up to 41% lower GHG emissions compared to the SMR + CC process. The results indicate that natural gas pyrolysis may be a feasible pathway for hydrogen production. • Commercial scale hydrogen production via natural gas pyrolysis pathways is explored. • Options for handling the carbon black product are examined. • Low-carbon hydrogen of $1.7/kgH 2 outperforms the SMR hydrogen at similar conditions. • Cradle to gate GHG emissions between 1.8 and 4.6 kgCO 2 eq/kgH 2 is computed. [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]

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]

Alternative hydrogen production technologies are sought in part to reduce the greenhouse gas (GHG) emissions intensity compared with Steam Methane Reforming (SMR), currently the most commonly employed hydrogen production technology globally. This study investigates hydrogen production via High Temperature Steam Electrolysis (HTSE) in terms of GHG emissions and cost of hydrogen production using a combination of Aspen HYSYS® modelling and life cycle assessment. Results show that HTSE yields life cycle GHG emissions from 3 to 20 kg CO 2e /kg H 2 and costs from $2.5 to 5/kg H 2 , depending on the system parameters (e.g., energy source). A carbon price of $360/tonne CO 2e is estimated to be required to make HTSE economically competitive with SMR. This is estimated to potentially decrease to $50/tonne CO 2e with future technology advancements (e.g., fuel cell lifetime). The study offers insights for technology developers seeking to improve HTSE, and policy makers for decisions such as considering support for development of hydrogen production technologies. • Highlighting economic and environmental trade-offs of high temperature electrolysis. • Aspen HYSYS® modelling and life cycle assessment of high temperature electrolysis. • Emissions of 3–20 kgCO 2 e/kgH 2 and cost of $2.5–5/kgH2 are possible. • Carbon price of $50-$360 might been needed to make the process competitive with SMR. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]