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1. Ride Substitution Using Electric Bike Sharing: Feasibility, Cost, and Carbon Analysis

   https://doi.org/10.1145/3448081  

   Wamburu, John; Lee, Stephen; Hajiesmaili, Mohammad H.; Irwin, David; Shenoy, Prashant (March 2021, Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies)

   null (Ed.)

   While ride-sharing has emerged as a popular form of transportation in urban areas due to its on-demand convenience, it has become a major contributor to carbon emissions, with recent studies suggesting it is 47% more carbon-intensive than personal car trips. In this paper, we examine the feasibility, costs, and carbon benefits of using electric bike-sharing---a low carbon form of ride-sharing---as a potential substitute for shorter ride-sharing trips, with the overall goal of greening the ride-sharing ecosystem. Using public datasets from New York City, our analysis shows that nearly half of the taxi and rideshare trips in New York are shorts trips of less than 3.5km, and that biking is actually faster than using a car for ultra-short trips of 2km or less. We analyze the cost and carbon benefits of different levels of ride substitution under various scenarios. We find that the additional bikes required to satisfy increased demand from ride substitution increases sub-linearly and results in 6.6% carbon emission reduction for 10% taxi ride substitution. Moreover, this reduction can be achieved through a hybrid mix that requires only a quarter of the bikes to be electric bikes, which reduces system costs. We also find that expanding bike-share systems to new areas that lack bike-share coverage requires additional investments due to the need for new bike stations and bike capacity to satisfy demand but also provides substantial carbon emission reductions. Finally, frequent station repositioning can reduce the number of bikes needed in the system by up to a third for a minimal increase in carbon emissions of 2% from the trucks required to perform repositioning, providing an interesting tradeoff between capital costs and carbon emissions. 

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2. Ride Substitution Using Electric Bike Sharing: Feasibility, Cost and Carbon Analysis

   Wambouru, John; Lee, Stephen; Hajiesmaili, Mohammad; Irwin, David; Shenoy, Prashant (March 2021, Proceedings of the ACM on interactive mobile wearable and ubiquitous technologies)

   null (Ed.)

   While ride-sharing has emerged as a popular form of transportation in urban areas due to its on-demand convenience, it has become a major contributor to carbon emissions, with recent studies suggesting it is 47% more carbon-intensive than personal car trips. In this paper, we examine the feasibility, costs, and carbon benefits of using electric bike-sharing—a low carbon form of ride-sharing—as a potential substitute for shorter ride-sharing trips, with the overall goal of greening the ride-sharing ecosystem. Using public datasets from New York City, our analysis shows that nearly half of the taxi and rideshare trips in New York are shorts trips of less than 3.5km, and that biking is actually faster than using a car for ultra-short trips of 2km or less. We analyze the cost and carbon benefits of different levels of ride substitution under various scenarios. We find that the additional bikes required to satisfy increased demand from ride substitution increases sub-linearly and results in 6.6% carbon emission reduction for 10% taxi ride substitution. Moreover, this reduction can be achieved through a hybrid mix that requires only a quarter of the bikes to be electric bikes, which reduces system costs. We also find that expanding bike-share systems to new areas that lack bike-share coverage requires additional investments due to the need for new bike stations and bike capacity to satisfy demand but also provides substantial carbon emission reductions. Finally, frequent station repositioning can reduce the number of bikes needed in the system by up to a third for a minimal increase in carbon emissions of 2% from the trucks required to perform repositioning, providing an interesting tradeoff between capital costs and carbon emissions. 

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3. An Agile Pathway Towards Carbon-aware Clouds

   https://doi.org/10.1145/3604930.3605722  

   Patel, Pratyush; Gregersen, Theo; Anderson, Thomas (July 2023, HotCarbon '23: Proceedings of the 2nd Workshop on Sustainable Computer Systems)

   Climate change is a pressing threat to planetary well-being that can be addressed only by rapid near-term actions across all sectors. Yet, the cloud computing sector, with its increasingly large carbon footprint, has initiated only modest efforts to reduce emissions to date; its main approach today relies on cloud providers sourcing renewable energy from a limited global pool of options. We investigate how to accelerate cloud computing's efforts. Our approach tackles carbon reduction from a software standpoint by gradually integrating carbon awareness into the cloud abstraction. Specifically, we identify key bottlenecks to software-driven cloud carbon reduction, including (1) the lack of visibility and disaggregated control between cloud providers and users over infrastructure and applications, (2) the immense overhead presently incurred by application developers to implement carbon-aware application optimizations, and (3) the increasing complexity of carbon-aware resource management due to renewable energy variability and growing hardware heterogeneity. To overcome these barriers, we propose an agile approach that federates the responsibility and tools to achieve carbon awareness across different cloud stakeholders. As a key first step, we advocate leveraging the role of application operators in managing large-scale cloud deployments and integrating carbon efficiency metrics into their cloud usage workflow. We discuss various techniques to help operators reduce carbon emissions, such as carbon budgets, service-level visibility into emissions, and configurable-yet-centralized resource management optimizations. 

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4. Integrated design for electrocatalytic carbon dioxide reduction

   https://doi.org/10.1039/D0CY00453G  

   Zhao, Xin; Du, Lijie; You, Bo; Sun, Yujie (May 2020, Catalysis Science & Technology)

   null (Ed.)

   The electrocatalytic carbon dioxide reduction reaction (CO 2 RR) to produce valuable fuels and chemicals with renewable energy inputs is an attractive route to convert intermittent green energy sources ( e.g. , solar and wind) to chemical energy, alleviate our dependence on fossil fuels, and simultaneously reduce net carbon dioxide emission. However, the generation of reduced multi-carbon products with high energy density and wide applicability from the CO 2 RR, such as oxygenates and hydrocarbons, suffers from high overpotential, slow reaction rate, and low selectivity due to its intrinsic multi-electron transfer nature. Moreover, the involved anodic oxygen evolution reaction (OER) also requires large overpotential and its product O 2 bears limited economic value. The potentially generated reactive oxygen species (ROS) during the OER may also degrade the membrane of a CO 2 reduction electrolyzer. Herein, we review the recent progress in novel integrated strategies to address the aforementioned challenges in the electrocatalytic CO 2 RR. These innovative strategies include (1) concurrent CO 2 electroreduction via co-feeding additional chemicals besides CO 2 gas, (2) tandem CO 2 electroreduction utilizing other catalysts for converting the in situ formed products from the CO 2 RR into more valuable chemicals, and (3) hybrid CO 2 electroreduction through integrating thermodynamically more favourable organic upgrading reactions to replace the anodic OER. We specifically highlight these novel integrated electrolyzer designs instead of focusing on nanostructured engineering of various electrocatalysts, in the hope of inspiring others to approach CO 2 electroreduction from a holistic perspective. The current challenges and future opportunities of electrocatalytic CO 2 reduction will also be discussed at the end. 

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5. Forest Carbon Emission Sources Are Not Equal: Putting Fire, Harvest, and Fossil Fuel Emissions in Context

   https://doi.org/10.3389/ffgc.2022.867112  

   Bartowitz, Kristina J.; Walsh, Eric S.; Stenzel, Jeffrey E.; Kolden, Crystal A.; Hudiburg, Tara W. (May 2022, Frontiers in Forests and Global Change)

   Climate change has intensified the scale of global wildfire impacts in recent decades. In order to reduce fire impacts, management policies are being proposed in the western United States to lower fire risk that focus on harvesting trees, including large-diameter trees. Many policies already do not include diameter limits and some recent policies have proposed diameter increases in fuel reduction strategies. While the primary goal is fire risk reduction, these policies have been interpreted as strategies that can be used to save trees from being killed by fire, thus preventing carbon emissions and feedbacks to climate warming. This interpretation has already resulted in cutting down trees that likely would have survived fire, resulting in forest carbon losses that are greater than if a wildfire had occurred. To help policymakers and managers avoid these unintended carbon consequences and to present carbon emission sources in the same context, we calculate western United States forest fire carbon emissions and compare them with harvest and fossil fuel emissions (FFE) over the same timeframe. We find that forest fire carbon emissions are on average only 6% of anthropogenic FFE over the past decade. While wildfire occurrence and area burned have increased over the last three decades, per area fire emissions for extreme fire events are relatively constant. In contrast, harvest of mature trees releases a higher density of carbon emissions (e.g., per unit area) relative to wildfire (150–800%) because harvest causes a higher rate of tree mortality than wildfire. Our results show that increasing harvest of mature trees to save them from fire increases emissions rather than preventing them. Shown in context, our results demonstrate that reducing FFEs will do more for climate mitigation potential (and subsequent reduction of fire) than increasing extractive harvest to prevent fire emissions. On public lands, management aimed at less-intensive fuels reduction (such as removal of “ladder” fuels, i.e., shrubs and small-diameter trees) will help to balance reducing catastrophic fire and leave live mature trees on the landscape to continue carbon uptake. 

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