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Green roofs can mitigate climate change through various mechanisms, including carbon sequestration, thermal process regulation, and building energy savings. While those mechanisms have been well studied, it remains unclear how to quantify carbon dioxide reduction and design green roofs properly for optimal performance. This review summarizes the processes, factors, and quantitative methods for carbon dioxide reduction from peer-reviewed literature. Firstly, the processes that account for how green roofs reduce carbon dioxide directly (by absorbing ambient CO 2 and storing it in biomass and substrate) and indirectly (thermal process regulation reduces energy consumption) are focused. The factors affecting CO 2 reduction (i.e., vegetation, substrate, building environment, and maintenance) are then discussed to investigate how these factors impact the performance of green roofs. Lastly, quantitative methods, including field experiments and simulation models to evaluate direct and indirect CO 2 reductions from green roofs, are discussed considering different spatial scales. The review found that a better understanding of green roofs' carbon reduction mechanisms is needed. Recommendations also should be developed on customized green roof system designs for various climate conditions. Lastly, there is a lack of green roof decarbonization evaluation at multiple spatial and temporal scales to effectively implement green roofs in urban areas. Overall, this comprehensive review facilitates an understanding of how green roofs reduce CO 2 , the driving factors, and quantitative methods, which will advance research on designing and building green roofs as effective climate mitigation solutions in urban areas. • Analysis of the carbon sequestration and energy savings processes of green roofs. • Evaluation of factors affecting carbon sequestration and thermal performance. • Summarizing methods to quantify the carbon dioxide reduction services of green roofs. [ABSTRACT FROM AUTHOR]

The decarbonization of industry and industrial systems is a pressing challenge given the relative lack of low-carbon options available for "hard to decarbonize" sectors such as steelmaking, cement manufacturing, and chemical production. Carbon capture utilization and storage (CCUS) represents a promising and crosscutting solution to this formidable problem. This review takes a systematic and sociotechnical perspective to examine how CCUS can support industrial decarbonization and relevant associated technical, economic, and social factors. This includes a focus on the energy and climate impacts of carbon emitting activities, the role, and options for CCUS in global responses to climate change, technical aspects of capture, transport, storage, and utilization, as well as policy implications and areas requiring further research. In doing so, the Review examines hundreds of published studies on the topic over the previous twenty years to offer a state-of-the-art investigation on technical options for capture (including direct air capture), transportation (including pipelines, ships, and rail), storage (including biotic and abiotic), and utilization (including enhanced oil recovery and biochar). The Review also investigates the evidence base within the literature on enablers and barriers to CCUS, policy mechanisms, and international frameworks as well as themes such as geopolitics, trade, and future research gaps. We conclude with insights about future CCUS pathways and sociotechnical systems dynamics. [Display omitted] • Carbon Capture Utilization and Storage can play a critical role in climate change mitigation. • Ample emerging technologies are available with adequate capture capacities and biotic and abiotic forms of storage. • Utilization processes include enhanced oil recovery and biochar. • Carbon Capture Utilization and Storage deployment has been largely limited by social and economic barriers. • Policy driven solutions may help drive costs down, engender social acceptance, and increase CCUS deployment. [ABSTRACT FROM AUTHOR]

Biochar has received increasing attention in agricultural and environmental fields as an integrated solution to agricultural waste recycling, soil amendment, carbon sequestration, and greenhouse gas (GHG) reduction. However, obtaining the environmental benefits of biochar is limited by an inadequate number of soil applications. Currently, the willingness to use biochar in soil management is relatively low, which results from the insufficient understanding and promotion of the roles of biochar in soil management and climate change mitigation. This review article presents biochar applications based on carbon-neutral strategies in agricultural soil systems. The primary roles of biochar in soil improvement and remediation are discussed and the main soil application methods are introduced. The focus of this article is on biochar-based soil management strategies for contributing to carbon neutrality. Carbon sequestration using biochar is an application-dependent strategy, as the key to obtaining this ecological benefit is to store biochar products in soil via effective agricultural management. This article offers insights into biochar-based soil management strategies and their contribution to carbon neutrality in agricultural soil systems, with recommendations for appropriate government involvement in promoting biochar-based soil management and for incorporating biochar into the carbon trading market. • The non-CO 2 GHGs account for the majority of carbon emission via agricultural soil. • Incorporating biochar into the global carbon trading market is recommended. • Using biochar to help achieve carbon neutrality is an application-dependent strategy. [ABSTRACT FROM AUTHOR]

Carbon capture and sequestration (CCS) is an important technology to reduce fossil CO 2 emissions and remove CO 2 from the atmosphere. Scenarios for CCS deployment consistent with global climate goals involve gigatonne-scale deployment of CCS within the next several decades. CCS technologies typically involve large water consumption during their energy-intensive capture process. Despite potential concerns, the water footprint of large-scale CCS adoption consistent with stringent climate change mitigation has not yet been explored. This study presents the water footprints (m3 water per tonne CO 2 captured) of four prominent CCS technologies: Post-combustion CCS, Pre-combustion CCS, Direct Air CCS, and Bioenergy with CCS. Depending on technology, the water footprint of CCS ranges from 0.74 to 575 m3 H 2 O/tonne CO 2. Bioenergy with CCS is the technology that has the highest water footprint per tonne CO 2 captured, largely due to the high water requirements associated with transpiration. The widespread deployment of CCS to meet the 1.5 °C climate target would almost double anthropogenic water footprint. Consequently, this would likely exacerbate and create green and blue water scarcity conditions in many regions worldwide. Climate mitigation scenarios with a diversified portfolio of CCS technologies have lower impacts on water resources than scenarios relying mainly on one of them. The water footprint assessment of CCS is a crucial factor in evaluating these technologies. Water-scarce regions should prioritize water-efficient CCS technologies in their mitigation goals. In conclusion, the most water-efficient way to stabilize the Earth's climate is to rapidly decarbonize our energy systems and improve energy efficiency. • Carbon capture and storage involve large green and blue water consumption. • Large-scale deployment of carbon capture and storage could double the water footprint of humanity. • Trade-offs between climate mitigation benefits and water resources should be weighed. • Carbon capture and storage should be prioritized in regions not affected by water scarcity. • Water sustainability should be accounted for in carbon dioxide removal policies. [ABSTRACT FROM AUTHOR]

As bioenergy produces neutral or even negative carbon emissions, the assessment of biomass resources and associated emissions mitigation is a key step toward a low carbon future. However, relevant comprehensive estimates lack in China. Here, we measure the energy potential of China's domestic biomass resources (including crop residues, forest residues, animal manure, municipal solid waste and sewage sludge) from 2000 to 2016 and draw the spatial-temporal variation trajectories at provincial resolution. Scenario analysis and life cycle assessment are also applied to discuss the greenhouse gas mitigation potentials. Results show that the collectable potential of domestic biomass resources increased from 18.31 EJ in 2000 to 22.67 EJ in 2016 with overall uncertainties fluctuating between (−26.6%, 39.7%) and (−27.6%, 39.5%). Taking energy crops into account, the total potential in 2016 (32.69 EJ) was equivalent to 27.6% of China's energy consumption. If this potential can be realized in a planned way to displace fossil fuels during the period 2020–2050, cumulative greenhouse gas emissions mitigation would be in the range of 1652.73–5859.56 Mt CO 2 -equivalent, in which the negative greenhouse gas emissions due to the introduction of bioenergy with carbon capture and storage would account for 923.78–1344.13 Mt CO 2 -equivalent. Contrary to increasing bioenergy potentials in most provinces, there are declining trends in Tibet, Beijing, Shanghai and Zhejiang. In addition, Yunnan, Sichuan and Inner Mongolia would have the highest associated greenhouse gas mitigation potentials. This study can provide valuable guidance on the exploitation of China's untapped biomass resources for the mitigation of global climate change. • China's bioenergy potential in 2016 accounted for 27.6% of its energy consumption. • The bioenergy potential in Tibet, Beijing, Shanghai and Zhejiang was declining. • GHG mitigation potentials of China's bioenergy would be 1653–5860 Mt CO 2 e by 2050. • China's bioenergy can contribute 6–21% to a global carbon mitigation goal in 2050. [ABSTRACT FROM AUTHOR]