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Large-scale carbon capture, utilization, and storage (CCUS) requires development of critical infrastructure to connect capture locations to geological storage sites. Here, we investigate what government policies would be required to make the development of CO2 pipelines and large-scale CCUS in the power sector economically viable. We focus on the transition from conventional coal to non-CO2-emitting natural gas-fired Allam-cycle power with CCUS and study a system in which 156 Allam-cycle power generators representing 100 GW of capacity send their captured CO2 emissions to three geological storage locations in the central United States through 7500 miles of new pipeline. Enabling policies for this system include low-interest government loans of approximately $20 billion for pipeline construction and an extended 20-year Section 45Q tax credit, or similar longer-term carbon price incentive. Additional policy support will be needed to enable initial construction of pipelines and early-mover power generators, such as cost-sharing, governments assuming future demand risk, or increased subsidies to early movers. The proposed system will provide reliable, dispatchable, flexible zero-emission power generation, complementing the intermittent generation by renewables in a decarbonized U.S. power sector. The proposed pipeline network could also connect into future regional infrastructure networks and facilitate large-scale carbon management.

Previous estimates of tropical forest carbon loss in the twenty-first century using satellite data typically focus on its magnitude, whereas regional loss trajectories and associated drivers are rarely reported. Here we used different high-resolution satellite datasets to show a doubling of gross tropical forest carbon loss worldwide from 0.97 ± 0.16 PgC yr−1 in 2001–2005 to 1.99 ± 0.13 PgC yr−1 in 2015–2019. This increase in carbon loss from forest conversion is higher than in bookkeeping models forced by land-use statistical data, which show no trend or a slight decline in land-use emissions in the early twenty-first century. Most (82%) of the forest carbon loss is at some stages associated with large-scale commodity or small-scale agriculture activities, particularly in Africa and Southeast Asia. We find that ~70% of former forest lands converted to agriculture in 2001–2019 remained so in 2020, confirming a dominant role of agriculture in long-term pan-tropical carbon reductions on formerly forested landscapes. The acceleration and high rate of forest carbon loss in the twenty-first century suggest that existing strategies to reduce forest loss are not successful; and this failure underscores the importance of monitoring deforestation trends following the new pledges made in Glasgow.

Aims Roots bridge above and belowground systems, and play a pivotal role in structuring root-associated organisms via influencing food resources and habitat conditions. Most studies focused on the relationships between plant identity and root-associated organisms, however, little is known about how root traits affect nematode communities within the rhizosphere. Methods We investigated the relationships between root traits of four plant species and nematode diversity, community structure and trophic complexity in an ex-arable field. Results While the relative abundance of herbivorous nematodes was negatively associated with specific root length (SRL), specific root area (SRA), root length density (RLD) and root C: N ratio, free-living nematodes were positively affected by these traits, implying a multifaceted effect of root traits on root-associated organisms. Importantly, we found that finer root systems promoted the complexity of the nematode community, by increasing the relative abundance of high trophic-level nematodes (i.e., omnivores and predators) and enhancing nematode diversity. Conclusion Our findings suggest that root traits could be reliable indicators of soil community structure and interactions, and provide new insights into soil biodiversity and functional maintenance.

The Belt and Road Initiative (BRI), proposed by China in Fall 2013, includes large-scale development of energy infrastructures in Eurasia and Africa, and therefore has the potential to affect global climate. In this work, we analyze BRI-associated development of the electric power sector in 15 representative countries from the Belt and Road regions and find that in the period between October 2013 and June 2019, 75% of newly added power generating capacity has gone to fossil fuel-burning power plants while the remaining 25% has gone to renewable energy, mostly hydropower. Although the installed solar photovoltaics capacity and the number of solar photovoltaics projects have experienced significant increases since 2017, the total solar photovoltaics capacity is still small compared to fossil-fuel power generating capacity. Based on current trends, the total BRI-associated power development by the end of 2030 could generate 56 (range 40-72) billion metric tons of carbon dioxide over the lifetime of the power plants. This corresponds to 7-17% of the remaining carbon budget for the 1.5 C climate goal.

Various modeling approaches, including fully three-dimensional (3D) models and vertical-equilibrium (VE) models, have been used to study the large-scale storage of carbon dioxide (CO2) in deep saline aquifers. 3D models solve the governing flow equations in three spatial dimensions to simulate migration of CO2 and brine in the geological formation. VE models assume rapid and complete buoyant segregation of the two fluid phases, resulting in vertical pressure equilibrium and allowing closed-form integration of the governing equations in the vertical dimension. This reduction in dimensionality makes VE models computationally much more efficient, but the associated assumptions restrict the applicability of VE models to geological formations with moderate to high permeability. In the present work, we extend the VE models to simulate CO2 storage in fractured deep saline aquifers in the context of dual-continuum modeling, where fractures and rock matrix are treated as porous media continua with different permeability and porosity. The high permeability of fractures makes the VE model appropriate for the fracture domain, thereby leading to a VE dual-continuum model for the dual continua. The transfer of fluid mass between fractures and rock matrix is represented by a mass transfer function connecting the two continua, with a modified transfer function for the VE model based on vertical integration. Comparison of the new model with a 3D dual-continuum model shows that the new model provides comparable numerical results while being much more computationally efficient.

Analysis of geological storage of carbon dioxide (CO 2 ) in deep saline aquifers requires computationally efficient mathematical models to predict the pressure evolution and the injected CO 2 plume migration. The subsurface system of CO 2 injection into saline aquifers can be modeled as a two-phase flow system, with a non-wetting less dense (supercritical) CO 2 phase and a denser brine as the wetting phase. For unfractured geological formations, one type of simplified model can be developed by integrating the three-dimensional governing equations in the vertical dimension. The vertically integrated models that assume buoyant segregation and vertical pressure equilibrium are referred to as vertical equilibrium (VE) models. VE models are computationally efficient owing to the dimension reduction from vertical integration, and have been extensively applied to field-scale modeling of CO 2 injection, migration, and leakage in the past decade. For fractured geological formations, it is challenging to directly use vertically integrated models, because CO 2 migration in fractured formations involves two different characteristic time scales due to significant contrast of permeability between the fractures and matrix. The high permeability of the fractures leads to fast buoyant segregation of CO 2 and brine in the vertical direction within the fractures, while lower permeability of the matrix typically leads to much slower flow dynamics that involve longer time scales for segregation. In this paper, we use a dual-continuum approach to conceptualize the fractured geological formation, treating the fractures and the rock matrix blocks as overlapping continua, and develop vertically integrated models for CO 2 injection in fractured geological formation. We use a VE model for the fracture domain and explore different model options for the matrix domain, including the classical dual-porosity model that treats the matrix as a source/sink term for the fracture as well as other more advanced models that explicitly account for the two-phase flow dynamics of the CO 2 and brine in the matrix domain. We present the modeling framework and show preliminary model comparison results to demonstrate the applicability of the new models.

The Belt and Road Initiative (BRI), initially proposed by China in Fall 2013, involves large-scale development of infrastructure, including energy infrastructure, in Asia, Europe, and Africa, and thus has the potential to affect global climate. In this work, we analyze publicly available information for 458 power plant development projects in 15 representative countries across the BRI regions from eight years prior to BRI (January 2005), to 6 years after BRI (June 2019) in which Chinese engineering contracting companies played a significant role. The data indicate that coal, gas, and solar photovoltaics (PV) activities increased to different degrees after BRI was introduced. We find that 75% of the new generation capacity after October 2013 has gone to fossil fuels, while the rest has gone to hydroelectricity (14%), solar PV (6%), wind (3%), and others (2%). Those numbers have important carbon emissions implications. Based on current trends, the total BRI-associated power development in the 15 countries could generate 37 (range 26–48) gigatonnes (Gt) of committed carbon dioxide (CO2) emissions by the end of 2030, corresponding to 4–11% of the remaining carbon budget for the 1.5-degree climate goal. Extrapolation of these results to all BRI countries gives an estimate of 56 (range 40–72) Gt CO2 for cumulative BRI-related committed emissions by 2030, corresponding to 7% to 17% of the remaining 1.5-degree carbon budget. If the projected growth of fossil fuel power generation in BRI slows down prior to 2030, there are commensurate reductions in emissions implications. To provide context for these numbers, we define a “greenness ratio,” which can be used to measure the level of environmental sustainability of BRI in the power sector.