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There has been a growing recognition in recent years that Electrofuels (e-fuels), also known as renewable and sustainable fuels, which are produced from hydrogen and carbon dioxide as the primary feedstocks, have great potential to reduce carbon footprint and address climate change. In the present study, contrary to most previous studies in which the sources of feedstock's preparation were considered as block boxes, two stand-alone processes are taken into account and incorporated into the e-fuels production system. H 2 is obtained by a high-temperature electrolysis system having an overall efficiency nearly twice that of a low-temperature electrolysis system. CO 2 is captured from a power plant flue gas stream with a purity of 99.81%. Investigating heat integration potential in such an integrated plant is an up-to-date and interesting topic and has not yet been well explored. Therefore, a heat integration within the three individual processes is implemented to reduce energy consumption. The design of the process-to-process heat transfer section is carried out using pinch design rules. By integrating individual units, approximately 42% of the required cold utility, traditionally supplied by chilled water and refrigerants, is allocated to generate high and medium-pressure steams. Having used the high-temperature steam electrolysis for H 2 production, a process that requires less external electricity compared to low-temperature water electrolysis, a power-to-liquid efficiency of 70% is achieved. Furthermore, the results reveal a carbon conversion ratio of 98.6%, indicating the effective converting the carbon from the feedstock into liquid hydrocarbons. [Display omitted] • Heat integration between e-fuels unit and its feedstocks supplier units is done. • Shell-and-tube and plate-fin exchangers are used to design heat exchanger network. • Required cold utilities in the processes decreases by 42% by steam generation. • Power-to-liquid efficiency is improved by 70% through the integration. • Effective converting carbon from the feedstock into liquid hydrocarbons by 98.62%. [ABSTRACT FROM AUTHOR]

• This study was conducted to estimate the carbon stocks of the Geramo forest. • The biomass of 73 woody species (trees and shrubs) was estimated using appropriate allometric equations. • The four forest carbon pools (AGB, BGB, LHG and SOC) were considered to determine carbon stock density in this study. • The estimated total carbon stock of the Geramo forest was about 57,994 Mg h−1. • The estimated climate change mitigation potential of the study forest was about 212,838.1 Mg h−1. Forests play a vital role in the global carbon balance and combating global climate change by sequestering and retaining carbon from the atmosphere in their biomass and soil. Thus, this study aims to estimate the carbon stocks in the biomass and soil along with various environmental factors in the Geramo forest in southern Ethiopia. Ninety-six plots (20 × 20 m2) were laid at a distance of 250 m along 16 line transects that were laid 300 m apart. Five 1 × 1 m2 subplots (4 at the corner and 1 at the center) were laid inside each main plot for LHG and soil data collection. The results revealed that the estimated total carbon stocks and mean carbon stock densities of the study forest were 57994 Mg h−1and 604 ± 344 Mg h−1, respectively, with a mean CO 2 equivalent of 2217 ± 1262 Mg h−1. This result indicates the remarkable role of the Geramo forest in carbon stock and sequestration potential compared with other remnant forests in Ethiopia. Thus, the Geramo forest plays a crucial role in climate change mitigation through carbon sequestration, and hence, this forest can generate carbon credits as financial benefits to the nearby population in the future. The results also revealed that anthropogenic disturbances were negatively associated with the carbon stocks of the forest. Therefore, sustainable forest conservation activities are needed to conserve forest resources, protect the forest from growing anthropogenic disturbances, and sustain its current global climate change mitigation and adaptation benefits. [ABSTRACT FROM AUTHOR]

To limit the effects of global warming, arid lands, which constitute approximately one-third of terrestrial surfaces and are not utilized for agriculture, could serve as an effective method for long-term carbon (C) storage. We propose that soil–plant–microbiome engineering with oxalogenic plants and oxalotrophic microbes could facilitate C sequestration on a global scale. [ABSTRACT FROM AUTHOR]

Carbon dioxide removal (CDR) technologies at a gigaton scale need to be developed and implemented within the next decades to keep global warming below 1.5 °C. Coastal enhanced silicate weathering is one of the proposed CDR techniques that aims to accelerate the natural process of CO 2 -sequestration during marine chemical weathering of silicate minerals. To this end, finely ground rock containing olivine (Mg x Fe 2− x SiO 4) could be dispersed in dynamic coastal environments, where local biotic and abiotic factors potentially enhance the weathering process. However, accurate predictions of the olivine dissolution rate and the associated CO 2 sequestration under in situ conditions are currently lacking and ecosystem impacts remain to be assessed. Previously, it has been hypothesized that in situ grain collisions, induced by bed load transport due to currents and waves, could accelerate the in situ chemical weathering of olivine particles. To examine this, we investigated the effects of continuous grain tumbling on olivine dissolution in natural seawater. A 70-day experiment was conducted in which forsterite olivine sand was continuously tumbled in filtered seawater at different rotation speeds, and dissolution rates were measured on a weekly basis. Results showed that continuously tumbled olivine dissolved 8 to 19 times faster compared to stagnant (no rotation) conditions. Olivine dissolution was complete and stoichiometric (except for Ni release), air-seawater CO 2 exchange was not significantly rate limiting, and minimal particle fragmentation and secondary mineral formation were observed. Hence, we infer that olivine weathering was mainly enhanced via advective pore water flushing, which limits saturation effects at the grain scale. Overall, this study provides evidence that ambient physical stresses in coastal environments could enhance marine silicate weathering, which has implications for both the natural silicon cycle as well as the use of enhanced coastal weathering of silicates as a CDR technique. [ABSTRACT FROM AUTHOR]

Agriculture contributes to global climate change by producing 20–25% of greenhouse gases (GHGs). CO 2 is released from deforestation and land conversion, methane from rice paddy fields, and nitrous oxides from overfertilization. An increasing world population requires a change in the agro food systems, including a reduction in chemical fertilizers and pesticides as well as the production and access to food. Greenhouse gas (GHG) emissions have created a global climate crisis which requires immediate interventions to mitigate the negative effects on all aspects of life on this planet. As current agriculture and land use contributes up to 25% of total GHG emissions, plant scientists take center stage in finding possible solutions for a transition to sustainable agriculture and land use. In this article, the PlantACT! (Plants for climate ACTion!) initiative of plant scientists lays out a road map of how and in which areas plant scientists can contribute to finding immediate, mid-term, and long-term solutions, and what changes are necessary to implement these solutions at the personal, institutional, and funding levels. [ABSTRACT FROM AUTHOR]

• Biogas upgrading is environmentally and energetically favourable over combustion. • Storage or utilisation of the captured CO 2 has larger savings than biogas upgrading. • Upgrading, CO 2 storage or utilisation perform well in all impact categories. • The energy system has a substantial impact on the environmental performance. • Methanation provides large climate change savings only in renewable energy systems. Biogas from anaerobic digestion is an important renewable energy source. Combining its utilisation with carbon capture and storage (CCS) or carbon capture and utilisation (CCU) may improve climate change performance. This study uses life cycle assessment to evaluate the environmental impacts of 17 biogas management technology configurations (TCs). The technologies include biogas combustion, upgrading to natural gas quality, CCS, direct utilisation of CO 2 and methanation. The focus is mainly on energy balances and climate change impacts, and the results are subjected to sensitivity-, uncertainty-, and energy system analysis. The TCs with CCS and CCU provide the largest climate change savings (-1400 to - 2100 kg CO 2 -eq/1000 Nm3 biogas). Specifically, the methanation TCs provide the highest savings, but they also depend strongly on the energy sources. When combustion and upgrading TCs are amended with CCS, the resulting climate change savings are robust across the energy systems. The biogas upgrading TCs exhibit substantial climate change savings, mainly due to the natural gas substitution. Combustion TCs without CCS have the lowest climate change savings and the highest quantified uncertainties. The biogas upgrading TCs with storage or direct utilisation of CO 2 provide a good compromise between climate change savings and energy recovery. In the remaining impact categories, the CCU TCs generally perform best, followed by the upgrading TCs and finally, the combustion TCs. The CCS TCs consistently perform worse than their counterparts without CCS, opposite to the climate change results. Overall, amending biogas utilisation with CCS or CCU can contribute to climate change mitigation. [ABSTRACT FROM AUTHOR]

CO 2 concentration in the atmosphere has crossed an unprecedented level of 420 ppm, causing catastrophic events like climate change. Climate change mitigation via carbon capture is crucial for reducing CO 2 emissions. Among various CO 2 capture technologies, adsorption is considered one of the most efficient and promising techniques. In recent times, substantial research has been conducted on producing cost-effective and efficient adsorbents for CO 2 capture via the thermal and chemical treatments of biomass. In this review, we discuss key scientific results to give broad insight into the recent progress in biomass conversion to activated porous carbon (APC). The effects of various chemical and thermal treatments on the textural properties and CO 2 adsorption capacity of APC are comprehensively discussed. CO 2 adsorption mechanism based on interaction with the surface functionality is thoroughly explained. The economic aspects of APC synthesis and post-combustion CO 2 capture using APC are systematically reviewed. [Display omitted] • Use of biomass based activate porous carbon (APC) for CO 2 capture is reviewed. • CO 2 adsorption mechanism on APC surface is thoroughly explained. • APC surface functionalization via metal doping and heteroatom doping is discussed. • Economics of APC synthesis & large-scale CO 2 capture on APC is critically reviewed. [ABSTRACT FROM AUTHOR]

This research aims to explore the current evidence on the sustainability of Bioenergy with Carbon Capture and Storage under a life cycle approach and to understand how research on this topic has evolved in the last decade. A systematic literature review was performed, and the main focus was identifying methodological shortcomings and analysing Global Warming Potential results. Forty-seven studies were selected for in-depth revision. Results show that the number of Life Cycle Assessment (LCA) studies on BECCS has increased in the last couple of years and that most of these studies report near-carbon neutral or carbon-negative results for electricity, biofuel energy, and other products. However, in many cases, some aspects have been omitted from the discussion, such as proper accounting of land use impacts, impact allocation procedure, accounting of leakage from storage sites, and impacts related to carbon utilisation. Despite this methodological variability, Global Warming Potential results are mostly carbon-negative and carbon-neutral for both power BECCS and industrial BECCS systems. Consequently, current scientific evidence suggests climate change mitigation benefits from BECCS despite methodological variability. However, it is still insufficient to reach a consensus on the sustainability of this technology as a solution for a global energy transition. It is recommended that further LCA research deals carefully with methodological and product systems variability, which may affect environmental impact results. Moreover, carbon capture approaches with high potential benefits should be further analysed, and the most optimal BECCS typologies should be identified. Finally, additional life cycle impact categories should be reported, along with the assessment of the economic and social dimensions of BECCS. [Display omitted] • Life Cycle Assessment (LCA) of Bioenergy with Carbon Capture and Storage (BECCS) was reviewed. • LCA methodology choices were discussed. • Global Warming Potential ranges between −3.873 and 0.366 kg CO 2 eq per MJ. • Current evidence is insufficient to confirm that BECCS is a sustainable solution for climate change mitigation. [ABSTRACT FROM AUTHOR]

Carbon neutrality strategies have a significant role in climate mitigation efforts. As global concerns regarding climate change continue to increase, achieving carbon neutrality has emerged as a paramount objective for reducing greenhouse gas emissions and limiting the adverse impacts of anthropogenic activities on the environment. This research investigates a wide range of scholarly works to conduct an in-depth analysis and synthesis of the relevant information about carbon neutrality strategies. The review introduces carbon neutrality principles and terminologies, highlighting their importance in climate mitigation. It then proceeds to explore the wide range of strategies employed across different sectors and industries, investigating their effectiveness, scalability, and potential challenges. A multidimensional analysis contrasts the United States Nationally Determined Contributions pathway 2023, China's Nationally Determined contributions 2023, and the EU Directive 2023/2413, assessing their economic, environmental, political, and social impacts. The study evaluates strategies' effectiveness, scalability, and innovation for transitioning to a sustainable, low-carbon future. It fills a gap by analyzing global approaches across the US, China, and the EU, which account for about 50% of the world's total GHG emissions. It evaluates the novel application of diverse strategies, from renewable energy transitions to innovative policy measures, highlighting their potential to mitigate climate change effectively. By providing a multidimensional analysis of these strategies' impacts, the research not only enhances understanding of effective carbon neutrality tactics but also underscores the importance of international cooperation in realizing a sustainable, low-carbon future. • Identifies and analyzes carbon neutrality strategies, emphasizing the need for diverse US, Chinese, and EU approaches. • Evaluate renewable energy, carbon capture, and policy tools for carbon reduction effectiveness, scalability, and innovation. • Highlights the study's novelty in synthesizing current knowledge on carbon neutrality, addressing a significant research gap. • Concludes with strategic ideas for international collaboration and policy development for low-carbon futures. [ABSTRACT FROM AUTHOR]

• CO 2 flows by forest dynamics and forest operations in one simulation tool. • Generic meta -model for plugging in any silvicultural concept of interest. • Freely available as an open source R-package on CRAN. Carbon stocks and flows in forest ecosystems play an important role in the context of climate change mitigation. Different aspects of the forest carbon balance, however, are often treated independently, leading to a fragmented, disciplinary knowledge. With the R-package care4cmodel we want to support a consolidated view of forest growth and forest operations with respect to carbon flows. The software is, in essence, a pragmatic simulation tool that allows juxtaposing the CO 2 uptake due to wood increment and the CO 2 emissions due to forest operations for given silvicultural concepts in an arbitrary area, over time. At the core, the approach is a dynamic forest area model where forest development stages are represented in a cyclical sequence, which can be broken by disturbances. The model scales up growth and yield information given per forest development stage and unit area to the dynamically simulated development stage areas. This allows to quantify the total forest area's CO 2 uptake, and to estimate the CO 2 emissions caused by forest operations. The forest operations in our implementation include the maintenance of the forest road network, felling trees, debranching and bucking the stems, and extracting the timber to a landing at a forest road. The transport from there to the industry is beyond the system boundary. For the CO 2 uptake of the forest system, the current model version focuses on the wood increment only. We use a practical example to demonstrate the basic features of the model and its plausible behaviour. Beyond the current focus of the model, we see a broad field of applications as a generic meta model, especially in the context of ecosystem service provision. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) in basalt is being actively investigated as a scalable climate change mitigation option. Accurate geochemical modeling prediction of the extent and rate of CO 2 mineralization is a critical component in assessing the local and global feasibility and efficacy of this strategy. In this study, we review basalt-CO 2 -water interaction experimental studies conducted during the last two decades to determine whether they provide useable information for geochemical modeling. Most of the cited experiments generate data on the temporal evolution of water composition, and a few provide identification of secondary precipitates and their compositions, offering information about the reactivity of basalts and the likelihood of secondary carbonate mineralization at various temperatures, pHs, and p CO 2 conditions. However, most experiments provide insufficient information on the properties and quantity of secondary minerals formed, prohibiting accurate mass balance calculations and hence more quantitative geochemical modeling studies. Primary Ca, Mg, and Fe-bearing minerals in basalt control the availability of major ions released into aqueous solution for carbonate precipitation, and many secondary minerals, i.e., smectites, Ca-Mg-Fe carbonates, and zeolites, provide sinks for the same major ions, some of which are difficult to quantify experimentally. Thus, we have a "multi-source and multi-sink" inverse mass balance modeling problem with insufficient constraints on the bulk system in which the temporal evolution of major ions does not provide sufficient information on which mineral(s) dissolve or the sequence of dissolution and precipitation reactions. Going forward, this review highlights the need for providing better-constrained experimental data to calibrate basalt-CO 2 -water geochemical models. Hence, we propose that future experimental work should focus on trace elements and multiple isotopic tracers as well as emphasize the need for better characterization of the solid reaction products with modern analytical instruments. [ABSTRACT FROM AUTHOR]

Cocoa production is a leading driver of deforestation in the humid-tropics of West Africa. Reconciling climate change mitigation with livelihoods of farmers requires identification of production strategies to concurrently improve yield and profit while curtailing emissions of greenhouse gases (GHG). Using a 2021 plot-survey conducted in Ghana's Eastern region, we evaluated yields, GHG emissions, and value of production (VOP) (a profit indicator) across a typology representing the diversity of systems at plot-level. The typology was constructed by first stratifying plots according to shade levels and variety (hybrid vs. Amazonia) which resulted in three systems: Hybrid sun , hybrid variety under full-sun (little to no shade); Hybrid shade , hybrid and moderate shade (13–25 shade trees ha−1); and Amazonia, Amazonia under predominantly moderate shade. Next, factor analysis and clustering were used to group plots within each system according to cocoa yield, vegetation, management, and (local) climate conditions. Cluster analysis showed that fertiliser, weeding, pruning, hand pollination, cocoa tree density, and shade tree densities of differing heights were most influential for determination across systems. Hybrid shade had the highest net GHG removal rate at −6.8 ± 1.7 (± 95% CI) Mg CO 2 eq ha−1 yr−1: 48% and 127% higher (emissions more negative) respectively over Amazonia and Hybrid sun. Hybrid shade additionally had the highest average and least variable VOP among production systems at 669 ± 564 USD ha−1 yr−1, compared to Hybrid sun and Amazonia at 404 ± 442 and 213 ± 280 USD ha−1 yr−1 respectively. These results point to hybrid cocoa grown under moderate shade of 13–25 shade trees ha−1 as optimal for reconciling climate change mitigation with development in West African cocoa. • Study concurrently evaluates financial profits and GHG balances (N 2 O & CH 4 emissions, CO 2 removals) in West African cocoa. • Plot-level indicators are evaluated across a typology obtained from sample-stratification and clustering. • Hybrid cocoa under moderate shade (13-25 shade trees ha-1) had GHG removal increment of 127% over same variety without shade. • This system too had higher mean profits, thus best reconciling GHG mitigation and economic development for the region. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of amine-impregnated polymer aerogels for CO 2 capture represents a groundbreaking advancement in combating the urgent challenges of carbon dioxide (CO 2) emissions and climate change mitigation. The traditional way of synthesizing aerogels for CO 2 capture is to use a one-step gelation process without functionalizing the aerogel, which, to some extent, has low CO 2 capture capacity and kinetics. This study finds a method of synthesizing the functionalized aerogel, which has high CO 2 adsorption capacity, faster kinetic, and is more stable. The polymer aerogel was developed using an oil-water emulsion polymerization method, followed by freeze-drying. It was impregnated with a mono-ethanolamine (MEA) solution to enhance CO 2 adsorption. The performance of the amine-impregnated poly (AAm-co-AAc) aerogels was tested in a continuous adsorption column filled with aerogel. The adsorption results showed the amine-impregnated aerogels having an amine equilibrium uptake value of 40% had significantly improved CO 2 capture capacity up to 2.34 mmole g−1 at 1 bar pressure, 25 °C reaction temperature, and 10 ml/min flow rate. The polymeric aerogel has a very fast adsorption rate, as it can capture 90% of its maximum capacity within just 10 minutes. Then the kinetic data of the CO 2 adsorption was modelled and found to best fit on both pseudo-1st and 2nd-order kinetic models, proposing that the adsorption mechanism on aerogel was controlled by surface diffusion and chemisorption. Furthermore, the isotherm data were evaluated and observed to be best represented by the Langmuir isotherm model, suggesting monolayer formation on the aerogel. After five adsorption-desorption cycles, the amine impregnated poly (AAm-co-AAc) aerogel was able to preserve the initial capacity without a significant decrease. These findings underscore the immense ability of amine-impregnated poly (AAm-co-AAc) aerogels as highly efficient adsorbents for CO 2 capture, thus offering a speedy adsorption process and showing stable regeneration capacity, thereby exhibiting greater industrial application potential. [Display omitted] • An emulsion polymerization method was used to synthesize aerogels for CO 2 capture capacity. • The morphology of the aerogel is fibrous, contributing to its high amine uptake. • Its CO 2 adsorption capacity is up to 2.34 mmole g−1 at 25°C, and regeneration stability is five cycles. • The aerogel exhibits a rapid adsorption rate, capturing 90% of its capacity within 10 minutes. [ABSTRACT FROM AUTHOR]

The Andalusian olive grove in South Spain is employed as a case study to assess the environmental and economic effects of the green architecture (eco-schemes) of the Common Agricultural Policy in relation to low carbon agriculture under different soil management policy scenarios to support more efficient agri-environmental policy making. To do so, we adopted a multidisciplinary approach in which we used: (i) an integrated modelling framework comprising geographic information systems (GIS); (ii) the RothC model; and (iii) a cost-benefit analysis. Results show that eco-schemes provide a significant increase of soil organic carbon (SOC) relative to cross-compliance. Practices involving vegetation covers are more efficient than using pruning residues as mulching. SOC accumulation increases rapidly in the first five-ten years to slow down afterwards. The cost-benefit ratios of eco-schemes policy implementation are higher than one when only SOC is considered. Nonetheless, the inclusion of additional co-benefits has the potential to invert this scenario and enhance policy efficacy. Various insights on optimizing the design and application of eco-scheme efficiency are provided. • The new eco-schemes CAP instrument proposed for woody crops contribute to increase SOC • Mowing cover crops leads to the highest SOC stocks, whereas pruning debris maintains SOC stocks. • Tillage and no-tillage with bare soil systems lead to a significant depletion of SOC stocks. • The economic benefits of eco-schemes would not off-set the costs borne by public authority • Environmental externalities are key to reach the profitability of the policy instruments. [ABSTRACT FROM AUTHOR]

Existing assessments of climate mitigation technologies, like carbon capture utilisation and storage (CCUS), often rely on life cycle assessments (LCA), which are helpful for quantification but may not always be the most complete tools for decision-making. The novel contribution of this study is to provide the first application of a consequential carbon accounting approach, presented as a time-series analysis, to measure the system-wide change in emissions from CCUS linked to CO 2 -enhanced oil recovery. This method includes emissions from marginal oil production, a variable typically excluded in other LCA methods. The method was applied to a hypothetical CCUS project in Mexico to understand critical factors determining whether such an intervention can effectively contribute to emissions reduction in alignment with net-zero goals. Four intervention scenarios were assessed, comparing two distinct CO 2 injection strategies in oil reservoirs (water alternating gas and continuous gas injection) and two energy policy scenarios (current and sustainability). The findings suggest that the energy grid's role in overall emissions is relatively minor, with only a ∼2% difference between the compared scenarios, in contrast, the injection strategy has a significant impact on emissions. Scenarios 1 and 3 report a total change in emissions of −28.39 and −29.87MtCO 2 e, and scenarios 2 and 4 account for −19.63 and −21.22MtCO 2 e, respectively. The results highlight the importance of conducting system-wide analysis and comparing different scenarios to identify the critical components that drive changes in emissions and, therefore, support decision-making and project planning. • Consequential carbon accounting quantifies the system-wide change caused by CCUS. • A time-series provides decision-relevant information on climate change mitigation. • Market-mediated effects are highly relevant for CCUS projects. • CCUS is not consistent with net zero due to as remaining emissions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hedgerows and adjacent croplands at 23 sites across Germany were sampled. • Under hedgerows, 36 ± 49 % more soil organic carbon (SOC) was stored compared to cropland. • 41 % of absolute SOC stock increase was found in subsoil below 30 cm soil depth. • SOC stocks were also increased along the transect from the hedgerow to the cropland. • Planting hedgerows on 3 % of German cropland could increase SOC stocks by 13 Tg C. Carbon dioxide removal strategies are becoming increasingly important as a fundamental component of comprehensive climate policies. One strategy to increase carbon (C) sinks is the integration of hedgerows into agricultural landscapes. Besides additional C storage in above-ground and below-ground hedgerow biomass, the establishment of hedgerows has the potential to increase soil organic carbon (SOC) stocks. However, empirical data regarding the magnitude of SOC accrual with hedgerow establishment are still limited. We sampled 23 sites across Germany in a paired-plot approach with the aim of estimating SOC stock change with hedgerow establishment on cropland. At 21 sites, SOC stocks were higher beneath hedgerows than in the reference cropland. On average, SOC stock accrual was 29 ± 22 Mg ha−1 (36 ± 49 %) in 0–100 cm soil depth. SOC stocks were significantly different in both topsoil and subsoil. Subsoils below 30 cm depth contributed 41 % (12 ± 17 Mg C ha−1) of the total SOC stock change, stressing the importance of subsoil SOC for the total SOC stocks of hedgerow systems. The positive effect of hedgerows on SOC stocks extended laterally beyond the hedgerow area itself. SOC stock in the grassy hedgerow edge also increased significantly by 22 ± 22 Mg C ha−1 (28 ± 30 %) and SOC stock in the cropland directly adjacent to the hedgerow were 9 ± 19 Mg C ha−1 (12 ± 25 %) higher than in the reference cropland. Particularly high C stock differences between hedgerows and reference cropland soils were found in old hedgerows (>200 years) planted on hedgebanks, which are typically found in northern Germany. Our study confirmed that SOC stocks increase with hedgerow establishment on cropland throughout the whole soil profile. If hedgerows were to be established on 3 % of Germany's cropland area, SOC stocks would increase by 13 Tg C equivalent 48 Mio. t CO 2 , highlighting that hedgerows are a promising and multi-functional climate change mitigation option. [ABSTRACT FROM AUTHOR]

• The 57.00% of the Yangtze River Economic Belt area exhibited a significant increase in annual NPP. • The response of NPP on climate factors was nonlinear, with greater sensitivity to temperature. • The impact of topographic factors on NPP changes had a threshold effect. Net primary productivity (NPP) of terrestrial ecosystems serves as a crucial carbon sink, playing a significant role in mitigating climate change. This study, focusing on the Yangtze River Economic Belt (YREB), a key area for both economic development and ecological conservation in China, evaluates the temporal and spatial changes in regional NPP and its responses to climatic factors against the backdrop of global change. Utilizing long-term NPP and meteorological grid data from 1981 to 2017, we analyzed the annual change patterns of NPP and its linear and nonlinear responses to climatic factors using copula functions. Our findings indicate that 57.00 % of the YREB has experienced a significant increase in NPP, with the most substantial decreases observed in Shanghai and its surrounding areas (P < 0.05). Temperature emerged as the primary climatic driver, positively correlating with NPP changes in over half of the study area (P < 0.05). Moreover, the nonlinear response of NPP to temperature and precipitation underscores the complex interactions between these factors, revealing a sensitivity to temperature variations that surpasses that to precipitation. The study also highlights the influence of solar radiation and topographic factors, with a significant positive correlation between NPP and solar radiation observed in 15.85 % of the area (P < 0.05). The practical significance of these findings lies in their implications for regional ecological management and climate resilience strategies. The positive correlation between temperature and NPP underscores the potential for targeted temperature management to optimize carbon sequestration across the YREB. Furthermore, the identified nonlinear responses and the role of solar radiation and topography in influencing NPP offer valuable insights for the formulation of adaptive strategies that enhance ecosystem productivity and contribute to achieving carbon neutrality goals. By elucidating the dynamics of NPP in response to a range of environmental factors, this study provides a foundation for informed decision-making in ecological conservation and climate change mitigation efforts within the YREB and similar regions globally. [ABSTRACT FROM AUTHOR]

Boreal forests are often managed to maximize wood production, but other goals, among which climate change mitigation, are increasingly important. Hence, it is necessary to examine synergies and trade-offs between forest production and its potential for carbon sequestration and climate change mitigation in forest stands. To this aim, we develop a novel mass-balanced process-based compartmental model that allows following the carbon path from its photosynthetic fixation until its return to the atmosphere by autotrophic or heterotrophic respiration, or by being burnt as wood product. Following carbon in the system allows to account for how long forest ecosystems and wood products retain carbon away from the atmosphere (i.e., the carbon transit time). As example, we apply the model to four management scenarios, i.e., mixed-aged pine, even-aged pine, even-aged spruce, and even-aged mixed forest, and contrast metrics of performance relative to wood production, carbon sequestration, and climate change mitigation potential. While at the end of an 80 yr rotation the even-aged forests held up to 31% more carbon than the mixed-aged forest, the mixed-aged forest was superior during almost the entire rotation when factoring in the carbon retention time away from the atmosphere, i.e., in terms of climate change mitigation potential. Importantly, scenarios that maximize production or amount of carbon stored in the ecosystems are not necessarily the most beneficial for carbon retention away from the atmosphere. These results underline the importance of considering carbon transit time when evaluating forest management options for potential climate change mitigation. [Display omitted] • We evaluate wood production and climate change mitigation potential of boreal forests. • We combine an ecophysiological growth model with forest inventory tree allometries. • Higher carbon sequestration does not ensure higher climate change mitigation potential. • Potential climate change mitigation depends on carbon time away from the atmosphere. [ABSTRACT FROM AUTHOR]

Desertification, the process of land degradation in arid, semi-arid, and dry sub-humid areas, poses significant environmental, social, and economic challenges worldwide. As desertification continues to threaten ecosystems and livelihoods, innovative strategies for its management are urgently needed. The article begins by elucidating the causes and consequences of desertification, emphasizing its complex interplay with human activities and natural factors. It highlights the growing recognition of soil microbes as a critical component in combatting desertification. Soil microbes, encompassing a diverse community of bacteria, fungi, archaea, and other microorganisms, play multifaceted roles in soil health, ecosystem function, and sustainable land management. This review delves into the mechanisms through which soil microbes can contribute to desertification management. It discusses their roles in nutrient cycling, soil fertility enhancement, carbon sequestration, soil stabilization, erosion control, and biodiversity conservation. Drawing on case studies and real-world examples, it offers insights into successful applications of soil microbe-based strategies across different geographical regions and ecosystems. Challenges and limitations in implementing these strategies are also examined, including factors such as environmental variability, scale of application, and potential risks. Furthermore, research gaps and areas for improvement in understanding the intricate relationships between soil microbes and desertification management are identified. The review explores prospects and research directions in soil microbe-based desertification management. It highlights innovative approaches, emerging technologies, and the importance of interdisciplinary collaboration. Additionally, it discusses policy implications and the potential of these strategies to contribute to sustainable land use practices. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is a critical measure for ecosystem health and offers opportunities to understand carbon fluxes and associated implications. However, SOC can be significantly influenced by anthropogenic land use change, with intensive and extensive disturbances resulting in considerable SOC loss. Consequently, understanding the spatial distribution of SOC across different land uses, particularly at national level characterised by different biomes, is vital for integrated land-use planning and climate change mitigation. Remote sensing and deep learning (DL) offer a reliable largescale mapping of SOC by leveraging on their big data provision and powerful analytical prowess, respectively. This study modelled SOC stocks across South Africa's major land uses using Deep Neural Networks (DNN) and Sentinel-3 satellite data. Based on 1936 soil samples and 31 spectral predictors, results show a relatively high accuracy with an R2 and RMSE value of 0.685 and 10.15 t/h (26% of the mean), respectively. From the seven land uses evaluated, grasslands (31.36%) contributed the most to the overall SOC stocks while urban vegetation (0.04%) contributed the least. Moreover, although SOC stock was found to be relatively proportional to land coverage, commercial (46.06 t/h) and natural (44.34 t/h) forests showed a higher carbon sequestration capacity. These findings provide an important guideline to managing SOC stocks in South Africa, useful in climate change mitigation through sustainable land-use practices. Whereas landscape restoration, and other relevant interventions are encouraged to improve SOC storage, care must be taken within land-use decision making to maintain an appropriate balance between carbon sequestration, biodiversity, and general ecosystem functions. [ABSTRACT FROM AUTHOR]

• Substitution factors for forest products for the Canadian context were developed. • Substitution factors ranging from 0.51 to 0.91 tC/tC were found. • They will lead to more accurate assessments of the forest GHG mitigation potential. • These factors will help governments to manage forest and fight climate change. Evaluating the climate change mitigation potential of the forest sector requires a holistic approach based on forest carbon (C) sequestration, C storage in harvested wood products (HWP) and substitution on markets. High uncertainty is associated with substitution factors, that express avoided fossil greenhouse gas (GHG) emissions from the use of forest-based products in replacement of GHG-intensive materials and fossil fuels. Few studies have focused on the development of substitution factors in Canada, resulting in the use of unrepresentative generic data. Here, we provide a framework to reduce uncertainties related to substitution factors for primary wood products in a Canadian context. A life cycle assessment framework is used to quantify fossil GHG emissions for a baseline and a wood-intensive scenario. For solid product substitution, we focused on the construction sector and analyzed a range of innovative wood buildings with steel and reinforced concrete as alternative materials. We found non-weighted averages of 0.80 tC/tC for sawnwood and 0.81 tC/tC for panels. For energy substitution, we analyzed cases with different specifications on biomass product, facility type and alternative fossil fuel source in non-residential heat production and biofuel transportation sectors. We found a non-weighted average of 0.80 tC/tC for non-residential heat production and 0.51 tC/tC for biofuel transportation, that can be interpreted as 0.91 tC/tC for heavy fuel oil, 0.69 tC/tC for light fuel oil and 0.68 tC/tC for natural gas substitution. These results provide a benchmark for substitution factors in Canada, to help guide forest management strategies for climate change mitigation. [ABSTRACT FROM AUTHOR]

The bioeconomic potential of monopodial and sympodial bamboos is not well understood. Therefore, Net primary productivity (NPP), total biomass, carbon (C) stock, soil organic carbon (SOC), CO 2 sequestration, and bioenergy potential were studied in a sympodial Chimonocalamus griffithianus and a monopodial Phyllostachys mannii bamboo in Meghalaya, north-eastern India. P. mannii stand with mean culm density 16,877 ha−1, height 14.8 m and diameter 4.4 cm, accumulated 107.56 Mg ha−1 biomass with a total NPP of 18.83 t ha−1yr−1. It stored 50.67 Mg C ha−1 in biomass, 77.28 Mg C ha−1 in soil, and had sequestration potential of 469.58 t CO 2 ha−1. C. griffithianus stand with mean clump density 1065 ha−1, mean culm density 52,185 ha−1, height 7.19 m and diameter 3.04 cm, accumulated 67.08 Mg ha−1 biomass with a total NPP of 15.30 t ha−1 yr−1. It stored 31.30 Mg C ha−1 in biomass, 83.25 Mg C ha−1 in soil, and had sequestration potential of 420.40 t CO 2 ha−1. Matured culms (>2–3 years old) of P. manni and C. griffithianus produced 143.08–166.65 MW h and 87.13–101.48 MW h of energy per ha, respectively. Although landuse history and site characteristics of the two stands were not 100 % identical, significantly greater (p < 0.05) standing biomass, NPP, growth rate, carbon sequestration potential, and energy values of P. mannii than C. griffithianus makes the monopodial bamboo a better choice for energy plantation and climate change mitigation tool than the sympodial. • Monopodial bamboo, Phyllostachys mannii , surpasses sympodial Chimonocalamus griffithianus in bioeconomic potential. • P. mannii exhibits higher biomass, NPP, carbon sequestration, and energy values. • Comparative analysis reveals the superior suitability of monopodial bamboo for energy plantations. • Results provide valuable insights for sustainable development in India's biobased economy. • Study contributes to understanding the role of bamboos in mitigating climate change. [ABSTRACT FROM AUTHOR]

The cultivation of deep-rooted vegetation greatly alters the tradeoffs between water and carbon dynamics, yet their impact on microbial carbon sequestration (MCS) remains inadequately documented, particularly in thick vadose zones. This information is crucial for global climate mitigation and ecosystem service enhancement. As such, we collected triplicate samples for each land use type, exploring the abundance and structure of cbbL -harboring microbial communities within 10-m deep profiles under cultivated farmland and two apple orchards of varying ages (n = 72). Our findings indicated a shift from water-dominated (improved water retention at the expense of reduced carbon sequestration) to carbon-dominated benefits (enhanced carbon sequestration at the expense of decreased water retention) in deep soil layers (2–10 m) after the transformation from farmland to apple orchards. Despite the lack of significant differences among the three land use types, the gene abundances and microbial diversity indices reduced with soil depths because of variations in substrates, resources, and microenvironments. The cbbL -harboring microorganisms consisted of 5 phyla, 7 classes, 19 orders, 30 families, and 55 genera, with Proteobacteria as the predominant bacterial phylum. The relative contributions of different genera varied with soil depths, reflecting their distinct survival strategies. The microbial network was positively connected in various soil layers under farmland and apple orchards. Furthermore, the results of correlation, redundancy analysis, and structural equation modeling jointly indicated that plant roots and soil properties, including total nitrogen and organic carbon, governed MCS processes in deep unsaturated zones. Specifically, the low microbial variation between farmland and apple orchards can be attributed to the predominant effects of climatic and pedogenic factors on soil properties, the restricted contribution of plant roots to soil nutrient levels per unit depth, and the adverse effects of plant-induced ecohydrological consequences on root systems and microbial populations. This study offers new insights within thick vadose zones containing deep-rooted plants, thereby contributing to a better understanding of global terrestrial carbon cycle processes. [Display omitted] • Microbial carbon sequestration processes were explored in 10-m deep profiles. • The farmland-to-apple orchards conversion led to water-carbon tradeoffs. • Microbial carbon sequestration differed with depths rather than land use types. • Depth-dependent plant roots and soil nutrients affects carbon sequestration. [ABSTRACT FROM AUTHOR]

Direct air capture (DAC) technology plays a crucial role in mitigating the effects of global warming by capturing carbon dioxide (CO 2) directly from the atmosphere. A significant technical challenge for DAC is its high thermal energy consumption, which results in an unacceptable overall cost (600 $ t CO 2 – 1). The combination of a high-temperature heat pump (HTHP) and DAC system offers a substantial reduction in thermal energy consumption, decreased reliance on renewable energy sources, and enhanced DAC system flexibility. This study presents three distinct thermal integration strategies that combine an HTHP with solid adsorbent-based DAC and verifies their effectiveness in reducing energy consumption and CO 2 emissions compared to a traditional DAC system. Among them, the deeply integrated DAC-HTHP system (I-DAC) exploits low-grade adsorption heat and waste heat, providing direct heating and cooling energy to the DAC system via refrigerant condensation and evaporation processes. Simulation results indicate that the I-DAC system achieves an extremely low operating energy consumption of 2.77 GJ t CO 2 – 1 , representing a 69.5% reduction than traditional DAC under the same conditions. Consequently, the I-DAC offers a cost-effective (32.0–46.2 $ t CO 2 – 1) negative emission solution. We also demonstrate that the I-DAC is promising for wide application in cities to recycle waste heat and remove CO 2 from the air. The comprehensive implementation of the I-DAC in 105 cities could yield a net annual productivity of 980 MtCO 2. • Proposed a deeply thermal integrated DAC system (I-DAC) with waste heat recovery heat pump. • I-DAC achieved a 69.5% reduction in specific energy consumption compared to base-DAC. • I-DAC offers a cost-effective and scalable negative emission solution for climate change mitigation. • Successful implementation of I-DAC in 105 cities could yield a net annual capture capacity of 980 MtCO 2 by 2050. • Highlights the potential of I-DAC to recycle waste heat and remove CO 2 from the air, with policy implications [ABSTRACT FROM AUTHOR]

Non-native species are expanding globally and can alter ecosystem functions, including food web dynamics, community structure and carbon storage. Seagrass are foundation species that contribute a variety of ecosystem services in near-shore coastal ecosystems, including a significant sink of carbon. In the Caribbean, the rapidly expanding non-native Halophila stipulacea has unknown impacts on carbon storage. To investigate the impacts on carbon storage, we quantified organic carbon (C org) content in sediment and seagrass tissues from monotypic H. stipulacea beds, mixed native seagrass beds dominated by Thalassia testudinum and Syringodium filiforme, and unvegetated substrate in St. John, USVI. We found native seagrass-vegetated sediment contained 1.3 times more C org than sediment covered by H. stipulacea , and 1.6 times more C org than unvegetated areas on average. Whereas, H. stipulacea -dominated substrate stored 1.2 times more C org than unvegetated substrate. Likewise, native species contained 2.2 times more aboveground biomass and 6.0 times more belowground biomass than H. stipulacea. Since seagrasses are critical sources of carbon sequestration, our results suggest that invading H. stipulacea is associated with lower carbon stocks which has potential implications for conservation activities and climate change mitigation. [Display omitted] • Non-native species are expanding globally and can alter ecosystem functions. • Our results suggest that invading H. stipulacea is associated with lower carbon stocks. • In the Caribbean, rapidly expanding Halophila stipulacea may reduce carbon storage. [ABSTRACT FROM AUTHOR]

Over millions of years, the interaction of marine basalt with percolating seawater in low-temperature ocean floor hydrothermal systems leads to the formation of calcite and aragonite. The presence of these minerals in marine basalts provides evidence for substantial CO 2 fixation in these rocks. Here, we report on laboratory experiments to study this process under enhanced CO 2 partial pressures (p CO 2) at 130 °C. Mid-ocean-ridge-basalt (MORB) glass was reacted with North Atlantic Seawater charged with CO 2 in batch experiments lasting up to 7 months. For experiments initiated with seawater charged with ~2.5 bar p CO 2 , calcite and aragonite are the first carbonate minerals to form, later followed by only aragonite (±siderite and ankerite). For experiments initiated with seawater charged with ~16 bar p CO 2 , magnesite was the only carbonate mineral observed to form. In total, approximately 20% of the initial CO 2 in the reactors was mineralized within five months. This carbonation rate is similar to corresponding rates observed in freshwater-basalt-CO 2 interaction experiments and during field experiments of the carbonation of basalts in response to CO 2 -charged freshwater injections in SW-Iceland. Our experiments thus suggest that CO 2 -charged seawater injected into submarine basalts will lead to rapid CO 2 mineralization. Notably, at p CO 2 of tens of bars, magnesite will form, limiting the formation of Mg-rich clays, which might otherwise compete for the Mg cation and pore-space in the submarine basaltic crust. This suggests that the injection of CO 2 -charged seawater into subsurface basalts can be an efficient and effective approach to the long-term safe mineral storage of anthropogenic carbon. [ABSTRACT FROM AUTHOR]

Despite numerous prior studies regarding public acceptance of climate change mitigation technologies, most academic papers focus on individual technologies in their analyses. Little is known about the acceptance of multiple low-carbon energy technologies. This study bridges this research gap and explores the cross-technology acceptance of various energy solutions at different locations. Thus, we provide a comprehensive understanding of public acceptance patterns by analysing a broader range of technologies concurrently, focusing on: (a) nuclear power, (b) district heating, (c) energy-saving technologies, (d) onshore, nearshore, and offshore wind power (WP), (e) photovoltaics (PV) installed on agricultural land, industrial roofs, and private roofs, and (f) carbon capture and storage (CCS) in offshore, nearshore, rural onshore, and urban onshore locations. Based on Danish nationally representative survey data, our results give strong policy indications that PV on industrial rooftops is accepted at the highest level. In contrast, nuclear power, onshore rural and urban CCS, and nearshore CCS are the least accepted technologies to combat climate change among the Danish public. Additionally, we discover that the acceptance of a specific technology is contingent on locations. Specifically, the public acceptance of PV, WP, and CCS depends on the place of living and the potential location of technology placement. Finally, this study explores subgroup analyses to compare acceptance differences according to gender, age, education, income, and location of residence. [Display omitted] [ABSTRACT FROM AUTHOR]

Plants capture atmospheric carbon dioxide (CO 2) for carbon (C) assimilation through photosynthesis, with the photosynthates stored as plant biomass (above- and below-ground plant parts). The C stored as living biomass is a short-term C sequestration strategy, whereas soil organic carbon (SOC) is a long-term C sequestration strategy. In this regard, plant roots are the primary route of C entry into the SOC pool. Through establishing a recalcitrant SOC pool, long-term sequestration can potentially offset the C losses caused by soil degradation in industrial and pre-industrial eras. Over the next 50–100 years, implementing effective agricultural practices could sequester 80–130 GT (109) C as SOC. Carbon, as the primary elemental component of soil organic matter, plays a significant role in shaping the soil's physical, chemical, and biological properties, ultimately influencing soil biomass productivity. By enhancing crop productivity and biomass production, farmers can increase C sequestration, creating a positive feedback loop that contributes to overall C sequestration. Carbon sequestration has numerous co-benefits, including climate change mitigation, ecosystem health, food security, and farm profitability. Adopting conservation agriculture and site-specific practices and developing crop and pasture genotypes with high yields and C sequestration potential should significantly improve crop productivity and C sequestration simultaneously. This opinion article delves into the nexus between photosynthesis and soil C sequestration, highlighting its significance in enhancing farm productivity while mitigating climate change. [Display omitted] • Good agricultural practices could sequester 80–130 GT (109) C as soil organic carbon (SOC). • Engineering of carbon-concentrating mechanisms can enhance carbon assimilation potential of plants. • Afforestation and restoration of degraded lands can improve SOC besides other ecosystem services. [ABSTRACT FROM AUTHOR]

Bioenergy with carbon capture and storage (BECCS) is regarded as a crucial negative emission technology (NET) in many prospective climate change mitigation scenarios that limit global warming below 2 °C. However, there is still insufficient understanding of the overall life cycle environmental performance of different BECCS configurations. Despite the fact that BECCS entails many technological combinations, the technology is still regarded as a single "black box" technology in most climate scenarios. This study presents a critical review of life cycle assessment (LCA) on a wide range of BECCS options: biomass direct-fired power generation, biomass gasification power generation, bio-hydrogen production, biomass application in industry sectors and other biomass conversion processes, such as pyrolysis and fermentation. It is evident from the review that the biomass direct-fired and gasification power plant with a 100% biomass firing ratio and the gasification-based bio-hydrogen processes have a strong potential to achieve negative emissions. However, the net negative life cycle emissions range widely among studies for each configuration due to variations in technology, LCA methodology and assumptions. Additionally, there is an insufficient assessment of comprehensive environmental impacts for BECCS systems other than GWP, making it still unclear about the trade-offs between the benefit from climate change mitigation and potential negative impacts. Main recommendations for improving LCA on BECCS include developing a generalized guideline and standardization for BECCS LCA, conducting LCAs with comprehensive impact categories, focusing on BECCS configurations being overlooked, considering the impact of land use change and the global warming potential of biomass, and extending LCA in both temporal and spatial dimension. [Display omitted] • Systematically review of life cycle assessment on BECCS systems. • Detailed review on various biomass conversion technologies. • Net negative life cycle emissions range widely among studies. • Insufficient studies of some biomass conversion pathways. • Insufficient studies on multi-environmental environment impact categories. [ABSTRACT FROM AUTHOR]

Achieving net zero emissions is a crucial challenge in the global climate change policy. It requires a substantial reduction in unabated fossil fuel use, the deployment of renewable energy sources, and the development of carbon capture, utilisation and storage technologies. The aim of this study was to investigate and compare two CO 2 capture retrofits for natural gas combined cycle (NGCC). First one, amine absorption, is already mature and characterised as commercial technology, whereas second one, calcium looping is a promising method but still under pilot studies. Energy required for capture process yields net efficiency penalty, which in conducted research totalled 8.4% points for amine unit and 7.4–15.5% points in calcium-looping units. The economic evaluation was performed to analyse the impact of both concepts on their profitability. Moreover, the climate change mitigation potential was assessed and indicated that carbon capture can lower the emissivity of a conventional power plant by 82–87% or even contribute to achieving negative emissions when biofuels are used. Carbon dioxide capture is one of the key elements of ongoing energy transition and its integration with NGCC power units could be determined as essential for maintaining energy security with net zero emissions. • The work provides the comparison between amine scrubbing and calcium-looping CO 2 capture for Natural Gas Combined Cycle. • CCS retrofit causes a net efficiency penalty between 7.4 and 15.5%p for analysed configurations. • Calcium-looping retrofit placed after the gas turbine yield lower SPECCA and higher unit power due to new steam cycle. • Using biogas as a feedstock to calciner of calcium-looping unit leads to negative CO 2 emissions. • Amine scrubbing retrofit has much lower CAPEX and OPEX than CaL units, yet they reach higher ΔNPV within 25 years. [ABSTRACT FROM AUTHOR]

• Negative emissions technologies present a viable pathway to the 2100 climate goals. • The study integrates direct air capture and bioenergy with carbon capture. • Agricultural waste is used as a feedstock for bioenergy with carbon capture system. • Bioenergy with carbon capture meets the energy requirements of direct air capture. • Carbon capture efficiency of the integrated solid sorbent system stands at 93.9%. Negative emissions technologies are gaining widespread acceptance as crucial tools in achieving climate goals, such as keeping global temperatures below 2 °C of pre-industrial levels by 2100. Two technologies central to carbon dioxide removal efforts are direct air capture and Bioenergy with carbon capture and storage. While both technologies have undergone extensive study, only a few studies have explored the potential of using biomass as an energy source for direct air capture technology. This is despite bioenergy with carbon capture having the ability to provide carbon-negative heat and power, as well as its potential impact on the climate mitigation goals of the century. This study aims to investigate the feasibility of meeting the energy requirements of a direct air capture unit using bioenergy. Combining these units will result in compounded negative emissions for the integrated system. The objective is to examine the thermal and electrical requirements of the two primary approaches used in direct air capture design: the liquid solvent and solid sorbent direct air capture units, and to calculate the compounded negative emissions achieved by integrating them with bioenergy. The results of this study demonstrate that for a direct air capture plant capturing 1 mega ton of carbon dioxide per year, approximately 1200 and 2400 tons of biomass per day would be sufficient to meet the energy needs of the solid sorbent and liquid solvent direct air capture systems, respectively. The combined capture efficiency of both types of direct air capture systems integrated with bioenergy stands at 91.19% to 93.9% with overall carbon captured up to 1.51 mega tons of carbon dioxide per year. Over the century, integrating bioenergy into direct air capture units can remove gigaton levels of carbon from the atmosphere without disrupting the demand–supply dynamics of existing and future energy systems. [ABSTRACT FROM AUTHOR]

This paper explores economic opportunities of Opuntia cultivation in Spain regarding fresh food production (comparing production structures of Mexico, Italy and Spain), cactus pear non-food uses (exploiting its bio-functional, medicinal, nutraceutical and cosmetic properties) and environmental issues related to climate change mitigation through soil carbon sequestration. Cactus pear production structures and costs are different in the three countries: Mexico (939.77 €), Italy (4.055.1 €) and Spain (9453.77 €). Spain does not present a real productive sector but only isolated farms. Opuntia is an interesting opportunity for non-food production due to the amount of its bioactive compounds. Main components (μg g−1 dried weight) are: kaempferol (34), myrcetin (65), isorhamnetin and derivatives (590), luteolin (8.4), ferulic acid and derivatives (1,050), and catechin (50). Obtaining these compounds could be a way of increasing cactus pear production profitability and creating jobs and value in rural areas. Cactus pear cultivation is a successful tool to mitigate climate change in arid and semiarid regions considering adequate farm and cultivation practices and systems. This crop is often located in high rurality areas, cultivated by small and micro-farmers. Cactus pear cultivation can be an effective tool for rural development in European arid and semiarid areas regarding production, job creation and environmental issues. • Opuntia is cultivated by micro-farmers in areas of high rurality. • Cactus pear cultivation could be a success to mitigate climate change in arid regions. • Opuntia can be an effective tool for rural development in European arid regions. • Italy presents a developed Opuntia sector and is the model to be followed. [ABSTRACT FROM AUTHOR]

• Opposed to potassium, exposures with calcium carbonate did not show any sign of severe agglomeration for any oxygen carrier. • Dicalcium phosphate showed to form a coating on oxygen carrier surfaces. • Oxygen carriers containing silicon agglomerated to greater extent while oxygen carriers including iron were more stable. • The oxygen carrier MnFeAl did not show as severely agglomerated samples compared to the other MnSi, MnSiTi and MnFe. • Further optimisation in thermodynamic databases related to manganese rich systems is required. Carbon capture and storage (CCS) has been acknowledged as an important strategy for mitigation of climate change. Although highly applicable for fossil fuels, CCS with biomass could have the added advantage of resulting in negative emissions of carbon dioxide. One promising carbon capture technology is chemical-looping combustion (CLC). In CLC the reactors are filled with metal oxide bed material called oxygen carriers. Before CLC can be implemented for biomass combustion at a large scale, biomass ash components interaction with oxygen carriers needs to be further understood. Four combined manganese oxides Mn 3 O 4 -SiO 2 , Mn 3 O 4 -SiO 2 -TiO 2 , Mn 3 O 4 -Fe 2 O 3 and Mn 3 O 4 -Fe 2 O 3 -Al 2 O 3 were exposed to common biomass ash components K, Ca and P. The ash components can exist in many forms, but here the compounds CaCO 3 , K 2 CO 3 and CaHPO 4 were used. Exposures were performed at 900 °C for six hours in oxidising, reducing and inert conditions. Crystalline phases were analysed by XRD and morphology examined with SEM-EDX. Results show that oxygen carrier particles containing silicon were more likely to form agglomerates, especially in combination with potassium, whereas the particles including iron were more stable. MnFeAl was the oxygen carrier that showed least agglomerating behaviour while simultaneously showing a propensity to absorb some ash components. Some inconsistencies between thermodynamic predictions and experimental results is observed. This may be explained by lack of relevant data in the used databases, were only a few of the oxygen carrier-ash systems and subsystems have been optimised. Further optimisation related to manganese rich systems should be performed to obtain reliable results. [ABSTRACT FROM AUTHOR]

Rapid climate change mitigation requires carbon sequestration in addition to greenhouse gas emission reductions. Agriculture may have a high potential for carbon sequestration due to improved practices. However, it is not known how the global warming impacts of crop production could be mitigated especially within an agricultural system. The aim of this study is to evaluate possibilities to neutralize global warming impacts in crop production using biochar produced from side flows and buffer zone biomass. A life cycle assessment methodology is utilized in this research for oat production in the boreal climate zone. Global warming impact reductions are compared for three different side flow utilization options. Traditionally, side flows have been utilized in energy or fodder production, and these options are compared to biochar production at a system level. The potential to use buffer zone biomass for biochar production is also studied. Willow has been selected as a biomass source in buffer zones. Oat production leads to greenhouse gas emissions especially due to the use of fossil and mineral fertilizers in cultivation and heat energy, electricity and fuels in various process phases. The production of one metric ton of oat flakes from cradle to gate generates 700 kg of CO 2 eq emissions. Biochar and energy production from side flows enables a greater reduction in global warming impacts than the feed use of side flows. Buffer zones in willow biomass and biochar production may enable the full neutralization of the global warming potential of oat production within an agricultural system. Further research with actual measurements is required especially on biochar impacts on soil emissions such as N 2 O. This research shows that it could be possible to neutralize global warming impacts from crop production using available technologies and available biomass in agricultural systems. A framework is created for carbon neutral crop production using side flows and buffer zone biomass through biochar. • Global warming potential of oat production is studied using LCA methodology. • Oat flakes production generates emissions of 700 kgCO 2eq t−1. • Side flow use for biochar production leads to the lowest overall GWP impacts. • Buffer zone biomass use for biochar production could mitigate the GWP impacts of oat production. [ABSTRACT FROM AUTHOR]

Cover crops are widely advocated for increasing soil organic carbon (SOC) levels, thereby benefiting soil health improvement and climate change mitigation. Few regional-scale studies have robustly explored SOC stocks under cover cropping, due to limited long-term experiments. We used the unique experimental data from the North American Project to Evaluate Soil Health Measurements conducted in 2019 to address this issue. This study included 19 agricultural research sites with 36 pairs of cover cropping established between 1896 and 2014. Explanatory variables related to site-specific environmental conditions and management practices were collected to identify and prioritize contributing factors that affect SOC stocks with cover crops, by coupling the Boruta algorithm and structural equation modeling. Overall, cover crops significantly (P < 0.05) improved several indicators of soil health, including greater SOC (concentration: +8%; stock: +7%), total nitrogen (+8%), water-stable aggregates (+15%), and potential carbon mineralization (+34%), on average, compared to no cover crop control. Likewise, on average, cover crops sequestered SOC 3.55 Mg C ha-1 (0–15 cm depth), with a sequestration rate of 0.24 Mg C ha-1 yr-1. In addition, we found climate (Hargreaves climatic moisture deficit) was important in explaining the variation of SOC stocks with cover crops, followed by soil properties (e.g., soil clay content). In terms of management practices, cover crop type had a significant positive (0.36) effect on SOC stocks, with non-legumes showing a greater impact, compared to legumes and mixtures. Crop rotational diversity also had a positive (0.28) effect on SOC accumulation. Our findings suggested that integrating non-legume cover crops into diverse crop rotation is likely to be a promising strategy to maximize SOC stocks with cover crops across North America. • Prioritized factors affecting soil organic carbon stocks under cover cropping. • Investigated 19 long-term experiments with cover crops in North America. • Used models coupling the Boruta algorithm and structural equation modeling. • Descending from climate > cover crop type > soil clay content > rotation > tillage. • Cover crops sequestrated carbon 3.55 Mg C ha-1, at a rate of 0.24 Mg C ha-1yr-1. [ABSTRACT FROM AUTHOR]

Recently, electric fuels (E-fuel), which are the chemicals produced from the conversion of renewable-based hydrogen (H 2), are actively being developed as a sustainable energy carrier. Renewable methane is particularly a promising alternative to fossil-based natural gas, which can be produced from CO 2 or syngas methanation. In this work, techno-economic assessment (TEA) and life-cycle assessment (LCA) for renewable methane production are performed through syngas methanation, where CO 2 is collected using direct air capture (DAC) and syngas is produced by solid oxide electrolysis (SOE) with renewable-based electricity. This research considers the different technical, economic, and environmental performances of the systems for renewable methane production. A favorable reduction in a maximum of 23.3% of CH 4 production cost is observed by the scale-up effects of SOE system from 1 MW to 10 MW. TEA draws the conclusion that economic infeasibility is proved at the current level, but additional research and improvement of SOE system and a plunge in renewable electricity prices can lead to the economic equivalent of conventional natural gas. Furthermore, given that certain energy resources with low energy intensity (0.0394 kg CO 2 -eq MJ−1) are integrated with SOE system for methane production, the LCA results that renewable methane production at a large scale has a potential to access negative CO 2 emissions and accelerate climate change mitigation. Consequently, it is concluded that syngas methanation with renewable-based energy systems and DAC can make a considerable opportunity for climate change mitigation under the assumption that SOE system and renewable energy are significantly improved. [Display omitted] • Feasibility of renewable methane production from syngas methanation is investigated • Solid oxide electrolysis for syngas production with renewable energy is covered • Direct air capture as CO 2 capture technology is considered for renewable methane • Possibility of negative CO 2 emission is confirmed by utilizing direct air capture • Mitigating climate change is proved by renewable methane with direct air capture [ABSTRACT FROM AUTHOR]

The continuous rise in global temperatures is an evidence of climate change. CO 2 emissions have caused major problems owing to its contribution to climate change. In particular, the construction industry has a considerable carbon footprint. Therefore, investigations into climate change mitigation are indeed a priority. All steps in the construction process, from raw materials preparation to cement production, contribute to CO 2 emissions. This can be mitigated to a certain extent by incorporating bio-based constituents into construction materials. However, bio-based materials may negatively affect cement reaction and structural performance, despite their positive environmental impacts. Biochar, a carbon-rich product of biomass pyrolysis, is considered a potential substitute for cement replacement that can enhance structural properties if used in appropriate amounts. Although biochar has conventionally been used as a soil amendment in the agricultural industry, researchers have recently investigated its applicability in concrete. Importantly, the results thus far have reported its contribution to the enhancement of the mechanical, thermal, and physical properties of cement. This review provides a comprehensive overview of the physicochemical properties of biochar added cementitious materials, including the fresh and hardened properties of biochar-cement mixtures considering both environmental and economic aspects. • The structure of biochar exhibits excellent compatibility with the cement matrix. • Biochar addition can modify the physical and mechanical properties. • Biochar improves concrete durability, sequesters carbon, and mitigates climate change. • Biochar can be used for carbon sequestration in cement applications. • Economic benefits of biochar-cement composites are not well elaborated in the literature. [ABSTRACT FROM AUTHOR]

The potential for large-scale afforestation, as a climate change mitigation strategy, has led to national afforestation targets being proposed. These targets raise many questions, including how to optimise carbon storage, whilst enhancing other ecosystem services (ES). Here, we assess how decision-making at different scales might affect the spatial distribution of new tree planting in England and hence ES provision. This was achieved by modelling the impact of afforestation on three example ES (carbon sequestration, recreation, and flood mitigation) to identify the best areas for planting at five scales of decision-making: national, regional, county, district, and parish. The modelling shows that carbon sequestration rates are relatively invariant across England (once unsuitable areas are excluded), whilst recreation and flood mitigation are more spatially variable, so full simultaneous optimisation of the three ES is not possible. Consequently, recreation and flood mitigation are also more impacted by changes in planning-scale than carbon, with the modelling showing over 200% difference between the parish and national-scenarios for flood mitigation benefits. Overall, targeted afforestation at national scale maximises ES benefits, but risks overwhelming some landscapes with trees. Targeting afforestation using smaller planning units generates more evenly distributed planting, but lower ES benefits. Our results show national-scale planning produces over 35% more combined ecosystem value than planning at parish-scale, and over 65% more than randomized planting. This highlights the benefits of targeting at a relevant scale, but also the potential trade-offs between widely-distributed new tree planting (e.g., parish-scenario), versus planting to optimise ES provision (e.g., the national-scenario). These results do not imply a single 'correct' scale for planning, but instead highlight the importance of considering the impact of a specific scale on the different ES, and that even spatial targeting at the smallest scale produces higher ES benefits than random planting. • Spatially targeting afforestation optimises provision of multiple ecosystem services. • Optimisation method demonstrated for national afforestation targets. • Substantial increase in ecosystem services over untargeted afforestation. • Service provision varies widely with governance level used to plan afforestation. [ABSTRACT FROM AUTHOR]

The injection and storage of anthropogenic CO 2 in the subsurface is being deployed as a climate change mitigation tool; however, diagenetic-paragenetic heterogeneity in sandstone reservoirs often contributes to interval specific chemomechanical changes that affect injection and can increase leakage risk. Here, we address reservoir heterogeneities' impact on chemomechanical changes in a macroporous-dominated lithofacies of Morrow B sandstone, a formation containing several diagenetically-distinct hydraulic facies while undergoing enhanced oil recovery (EOR) and carbon dioxide (CO 2) sequestration. We performed three flow-through experiments using a CO 2 -charged or uncharged formation water combined with four indirect tensile strength tests per post-test sample. We then used the microstructure and paragenetic sequence to understand chemomechanical weakening with key observations as follows: dissolution of carbonates and feldspars changed porosity; increased permeability led to reclassifying each sample in a different hydraulic flow unit; decreased ultrasonic velocity; and did not lead to a loss of tensile strength. Tensile strength maintenance occurred due to the low abundance and minor dissolution of siderite, the stability of quartz, and the relative position of diagenetic ankerite within feldspar. This macroporous-dominated lithofacies is the primary reservoir for the Morrow B Sandstone, and is analogous to other porous sandstone reservoirs. It represents an end-member of a chemomechanically low-risk siliceous CO 2 sequestration and CO 2 -EOR reservoir. • Despite significant geochemical alteration, CO 2 -fluid rock interaction did not result in loss of tensile strength. • Paragenesis and microstructure are controlling mechanisms of tensile strength maintenance in acidic/neutral fluid conditions. • CO 2 -charged fluids dissolve carbonates and feldspars with concurrent and observable precipitation of iron-rich phases. • Rock interaction with a CO2-charged or uncharged fluid results in large macropores and permeability increases of.51 – 3 mD. • Ultrasonic velocity decreased modestly (2–8%) in all experiments. [ABSTRACT FROM AUTHOR]

The Intergovernmental panel on climate change raised awareness on the urgent need for action to limit climate change. Answers include bioenergy with carbon capture and storage (BECCS), which could theoretically generate negative emissions. The life cycle assessment (LCA) method needs to be applied to BECCS systems to assess their negative emission potential and prevent transfers from one environmental impact category to another. To allow for informed decision-making, the quality of LCA results should be evaluated. The quality of results is related to the quality of the data used. The purpose of this article is thus to review the life cycle inventory data that are used for BECCS LCA. To this end, 35 recent BECCS LCA were selected and the inventory data they used was collected. Synthesis inventory tables were then compiled, including the observed range of variability for each data item. These tables cover biomass harvesting, pre-treatment, combustion, gasification, and carbon dioxide capture with a monoethanolamine (MEA) based solvent. Data quality is also reviewed, through the representativeness, reproducibility and completeness of the life cycle inventories highlighted in the selected articles. Only a third of the articles (13/35) provide life cycle inventory tables. Only half of the articles assess the impact on climate change leading to inventory cut-offs. BECCS systems including combustion followed by MEA-based capture have been most referenced (12/35 articles). More transparency on data quality is recommended. Certain promising BECCS systems should also be further studied. This applies, for instance, to BECCS systems that involve second-generation solvents. • A review of the data quality used in life cycle assessment (LCA) of BECCS is assessed. • Only a third of the studied articles provide their life cycle inventory tables. • Inventory data currently used in LCA of BECCS is compiled into synthesis tables. • BECCS systems including MEA-based capture are most frequently referenced. • BECCS systems that should be further assessed with LCA are identified. [ABSTRACT FROM AUTHOR]

Coastal salt marshes suffering from anthropogenic coastal development and sea level rise have attracted much attention because of their capacity for carbon sequestration and global climate change mitigation. Accurate mapping of coastal salt marshes is always the first step for their protection, management, and restoration. The inherent complexities of vegetation, dynamics of tides, and anthropogenic disturbances pose challenges for remote sensing-based approaches. Existing studies have utilized phenology information and various black-box algorithms to reduce misclassifications. However, the approaches with dual-temporal images containing phenology information have suffered from inefficiency; the misclassifications have been objectively post-processed rather than considered in the method design, and the tacit knowledge of the trained black-box models has not been revealed. To address the above issues, we proposed a new approach with solid improvements in dual-temporal image construction, misclassification processing, and tacit knowledge analysis, including an efficient method to synthesize dual-temporal images based on the common divisor of the green-up season or senescence season resulting from latitudinal gradients in narrow coastal areas of China, a detailed classification scheme by interpretation of iteratively collected samples, and a key decision rule approximating the trained model. We applied the approach to Sentinel-1/2 images and DEM data, thus deriving a 10-m resolution coastal salt marsh map of China with an overall accuracy of 92.5%. A qualitative comparison showed that the map produced in this study was fitted well with actual salt marsh distributions, resulting in improved accuracy when compared to recently generated maps. The most important contribution is that the overall nature of the trained model observed from the training samples was approximated by a four-feature decision rule following the principle of explainable artificial intelligence, i.e., B8 senescence /B4 senescence < 2.06 & B4 green /B8 green < 0.78 & B12 green /B11 green < 0.72 & elevation < 2.13 , and thus established a new potential classification mechanism for dual-temporal black-box algorithms, i.e., the water signal was covered up by flourishing vegetation, but the situation changed when vegetation withered. This study not only generates an accurate coastal salt marsh map at a national scale but also provides a classification mechanism for dual-temporal image-based coastal salt marsh identification and mapping. • Developed an efficient method for constructing senescence and green images. • Established a mechanism for dual-temporal image-based coastal salt marsh mapping. • Provided a coastal salt marsh map with solid improvements on the most recent one. • Explored a case of explainable artificial intelligence (XAI) in the coastal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon sequestration potential of the clay fraction. • Determination of the carbon saturation deficit of each mineral of the clay fraction. • Identification of the equation for the prediction of carbon sequestration potential. • Identification of land uses with the greatest carbon sequestration potential. The capacity of soil to sequester carbon (C) is a key process that promotes the reduction of CO 2 in the atmosphere. Soils can absorb as much as 20% of anthropogenic carbon emissions, which can contribute to mitigate climate change. This capacity relies on the organo-mineral association, which includes different minerals, Fe and Al oxides, which have a critical soil organic carbon (SOC) sorption surface. Based on an equation of the potential C saturation deficit of fine soil particles (<20 μm/silt and clay fractions) for tropical regions, this study investigated the SOC sequestration potential of the clay fraction for soils in Piracicaba region, São Paulo State, Brazil as influenced by the clay minerals. This potential was fitted to a spatial regression model for soil depths 0–20 cm and 80 to 100 cm. In the surface layer, the sequestration potential was mostly explained by the relative abundance of soil minerals (Kaolinite, Hematite, Goethite and Gibbsite) determined using vis-NIR-SWIR spectroscopy. A direct relationship was observed with Goethite and Gibbsite, indicating that low concentrations would reduce the sequestration potential. At 80 to 100 cm depth, Kaolinite and Hematite explained most variation in SOC sequestration potential. Additionally, the C associated with the mineral fraction and the C saturation potential as a function of minerals were modeled and a strong importance of hematite in the C sequestration and stabilization cycle was identified at both depths. The individual mineral contribution to SOC sequestration potential was also mapped, which identified high contributions of goethite and gibbsite for deep soil layers. The influence of land use on the carbon sequestration potential of minerals was observed, with the greatest potential being found in areas with pasture and cropping mosaics and grassland and forest mosaics, with a high presence of kaolinite and hematite. These minerals have a greater potential for carbon sequestration at greater depths and, therefore, could be critical in climate change mitigation strategies. [ABSTRACT FROM AUTHOR]

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]

Scattered trees in wood-pastures represent outstanding conservation value by providing microhabitats for a variety of organisms. They also diversify ecosystem services by creating shade for livestock, and capturing and storing carbon. However, trees in wood-pastures are declining Europe-wide and an appropriate legal environment to maintain them is mostly lacking. Here we looked beyond the well-documented beneficial effects of trees and assessed potential ecosystem disservices, which may drive the controversial appreciation of trees. In a grazing exclusion experiment, we assessed the effect of trees on herbage production in wood-pastures from semi-arid continental to humid montane areas in the temperate deciduous forest ecoregion, and found that trees have a suppressive effect throughout the year, although herbage nutritive value, as indicated by herbage nitrogen content, seems to be improved in spring. When we up-scaled the local ecosystem disservice on herbage yield to entire wood-pastures, the loss remained below 3%, which is lower than reported gains in livestock production due to free access to shade. Thus, the motivation for the under-appreciation of trees by land managers and decision makers may lie in that trees suppress herbage production, but the importance of this effects is offset by the magnitude of the beneficial services of trees. We recommend current wood-pasture stakeholders to revisit their attitude towards scattered trees and encourage tree planting campaigns and tree-based climate mitigation strategies to consider the protection of trees in wood-pastures and the establishment of young ones in currently open pastures up to traditionally low tree cover proportions, as livestock production is unlikely to be compromised by this action. • Wood-pastures are widespread, high nature and cultural value landscapes. • Scattered trees in wood-pastures boost biodiversity and diversify ecosystem services. • In temperate deciduous forest ecoregions, they reduce sub-canopy biomass production. • When scaled up to the whole wood-pasture, the loss of biomass remains negligible. • Climate strategies are encouraged to involve scattered trees on pastureland. [ABSTRACT FROM AUTHOR]

Highlights • LAC GHG efficiency in agricultural sector using within and across country metrics. • 5 Countries offset agriculture emissions with land-use-related carbon sequestration. • Small Caribbean island-states report the worst-case decoupling elasticity scenario. • Top decoupling countries are not equivalent to high factor productivity countries. Abstract The paper explores the relationship between production and greenhouse gas (GHG) emissions in the agricultural sector of Latin America and the Caribbean (LAC) between 1990 and 2015. By appraising how GHG emissions have changed with respect to agricultural production (elasticity), we are able to classify countries into six decoupling states. While the decoupling elasticity provides information for assessing the evolution within countries, we introduce a performance ratio for country comparison by calculating GHG emissions over agricultural production for 2015 and using the global distribution as benchmark. The information from both measurements serves to identify various country and sub regional situations. The findings illustrate that countries with performance ratios in the top 25% and under the best-case elasticity scenario (of strong decoupling) are not necessarily the same as the ones usually identified under factor productivity analyses, suggesting that environment-specific policy incentives and tools play a key role in enhancing sustainable agricultural production. Another major finding is that very few countries in the region (and worldwide) are able to offset agriculture emissions with land use-related carbon sequestration practices. Lastly, the evidence on small Caribbean island-states reporting the worst-case elasticity scenario (of strong negative decoupling) and performance ratios close to the world median, further supports the need for development plans related to climate change mitigation and adaptation in this sub region. [ABSTRACT FROM AUTHOR]

• Conservation Agriculture is able to mitigate climate change in Africa. • Both annual and perennial crops are able to contribute to C sequestration. • Potential estimate of C sequestration is 145 Mt per year, which is 533 Mt CO 2. • This figure represents about 95 times the current sequestration figure. Africa is the smallest contributor to global greenhouse gas emissions among the continents, but the most vulnerable to the impacts of climate change. The effects will not be limited to a rising average temperature and changing rainfall patterns, but also to increasing severity and frequency in droughts, heat stress and floods. Agriculture is not only impacted upon by climate change but also contributes to global warming. However, not all agricultural systems affect negatively climate change. Conservation Agriculture (CA) is a farming system that promotes continuous no or minimum soil disturbance (i.e. no tillage), maintenance of a permanent soil mulch cover, and diversification of plant species. Through these principles it enhances biodiversity and natural biological processes above and below the ground surface, so contributing to increased water and nutrient use efficiency and productivity, to more resilient cropping systems, and to improved and sustained crop production. Conservation Agriculture is based on the practical application of three interlinked principles along with complementary good agricultural practice. The characteristics of CA make it one of the systems best able to contribute to climate change mitigation by reducing atmospheric greenhouse gas concentration. In this article, the carbon sequestration potential of CA is assessed, both in annual and perennial crops, in the different agro-climatic regions of Africa. In total, the potential estimate of annual carbon sequestration in African agricultural soils through CA amounts to 143 Tg of C per year, that is 524 Tg of CO 2 per year. This figure represents about 93 times the current sequestration figure. [ABSTRACT FROM AUTHOR]

Understanding sequestration of carbon by coastal ecosystems is central to addressing the role they play in climate change mitigation. To quantify this process, accurate measurements of CO 2 fluctuation, coupled with variations in residence time of coastal water-bodies are required. Nearshore ecosystems, including coastal lagoons, may provide an effective sink for atmospheric carbon dioxide, particularly those containing productive biota such as seagrass. However, the rate and pattern of carbon sequestration in seagrass meadows across a range of environmental settings is still poorly constrained. In this study, we utilize a robust physical tidal model, along with biogeochemical dissolved inorganic carbon (DIC) assessment, to estimate water residence time and net sequestration of atmospheric CO 2 in an intertidal lagoon containing a seagrass (Zostera noltii) meadow. Total alkalinity and pH measurements taken from advected water mass exchanged with the open ocean at inlet boundaries are used to calculate DIC and p CO 2. A predictive model of hydrodynamics provides good approximation of mean water residence time to within 6 h (±3 s.d). Results indicate that during the daytime study period the lagoon is a sink for carbon, having a mean net ecosystem productivity (NEP) of 3.0 ± 0.4 mmol C m−2 hr−1. An equivalent diel NEP range of between 15.23 and −9.24 mmol C m−2 d−1 is calculated based on reported shallow water pelagic respiration rates. Moreover, approximately 4% of DIC availability occurs from atmospheric CO 2 transfer to lagoon water. However, a negative diel rate of −82 ± 81 mmol C m−2 d−1 is found, assuming overnight respiration ascertained from converted Zostera noltii O 2 utilization. We hypothesize that analogous regional nearshore ecosystems provide baseline study sites suitable to elucidate the carbon capture potential of planned, nearby tidal range energy schemes. • Tidal range energy schemes require additional benefits to boost feasibility. • Carbon offsetting could provide an additional income source. • Man-made nearshore lagoons containing seagrass may enhance carbon sequestration. • Results show existing regional lagoons may help elucidate this potential. • High-resolution, multi-disciplinary studies are required to constrain uncertainty. [ABSTRACT FROM AUTHOR]

Abstract Land-use changes can alter soil carbon (C) contents, and in particular deforestation has been responsible for a large part of the cumulative human-induced greenhouse gas (GHG) emissions. This study aimed to determine the influence of land-use and land cover change on soil organic carbon (SOC) content, microbial biomass C (MBC) and microbial respiration (MR) in the Hyrcanian forests, north of Iran. We compared an agricultural field (AF), plantations of Alnus subcordata (AS), Acer velutinum (AV), Quercus castaneifolia (QC) and Cupressus sempervirens (CS), and a natural forest (NF). Soil samples were collected at three different depths (0–20, 20–40 and 40–60 cm). Results showed that different land covers significantly affected soil characteristics, and SOC increased by 25% and 1.11% after the conversion of NF to CS and AS plantations respectively, and decreased by 4%, 12.11% and 53% when NF was converted to QC, AV and AF respectively. In all treatments, MBC and MR were significantly higher (p < 0.05) in the 0–20 cm depth, and MR was also correlated positively with MBC and SOC. Microbial biomass was near the half in the agriculture field than in plantations and natural forest in the upper layer, but the effects of land use on microbial biomass C decreased with soil depth. However, we observed considerable amounts microbial biomass C in 40–60 cm depth. Also, results showed that topographical feature, altitude and slope, will affect SOC content. Our results indicated that forest plantation is a key measure to enhance SOC content and mitigate global CO 2 emission, especially when soils are degraded and have low soil C content. In particular, afforestation had a crucial effect on elevating SOC content in the Hyrcanian forest, but plantations of oak (QC) and maple (AV) were less effective in terms of soil C increase. Graphical abstract Unlabelled Image Highlights • SOC increased after the conversion of NF to CS and AS plantations. • SOC stock of the agricultural field was about 50% lower compared to the NF. • Half of SOC content in agriculture field is concentrated in 0–20 cm of soil. • MBC decrease with depth, but there was a considerable MBC in the 40–60 cm depth. • The effects of land use on microbial biomass C decrease with depth. [ABSTRACT FROM AUTHOR]

Highlights • The 4‰ Initiative aims to increase global soil organic carbon (SOC) at 4‰ yr−1. • SOC data under agroforestry and conservation agriculture in Africa were reviewed. • Published data show very large variability in SOC storage rates. • SOC storage rates under fallows and multistrata systems are higher than 4‰ yr−1. • Only rates under full conservation agriculture are higher than 4‰ yr−1. Abstract The 4‰ initiative launched by the French government at COP21 in Paris in December 2015 aspires to increase global soil organic carbon (SOC) stocks at a rate of 0.4% per year. We conducted a systematic literature review on SOC storage under agroforestry and conservation agriculture systems in sub-Saharan Africa, where we reported 66 and 33 cases for both systems respectively. The results showed that SOC storage rates were significantly higher than 4‰ yr−1 in fallows and in multistrata agroforestry systems (P = 0.0001 and 0.0178, respectively), but not in alley cropping and parklands systems. For conservation agriculture, SOC storage rates were only significantly higher than 4‰ yr−1 (P = 0.0438) when all three principles were applied, i.e. no- or minimum tillage combined with crop residue retention and intercropping or rotation. The data showed very large variability in SOC storage rates as the result of various factors, including previous land-use history, experimental set up and approach used to determine SOC storage (diachronic versus synchronic approach), soil type, depth of soil sampling, type of crops and management, and duration of the experiment. SOC storage rates significantly decreased with time in the agroforestry systems (P = 0.0328). However, we were unable to find significant relationships with initial SOC stocks or tree density. Given the limited published data and the high variability in results, no significant relationships between SOC storage rates and site variables were found for conservation agriculture. We argue that there is a potential for SOC storage in agricultural soils of sub-Saharan Africa, as illustrated by SOC gaps observed on smallholder farms. Low SOC levels are, however, to a great extent the result of limited resources of most smallholder farmers. Practices such as agroforestry and conservation agriculture can restore SOC in these soils, but the 4‰ initiative has to be implemented on the grounds of the positive impact on crop productivity rather than on climate change mitigation. The efficiency in doing so will depend on the specific situations and will need economic support to smallholder farmers, including the promotion of good markets for sale of extra produce and for input supply, effective private support and policy, such as credit schemes and subsidies for inputs, and efficient extension services which incentivize farmers to invest in new technologies. [ABSTRACT FROM AUTHOR]