The sponge effect and carbon emission mitigation potentials of the global cement cycle

Global decarbonization potential of CO2 mineralization in concrete materials

CO2 mineralization products are often heralded as having outstanding potentials to reduce CO2-eq. emissions. However, these claims are generally undermined by incomplete consideration of the life cycle climate change impacts, material properties, supply and demand constraints, and economic viability of CO2 mineralization products. We investigate these factors in detail for ten concrete-related CO2 mineralization products to quantify their individual and global CO2-eq. emissions reduction potentials. Our results show that in 2020, 3.9 Gt of carbonatable solid materials were generated globally, with the dominant material being end-of-life cement paste in concrete and mortar (1.4 Gt y-1). All ten of the CO2 mineralization technologies investigated here reduce life cycle CO2-eq. emissions when used to substitute comparable conventional products. In 2020, the global CO2-eq. emissions reduction potential of economically competitive CO2 mineralization technologies was 0.39 Gt CO2-eq., i.e., 15% of that from cement production. This level of CO2-eq. emissions reduction is limited by the supply of end-of-life cement paste. The results also show that it is 2 to 5 times cheaper to reduce CO2-eq. emissions by producing cement from carbonated end-of-life cement paste than carbon capture and storage (CCS), demonstrating its superior decarbonization potential. On the other hand, it is currently much more expensive to reduce CO2-eq. emissions using some CO2 mineralization technologies, like carbonated normal weight aggregate production, than CCS. Technologies and policies that increase recovery of end-of-life cement paste from aged infrastructure are key to unlocking the potential of CO2 mineralization in reducing the CO2-eq. footprint of concrete materials.

The climate benefits from cement carbonation are being overestimated

Rapid decarbonization of the cement industry is critical to meeting climate goals. Oversimplification of direct air capture benefits from hydrated cement carbonation has skewed the ability to derive decarbonization solutions. Here, we present both global cement carbonation magnitude and its dynamic effect on cumulative radiative forcing. From 1930-2015, models suggest approximately 13.8 billion metric tons (Gt) of CO2 was re-absorbed globally. However, we show that the slow rate of carbonation leads to a climate effect that is approximately 60% smaller than these apparent benefits. Further, we show that on a per kilogram (kg) basis, demolition emissions from crushing concrete at end-of-life could roughly equal the magnitude of carbon-uptake during the demolition phase. We investigate the sensitivity of common decarbonization strategies, such as utilizing supplementary cementitious materials, on the carbonation process and highlight the importance of the timing of emissions release and uptake on influencing cumulative radiative forcing. Given the urgency of determining effective pathways for decarbonizing cement, this work provides a reference for overcoming some flawed interpretations of the benefits of carbonation.

Industrial by-products-derived binders for in-situ remediation of high Pb content pyrite ash: Synergistic use of ground granulated blast furnace slag and steel slag to achieve efficient Pb retention and CO2 mitigation

Ordinary Portland cement (OPC) is a cost-effective and conventional binder that is widely adopted in brownfield site remediation and redevelopment. However, the substantial carbon dioxide emission during OPC production and the concerns about its undesirable retention capacity for potentially toxic elements strain this strategy. To tackle this objective, we herein tailored four alternative binders (calcium aluminate cement, OPC-activated ground-granulated blast-furnace slag (GGBFS), white-steel-slag activated GGBFS, and alkaline-activated GGBFS) for facilitating immobilization of high Pb content pyrite ash, with the perspectives of enhancing Pb retention and mitigating anthropogenic carbon dioxide emissions. The characterizations revealed that the incorporation of white steel slag efficiently benefits the activity of GGBFS, herein facilitating the hydration products (mainly ettringite and calcium silicate hydrates) precipitation and Pb immobilization. Further, we quantified the cradle-to-gate carbon footprint and cost analysis attributed to each binder-Pb contaminants system, finding that the application of these alternative binders could be pivotal in the envisaged carbon-neutral world if the growth of the OPC-free roadmap continues. The findings suggest that the synergistic use of recycled white steel slag and GGBFS can be proposed as a profitable and sustainable OPC-free candidate to facilitate the management of lead-contaminated brownfield sites. The overall results underscore the potential immobilization mechanisms of Pb in multiple OPC-free/substitution binder systems and highlight the urgent need to bridge the zero-emission insights to sustainable in-situ solidification/stabilization technologies.

Reducing China's building material embodied emissions: Opportunities and challenges to achieve carbon neutrality in building materials

Embodied emissions from the production of building materials account for 17% of China's carbon dioxide (CO2) emissions and are important to focus on as China aims to achieve its carbon neutrality goals. However, there is a lack of systematic assessments on embodied emissions reduction potential of building materials that consider both the heterogeneous industrial characteristics as well as the Chinese buildings sector context. Here, we developed an integrated model that combines future demand of building materials in China with the strategies to reduce CO2 emissions associated with their production, using, and recycling. We found that measures to improve material efficiency in the value-chain has the largest CO2 mitigation potential before 2030 in both Low Carbon and Carbon Neutrality Scenarios, and continues to be significant through 2060. Policies to accelerate material efficiency practices, such as incorporating embodied emissions in building codes and conducting robust research, development, and demonstration (RD&D) in carbon removal are critical.

Managing carbon waste in a decarbonized industry: Assessing the potential of concrete mixing storage

The effort towards a greener future will entail a shift to more environmentally friendly alternatives of many human activities. Within this context, the path towards a decarbonized society in general, and industrial decarbonization in particular, will require using low carbon solutions and/or capturing carbon emissions at the source. This flux of captured carbon will then require management and one option is to store it in concrete. The incorporation of the captured CO2 can be done during the mixing and/or curing. While the latter is more efficient and effective in terms of the amount of CO2 incorporated, it is limited to concrete in elements that are compatible with chamber curing. In practice, this would be restricted to the concrete pre-fabrication industry and, most probably, only to small size elements. Despite the lower performance, incorporation of CO2 into concrete during the mixing stage is a relatively universal alternative. The present research effort reveals that the latter solution is beneficial from an environmental point of view, with an estimated yearly carbon storage of 23 million tonnes worldwide against emissions of 2.5 million tonnes to do it.

Net-Zero Embodied Carbon in Buildings with Today's Available Technologies

Greenhouse gas emissions from building construction─i.e., the embodied carbon in buildings─are a significant and growing contributor to the climate crisis. However, our understanding of how to decarbonize building construction remains limited. This study shows that net-zero embodied carbon in buildings is achievable across Japan by 2050 using currently available technologies: decarbonized electricity supply, low-carbon steel, low-carbon concrete, increased timber structures, optimized design, and enhanced building lifespan. The largest emissions savings would come from increased use of timber structures, with annual savings of up to ∼35% by 2050, even in cases where timber replaces low-carbon steel and concrete. Moreover, we show that an expanded domestic timber supply, coupled with responsible reforestation, could improve forest carbon uptake by up to ∼60% compared to the business-as-usual scenario, without the need to increase forest area. This is achieved through a forest-city carbon cycle that transfers carbon stocks of mature trees to cities as building materials and rejuvenates forests through reforestation. Collectively, our analysis demonstrates that the decarbonization of building construction depends not on future technological innovation, but rather on how we design and use buildings with the options we already have.

Feasible supply of steel and cement within a carbon budget is likely to fall short of expected global demand

The current decarbonization strategy for the steel and cement industries is inherently dependent on the build-out of infrastructure, including for CO2 transport and storage, renewable electricity, and green hydrogen. However, the deployment of this infrastructure entails considerable uncertainty. Here we explore the global feasible supply of steel and cement within Paris-compliant carbon budgets, explicitly considering uncertainties in the deployment of infrastructure. Our scenario analysis reveals that despite substantial growth in recycling- and hydrogen-based production, the feasible steel supply will only meet 58-65% (interquartile range) of the expected baseline demand in 2050. Cement supply is even more uncertain due to limited mitigation options, meeting only 22-56% (interquartile range) of the expected baseline demand in 2050. These findings pose a two-fold challenge for decarbonizing the steel and cement industries: on the one hand, governments need to expand essential infrastructure rapidly; on the other hand, industries need to prepare for the risk of deployment failures, rather than solely waiting for large-scale infrastructure to emerge. Our feasible supply scenarios provide compelling evidence of the urgency of demand-side actions and establish benchmarks for the required level of resource efficiency.

Study on the fluidity of foamed alkali-activated slag cementitious material (AASCM)

This study aims to investigate the evolution patterns of fluidity and rheological properties of AASCM under varying dosages of foaming agent and particle sizes of filling aggregate. The flow characteristics of AASCM are significantly affected by the filling aggregate's size and the foaming agent's dosage. Specifically, an increase in filling aggregate size (D(4,3) ϵ [26 μm, 69 μm]) enhances the fluidity of foamed AASCM, while an increase in foaming agent dosage reduces fluidity. These observed variations can be attributed to the presence of particle voids, the specific surface area of the aggregate, as well as the quantity and spatial distribution of bubbles within the slurry. A bubble-particle packing model is established, and by calibrating the simulation error coefficient to 1.1, the study investigates the evolution of water film thickness (WFT) in foamed AASCM with slurry expansion degree. It is observed that bubbles in the slurry affect the fluidity by altering the overall compactness and specific surface area of the foamed slurry, subsequently modifying the WFT.

The Effect of Alkali Metals (Li, Na, and K) on Ni/CaO Dual-Functional Materials for Integrated CO2 Capture and Hydrogenation

Ni/CaO, a low-cost dual-functional material (DFM), has been widely studied for integrated CO2 capture and hydrogenation. The core of this dual-functional material should possess both good CO2 capture-conversion performance and structural stability. Here, we synthesized Ni/CaO DFMs modified with alkali metals (Na, K, and Li) through a combination of precipitation and combustion methods. It was found that Na-modified Ni/CaO (Na-Ni/CaO) DFM offered stable CO2 capture-conversion activity over 20 cycles, with a high CO2 capture capacity of 10.8 mmol/g and a high CO2 conversion rate of 60.5% at the same temperature of 650 °C. The enhanced CO2 capture capacity was attributed to the improved surface basicity of Na-Ni/CaO. In addition, the incorporation of Na into DFMs had a favorable effect on the formation of double salts, which shorten the CO2 capture and release process and promoted DFM stability by hindering their aggregation and the sintering of DFMs.

Near-term pathways for decarbonizing global concrete production

Growing urban populations and deteriorating infrastructure are driving unprecedented demands for concrete, a material for which there is no alternative that can meet its functional capacity. The production of concrete, more particularly the hydraulic cement that glues the material together, is one of the world's largest sources of greenhouse gas (GHG) emissions. While this is a well-studied source of emissions, the consequences of efficient structural design decisions on mitigating these emissions are not yet well known. Here, we show that a combination of manufacturing and engineering decisions have the potential to reduce over 76% of the GHG emissions from cement and concrete production, equivalent to 3.6 Gt CO₂-eq lower emissions in 2100. The studied methods similarly result in more efficient utilization of resources by lowering cement demand by up to 65%, leading to an expected reduction in all other environmental burdens. These findings show that the flexibility within current concrete design approaches can contribute to climate mitigation without requiring heavy capital investment in alternative manufacturing methods or alternative materials.

Built structures influence patterns of energy demand and CO2 emissions across countries

Built structures, i.e. the patterns of settlements and transport infrastructures, are known to influence per-capita energy demand and CO₂ emissions at the urban level. At the national level, the role of built structures is seldom considered due to poor data availability. Instead, other potential determinants of energy demand and CO₂ emissions, primarily GDP, are more frequently assessed. We present a set of national-level indicators to characterize patterns of built structures. We quantify these indicators for 113 countries and statistically analyze the results along with final energy use and territorial CO₂ emissions, as well as factors commonly included in national-level analyses of determinants of energy use and emissions. We find that these indicators are about equally important for predicting energy demand and CO₂ emissions as GDP and other conventional factors. The area of built-up land per capita is the most important predictor, second only to the effect of GDP.

Spatio-temporal interaction heterogeneity and driving factors of carbon emissions from the construction industry in China

Global warming caused by carbon emissions has become a major issue that countries need to address. As the largest carbon emitter globally, the construction industry is one of the major contributors to carbon emissions in China. It is of significance for carbon reduction to study carbon emission from construction industry. Based on various methods, this study explored the spatio-temporal characteristics of carbon emissions and the driving factors of construction industry. This study found, in 2007, 2010, and 2012, carbon emissions from the construction industry exhibited an increasing trend, and the indirect carbon emissions accounted for approximately 77% of the total carbon emissions overall; in addition, the regional gaps in carbon emissions are widening. The space centers of gravity of direct, indirect, and total carbon emissions showed similar rotations in the counterclockwise direction and gradually shifted to the northeast direction. Carbon emissions from the construction industry were predominantly influenced by the total population, number of employees in construction industry, labor productivity in construction industry, added value of the construction industry, energy consumption in construction industry in 2007, evolution to the mutual influence of the total population, labor productivity in construction industry, and energy consumption in construction industry in 2012. The finds can make references for the regional sustainable development.

Growing role of concrete in sand and climate crises

Concrete production poses multiple sustainability challenges, including resource over-exploitation and climate change. Here we show that growing global demand for buildings and infrastructure over the past three decades has quadrupled concrete production, reaching ∼26 Gt/year in 2020. As a result, annual requirements for virgin concrete aggregates (∼20 Gt/year) exceeded the extraction of all fossil fuels (∼15 Gt/year), exacerbating sand scarcity, ecosystem destruction, and social conflict. We also show that despite industry efforts to reduce CO₂ emissions by ∼20% per unit of production, mainly through clinker substitution and improved thermal efficiency, increased production has outweighed these gains. Consequently, concrete-related CO₂ emissions have tripled between 1990 and 2020, and its contribution to global emissions has risen from 5% to 9%. We propose that the policy agenda should focus more on limiting production growth by changing how concrete structures are designed, constructed, used, and disposed of to address the sand and climate crises.

Role of financial decentralization on carbon taxation and carbon emission: Way forwards for economic recovery

The study intends to assess the role of financial decentralization on carbon taxation and carbon emission to recommend the way forwards for economic recovery. To estimate the nexus, study applied the cointegration analysis technique, CGE estimation model, long-run analysis using t-CGE model, and robustness analysis technique on Chinese data. Research findings declare that financial decentralization has significant role on extending the carbon taxation in China and financial decentralization supported 14.92% to expand carbon taxation throughout the Chinese industries. In such industries, pollution emission industries are the top of the list including transportation industry and other manufacturing companies. Overall, manufacturing industries size is about 78% and 11% size of transportation industry is included. Correspondingly, the findings also revealed that financial decentralization supports climate change mitigation with 29% and carbon taxation limits carbon emission with 44% in Chinese industries. Study directs to the stakeholders to enhance carbon taxation schemes in all sectors of the all the industries of China and come up with the viable policy action so that the desired sustainable development goals may achieve effectively. Hence, stakeholders need to consider recommendations of preceding research to enhance green economic recovery.

The eco-efficiency evaluation in China's cement industry: A city-level study

To implement strict environmental targets in China's cement industry into small regions, one should evaluate the city-level eco-efficiency that provides comprehensive instruction. This study establishes a plant-level database with 4000+ production lines located in 341 cities, calculates the energy consumption and CO₂, SO₂, NO_x, and PM emissions, evaluates the eco-efficiency in each city via Slacks-based Measure, and verifies the spatial features of these indicators. Results show that the energy consumption and emissions of the industry are highly concentrated, with ~10 % of the land area contributing to 28.4 %-34.6 % of the total amounts in 2019. The average eco-efficiency value of the clinker calcination and cement grinding processes are 0.761 and 0.714, but the city clusters having low eco-efficiency values are inconsistent with the ones having large energy consumption and emission amounts. The results can contribute to the implementation of the targets such as carbon peaking and pollution cap in China's cement industry.

Human carcinogenic risk analysis and utilization of shale gas water-based drilling cuttings in road materials

Water-based drilling cuttings (WDC) generated during shale gas development will endanger human health and ecological security. The modern analytical techniques are used to analyze the organic pollutants in WDC, and the human health and ecological security risks of harmful pollutants in WDC under specific scenarios are evaluated. The results showed that the content of organic pollutants in WDC was evaluated by human health and safety risk assessment. The comprehensive carcinogenic risks of all exposure pathways of single pollutant benzo(a)anthracene, benzo(a)pyrene, benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene were acceptable. However, the cumulative carcinogenic risk of exposure to dibenzo(a,h)anthracene particles via skin exposure was not acceptable. It was considered that only dibenzo(a,h)anthracene had carcinogenic effect, and the risk control limit of dibenzo(a,h)anthracene in WDC was 1.8700 mg/kg by calculation. As well as, the "WDC-cement" gel composite structure was deeply analyzed, and the physical and chemical properties and mechanism of organic pollutants in cement solidified WDC were analyzed, which provided theoretical support for the study of WDC pavement cushion formula. Based on the above conclusions and combined with the actual site, by studying and adjusting the formula of WDC pavement cushion, the WDC pavement cushion was finally designed by 6% cement + 50% WDC + 44% crushed stone. The 7d unconfined compressive strength met the requirements of the Chinese standard "Technical Guidelines for Construction of Highway Roadbases" (JTG/T F20-2015). Also, the process route of WDC as road cushion product was sampled and analyzed. In addition, the leaching concentration of main pollutants all met the relevant standards of China. Therefore, this study can provide a favorable way for the efficient, safe, and environmentally friendly utilization of WDC, and ensure the ecological environment safety and human health safety of WDC in resource utilization.

Exploring the spatiotemporal heterogeneity and influencing factors of agricultural carbon footprint and carbon footprint intensity: Embodying carbon sink effect

Due to the combined effects of carbon emission and carbon sink, agriculture is acknowledged as an essential contributor to achieve the Chinese government's carbon neutrality goal of 2060, and carbon footprint (CF) and carbon footprint intensity are substantial indicators to reveal the carbon emission level. For these reasons, the Theil index technique and extended STIRPAT model were employed to evaluate their spatiotemporal heterogeneity and influencing factors using panel data from 31 provinces for the period 1997-2019. The findings revealed that the CF showed an increasing trend with an annual growth rate of 24.6 %. The carbon footprint intensity (CFI) indicated an evident spatiotemporal heterogeneity and transferred over time, with an average growth rate of 19.82 %. The CFI Theil index and its contribution rate both confirmed that intra-regional difference is the main source of the overall difference, among which, the CFI Theil index displayed the distribution feature of "western (11.50 %) > central (11.12 %) > eastern (10.56 %) > northeast (6.61 %). The contribution rate of CFI illustrated the spatial pattern of "eastern (33.74 %) > central (21.07 %) > western (19.87 %) > northeast (5.24 %). Furthermore, the influencing effects of GDP per capita, planting structure, population density and urbanization level on CF and CFI also demonstrate evident spatiotemporal heterogeneity.

Cement substitution with secondary materials can reduce annual global CO2 emissions by up to 1.3 gigatons

Population and development megatrends will drive growth in cement production, which is already one of the most challenging-to-mitigate sources of CO₂ emissions. However, availabilities of conventional secondary cementitious materials (CMs) like fly ash are declining. Here, we present detailed generation rates of secondary CMs worldwide between 2002 and 2018, showing the potential for 3.5 Gt to be generated in 2018. Maximal substitution of Portland cement clinker with these materials could have avoided up to 1.3 Gt CO₂-eq. emissions (~44% of cement production and ~2.8% of anthropogenic CO₂-eq. emissions) in 2018. We also show that nearly all of the highest cement producing nations can locally generate and use secondary CMs to substitute up to 50% domestic Portland cement clinker, with many countries able to potentially substitute 100% Portland cement clinker. Our results highlight the importance of pursuing regionally optimized CM mix designs and systemic approaches to decarbonizing the global CMs cycle.

In this paper we report the maximum potential for cement substitution with secondary materials to reduce CO2 emissions globally (1.3 Gt CO2-eq. in 2018) and on a country-by-country basis.

Land use change and carbon emissions of a transformation to timber cities

Using engineered wood for construction has been discussed for climate change mitigation. It remains unclear where and in which way the additional demand for wooden construction material shall be fulfilled. Here we assess the global and regional impacts of increased demand for engineered wood on land use and associated CO₂ emissions until 2100 using an open-source land system model. We show that if 90% of the new urban population would be housed in newly built urban mid-rise buildings with wooden constructions, 106 Gt of additional CO₂ could be saved by 2100. Forest plantations would need to expand by up to 149 Mha by 2100 and harvests from unprotected natural forests would increase. Our results indicate that expansion of timber plantations for wooden buildings is possible without major repercussions on agricultural production. Strong governance and careful planning are required to ensure a sustainable transition to timber cities even if frontier forests and biodiversity hotspots are protected.

Tracking the inequalities of global per capita carbon emissions from perspectives of technological and economic gaps

Facing up to global carbon inequality is an important prerequisite for the fair allocation of carbon emission reduction tasks. This study proposed a new index to measure carbon inequality and then constructed a data envelopment analysis-based decomposition framework to focus on the impacts of the economic development gap and the technology gap on carbon inequality. Based on a dataset of 83 countries (or regions) during 1990-2017, we discuss global carbon inequality and its driving factors and further reveal the discrepancies among different income groups and countries. The main findings indicate that: (1) global carbon emissions showed significant inequality in all years and have an overall decreasing tendency. (2) High-income countries tended to display larger carbon inequality and witnessed great variation in different years. Upper middle-income and lower middle-income countries had relatively low carbon inequality and only experienced very minor variation. (3) Economic development disparity was the foremost factor leading to carbon inequality enlargement in most countries, especially the countries with higher income. The production technology gap played an important role in narrowing carbon inequality, whereas the energy-saving technology gap only exerted a minor effect on carbon inequality.

Efficient use of cement and concrete to reduce reliance on supply-side technologies for net-zero emissions

Decarbonization strategies for the cement and concrete sector have relied heavily on supply-side technologies, including carbon capture and storage (CCS), masking opportunities for demand-side intervention. Here we show that cross-cutting strategies involving both the supply and demand sides can achieve net-zero emissions by 2050 across the entire Japanese cement and concrete cycle without resorting to mass deployment of CCS. Our analysis shows that a series of mitigation efforts on the supply side can reduce 2050 CO₂ emissions by up to 80% from baseline levels and that the remaining 20% mitigation gap can be fully bridged by the efficient use of cement and concrete in the built environment. However, this decarbonization pathway is dependent on how CO₂ uptake by carbonation and carbon capture and utilization is accounted for in the inventory. Our analysis underscores the importance of including demand-side interventions at the heart of decarbonization strategies and highlights the urgent need to discuss how to account for CO₂ uptake in national inventories under the Paris Agreement.

A new study finds supply-side efforts alone are unlikely to lead to net-zero emissions across the cement and concrete cycle by 2050, advocating for more efficient use of cement and concrete in the built environment and more strategic options for decarbonization.

Material Diets for Climate-Neutral Construction

The climate crisis is urging us to act fast. Buildings are a key leverage point in reducing greenhouse gas (GHG) emissions, but the embodied emissions related to their construction often remain the hidden challenge of any ambitious policy. Therefore, in this paper, we explored material GHG neutralization where herbaceous biobased insulation materials with negative net-global warming potentials (GWPs) were used to compensate for building elements that necessarily release GHGs. Different material diets, as well as different building typologies, were modeled to assess the consequences in terms of biobased insulation requirements to reach climate neutrality. Our results show that climate-neutral construction can be built with sufficient energy performance to fulfill current standards and with building component thicknesses within a range of 1.05-0.58 m when timber- and bamboo-based construction is chosen. Concrete-based ones require insulation sizes that are too large and heavy to be supported by the dimensioned structures or accepted by urban regulations. Moreover, a time horizon of 20 years is more appropriate for assessing the contribution of material shifts to biobased materials in the transition period before 2050. This paper demonstrates that this is technically feasible and that climate neutrality in the construction sector just depends on the future that we choose.

Battery technology and recycling alone will not save the electric mobility transition from future cobalt shortages

In recent years, increasing attention has been given to the potential supply risks of critical battery materials, such as cobalt, for electric mobility transitions. While battery technology and recycling advancement are two widely acknowledged strategies for addressing such supply risks, the extent to which they will relieve global and regional cobalt demand–supply imbalance remains poorly understood. Here, we address this gap by simulating historical (1998-2019) and future (2020-2050) global cobalt cycles covering both traditional and emerging end uses with regional resolution (China, the U.S., Japan, the EU, and the rest of the world). We show that cobalt-free batteries and recycling progress can indeed significantly alleviate long-term cobalt supply risks. However, the cobalt supply shortage appears inevitable in the short- to medium-term (during 2028-2033), even under the most technologically optimistic scenario. Our results reveal varying cobalt supply security levels by region and indicate the urgency of boosting primary cobalt supply to ensure global e-mobility ambitions.

New study finds cobalt-free batteries and recycling progress can significantly alleviate long-term cobalt supply risks, however a cobalt supply shortage appears inevitable in the short- to medium-term, even under the most technologically optimistic scenario.

Prioritizing sponge city sites in rapidly urbanizing watersheds using multi-criteria decision model

Spatial planning is crucial for sponge city (SC) construction; however, prioritizing SC sites at the watershed scale has not been fully explored. In this study, a multi-criteria decision model, considering demand and suitability of SC construction, was established by monitoring, model simulation, and index calculation. This new model was then tested in a rapidly urbanizing watershed, Beijing, China, and the priority of SC construction at both grid scale (1km×1km) and subwatershed scale was ranked. The results showed that the highest priority was found in emerging regions where urbanization is ongoing and followed by urban core areas. In addition, six indexes were identified by clustering heatmaps as key factors affecting the priority of SC planning, including topographic index, water pollution index, pollution rate based on the state standard of surface water environment quality, urbanization planning, urban levels, and vegetation index, which could guide SC planning in data-lacking regions. The approach and findings in this study cannot only provide helpful references for watershed managers and urban planners but also can be easily used in other regions.

Global greenhouse gas emissions from residential and commercial building materials and mitigation strategies to 2060

Building stock growth around the world drives extensive material consumption and environmental impacts. Future impacts will be dependent on the level and rate of socioeconomic development, along with material use and supply strategies. Here we evaluate material-related greenhouse gas (GHG) emissions for residential and commercial buildings along with their reduction potentials in 26 global regions by 2060. For a middle-of-the-road baseline scenario, building material-related emissions see an increase of 3.5 to 4.6 Gt CO2eq yr-1 between 2020-2060. Low- and lower-middle-income regions see rapid emission increase from 750 Mt (22% globally) in 2020 and 2.4 Gt (51%) in 2060, while higher-income regions shrink in both absolute and relative terms. Implementing several material efficiency strategies together in a High Efficiency (HE) scenario could almost half the baseline emissions. Yet, even in this scenario, the building material sector would require double its current proportional share of emissions to meet a 1.5 °C-compatible target.

Spiers Memorial Lecture: CO2 utilization: why, why now, and how?

This introduction to the Faraday Discussion on carbon dioxide utilization (CDU) provides a framework to lay out the need for CDU, the opportunities, boundary conditions, potential pitfalls, and critical needs to advance the required technologies in the time needed. CDU as a mainstream climate-relevant solution is gaining rapid traction as measured by the increase in the number of related publications, the investment activity, and the political action taken in various countries.

Curing time: a temporally explicit life cycle CO2 accounting of mineralization, bioenergy, and CCS in the concrete sector

The decarbonization of concrete production requires a multi-pronged approach including the abatement of CO2 emissions from cement production as well as storage of CO2 within concrete itself. This study explores the decarbonization potential of combining bioenergy and carbon capture and storage (CCS) during cement production with the accelerated carbonation of fresh concrete and the natural carbonation of demolished concrete for the life cycle net CO2 of 30 MPa ordinary Portland concrete. As both biomass and concrete reuptake CO2 over time, the timing of CO2 emissions and removals is explicitly accounted for. At current technology levels, the combination of bioenergy and CCS in cement production combined with the carbonation of demolished concrete was seen in our model to allow for net CO2-negative concrete. However, the concrete is CO2-positive until the CO2 of production is reabsorbed by biomass regrowth and the carbonation of demolished concrete at end-of-life. In our model, accelerated carbonation was, by itself, an inefficient CO2 storage mechanism, due to the penalty of energy use and injection losses. However, if it led to a gain in concrete strength, accelerated carbonation could result in lower CO2via reduced resource demand and cement production.