Embodied CO2 Emissions Research Articles

A Comparative Evaluation of Embodied Environmental Impacts of Channel Stabilisation Using Concrete Lining and Alternative Pozzolanic Materials

Channel stabilisation with the lining of bed/ banks using cement-concrete (with/ without steel reinforcement as per the size, depth, and capacity), geomembrane, polymers, canvas, ramped earth, vegetation, gravel/ stone pitching, and brick blast is a common practice worldwide to save the adjacent flood plain areas from bank overflowing, seepage, water logging/ salinity, loss of water in irrigation channels, maintaining required water levels and strengthening of channels to be used as transportation means. A trapezoidal channel of cross-section 165 m2 and a lined perimeter of 42m was proposed to accommodate a super flood of 360 m3/sec discharge for a catchment area of 1446 km2 and 118 km length, using a projected heavy flood event of 6 cm precipitation in 8 hours for Swale River to ascertain the material calculation and its environmental impact. This concrete lining would likely produce an equivalent global warming potential/ embodied carbon dioxide (CO2) of 284 million kgCO2eq (kilogram CO2 equivalent) with the projected use of around 271 million kg of cement concrete and 78 million kg of steel. The enormous amount of embodied CO2 emissions from this projected lining project suggested using natural means of flood/ channel protection if feasible, or alternative supplementary cementitious materials with fibres should be used to minimise the environmental impacts.

Feasibility of upcycling red mud for low-CO2 cement via calcination: A comparative study with FA and GGBFS based in China

This study examines the feasibility of developing low-CO2 cement using calcined red mud (RM) and explores positive scenarios that simultaneously attain technical, environmental, and economic benefits in reference to conventional fly ash (FA) and ground granulated blast furnace slag (GGBFS) cements. Based on the variables of RM's content and calcination temperature, we investigated the fresh properties (paste rheology and mortar flowability), strength development, microstructure, embodied CO2 emissions, and cost of the RM-blended cement. The results show that there was an optimal range of RM's calcination temperature (400–600 °C) that improved the cement paste viscosity while attaining a higher strength than that of FA cement. Considering the cradle-to-gate CO2 emissions and cost of cement production, the optimal cement composition is comprised of up to 30% RM calcined at 600 °C, where the cement cost is lowered by 19.3% compared to the FA reference having a comparable CO2 footprint. According to the geographical analysis, the calcined RM shows minimal advantages over GGBFS but could substitute FA as a cleaner, cheaper, and more reactive supplementary cementitious material in regions where electricity grid is dominated by clean energy. Therefore, RM offers a plausible solution to future low-CO2 cement in light of the increasing shortage of FA led by the declining use of coal-powered electricity.

Sustainability-driven application of waste steel and tyre rubber fibres as reinforcement in concrete: An optimization study using response surface methodology

Innovative use of waste materials has proven to be effective for improving concrete’s technical properties while eliminating the threat of environmental pollution. There is paucity of research regarding the combined use of Waste Steel Fibres (WSFs) and Waste Tire Rubber Fibres (WTRFs) in concrete. Thus, this study aimed to investigate the influence of WSFs and WTRFs as reinforcement in concrete and determine their optimal fractions for enhancing the concrete strength properties using Response Surface Methodology (RSM). WSFs of 0.3-1.5% with a 0.6% increment and WTRFs of 0.3-1.5% with a 0.6% increment by concrete volume as reinforcement in concrete with water-to-cement ratio (W/C) of 0.25–0.65 with 0.2 increment were designed using the Box-Behnken Design of RSM. A total of fourteen (14) concrete mixes with a design strength of 25 N/mm2 were prepared. The fresh and hardened properties (slump, density, water absorption, 7- and 28-day compressive and split tensile strengths) of concrete were determined using standard procedures. The RSM was used to evaluate the interaction between the concrete variables and identify their optimum combination which gave the peak values of responses. Furthermore, the characteristics and sustainability of the concrete under optimum variables were compared with that of the conventional concrete. The outcomes revealed that the inclusion of WSFs and WTRFs yielded concretes with maximum slump, density, water absorption and 28-day compressive and split tensile strengths of 25 mm, 2633 kg/m3, 5%, 41 N/mm2 and 4.54 N/mm2, respectively. The optimization technique showed the optimal variables combination which yielded the peak response values of WSFs (1.40%), WTRFs (0.66%) and W/C (0.54). The nominal variance with the absolute percent error of less than (9%) between the actual experimental verified results and predicted results for all the responses validates the predictability of the model. The split tensile strength and compressive strength increased by 28.33% and 48.85%, respectively at the optimum setpoint of variable with respect to the reference concrete. In addition, the WSFs and WTRFs-reinforced concrete exhibited lower embodied CO2 emission but the embodied energy and cost are slightly higher relative to conventional concrete. Nevertheless, the embodied energy of the concrete was significantly lesser than that of concrete that used individual fibers for reinforcement. Thus, the enhancement of concrete strength properties with the prospect for sustainable fibre-reinforced concrete production through the use of waste steel and tyre rubber fibres is feasible.

New robust multi-criteria decision-making framework for thermal insulation of buildings under conflicting stakeholder interests

The choice of thermal insulation technology for existing building retrofit can be a complex multi-criteria decision-making (MCDM) problem characterized by multiple stakeholders with conflicting interests. The conflicting interests of the building owners and the policymakers could negatively influence the adoption of low-carbon energy retrofit measures by building possessors, slowing down the progress toward sustainable development. The investigation of this issue is, therefore, crucial to support more informed decisions and offer policymakers useful insights to develop future economic incentives for energy refurbishment of buildings. Most of the existing MCDM studies on the subject do not emphasize the differences among different stakeholders nor consider the outcomes' robustness. To overcome this gap, this paper integrates multi-stakeholder analyses and robustness assessments to provide broad-spectrum and reliable results. An innovative robust MCDM framework for building thermal insulation under conflicting stakeholder interests is proposed and tested on a real case study building (located in Southern Italy) using building dynamic energy simulation. Several alternatives of thermal insulation are evaluated under environmental, energy, and economic key performance indicators (KPIs). The Analytic Hierarchy Process is used to define criteria weights for conflicting decision-makers representing collectivity (policymakers) and private interests. TOPSIS, VIKOR, WASPAS, and MULTIMOORA methods are integrated to perform initial rankings of the alternatives. A rank similarity analysis is performed to evaluate the consensus between MCDM methods, and an ensemble ranking is obtained for each decision-maker using an approach based on the half-quadratic theory. A Confidence Index and a Trust Level are used to evaluate the agreement among the MCDM approaches, verifying the reliability of the final ensemble ranking. The robustness of the framework is attained by complying with well-established literature guidance. The hybrid MCDM analysis showed that porous materials like expanded clay and expanded perlite lead to better results under the KPIs investigated. The worst performances are attained by vacuum insulation panels and aerogel, mainly due to high values of embodied CO2 emissions and long payback periods. Insights upon the performance of different thermal insulating alternatives are also highlighted by the study and a stakeholder comparative analysis demonstrates that global rankings obtained for the different decision-makers show some similarities, but also important deviations, and a full compromise solution is not achieved.

Assessment of export-embodied CO2 emissions from China’s ocean industries: implications for formulating sustainable ocean policies

The ocean industries are characterized by being export-driven. The exports of ocean industries (hereafter termed ocean exports) caused environmental pollution with amounts of CO2 emissions and thereby affected climate change. There is a need, therefore, for accurate assessments of CO2 emissions embodied in ocean exports—which can help policymakers adopt targeted emission-reduction measures to formulate sustainable ocean policies. However, few studies of ocean-industry emissions considered impacts in sectoral and trade pattern heterogeneity, especially from export perspective. To fill this gap, we measured and evaluated the export-embodied CO2 emissions from China’s ocean industries, based on our newly developed high-resolution and comparable time-series environmentally extended input–output database, called EE-DPN-OEIOT. The results showed that China’s ocean exports generated 94.3 Mt of embodied CO2 emissions in 2017, with nearly 40% originating from processing ocean exports. Regarding the evolution from 2007 to 2017, the total export-embodied CO2 emissions from ocean industries decreased by 7.3%, while the embodied CO2 emissions in processing ocean exports increased by 50.1%. From 2007 to 2017, the decrease in carbon emission intensity was the major driving factor of the downturn in export-embodied CO2 emissions across the total ocean economy and for seven ocean subsectors (60%), while the export-scale effect primarily drove the increases in CO2 emissions. Moreover, there were disparities in the driving factors behind changes in embodied CO2 emissions between processing and non-processing ocean exports. Based on our findings, we proposed three recommendations from a trade perspective to facilitate low-carbon sustainable transition of China’s ocean economy, thus better fulfilling Sustainable Development Goal 14.

Trade-induced carbon-economic inequality within China: Measurement, sources, and determinants

Carbon-economic inequality (CEI) occurs due to the unequal exchange between embodied CO2 emissions and value-added in interregional trade. How to reduce CEI has become an urgent task to realize the Sustainable Development Goals. In this study, we quantify the CEI in bilateral and regional trade in China using the embodied CO2 emission and value-added during 2012–2017. Then, we analyze the drivers of CEI changes using the multiplicative structural decomposition analysis. Finally, we measure national CEI using an extended Gini coefficient and further identify the sources of inequality using the Shapley decomposition approach. The results indicate that 1) inequalities in bilateral trade mainly occur between the three north regions (North, Northwest, and Northeast) and eastern coastal regions (Beijing–Tianjin, South coast, and Central coast), and the inequalities generally exhibit worsening trends during 2012–2017. In regional trade, the Northwest suffers the worst and widening inequalities, while the Southwest has obtained an expanded advantage. 2) the decomposition results show that coal efficiency and input structure disparities are the main factors that exacerbate CEI in bilateral trade between the three north and Beijing–Tianjin/South coast regions. Improved input structure is the leader in helping the Southwest reduce CEI in bilateral and regional trade. 3) the overall CEI continues to deteriorate, with the Gini coefficient increasing from 0.260 to 0.305 during 2012–2017, where regional gap and intra-regional inequality, coal-induced CO2 emission, and the electricity production industry are the leading causes. This exacerbated CEI calling for optimizing regional trade patterns and providing holistic solutions for sustainable development.

Delineating the embodied CO2 emissions in Canada's exports: Routes, drivers, and paths

AbstractThis study combined the World Input–Output Database and Asian Development Bank's Multiregional Input–Output database to investigate Canada's embodied CO2 emissions in exports (EEE) for the period of 2000–2018. We examined the key drivers and paths through structural decomposition analysis and structural path analysis. First, the results showed that embodied emissions in the intermediate exports were the major contributor to Canada's EEE, and emission paths involving more than three countries were on the rise, indicating that the expansion of the global industrial supply chains has complicated the paths of Canada's EEE. Second, the factors such as emission intensity of sectors, export structure, and export scale, had varying influences on Canada's EEE over time. For several sectors, the benefit from reduced emission intensity was largely offset by the additional emissions from the increased export scale. Hence, the design of emission regulations should consider the heterogeneity of industrial sectors in order to mitigate emissions for the diverse industries in Canada. Third, energy and resource industries (e.g., electricity, petroleum, wood, metals, and so on) played an essential role in Canada's exports. A significant amount of embodied emissions was transferred from these sectors to the downstream sectors along the supply chain, indicating that abatement measures should be adopted from the whole life cycle perspective of a product/service through an integrated governance of the supply chain. This article met the requirements for a Gold–Silver JIE data openness badge described at http://jie.click/badges.

Embodied CO2 emissions of equity portfolios for Chinese asset managers

The 2015 Paris Agreement has set out the climate change target of limiting global warming to 1.5 °C, which poses a serious challenge to countries to reduce emissions. As the world’s largest carbon emitter, promoting the realization of the “dual-carbon” goal is the key to realizing China’s green transformation and high-quality development. Chinese asset managers play active roles in the capital market as an important channel of asset allocation. Currently, the vast majority of Chinese asset managers hold high percentages of high-carbon industries in their portfolios, and lack quantitative data of their carbon footprints embodied in equity investments, which faces huge carbon-related risks. Therefore, it’s an urgent need to comprehensively and scientifically measure financed emissions of Chinese asset managers, which is of great significance for asset managers’ carbon risk management and sustainable investment. This paper develops a detailed inventory of carbon emissions for equity portfolios managed by Chinese asset managers from 2010 to 2020, which stands as a pivotal reference for in-depth analysis of emission characteristics.

Bond Stress Behavior of a Steel Reinforcing Bar Embedded in Geopolymer Concrete Incorporating Natural and Recycled Aggregates

The rise in greenhouse gases, particularly carbon dioxide (CO2) emissions, in the atmosphere is one of the major causes of global warming and climate change. The production of ordinary Portland cement (OPC) emits harmful CO2 gases, which contribute to sporadic heatwaves, rapid melting of glaciers, flash flooding, and food shortages. To address global warming and climate change challenges, this research study explores the use of a cement-less recycled aggregate concrete, a sustainable approach for future constructions. This study uses fly ash, an industrial waste of coal power plants, as a 100% substitute for OPC. Moreover, this research study also uses recycled coarse aggregates (RCAs) as a partial to complete replacement for natural coarse aggregates (NCAs) to preserve natural resources for future generations. In this research investigation, a total of 60 pull-out specimens were prepared to investigate the influence of steel bar diameter (9.5 mm, 12.7 mm, and 19.1 mm), bar embedment length, db (4db and 6db), and percentage replacements of NCA with RCA (25%, 50%, 75%, and 100%) on the bond stress behavior of cement-less RA concrete. The test results exhibited that the bond stress of cement-less RCA concrete decreased by 6% with increasing steel bar diameter. Moreover, the bond stress decreased by 5.5% with increasing bar embedment length. Furthermore, the bond stress decreased by 7.6%, 7%, 8.8%, and 20.4%, respectively, with increasing percentage replacements (25%, 50%, 75%, and 100%) of NCA with RCA. An empirical model was developed correlating the bond strength to the mean compressive strength of cement-less RCA concrete, which matched well with the experimental test results and predictions of the CEB-FIP model for OPC. The CRAC mixes exhibited higher costs but significantly lower embodied CO2 emissions than OPC concrete.

Assessing the Environmental Sustainability of UHPC in Modern Construction Practices

A comprehensive examination was undertaken to investigate various aspects related to the development and application of Ultra-High-Performance Concrete (UHPC). The research explored eco-friendly approaches, such as incorporating supplementary cementitious materials and nanoparticles, optimizing binder systems, and assessing chemical activators. These modifications improved mechanical properties and reduced environmental impact, including embodied CO2 emissions. Additionally, the utilization of waste materials like CRT glass showed energy savings and reduced emissions. Studies focused on optimizing UHPC mix designs, emphasizing a balance between performance and environmental impact. Techniques like statistical mixture design methods and dynamic testing assessed UHPC's environmental and economic impacts, highlighting significant energy savings and reduced CO2 emissions with waste material recycling. Overall, the research contributes valuable insights into UHPC development and its ecological footprint in construction

A comparison of deflation methods for carbon footprint calculations using Japanese data

An embodied CO2 emissions intensity database estimated from input–output data at current prices is now available in Japan. This study compares two non-survey methods: The double-deflation (DD) method and an elaborated approach combining the DD method with the generalized RAS method to deflate an input–output table (IOT). We used these methods to estimate new datasets of embodied CO2 emission intensity data in Japan, utilizing Japan's IOTs for 2005, 2011, and 2015 at constant prices in 2015. Furthermore, we compare the estimated data of 367 commodity sectors for a specific year (2005 or 2011). The results reveal that the intensity for certain aggregated sector groups, such as non-ferrous metals and finance and insurance, exhibits higher uncertainty owing to the extreme price homogeneity assumption associated with the DD method. Consequently, we recommend that life-cycle-assessment practitioners use an open database when analyzing changes in the carbon footprint of products over time.

Key durability characteristics of GGBS-cement kiln dust based concretes

With the advent of global warming, the concrete industry has the potential to drive the future of construction through sustainable cement technologies. These technologies rely on activation of industrial waste materials, such as Cement Kiln Dust (CKD) and Ground Granulated Blast Furnace Slag (GGBS) while Portland cement (PC) content is maintained at a minimum, resulting in concrete products of reduced embodied carbon footprint. This work reports on the durability of mixes made from PC, GGBS and CKD at incremental contents of 40-75% and 0-35% for GGBS and CKSD, respectively, in an attempt to identify durable formulations while maintaining blends at low embodied CO2 emissions in the Sultanate of Oman. Dimensional changes, sulfate and chloride resistance, as well as surface resistivity were determined and compared to those of a PC-based concrete formulation. The results suggest that, when GGBS and CKD were incorporated within the mix at an optimum content of 55% and 20% respectively, the concretes appeared to have exhibited promising durability characteristics which could lead towards the material’s implementation within a greater context.

Sulfate resistance of carbonated basic oxygen furnace slag-metakaolin-Portland cement blends

Basic oxygen furnace slag (SS) is prone to carbonation due to its alkaline properties. The combined use of carbonated basic oxygen furnace slag (CSS) with metakaolin (MK) as a composite supplementary cementitious material (CSS-MK) can improve the reactivity of CSS and significantly lower the overall embodied CO2 emission. However, the impact of CSS-MK on the resistance of external sulfate attack (ESA) of cement remains unclear. This study aims to clarify the influence of CSS-MK on the resistance of cement to ESA. Compressive strength, water absorption, and electrical flux before ESA, and macro-scale expansion, microstructure, and evolution of phase assemblage during ESA were investigated. Results indicate that CSS-MK exhibits higher strength reactivity compared to SS-MK, enabling a 30% cement replacement level without compromising compressive strength after 7 days. CSS-MK reduces water absorption by 37.9% and electrical flux by 67.6%, enhancing transport property and reducing sulfate ion intrusion into the cement paste. The carbonation treatment transforms calcium silicate in SS into CaCO3, decreasing soluble calcium content, and creating a CaCO3-based passivation layer that inhibits sulfate ion corrosion. Meanwhile, the reaction in CSS-MK blends between the CaCO3 in CSS and MK consumes Ca(OH)2, forms ettringite and thermodynamically more stable carboaluminate, and results in the absence of monosulfate prior to ESA and the presence of carboaluminate during ESA, which consequently decreases ettringite content by 40% in paste after 240 days of ESA. Furthermore, at the macroscopic level, the expansion decreased by 85.2% after 360 days of ESA, effectively mitigating specimen cracking and damage.

Spatiotemporal characteristics and driving factor analysis of embodied CO2 emissions in China's building sector

Since the embodied emissions of the building sector play a pivotal role in the total emission profile of developing countries, represented by China, it is crucial to uncover its emission characteristics and the underlying drivers. Most existing studies focus on building operational emissions, and there is a lack of in-depth studies on embodied emissions, especially in spatiotemporal heterogeneity and spatial correlation. Thus, this study calculates embodied emissions of the building sector in China's 29 provinces during 2011–2020 and develops an innovative factor analysis model that integrates the extended STIRPAT model, network analysis, and spatial Durbin model to explore the influence mechanisms of various factors on emissions from local, spillover, overall and temporal perspectives. The empirical results reveal notable spatiotemporal differences and spatial dependence across regions. The area has consistently been the most crucial driver. The building performance demands are increasingly influencing emissions through direct and spillover effects. The slowdown decarbonization of the material industry diminishes its impact. Limited technical improvement and regional shifts of carbon-intensive enterprises have weakened the technological emission reduction effects. Therefore, regulating ineffective construction, discouraging excessive building performance, implementing demand-side material efficiency strategies, bolstering interregional coordination, and developing low-carbon technologies are keys to cutting emissions.

The multi-objective optimization and mix parameter evaluation of one-part alkali-activated grouting material

To obtain a green and cost-effective one-part alkali-activated grouting material (OAGM) with good comprehensive performance for subgrade reinforcement and determine its proper mix parameters. In this study, using response surface methodology (RSM), multiple objective particle swarm optimization (MOPSO) algorithm and the technique for order preference by similarity to an ideal solution (TOPSIS) algorithm coupled with entropy weight method, two multi-objective optimization schemes for OAGM were performed, one only considering performance and another considering performance, embodied CO2 emission (ECO2e) and cost. Then, the correlation-based feature selection (CFS) algorithm was used to evaluate the importance of various molar ratios as mix parameters on the performance of OAGM. Finally, the effects of key mix parameters on the microstructure and reaction products of OAGM were studied. RSM results show that W/S (water to solid) ratio, borax (BR) content and UCG content chiefly govern the flowability, initial setting time and mechanical strength of OAGM respectively, and the interactions between some factors also significantly affect these properties. MOPSO and entropy-TOPSIS algorithm can be used to optimize OAGM objectively. Two optimal OAGM pastes both have better comprehensive performance and much lower ECO2e than ordinary Portland cement (OPC) paste. And the optimal OAGM considering performance, ECO2e and cost even has 7.68% lower cost than OPC paste. But another optimal OAGM has the best comprehensive performance. CFS results show that the molar ratios of Si/Al, Al/Ca, Na2O/H2O, B2O3/CaO and B2O3/Al2O3 are the key mix parameters of OAGM. Al/Ca rather than Si/Al is the most important mix parameter to the 28-day compressive strength. And higher Si/Al and Al/Ca deteriorates the microstructure and hinders the formation of C-A-S-H gel, while higher Na2O/H2O has the opposite effect. This study provides guidance for objective optimization and the determination of proper mix parameters of OAGM, and promotes the market-oriented application of OAGM.

Innovative one-part Alkali activated binder from activator derived from agricultural waste: Synthesis and application for sustainable construction

Commercial powder activators are commonly used to produce one-part alkali-activated binders (AAB) despite their manufacturing method using more energy and generating more CO2 emissions. To address this concern, the study employed a mechanical process to synthesize an agricultural waste-based powder activator, derived from rice husk ash (RHA) and NaOH powder at six different ratios. Paste samples were prepared by blending the derived activator with ground granulated blast furnace slag (GGBFS) precursor in a 1:4 ratio. Fresh properties and compressive strength (range of 33–77 MPa) was evaluated. Besides, microstructural analysis and ecological factors were estimated, including embodied CO2 emissions and energy analysis, and the approach employed in this investigation significantly reduced both embodied CO2 emissions and embodied energy requirements compared to conventional practices. The result indicates that the activator powder synthesized in this study can produce AAB with qualities comparable to Portland cement.

Mechanical, microstructural characteristics and sustainability analysis of concrete incorporating date palm ash and eggshell powder as ternary blends cementitious materials

Cement production causes a threat to environmental sustainability owing to the enormous volume of greenhouse gas releases and high energy consumption. Similarly, agro-industrial waste contributed significantly to environmental pollution when disposed of in landfills. Waste from date palms is one of the main agro-waste generated in Saudi Arabia. This waste is normally disposed of without treatment or burnt for energy. The date palm ash (DPA) due to its pozzolanic properties could be suitable for use as supplementary cementitious material (SCM) in concrete. However, due to its weak or slower pozzolanic reactivity, the DPA negatively affects the performance of concrete. In this research, the DPA was used as a SCM in concrete. Eggshell powder (ESP) owing to its abundant calcium oxide content was used as an additive to the concrete containing other pozzolanic materials with high silica content. Cement was partially replaced with DPA at dosages between 10% to 40%, and ESP was added at different proportions between 1% to 4% by weight of the binder. The workability of the concrete was decreased with adding blends of DPA and ESP. The mechanical strengths (compressive, flexural, and tensile strengths), modulus of elasticity (MoE), water absorption, and porosity of the concrete were negatively affected by adding DPA. Blending up to 30% DPA with up to 3% ESP as cementitious materials help alleviate the adverse effects of the DPA on the strengths, MoE, and durability performance of the concrete. DPA increases pore volume and porosity by decelerating C-S-H production through its slower pozzolanic reaction at early ages. DPA reduced total embodied CO2 emissions and enhanced the eco-strength efficiency of the concrete. Using DPA and ESP blends in concrete improves performance, minimizes environmental effects, and reduces CO2 emissions during cement production.

Material intensity and embodied CO2 benchmark for reinforced concrete structures in Brazil

Cement and steel production significantly contribute to global CO2 emissions, with reinforced concrete structures accounting for a substantial portion. Therefore, optimizing the structural design helps reduce material and carbon intensity. However, industry-based benchmarks for material and carbon intensity of structures are scarce and lack transparency. This study fills this gap by analyzing detailed industry data derived from construction designs of 53 reinforced concrete structures for multifamily residential buildings in Brazil and assessing their cradle-to-gate material intensity and embodied CO2 emissions. The findings revealed significant variations in the usage of steel (70–159 kg/m³) and concrete (0.17–0.29 m³/m2). The quantity of structural materials ranged from 418 to 731 kg/m2, and the embodied CO2 ranged from 35 to 140 kg CO2/m2, including the variability in CO2 emissions during material production. Building height is the primary geometric parameter that determined material intensity and embodied CO2, particularly for columns. However, structural materials quantity varies considerably among buildings with the same number of stories, suggesting the presence of additional design parameters influencing material intensity. The results emphasize the role of designers in promoting decarbonization through dematerialization. Also, selecting the right material supplier is important as, on average, differences between manufacturers corresponds to a difference of 38 kg CO2/m2 in structural embodied CO2. Selecting low-carbon material suppliers and employing structural design benchmarking practices can efficiently reduce the embodied carbon of reinforced concrete structures.

Performance assessment and economic and ecological analysis of carbon-negative recycled crumb rubber-based geopolymers

Geopolymer technology offers several compelling ecological and economic advantages regarding waste management. This research investigates the effect of size (less than equal to 4 mm) and amount (5–15 vol%) of crumb rubber (CR) as fine aggregate on the physical, mechanical, and durability properties of geopolymers. The economic and ecological analyses were also performed to determine the effect of producing CR-based geopolymers on cost and the environment. The results revealed that the addition of CR negatively influences the physical, mechanical, and durability properties; nonetheless, incorporation of 5–10 vol% CR with a size less than 2 mm exhibited satisfactory performance fit for medium-strength structures such as foundations, partition walls, sidewalks, drainage structures, etc. Additionally, although the incorporation of CR slightly increases the production cost (3.99–11.97%) and embodied energy (0.08–0.24%) of resulting geopolymers, the embodied CO2 emission of 5, 10, and 15 vol% CR-incorporated geopolymer mixes is 90.4, −143.6 and −377.6 kgCO2e/m3, respectively. In contrast, the embodied CO2 emissions of conventional geopolymer mix is 324.4 kgCO2e/m3, which shows the negative carbon emission potential of CR-modified geopolymers, providing a glimmer of hope for sustainable development in the construction industry.

How to minimise the cost of green hydrogen with hybrid supply: A regional case study in China

Hydrogen produced from renewables-fuelled electrolysis has the potential to provide deep decarbonisation for sectors that are the most difficult to decarbonise, but the intermittency of renewable sources may result in low electrolyser utilisation and, consequently, high costs. This study determines the greenhouse gas (GHG) emissions and levelised cost of hydrogen (LCOH) associated with blending wind electricity with the grid to increase electrolyser utilisation. A novel cost model was developed to determine the production performance, costs and embodied CO2 emissions of an electrolyser with hybrid fuel supply (wind and grid) considering dynamic load constraints of alkaline (ALK) and Proton exchange membrane (PEM) electrolysers and using high-resolution historical weather data to determine wind production profiles in two case study regions: northern (Bayannur) and southern (Pingtan) China. The results show that using 52% of grid electricity in an ALK electrolyser in Bayannur reduces LCOH by 11%, increasing hydrogen production by 74% but with 17.4 kg CO2/ kg H2 generated in CO2 emissions. When a carbon price is accounted for, the optimal electrolyser utilisation is reduced to 40%, with the LCE 44% reduced. Emissions of 9.8 kg CO2/kg H2 are lower than for stream methane reforming with carbon capture. In Southern China (Pingtan), LCOH is higher than Bayanur because of the high electricity cost. The economic benefits of increasing grid power depend primarily on the total CAPEX cost, grid power cost, and carbon tax. By altering the carbon tax, the optimal blend of wind/ grid differs. The grid contribution to the optimal blend diminishes as a carbon tax approaches 35 USD/ t CO2.