No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Towards Electrochemical Synthesis of Cement — an Electrolyzer-Based Process for Decarbonating CaCO 3 while Producing Useful Gas Streams
Abstract
Cement production is currently the largest single industrial emitter of CO 2 , accounting for 8% (2.8 Gtons/year) of global CO 2 emissions in 2015. Deep decarbonization of cement manufacturing will require remediation of both the CO 2 emissions due to the decomposition of CaCO 3 to CaO, and that due to combustion of fossil fuels (primarily coal) in the calcining (~900°C) and sintering (~1,450°C) processes. Here, we demonstrate an electrochemical process that uses neutral water electrolysis to produce a pH gradient in which CaCO 3 is decarbonated at low pH and Ca(OH) 2 is precipitated at neutral to high pH, concurrently producing a high purity O 2 /CO 2 gas mixture (1:2 molar ratio at demonstrated stoichiometric operation) at the anode and H 2 at the cathode, as shown in Figure 1. We show that the solid Ca(OH) 2 product readily decomposes and reacts with SiO 2 to form alite, the majority cementitious phase in Portland cement. Our electrochemical calcination approach produces concentrated gas streams from which the CO 2 may be readily separated and sequestered, the H 2 and/or O 2 may be used to generate electric power via fuel cells or combustors, the O 2 may be used as a component of oxyfuel in the cement kiln to further lower CO 2 and NO x emissions, or the output gases may be used for other value-added processes including liquid fuel production. Analysis shows that in a scenario where the hydrogen produced by the reactor is combusted to heat the high temperature kiln, the electrochemical cement process can be powered solely by renewable electricity.
Figure 1. Schematic of the electrolyzer-based decarbonation cell. Reactions 1a and 1b are the O 2 evolution and H 2 evolution half-cell reactions respectively, under near-neutral pH. Reactions 2a and 2b represent the decomposition of CaCO 3 and release of CO 2 . Reaction 3 is the normal formation of water from its component ions. In Reaction 4, the hydroxide ions in Reaction 3 instead go towards the formation of Ca(OH) 2 , and the protons protonate carbonate ions (Reaction 2b). The overall reaction in which CaCO 3 is converted to Ca(OH) 2 with the attendant release of H 2 , O 2 and CO 2 is shown at the bottom.
Figure 1
... Over the past few decades, there has been a growing interest in optimising the environmental impact of structures to cope with global circumstances and urge governmental and constitutional obligations. On the one hand, researchers have been looking into cutting the carbon emissions associated with material production as steel and cement manufacturing account for 4% and 8% of global carbon emissions respectively [6][7][8]. This resulted in a wide body of research addressing producing cleaner steel from recycled content and less emitting manufacturing techniques [9][10][11] as well as developing innovative non-cementitious binders [12][13][14][15]. ...
... Accordingly, the friction coefficient can be calculated as shown in Eqs. (5)(6)(7)(8). ...
Concrete production and construction are responsible for a considerable share of the total carbon emissions annually. With the emerging need to cut carbon emissions from the construction sector, there has been a big interest in optimising the embodied carbon of superstructures. However, limited attention is given to optimising the embodied carbon of foundations as most designers are more interested in addressing the optimal foundations cost instead. For the first time in the open literature, this paper presents a generic genetic-algorithm-based tool to optimise the design of reinforced concrete piles. The algorithm is capable of allocating the optimal design parameters and geometry for reinforced concrete piles at any given soil conditions and required pile capacities. The algorithm is used to compare the environmental impact of different concrete pile types; solid cylindrical piles, hollow cylindrical piles, solid tapered piles and hollow tapered piles at different load capacities, the optimisation results are then compared to common industrial pile designs to quantify the possible carbon and material savings. Results show that a significant cut of more than 70% of the embodied carbon values can be achieved if the optimal pile type is used compared to common industrial design. Moreover, a finite element model built and validated over ABAQUS is used to compare the geotechnical performance of the different pile geometries. Finite element analysis results show a negligible difference between the stiffness of the different pile types when tested in the same soil conditions highlighting an outstanding optimisation efficiency of the proposed optimisation tool.
... Similar problems exist in the construction sector. Global cement production alone is the largest single industrial contributor to climate change, accounting for 8% of all GHG emissions [9]. The expected population growth of a further 2 billion people by 2050 corresponds to the entire builtup world of 1930 [10]. ...
... The International Energy Agency has reported that in 2022 alone, about 1.6 million metric tons of carbon dioxides will be produced from the cement industry [24]. This amounted to around 8% of global emissions coming solely from the cement industry [25]. It is also estimated that cement produces at least 900 kilograms of carbon dioxide into the atmosphere for every 1000 kilograms of cement [26]. ...
Concretes have been the favoured material to make concrete railway sleepers due to better accessibility and weather compared to their timber counterparts. Railway sleepers are crucial infrastructure and 5% of concrete sleepers fail prematurely. Sleeper failure could result in catastrophic railway accidents. Hence, improvement is needed in the concrete sleeper mixes. Previous literature has identified two methods of improving concrete strength in concrete mixes with wastes, through replacement of concrete constituents or the use of alkali-activated materials. Use of wastes as partial concrete material replacements reduces the volume of concrete materials while alkali-activated material forms a concrete-like compound that eliminates the use of cement. These methods improve the strength performance and sustainability aspects of the concrete. While many studies have been conducted on these two types of sustainable concrete, their application in concrete railway sleepers has not been investigated. Thus, this paper looks to review the two different types of sustainable concretes through some previous literature that has been conducted on its application in concrete railway sleepers as well as those that have yet to be studied. Ultimately, identifying the best sustainable materials for concrete railway sleepers.
... To put the scale of the urbanisation challenge and opportunity in context, since 2003, China poured more cement every two years than the US did in the entire 20th century [4]. Concrete manufacture accounts for at least 8% of global carbon emissions [5]. This will have a significant impact on environmental health which has both direct and indirect impact on population health. ...
Background
Global health will increasingly be determined by cities. Currently over half of the world’s population, over 4 billion people, live in cities. This systematic scoping review has been conducted to understand what cities are doing to improve health and healthcare for their populations.
Methods
We conducted a systematic search to identify literature on city-wide initiatives to improve health. The study was conducted in accordance with PRISMA and the protocol was registered with PROSPERO (CRD42020166210).
Results
The search identified 42,137 original citations, yielding 1,614 papers across 227 cities meeting the inclusion criteria. The results show that the majority of initiatives were targeted at non-communicable diseases. City health departments are making an increasing contribution; however the role of mayors appears to be limited.
Conclusion
The collective body of evidence identified in this review, built up over the last 130 years, has hitherto been poorly documented and characterised. Cities are a meta-system with population health dictated by multiple interactions and multidirectional feedback loops. Improving health in cities requires multiple actions, by multiple actors, at every level. The authors use the term ‘The Vital 5’. They are the five most important health risk factors; tobacco use; harmful alcohol use; physical-inactivity, unhealthy diet and planetary health. These ‘Vital 5’ are most concentrated in deprived areas and show the greatest increase in low and middle income countries. Every city should develop a comprehensive strategy and action plan to address these ‘Vital 5’.
... Out of all the materials, cement (clinker) was found to have the most significant impact on global warming in both the BCS and ACS mix, with 230.64 kg CO2 eq. A total of 8% of the global CO2 is from the cement industry [33], justifying the findings. Therefore, according to the analysis, cement significantly contributes to CO2 rise in the atmosphere. ...
Developing a concrete mixture with the lowest possible environmental impacts while improving durability performance is crucial for a sustainable environment. In this study, a Base Case Scenario (BCS) and Alternative Case Scenario (ACS) concrete mixtures were developed with identical water-to-cement ratio (w/c) of 0.4, having cement substitution of 0% and 34%, respectively. Supplementary cementitious materials (SCMs) such as silica fume, fly ash, and slag cement were implemented as cement replacing mineral admixture. A simplified life-cycle assessment (LCA) was performed to determine environmental impact reduction factors such as fossil fuel depletion, ecotoxicity, ozone depletion, carcinogenic, and global warming. Then a simulation-based approach was carried out to optimize the durability performance of concrete mixtures using Life365™. As a result, a 24.9% reduction of environmental impacts was observed with a decent service life optimization in ACS compared to the BCS mixture.
ResearchGate has not been able to resolve any references for this publication.