Circular Carbon Economy (CCE): A Way to Invest CO2 and Protect the Environment, a Review

Catalytic Transformation of Carbohydrates into Renewable Organic Chemicals by Revering the Principles of Green Chemistry

Adherence to the principles of green chemistry in a biorefinery setting ensures energy efficiency, reduces the consumption of materials, simplifies reactor design, and rationalizes the process parameters for synthesizing affordable organic chemicals of desired functional efficacy and ingrained sustainability. The green chemistry metrics facilitate assessing the relative merits and demerits of alternative synthetic pathways for the targeted product(s). This work elaborates on how green chemistry has emerged as a transformative framework and inspired innovations toward the catalytic conversion of biomass-derived carbohydrates into fuels, chemicals, and synthetic polymers. Specific discussions have been incorporated on the judicious selection of feedstock, reaction parameters, reagents (stoichiometric or catalytic), and other synthetic auxiliaries to obtain the targeted product(s) in desired selectivity and yield. The prospects of a carbohydrate-centric biorefinery have been emphasized and research avenues have been proposed to eliminate the remaining roadblocks. The analyses presented in this review will steer to developing superior synthetic strategies and processes for envisaging a sustainable bioeconomy centered on biomass-derived carbohydrates.

Emerging bio-capture strategies for greenhouse gas reduction: Navigating challenges towards carbon neutrality

Greenhouse gas emissions are significantly contributing to climate change, posing one of the serious threats to our planet. Addressing these emissions urgently is imperative to prevent irreversible planetary changes. One effective long-term mitigation strategy is achieving carbon neutrality. Although numerous countries aim for carbon neutrality by 2050, only a few are on track to realize this ambition. Existing technological solutions, including chemical absorption, cryogenic separation, and membrane separation, are available but tend to be costly and time intensive. Bio-capture methods present a promising opportunity in greenhouse gas mitigation research. Recent developments in biotechnology for capturing greenhouse gases have demonstrated both effectiveness and long-term benefits. This review emphasizes the recent advancements in bio-capture techniques, showcasing them as dependable and economical solutions for carbon neutrality. The article briefly outlines various bio-capture methods and underscores their potential for industrial application. Moreover, it investigates into the challenges faced when integrating bio-capture with carbon capture and storage technology. The study concludes by exploring the recent trends and prospective enhancements in ecosystem revitalization and industrial decarbonization through green conversion techniques, reinforcing the path towards carbon neutrality.

Possibilities of Managing Waste Iron Sorbent FFH after CO2 Capture as an Element of a Circular Economy

With a growing need to reduce greenhouse gas emissions, innovative carbon dioxide sorbents are being sought. One of the sorbents being tested is nanoparticle ferric hydrosol (FFH). In parallel with sorbent testing, it is also necessary to test the used sorbent after carbon dioxide capture (FFHCO2) and to develop an optimal method for its processing and management. The research described in this article evaluated the potential use of FFHCO2 in dewatering, coagulation and bioleaching processes. The research results indicate that the basic strategy for dealing with waste FFHCO2 sorbent should be to minimize the amount of waste by volume reduction-dewatering. Recycling of FFHCO2 as an iron waste coagulant or its processing products by bioleaching had no technological justification. It is only proposed to recover the material-iron compounds-if it is environmentally and economically justified.

Tsuchime-like Aluminum Film to Enhance Absorption in Ultra-Thin Photovoltaic Cells

Ultra-thin solar cells enable materials to be saved, reduce deposition time, and promote carrier collection from materials with short diffusion lengths. However, light absorption efficiency in ultra-thin solar panels remains a limiting factor. Most methods to increase light absorption in ultra-thin solar cells are either technically challenging or costly, given the thinness of the functional layers involved. We propose a cost-efficient and lithography-free solution to enhance light absorption in ultra-thin solar cells-a Tsuchime-like self-forming nanocrater (T-NC) aluminum (Al) film. T-NC Al film can be produced by the electrochemical anodization of Al, followed by etching the nanoporous alumina. Theoretical studies show that T-NC film can increase the average absorbance by 80.3%, depending on the active layer's thickness. The wavelength range of increased absorption varies with the active layer thickness, with the peak of absolute absorbance increase moving from 620 nm to 950 nm as the active layer thickness increases from 500 nm to 10 µm. We have also shown that the absorbance increase is retained regardless of the active layer material. Therefore, T-NC Al film significantly boosts absorbance in ultra-thin solar cells without requiring expensive lithography, and regardless of the active layer material.

CCUS technology, digital economy, and carbon emission efficiency: Evidence from China's provincial panel data

Improving carbon emission efficiency is crucial for realizing carbon neutralization. Many critical influencing factors of carbon emission efficiency were identified by previous studies, but they ignored the impact of carbon capture, utilization, and storage (CCUS) technology, which is considered in this study. By employing the panel fixed effect, the moderating effect, and the panel threshold regression models, this study investigates the influence of CCUS technology on carbon emission efficiency and how that impact fluctuates when digital economy is incorporated. Data for China's 30 provinces from 2011 to 2019 is adopted. The results suggest that improving CCUS technology significantly promotes carbon emission efficiency and the promotion effect is positively moderated by digital economy. Considering the level of CCUS technology or digital economy, the effect of CCUS technology on carbon emission efficiency is nonlinear and has significant double-threshold effects. Only when CCUS technology reaches a certain threshold, can it has a significantly positive impact on carbon emission efficiency and that effect has an increasing trend in marginal utility. Meanwhile, with the deepening of digital economy, the relationship between CCUS technology and carbon emission efficiency shows an S-shaped curve trend. Those findings, first combining CCUS technology, digital economy, and carbon emission efficiency together, reflect the significance of advancing CCUS technology and adjusting the development of digital economy for achieving sustainable low-carbon development.

Denitrification performance and in-situ fermentation mechanism of the wastepaper-flora slow-release carbon source

Using wastepaper as external carbon sources is an optional way to achieve total nitrogen removal faced with low carbon to nitrogen ratio municipal sewage. Most of studies have primarily focused on using cellulose-rich wastes establishing the separate denitrification units to achieve in-situ fermentation, which can cause blockages and prolong the process chain. In response, a novel in-situ fermentation wastepaper-flora slow-release carbon source (IF-WF) was proposed using in the original denitrification unit. IF-WF could be efficiently utilized in situ and the denitrification rate increased with the increase of nitrate nitrogen. The fermentation products were highly available, but internal acidification of IF-WF inhibited fermentation. Moreover, IF-WF limited the growth of polysaccharides in the extracellular polymeric substances of denitrified sludge. IF-WF finally formed the structure dominated by nitrate-reduction bacteria outside and cellulose-degrading bacteria inside. These results provide guidance for understanding the mechanism of IF-WF for in-situ fermentation to promote nitrogen removal.

Magnesium: properties and rich chemistry for new material synthesis and energy applications

Magnesium (Mg) has many unique properties suitable for applications in the fields of energy conversion and storage. These fields presently rely on noble metals for efficient performance. However, among other challenges, noble metals have low natural abundance, which undermines their sustainability. Mg has a high negative standard reduction potential and a unique crystal structure, and its low melting point at 650 °C makes it a good candidate to replace or supplement numerous other metals in various energy applications. These attractive features are particularly helpful for improving the properties and limits of materials in energy systems. However, knowledge of Mg and its practical uses is still limited, despite recent studies which have reported Mg's key roles in synthesizing new structures and modifying the chemical properties of materials. At present, information about Mg chemistry has been rather scattered without any organized report. The present review highlights the chemistry of Mg and its uses in energy applications such as electrocatalysis, photocatalysis, and secondary batteries, among others. Future perspectives on the development of Mg-based materials are further discussed to identify the challenges that need to be addressed.

Environmental assessment of casual dining restaurants in urban and suburban areas of peninsular Malaysia during the COVID-19 pandemic

Food waste has been considered a global problem due to its adverse impacts on food security, the environment, and the economy; hence needs urgent attention and action. Its generation is expected to increase as the world population grows rapidly, leading to more global waste. This study sought the impacts of the COVID-19 outbreak on the 1-week operation of selected casual dining restaurants in urban (Ampang, Kuala Lumpur) and suburban areas (Kota Bharu, Kelantan and Jasin, Melaka) of Peninsular Malaysia, as the local community adjusted to life with COVID-19. The food waste in this study was classified into three categories: preparation loss, serving loss, and customer's plate waste. Our material flow analysis revealed that the highest food loss at these locations came from preparation loss (51.37%), followed by serving loss (30.95%), and preparation loss (17.8%). Meanwhile, the total average electricity consumption and its carbon footprint for Ampang were 127 kWh and 13.87 kgCO₂e, Kota Bharu 269.8 kWh and 29.47 kgCO₂e, and Jasin 142.2 kWh and 15.54 kgCO₂e, respectively. As for water, Ampang exhibited 22.93 m³ total average consumption and 7.91 kgCO₂e greenhouse emissions from this source, Jasin consuming 17.11 m³ of water and releasing 5.88 kgCO₂e of carbon footprint, while Kota Bharu emitted 20.21 kgCO₂e of greenhouse gases from its 58.71 m³ water consumption. Our findings indicate a major 'food leak' at the preparation stage, from which the waste could be utilised as livestock feed, and that electricity consumption is a greater carbon emitter than water consumption, suggesting a need for improvement to the kitchen practices and equipment.

Microbial electrolysis cells for the production of biohydrogen in dark fermentation - A review

To assess biohydrogen for future green energy, this review revisited dark fermentation and microbial electrolysis cells (MECs). Hydrogen evolution rate in mesophilic dark fermentation is as high as 192 m³ H₂/m³-d, however hydrogen yield is limited. MECs are ideal for improving hydrogen yield from carboxylate accumulated from dark fermentation, whereas hydrogen production rate is too slow in MECs. Hence, improving anode kinetic is very important for realizing MEC biohydrogen. Intracellular electron transfer (IET) and extracellular electron transfer (EET) can limit current density in MECs, which is proportional to hydrogen evolution rate. EET does not limit current density once electrically conductive biofilms are formed on anodes, potentially producing 300 A/m². Hence, IET kinetics mainly govern current density in MECs. Among parameters associated with IET kinetic, population of anode-respiring bacteria in anode biofilms, biofilm density of active microorganisms, biofilm thickness, and alkalinity are critical for current density.

Knowledge Mapping and Institutional Prospects on Circular Carbon Economy Based on Scientometric Analysis

The circular carbon economy is receiving increasing research attention as an essential tool for reducing carbon emissions and mitigating climate change. However, there is no research on the literature distribution and the current situation of the circular carbon economy studies. This paper presents a scientometric analysis of 1452 academic papers on the circular carbon economy and their references from 2010-2021 using the Citespace visualization network. The results show that research on the circular carbon economy has experienced a relatively gradual growth from 2010 to 2016, followed by an explosive growth from 2016 to 2021. Research cooperation among countries is close, forming a relatively concentrated cooperation network, while the core author group has not yet formed. Furthermore, the research on circular carbon economy strongly correlates with relevant international hotspots and national policy changes, reflecting the instrumental characteristics of circular carbon economy research. We summarized three main research topics through keywords clustering. In addition, we point out the future research directions from technical progress considering industry differences and cooperation, multiple environmental policies and legal system construction, interregional and international cooperation, etc., from an institutional research perspective. This article provides an essential and valuable reference for related research.

Communication Channels for the Rule of Law and Environmental Sustainability: Reflections from a Green Economy Perspective

To realize the sustainable development of the environment from the perspective of green economy, it is necessary to effectively utilize the communication channels of environmental sustainability under the rule of law. As a new driving force for economic growth and ecological environment, green economy is analyzed from the perspective of coordinating economic and environmental development. This paper fully analyzes the impact of green economy on economic growth and ecological environment. Based on the inherent relationship, the rule of law and environmental sustainability are conducive to promoting economic growth and also play a continuous role in environmental improvement. Areas with a high level of economic development also have a higher proportion of resource consumption. Driven by technological innovation, green economy can effectively reduce the impact of the environment, promote sustainability, and further promote the coordinated development of the economy and the environment. The results of the case analysis show that, in the proportion of the green economy with a large amount of investment, compared with the traditional policies and regulations, it greatly reduces the aggravation of environmental sustainability and has a positive role in promoting the long-term development of the Chinese economy. It can not only effectively accelerate economic growth, but also realize the reflection from the perspective of green economy and promote the optimization of economic structure.

A Review on SAPO-34 Zeolite Materials for CO2 Capture and Conversion

Among several known zeolites, silicoaluminophosphate (SAPO)-34 zeolite exhibits a distinct chemical structure, unique pore size distribution, and chemical, thermal, and ion exchange capabilities, which have recently attracted considerable research attention. Global carbon dioxide (CO₂ ) emissions are a serious environmental issue. Current atmospheric CO₂ level exceeds 414 parts per million (ppm), which greatly influences humans, fauna, flora, and the ecosystem as a whole. Zeolites play a vital role in CO₂ removal, recycling, and utilization. This review summarizes the properties of the SAPO-34 zeolite and its role in CO₂ capture and separation from air and natural gas. In addition, due to their high thermal stability and catalytic nature, CO₂ conversions into valuable products over single metal, bi-metallic, and tri-metallic catalysts and their oxides supported on SAPO-34 were also summarized. Considering these accomplishments, substantial problems related to SAPO-34 are discussed, and future recommendations are offered in detail to predict how SAPO-34 could be employed for greenhouse gas mitigation.

Metal Oxides as Catalyst/Supporter for CO2 Capture and Conversion, Review

Various carbon dioxide (CO2) capture materials and processes have been developed in recent years. The absorption-based capturing process is the most significant among other processes, which is widely recognized because of its effectiveness. CO2 can be used as a feedstock for the production of valuable chemicals, which will assist in alleviating the issues caused by excessive CO2 levels in the atmosphere. However, the interaction of carbon dioxide with other substances is laborious because carbon dioxide is dynamically relatively stable. Therefore, there is a need to develop types of catalysts that can break the bond in CO2 and thus be used as feedstock to produce materials of economic value. Metal oxide-based processes that convert carbon dioxide into other compounds have recently attracted attention. Metal oxides play a pivotal role in CO2 hydrogenation, as they provide additional advantages, such as selectivity and energy efficiency. This review provides an overview of the types of metal oxides and their use for carbon dioxide adsorption and conversion applications, allowing researchers to take advantage of this information in order to develop new catalysts or methods for preparing catalysts to obtain materials of economic value.

Evaluation of the Circular Economy in a Pitahaya Agri-Food Chain

Over the last decade, the circular economy (CE) has attracted attention due to the current unsustainable model of production and consumption, which involves an increased resource use and depletion. Agri-food is one of the key sectors where action must be taken to ensure the transition to a more sustainable development model in line with circular economy principles. This study aims to evaluate the potential of implementing the circular economy in the pitahaya agri-food chain in Ecuador. The research was conducted from 2019 to 2021, during which a checklist was applied that included 91 items grouped into nine dimensions: source or supply of materials, design, manufacturing, economic circle, distribution and sales, consumption/use, 4R, remanufacturing, and sustainability. The level of the circular economy evaluated in the study was low (2.14 points out of 5). Therefore, improvements are required in the agri-food management of fruit cultivation and processing. Critical points were identified and strategies were proposed to increase competitiveness, improve environmental performance, and promote the implementation of the circular economy in this production chain. A final recommendation is to explore research on the concept of CE in the sector, mainly focused on the valorization of biomass as a contribution to the bioeconomy in order to contribute to the country’s growth within the context of sustainability.

Compressive Stress and Charge Redistribution during CO Adsorption onto Pt

The change in surface stress associated with the adsorption and oxidative stripping of carbon monoxide (CO) on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO3 electrolyte. The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO-free and CO-saturated electrolytes. Although CO adsorbs as a neutral molecule, significant compressive stress, up to -1.3 N/m, is induced in the Pt. The magnitude of the stress change correlates directly with the CO coverage and, within the detection limits of the stress measurement, is elastically reversible. Density functional theory calculations of a CO-bound Pt surface indicate that charge redistribution from the first atomic layer of Pt to subsurface layers accounts for the observed compressive stress induced by the charge neutral adsorption of CO. A better understanding of adsorbate-induced surface stress is critical for the development of material platforms for sensing and catalysis.

An Empirical Analysis of the Common Factors Influencing the Sharing and Green Economies

The digital revolution, driven and accelerated by the current pandemic, involves changes to known business models. The innovative model of the sharing economy can be a real and sustainable solution for long-term green economic development. The aim of our research was to determine the common factors of the sharing economy and the green economy and the perceptions of Romanian users regarding them. Our research questionnaire was based on the elements we found in the academic literature. To evaluate the collected data, we used the factor analysis method with the support of the SPSS program. As our study reveals, digitalization as well as inclinations towards saving are factors impacting both the propensity towards sharing and support for the green economy. The demarcation line between the sharing and the green economies is rather fluid, the two realities being under a reciprocal influence. In our model, the green economy develops according to the principles of the sharing economy, going a step further in considering the relationship between society and environment, society and sustainable, eco-friendly behaviour. Although the sharing economy is not necessarily a prerequisite of the green economy, it is, nevertheless, easy for societies or groups that have internalized the lessons of the sharing economy to move forward towards the green economy. This study can be an important tool and a first step for businesses, and, more importantly, for the Romanian public institutions to accelerate the implementation of necessary measures, including legislative ones, in order to promote the further development of these economies.