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Graphitic carbon nitride (g-C3N4) is a promising material for photocatalytic applications. However, it suffers from poor visible-light absorption and a high recombination rate of photogenerated electron–hole pairs. Here, Co/La@g-C3N4 with enhanced photocatalytic activity was prepared by co-doping Co and La into g-C3N4 via a facile one-pot synthesis. Co/La@g-C3N4 displayed better performance, achieving 94% tetracycline (TC) removal within 40 min, as compared with g-C3N4 (BCN, 65%). It also demonstrated promising performance in degrading other pollutants, which was ~2–4-fold greater relative to BCN. The improved photocatalytic activity of Co/La@g-C3N4 was associated with improved photogenerated charge separation, reduced charge transfer resistance, a built-in electric field arising from the p-n-p heterojunction, and the synergistic effect of ternary components for the separation and transfer of the photogenerated charge carriers. Superoxide radicals are suggested to be the most notable reactive species responsible for the photocatalytic reaction. Environmental factors, including the pollutant concentration, catalyst dosage, solution pH, inorganic salts, water matrices, and mixture with dyes, were considered in the photocatalytic reactions. Co/La@g-C3N4 showed good reusability for five cycles of the photocatalytic degradation of TC. The facile one-pot co-doping of Co and La in g-C3N4 formed a p-n-p heterojunction with boosted photocatalytic activity for the highly efficient removal of TC from various water matrices. [ABSTRACT FROM AUTHOR]

With an extensive presence in the world of Industrial Symbiosis literature, the Kwinana industrial area in Perth, Western Australia is a powerhouse of integrated heavy industrial activity. From when its first entrant arrived in 1955, development has been strong, and now it presents a complex industrial cluster with a wide range of industrial enterprises present, ranging from several major industrial multi-product manufacturers to those filling niche markets. Formal reporting of its economic contribution has occurred periodically over 40 yr, with one of the features of this being a series of four earlier iterations, and in this paper, the fifth, of a schematic diagram that identifies the enterprises engaged in symbiotic relationships and the nature of the associated materials exchanged. While the earlier reports concentrated solely on the traditional materials exchanges, the present study (data collected in 2021) went beyond these to gather additional data on what the authors are proposing as additional dimensions of the traditional Industrial Symbiosis framework. Aspects of Kwinana's skilled workforce, its support industry base, and its overlying governance framework were studied to provide insights into what role they play in explaining why some industrial clusters appear to provide a supportive business environment, and why other clusters struggle to gain momentum. The new study identified that the novel posited dimensions of Industrial Symbiosis are interlinked at the precinct level, and that at the macro (societal) level, they combine to contribute to the effectiveness of the Circular Economy.

Industrial enterprises around the world are grappling with greenhouse gas emission reduction expectations, whether being driven by respective government policy for climate change or by shareholders to drive corporate sustainability through maintaining access to their ‘net zero’-demanding markets. In some instances, the enterprises co-located within complex industrial areas are coming together to face the common carbon reduction challenge as a collective. The Kwinana Industrial Area in Perth, Western Australia is well regarded on the world's stage as a successful integrated heavy industrial precinct, presenting as an extensive, complex, and broad-based example of Industrial Symbiosis. In earlier papers, the authors have posited a novel four-dimensional framework to expand the definition of Industrial Symbiosis to be used to understand why one industrial precinct may be more successful for its resident industries to operate within than another, and for application in the design of new industrial areas. The four dimensions are described as Materials Exchange, Skilled Workforce, Support Industry, and Governance. Through the lens of climate change literature and policy frameworks, we investigate the governance dimension and industry's response to the contemporary climate challenge. The outputs of the paper include a literature review of the governance dimension, and a description of the cascading nature of climate change policy from global through to the enterprise level. We illustrate how climate change governance is enhanced in practice by detailing how the enterprises in Kwinana collectively responded to the global requirement for carbon reduction, achieved through the facilitative governance-based intervention of their industry association, the Kwinana Industries Council. Exploring this in-practice example helped to consolidate the hypothesis that successful industrial symbiosis is about positive relationships across several dimensions building towards improved Circular Economy outcomes.

Bioelectrochemical systems (BESs) can be integrated in situ into anaerobic digesters for increasing methane (CH4) content of biogas. Using BES ex situ for improving biogas quality has recently been gaining attention. However, information on the process under thermophilic conditions is very limited. In this study, we placed a BES cathode in-line at the exit gas from a thermophilic anaerobic digester to convert carbon dioxide (CO2) in the biogas into CH4. The performance of the ex situ BES reactor under thermophilic conditions was evaluated. When poising the cathode at −1.1 V versus Ag/AgCl in the ex situ BES reactor, CH4 content increased from 50% to 85%. Of the incoming CO2 73% was biologically converted to CH4 and 23% absorbed by alkalinity generated in the cathode. The energy output as additional CH4 as a percentage of the energy input to operate the BES was calculated at 56%. The biocathode of the BES reactor was dominated by Methanothermobacter spp., which are thermophilic hydrogen consuming methanogens. This study confirms that thermophilic BES can be used as an ex situ treatment process for enriching the CH4 content of biogas. However, energy efficiency of the process was found to be limited by the lack of an energetically efficient anodic reaction. For industrial applications, optimisation of energy efficiency is an area for further research.

The traditional electrochemical caustic soda recovery system uses the generated pH gradient across the ion exchange membrane for the regeneration of spent alkaline absorbent from CO2 capture. This electrochemical CO2 capture system releases the by-products H2 and O2 at the cathode and anode, respectively. Although effective for capturing CO2, the slow kinetics of the oxygen evolution reaction (OER) limit the energy efficiency of this technique. Hence, this study proposed and validated a hybrid electrochemical cell based on the H2-cycling from the cathode to the anode to eliminate the reliance on anodic oxygen generation. The results show that our lab-scale prototype enabled effective spent caustic soda recovery with an electron utilisation efficiency of 90%, and a relative carbonate/bicarbonate diffusional flux of approximately 40%. The system also enabled the regeneration of spent alkaline absorbent with a minimum electrochemical energy input of 0.19 kWh/kg CO2 at a CO2 recovery rate of 0.7 mol/m2/h, accounting for 30% lower energy demand than a control system without H2-recycling, making this technique a promising alternative to the conventional thermal regeneration technology. [ABSTRACT FROM AUTHOR]

Waste generation is an inevitable by-product of human activity, and it is on the rise due to rapid urbanisation, industrialisation, increased wealth and population. The composition of municipal solid waste (MSW) in developed and developing economies differ, especially with the organic fraction. Research shows that the food waste stream of MSW in developing countries is over 50%. The case study for this investigation, Nigeria, has minimal formal recycling or resource recovery programs. The average composition of waste from previous research in the country is between 50–70% putrescible and 30–50% non-putrescible, presenting significant resource recovery potential in composting and biogas production. Waste-to-energy (WtE) is an important waste management solution that has been successfully implemented and operated in most developed economies. This contribution reports the conditions that would be of interest before WtE potentials of MSW is harnessed, in an efficient waste management process in a developing economy like Nigeria. The investigation presents a set of socio-technical parameters and transition strategy model that would inform a productive MSW management and resource recovery, in which WtE can be part of the solution. This model will find application in the understanding of the interactions between the socio-economic, technical and environmental system, to promote sustainable resource recovery programs in developing economies, among which is WtE.