Ambient CO2 capture and storage in bioelectrochemically mediated wastewater treatment

Wastewater as a resource for carbon capture: A comprehensive overview and perspective

As two important but energy-intense processes, carbon capture and wastewater treatment always attract wide research interests to improve their operational efficiency and technological feasibility. Consequently, utilizing wastewater for carbon capture or integrating carbon capture plants into wastewater treatment facilities has become a promising concept drawing great attention to investigate and demonstrate its feasibility and efficiency. In this study, recent research progress and concept validation studies of utilizing wastewater for carbon capture were briefly reviewed and summarized with the status and main challenges of this concept provided accordingly. Three integration strategies for combining carbon capture with wastewater treatment-utilization of wastewater as the absorbent to capture CO2, biological pathway for simultaneous carbon capture and wastewater treatment, and electrochemical approach to integrate wastewater purification with carbon capture-were primarily reviewed and discussed in this study. Meanwhile, the perspectives of these integrated technology strategies were also discussed providing guidance for future investigations and development of carbon capture with wastewater treatment. Based on our study, the integrated wastewater treatment and carbon capture shows promising prospects in terms of reducing energy consumption and cost of carbon capture and wastewater treatment. However, more relevant studies and demonstrations are still necessary to improve efficiency and reduce possible carbon emissions. As a promising technology contributing to achieving net-zero emission and mitigating global warming, the integration of wastewater treatment and carbon capture will attract more attention in the future.

Toward sustainable space exploration: a roadmap for harnessing the power of microorganisms

Finding sustainable approaches to achieve independence from terrestrial resources is of pivotal importance for the future of space exploration. This is relevant not only to establish viable space exploration beyond low Earth-orbit, but also for ethical considerations associated with the generation of space waste and the preservation of extra-terrestrial environments. Here we propose and highlight a series of microbial biotechnologies uniquely suited to establish sustainable processes for in situ resource utilization and loop-closure. Microbial biotechnologies research and development for space sustainability will be translatable to Earth applications, tackling terrestrial environmental issues, thereby supporting the United Nations Sustainable Development Goals.

Anaerobic digestion as a tool to manage eutrophication and associated greenhouse gas emission

Eutrophicated inland water bodies are noticed to be one of the contributing factors to greenhouse gas (GHGs) emissions. Direct discharge of untreated or partially treated water is a major concern. Microalgae-based technology and management are regarded as one of the potential nature-based approaches to combat eutrophication. In turn, the microalgae facilitate the recovery of GHGs contributing compounds in the form of organic biomass. The recovered algal biomass can be harnessed for the production of biofuels and other bio-products, like biofertilizer, using anaerobic digestion. By virtue, circular bio-economy can be achieved alongside mitigating GHGs emissions. Before implementing, it is vital to thoroughly explore the links between the process and potential alternatives for wastewater treatment, waste valorization, biofuel production, and land usage. Thus, the present review discusses the impact of eutrophication on ecology and environment, current technologies for mitigating eutrophication and GHGs, and energy recovery through the anaerobic digestion of algal biomass. Further, the processes at the intercept of wastewater treatment and biogas production were reviewed to leverage the potential of anaerobic digestion for making a circular bioeconomy framework.

The role of microbiome in carbon sequestration and environment security during wastewater treatment

Wastewater treatment is an essential aspect of the earth's sustainable future. However, different wastewater treatment methods are responsible for carbon discharge into the environment, raising environmental risks. Hence, such wastewater treatment methods are required that can minimize carbon release without compromising the treatment quality. Microbiome-based carbon sequestration is a potential method for achieving this goal. Limited studies have been carried out to investigate how microbes can capture and utilize CO₂. This review summarizes the approaches including microbial electrolytic carbon capture, microbial electrosynthesis, microbial fuel cell, microalgae cultivation, and constructed wetlands that employ microbes to capture and utilize CO₂. Electroactive Bacteria (EAB) convert carbon dioxide to carbonates and bicarbonates in subsequent steps after organic matter decomposition. Similarly, microbial electrosynthesis (MES) not only helps capture carbon but also produces secondary products (production of polyhydroxyalkanoates by Gram-negative rod Aeromonas hydrophila bacteria) of commercial importance during wastewater treatment. In addition to this, microbial carbon capture cells (MCCs) have been now utilized for energy generation and carbon sequestration at the same time during wastewater treatment. Moreover, microalgae cultivation has also been found to capture CO₂ at a rapid pace while releasing O₂ as a consequence of photosynthesis. Hence, microbe-based wastewater treatment has quite a potential due to two-fold benefits like carbon sequestration and by-product formation.

Sewage-Water Treatment and Sewage-Sludge Management with Power Production as Bioenergy with Carbon Capture System: A Review

Sewage-water treatment comprehends primary, secondary, and tertiary steps to produce reusable water after removing sewage contaminants. However, a sewage-water treatment plant is typically a power and energy consumer and produces high volumes of sewage sludge mainly generated in the primary and secondary steps. The use of more efficient anaerobic digestion of sewage water with sewage sludge can produce reasonable flowrates of biogas, which is shown to be a consolidated strategy towards the energy self-sufficiency and economic feasibility of sewage-water treatment plants. Anaerobic digestion can also reduce the carbon footprint of energy sources since the biogas produced can replace fossil fuels for electricity generation. In summary, since the socio-economic importance of sewage treatment is high, this review examined works that contemplate: (i) improvements of sewage-water treatment plant bioenergy production and economic performances; (ii) the exploitation of technology alternatives for the energy self-sufficiency of sewage-water treatment plants; (iii) the implementation of new techniques for sewage-sludge management aiming at bioenergy production; and (iv) the implementation of sewage-water treatment with bioenergy production and carbon capture and storage.

The key role of Geobacter in regulating emissions and biogeochemical cycling of soil-derived greenhouse gases

In the past two decades, more and more attentions have been paid to soil-derived greenhouse gases (GHGs) including carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) because there are signs that they have rising negative impacts on the sustainability of the earth surface system. Farmlands, particularly paddy soils, have been regarded as the most important emitter of GHGs (nearly 17%) due to a large influx of fertilization and the abundance in animals, plants and microorganisms. Geobacter, as an electroactive microorganism widely occurred in soil, has been well studied on electron transport mechanisms and the direct interspecies electron transfer. These studies on Geobacter illustrate that it has the ability to be involved in the pathways of soil GHG emissions through redox reactions under anaerobic conditions. In this review, production mechanisms of soil-derived GHGs and the amount of these GHGs produced had been first summarized. The cycling process of CH₄ and N₂O was described from the view of microorganisms and discussed the co-culture relationships between Geobacter and other microorganisms. Furthermore, the role of Geobacter in the production of soil-derived GHGs is defined by biogeochemical cycling. The complete view on the effect of Geobacter on the emission of soil-derived GHGs has been shed light on, and appeals further investigation.

Microbial fuel cells: From fundamentals to applications. A review

In the past 10-15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described.

Three-dimensional graphene nanosheets as cathode catalysts in standard and supercapacitive microbial fuel cell

Three-dimensional graphene nanosheets (3D-GNS) were used as cathode catalysts for microbial fuel cells (MFCs) operating in neutral conditions. 3D-GNS catalysts showed high performance towards oxygen electroreduction in neutral media with high current densities and low hydrogen peroxide generation compared to activated carbon (AC). 3D-GNS was incorporated into air-breathing cathodes based on AC with three different loadings (2, 6 and 10 mgcm-2). Performances in MFCs showed that 3D-GNS had the highest performances with power densities of 2.059 ± 0.003 Wm-2, 1.855 ± 0.007 Wm-2 and 1.503 ± 0.005 Wm-2 for loading of 10, 6 and 2 mgcm-2 respectively. Plain AC had the lowest performances (1.017 ± 0.009 Wm-2). The different cathodes were also investigated in supercapacitive MFCs (SC-MFCs). The addition of 3D-GNS decreased the ohmic losses by 14-25%. The decrease in ohmic losses allowed the SC-MFC with 3D-GNS (loading 10 mgcm-2) to have the maximum power (Pmax) of 5.746 ± 0.186 Wm-2. At 5 mA, the SC-MFC featured an "apparent" capacitive response that increased from 0.027 ± 0.007 F with AC to 0.213 ± 0.026 F with 3D-GNS (loading 2 mgcm-2) and further to 1.817 ± 0.040 F with 3D-GNS (loading 10 mgcm-2).