Human activities have led to a massive increase in $$\hbox {CO}_{2}$$ CO 2 emissions as a primary greenhouse gas that is contributing to climate change with higher than $$1\,^{\circ }\hbox {C}$$ 1 ∘ C global warming than that of the pre-industrial level. We evaluate the three major technologies that are utilised for carbon capture: pre-combustion, post-combustion and oxyfuel combustion. We review the advances in carbon capture, storage and utilisation. We compare carbon uptake technologies with techniques of carbon dioxide separation. Monoethanolamine is the most common carbon sorbent; yet it requires a high regeneration energy of 3.5 GJ per tonne of $$\hbox {CO}_{2}$$ CO 2 . Alternatively, recent advances in sorbent technology reveal novel solvents such as a modulated amine blend with lower regeneration energy of 2.17 GJ per tonne of $$\hbox {CO}_{2}$$ CO 2 . Graphene-type materials show $$\hbox {CO}_{2}$$ CO 2 adsorption capacity of 0.07 mol/g, which is 10 times higher than that of specific types of activated carbon, zeolites and metal–organic frameworks. $$\hbox {CO}_{2}$$ CO 2 geosequestration provides an efficient and long-term strategy for storing the captured $$\hbox {CO}_{2}$$ CO 2 in geological formations with a global storage capacity factor at a Gt-scale within operational timescales. Regarding the utilisation route, currently, the gross global utilisation of $$\hbox {CO}_{2}$$ CO 2 is lower than 200 million tonnes per year, which is roughly negligible compared with the extent of global anthropogenic $$\hbox {CO}_{2}$$ CO 2 emissions, which is higher than 32,000 million tonnes per year. Herein, we review different $$\hbox {CO}_{2}$$ CO 2 utilisation methods such as direct routes, i.e. beverage carbonation, food packaging and oil recovery, chemical industries and fuels. Moreover, we investigated additional $$\hbox {CO}_{2}$$ CO 2 utilisation for base-load power generation, seasonal energy storage, and district cooling and cryogenic direct air $$\hbox {CO}_{2}$$ CO 2 capture using geothermal energy. Through bibliometric mapping, we identified the research gap in the literature within this field which requires future investigations, for instance, designing new and stable ionic liquids, pore size and selectivity of metal–organic frameworks and enhancing the adsorption capacity of novel solvents. Moreover, areas such as techno-economic evaluation of novel solvents, process design and dynamic simulation require further effort as well as research and development before pilot- and commercial-scale trials.

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Dihydrogen (H2), commonly named ‘hydrogen’, is increasingly recognised as a clean and reliable energy vector for decarbonisation and defossilisation by various sectors. The global hydrogen demand is projected to increase from 70 million tonnes in 2019 to 120 million tonnes by 2024. Hydrogen development should also meet the seventh goal of ‘affordable and clean energy’ of the United Nations. Here we review hydrogen production and life cycle analysis, hydrogen geological storage and hydrogen utilisation. Hydrogen is produced by water electrolysis, steam methane reforming, methane pyrolysis and coal gasification. We compare the environmental impact of hydrogen production routes by life cycle analysis. Hydrogen is used in power systems, transportation, hydrocarbon and ammonia production, and metallugical industries. Overall, combining electrolysis-generated hydrogen with hydrogen storage in underground porous media such as geological reservoirs and salt caverns is well suited for shifting excess off-peak energy to meet dispatchable on-peak demand.

The global energy demand is projected to rise by almost 28% by 2040 compared to current levels. Biomass is a promising energy source for producing either solid or liquid fuels. Biofuels are alternatives to fossil fuels to reduce anthropogenic greenhouse gas emissions. Nonetheless, policy decisions for biofuels should be based on evidence that biofuels are produced in a sustainable manner. To this end, life cycle assessment (LCA) provides information on environmental impacts associated with biofuel production chains. Here, we review advances in biomass conversion to biofuels and their environmental impact by life cycle assessment. Processes are gasification, combustion, pyrolysis, enzymatic hydrolysis routes and fermentation. Thermochemical processes are classified into low temperature, below 300 °C, and high temperature, higher than 300 °C, i.e. gasification, combustion and pyrolysis. Pyrolysis is promising because it operates at a relatively lower temperature of up to 500 °C, compared to gasification, which operates at 800–1300 °C. We focus on 1) the drawbacks and advantages of the thermochemical and biochemical conversion routes of biomass into various fuels and the possibility of integrating these routes for better process efficiency; 2) methodological approaches and key findings from 40 LCA studies on biomass to biofuel conversion pathways published from 2019 to 2021; and 3) bibliometric trends and knowledge gaps in biomass conversion into biofuels using thermochemical and biochemical routes. The integration of hydrothermal and biochemical routes is promising for the circular economy.

Adsorption to date is the most effective and utilized technology globally to remove several pollutants in wastewater. In this approach, many adsorbents have been synthesized, tested and used for the elimination and separation of the contaminants such as radionuclides, heavy metals, dyes and pharmaceutical compounds both at lab and industrial scale. However, there are many challenges to adsorption processes such as reducing the high cost, through means of separation of suspending adsorbents to be used again, as well as the ease to synthesize. Two methods that have shown promising results and gained significant interest is that of magnetic nanomaterials and biosorbents due to their effective, safe, eco-friendly, low cost and low-energy intensive material properties. Magnetic nanomaterials act as efficient adsorbents due to their ease of removal of contaminants from wastewater using an applied magnetic field but also their advantageous surface charge and redox activity characteristics. On the other hand, biosorbents have a synergistic effect with their efficient adsorption capacity to remove contaminants, high abundance and participation in waste minimization, helping alleviate ecological and environmental problems. This review highlights, discusses and reports on the state-of-the-art of these two promising routes to adsorption and provides indications as to what are the optimum materials for utilization and insight into their efficiency, reusability and practicality for the removal of pollutants from wastewater streams. Some of the main material focuses are zero-valent iron, iron oxides, spinel ferrites, natural and waste-based biosorbents.

In the context of climate change and the circular economy, biochar has recently found many applications in various sectors as a versatile and recycled material. Here, we review application of biochar-based for carbon sink, covering agronomy, animal farming, anaerobic digestion, composting, environmental remediation, construction, and energy storage. The ultimate storage reservoirs for biochar are soils, civil infrastructure, and landfills. Biochar-based fertilisers, which combine traditional fertilisers with biochar as a nutrient carrier, are promising in agronomy. The use of biochar as a feed additive for animals shows benefits in terms of animal growth, gut microbiota, reduced enteric methane production, egg yield, and endo-toxicant mitigation. Biochar enhances anaerobic digestion operations, primarily for biogas generation and upgrading, performance and sustainability, and the mitigation of inhibitory impurities. In composts, biochar controls the release of greenhouse gases and enhances microbial activity. Co-composted biochar improves soil properties and enhances crop productivity. Pristine and engineered biochar can also be employed for water and soil remediation to remove pollutants. In construction, biochar can be added to cement or asphalt, thus conferring structural and functional advantages. Incorporating biochar in biocomposites improves insulation, electromagnetic radiation protection and moisture control. Finally, synthesising biochar-based materials for energy storage applications requires additional functionalisation.

Microplastic pollution is becoming a major issue for human health due to the recent discovery of microplastics in most ecosystems. Here, we review the sources, formation, occurrence, toxicity and remediation methods of microplastics. We distinguish ocean-based and land-based sources of microplastics. Microplastics have been found in biological samples such as faeces, sputum, saliva, blood and placenta. Cancer, intestinal, pulmonary, cardiovascular, infectious and inflammatory diseases are induced or mediated by microplastics. Microplastic exposure during pregnancy and maternal period is also discussed. Remediation methods include coagulation, membrane bioreactors, sand filtration, adsorption, photocatalytic degradation, electrocoagulation and magnetic separation. Control strategies comprise reducing plastic usage, behavioural change, and using biodegradable plastics. Global plastic production has risen dramatically over the past 70 years to reach 359 million tonnes. China is the world's top producer, contributing 17.5% to global production, while Turkey generates the most plastic waste in the Mediterranean region, at 144 tonnes per day. Microplastics comprise 75% of marine waste, with land-based sources responsible for 80–90% of pollution, while ocean-based sources account for only 10–20%. Microplastics induce toxic effects on humans and animals, such as cytotoxicity, immune response, oxidative stress, barrier attributes, and genotoxicity, even at minimal dosages of 10 μg/mL. Ingestion of microplastics by marine animals results in alterations in gastrointestinal tract physiology, immune system depression, oxidative stress, cytotoxicity, differential gene expression, and growth inhibition. Furthermore, bioaccumulation of microplastics in the tissues of aquatic organisms can have adverse effects on the aquatic ecosystem, with potential transmission of microplastics to humans and birds. Changing individual behaviours and governmental actions, such as implementing bans, taxes, or pricing on plastic carrier bags, has significantly reduced plastic consumption to 8–85% in various countries worldwide. The microplastic minimisation approach follows an upside-down pyramid, starting with prevention, followed by reducing, reusing, recycling, recovering, and ending with disposal as the least preferable option.

Metals/minerals-incorporated materials have received significant attention over the last decades given the outstanding adsorption behavior towards various pollutants especially Cr(VI) in aqueous solutions. Here, the pattern of sorption of some...