CO2 storage in geological media: Role,means, status and barriers to deployment

Carbon dioxide capture and geological storage is an enabling technology that will allow the continued use well into this century of fossil fuels, mainly coal, for power generation and combustion in industrial processes because they are relatively abundant, cheap, available and globally distributed, thus enhancing the security and stability of energy systems. Geological media suitable for CO₂ storage through various physical and chemical trapping mechanisms must have the necessary capacity and injectivity, and must confine the CO₂ and impede its lateral migration and/or vertical leakage to other strata, shallow potable groundwater, soils and/or atmosphere. Such geological media are mainly oil and gas reservoirs and deep saline aquifers that are found in sedimentary basins. Storage of gases, including CO₂, in these media has been demonstrated on a commercial scale by enhanced oil recovery operations, natural gas storage and acid gas disposal. Some of the risks associated with CO₂ capture and geological storage are similar to, and comparable with, any other industrial activity for which extensive safety and regulatory frameworks are in place. Specific risks associated with CO₂ storage relate to the operational (injection) phase and to the post-operational phase, of which the risks of most concern are those posed by the potential for acute or chronic CO₂ leakage from the storage site. Notwithstanding the global climate effect of CO₂ returning to the atmosphere, the local risks to health and safety, environment and equity need to be properly assessed and managed. Currently there are very few operations in the world where CO₂ is injected and stored in the ground, mostly if not exclusively as a by-product of an operation driven by other considerations than climate change, such as oil production or regulatory requirements regarding H₂S. These operations show that there are no major technological barriers to CO₂ geological storage, and that challenges and barriers lie elsewhere. A major challenge in the implementation of CO₂ geological storage is the high cost of CO₂ capture, particularly for dilute streams like those from power plants and industrial combustion processes. There are concerns that public opinion and public's acceptance or rejection of this technology will likely affect the large-scale implementation of CO₂ geological storage. The current paucity of policy, legislation and a proper regulatory framework in most jurisdictions is presently the most significant barrier. The resolution of these challenges will affect the economics and financial risk of CO₂ geological storage and will accelerate or delay the deployment of this technology for reducing anthropogenic CO₂ emissions into the atmosphere.     

Carbon capture and storage

Carbon capture and storage (CCS) covers a broad range of technologies that are being developed to allow carbon dioxide (CO₂) emissions from fossil fuel use at large point sources to be transported to safe geological storage, rather than being emitted to the atmosphere. Some key enabling contributions from technology development that could help to facilitate the widespread commercial deployment of CCS are expected to include cost reductions for CO₂ capture technology and improved techniques for monitoring stored CO₂. It is important, however, to realise that CCS will always require additional energy compared to projects without CCS, so will not be used unless project operators see an appropriate value for reducing CO₂ emissions from their operations or legislation is introduced that requires CCS to be used. Possible key advances for CO₂ capture technology over the next 50 years, which are expected to arise from an eventual adoption of CCS as standard practice for all large stationary fossil fuel installations, are also identified. These include continued incremental improvements (e.g. many potential solvent developments) as well as possible step-changes, such as ion transfer membranes for oxygen production for integrated gasifier combined cycle and oxyfuel plants.     

Negative carbon intensity of renewable energy technologies involving biomass or carbon dioxide as inputs

Conventional fossil fuel-based energy technologies can achieve efficiency in energy conversion but they are usually completely inefficient in carbon conversion because they generate significant CO₂ emissions to the atmosphere per unit energy converted. In contrast, some renewable energy technologies characterized by negative carbon intensity can simultaneously achieve efficiency in the conversion of energy and in the conversion of carbon. These carbon negative renewable energy technologies can generate useful energy and remove CO₂ from the atmosphere, either by direct capture and recycling of atmospheric CO₂ or indirectly, by involving biofuels. Interestingly, the deployment of carbon negative renewable energy technologies can offset carbon emissions from conventional fossil fuel-based energy technologies and thus reduce the overall carbon intensity of energy systems.The current review analyzes two groups of renewable energy technologies involving biomass or CO₂ as inputs. The discussions focus on useful techniques which enable to achieve negative carbon intensity of energy while being technologically promising in near-term as well as cost-effective. These analyzes include advanced carbon sequestration concepts such as soil carbon sequestration and CO₂ recycling to useful C-rich products such as fuels and fertilizers. The 'drop-in' of renewable energy is achieved by allowing bioenergy and renewable energies in the form of renewable electricity, renewable thermal energy, solar energy, renewable hydrogen, etc. The carbon negative renewable energy technologies are analyzed and perspectives and constraints of each technology are expounded.     

Sustainable carbon-dioxide storage assessment in geological media using modified Pythagorean fuzzy VIKOR and DEMATEL approach

In a developing country like India, the primary source of power generation is fossil fuels. The lion's share of India's electricity production is from fossil fuels leading to massive greenhouse gas emissions (GHG) like CO₂, which causes global warming. To deal with climate change and control global warming, the carbon capture utilization and storage (CCUS) project in geological formation is a practical, comparatively secure, inevitable and emergent method to be materialized. However, CO₂ storage in deep geological structures in the sedimentary basin has a risk of leakage due to the geological formation of different seams, which might harm human beings, including different underground, terrestrial, and aquatic species. It could affect the energy sources of our environment also. Therefore the selection of CO₂ storage site in geological media is based on some criteria, and therefore it is a multi-criteria decision-making (MCDM) problem. The multi-criteria group decision-making (MCGDM) method is proposed to get a more impartial result, using the soft computing methodology Pythagorean fuzzy VIKOR (“VIekriterijumsko KOmpromisno Rangiranje”, a Serbian term for “multi-criteria optimization and compromise solution”) modified with a novel divergence called Pythagorean fuzzy Jensen-Shannon Song (PJSS). The fuzzy DEMATEL (DEcision MAking Trial and Evaluation Laboratory) method is introduced to evaluate the criteria weights. A Comparative Study and Sensitivity analysis are also presented in this article. Finally, the outcomes of the work show that the proposed methodology is feasible.     

Techno-economic appraisal of fossil-fuelled power generation systems with carbon dioxide capture and storage

Carbon capture and storage (CCS) facilities coupled to power plants provide a climate change mitigation strategy that potentially permits the continued use of fossil fuels whilst reducing the carbon dioxide (CO₂) emissions. This process involves three basic stages: capture and compression of CO₂ from power stations, transport of CO₂, and storage away from the atmosphere for hundreds to thousands of years. Potential routes for the capture, transport and storage of CO₂ from United Kingdom (UK) power plants are examined. Six indicative options are evaluated, based on ‘Pulverised Coal’, ‘Natural Gas Combined Cycle’, and ‘Integrated (coal) Gasification Combined Cycle’ power stations. Chemical and physical CO₂ absorption capture techniques are employed with realistic transport possibilities to ‘Enhanced Oil Recovery’ sites or depleted gas fields in the North Sea. The selected options are quantitatively assessed against well-established economic and energy-related criteria. Results show that CO₂ capture can reduce emissions by over 90%. However, this will reduce the efficiency of the power plants concerned, incurring energy penalties between 14 and 30% compared to reference plants without capture. Costs of capture, transport and storage are concatenated to show that the whole CCS chain ‘cost of electricity’ (COE) rises by 27-142% depending on the option adopted. This is a significant cost increase, although calculations show that the average ‘cost of CO₂ captured’ is £15/tCO₂ in 2005 prices [the current base year for official UK producer price indices]. If potential governmental carbon penalties were introduced at this level, then the COE would equate to the same as the reference plant, and make CCS a viable option to help mitigate large-scale climate change.     

Improving the technical, environmental and social performance of wind energy systems using biomass-based energy storage

A completely renewable baseload electricity generation system is proposed by combining wind energy, compressed air energy storage, and biomass gasification. This system can eliminate problems associated with wind intermittency and provide a source of electrical energy functionally equivalent to a large fossil or nuclear power plant. Compressed air energy storage (CAES) can be economically deployed in the Midwestern US, an area with significant low-cost wind resources. CAES systems require a combustible fuel, typically natural gas, which results in fuel price risk and greenhouse gas emissions. Replacing natural gas with synfuel derived from biomass gasification eliminates the use of fossil fuels, virtually eliminating net CO₂ emissions from the system. In addition, by deriving energy completely from farm sources, this type of system may reduce some opposition to long distance transmission lines in rural areas, which may be an obstacle to large-scale wind deployment.     

Cost-effective CO2 emission reduction through heat,power and biofuel production from woody biomass: A spatially explicit comparison of conversion technologies

Bioenergy is regarded as cost-effective option to reduce CO₂ emissions from fossil fuel combustion. Among newly developed biomass conversion technologies are biomass integrated gas combined cycle plants (BIGCC) as well as ethanol and methanol production based on woody biomass feedstock. Furthermore, bioenergy systems with carbon capture and storage (BECS) may allow negative CO₂ emissions in the future. It is still not clear which woody biomass conversion technology reduces fossil CO₂ emissions at least costs. This article presents a spatial explicit optimization model that assesses new biomass conversion technologies for fuel, heat and power production and compares them with woody pellets for heat production in Austria. The spatial distributions of biomass supply and energy demand have significant impact on the total supply costs of alternative bioenergy systems and are therefore included in the modeling process. Many model parameters that describe new bioenergy technologies are uncertain, because some of the technologies are not commercially developed yet. Monte-Carlo simulations are used to analyze model parameter uncertainty. Model results show that heat production with pellets is to be preferred over BIGCC at low carbon prices while BECS is cost-effective to reduce CO₂ emissions at higher carbon prices. Fuel production – methanol as well as ethanol – reduces less CO₂ emissions and is therefore less cost-effective in reducing CO₂ emissions.     

Natural emissions of CO2 from the geosphere and their bearing on the geological storage of carbon dioxide

Carbon dioxide (CO₂) capture and storage has the potential to reduce CO₂ emissions from fossil fuel combustion. Although leakage from monitored CO₂ injection sites has been minimal to non-existent, experience from the natural gas storage industry suggests that, if it becomes a widely deployed technology, leaks may be expected from some storage sites. Natural occurrences of CO₂ in the geosphere, some of which have been exploited, provide insights into the types of emissions that might be expected from anthropogenic CO₂ storage sites. CO₂ emission sites are commonly found in clusters in CO₂-prone geological provinces: the most common natural emissions sites in sedimentary basins consist of carbonated springs and mofettes. These represent at worst only a local hazard. In volcanic and hydrothermal provinces, more energetic emissions may occur due to active supply from degassing magma. These include rare, sudden emissions from fissures and craters that have caused fatalities. It is unlikely that such provinces would be considered for CO₂ storage Major lake overturn events such as occurred at Lake Nyos in 1986 are considered highly unlikely to occur as a result of CO₂ storage, not least because CO₂ levels in lake waters can be monitored and remediated. Natural CO₂ fields indicate that under favourable conditions CO₂ can be retained in the subsurface for millions of years. The main risk from man-made CO₂ storage sites that does not have any close analogy in nature is considered to be a well blowout. A blowout that took place at a natural CO₂ field provides some indication of the likely hazard.     

Costs and CO2 benefits of recovering,refining and transporting logging residues for fossil fuel replacement

There are many possible systems for recovering, refining, and transporting logging residues for use as fuel. Here we analyse costs, primary energy and CO₂ benefits of various systems for using logging residues locally, nationally or internationally. The recovery systems we consider are a bundle system and a traditional chip system in a Nordic context. We also consider various transport modes and distances, refining the residues into pellets, and replacing different fossil fuels. Compressing of bundles entails costs, but the cost of chipping is greatly reduced if chipping is done on a large scale, providing an overall cost-effective system. The bundle system entails greater primary energy use, but its lower dry-matter losses mean that more biomass per hectare can be extracted from the harvest site. Thus, the potential replacement of fossil fuels per hectare of harvest area is greater with the bundle system than with the chip system. The fuel-cycle reduction of CO₂ emissions per harvest area when logging residues replace fossil fuels depends more on the type of fossil fuel replaced, the logging residues recovery system used and the refining of the residues, than on whether the residues are transported to local, national or international end-users. The mode and distance of the transport system has a minor impact on the CO₂ emission balance.     

Co-benefit analysis of incentives for energy generation and storage systems; a multi-stakeholder perspective

In this work, we are analyzing the advantages of energy incentives for all the stakeholders in an energy system. The stakeholders include the government, the energy hub operator, and the energy consumer. Two streams of energy incentives were compared in this work: incentives for renewable energy generation technologies and incentives for energy storage technologies. The first type aims increasing the share of renewable energies in the electricity system while the second type aims development of systems which use clean electricity to replace fossil fuels in other sectors of an energy system such as the transportation, residential and industrial sector. In this work, we are analyzing the advantages of energy incentives for all the stakeholders in an energy system. The stakeholders include the government, the energy hub operator, and the energy consumer. Two streams of energy incentives were compared in this work: incentives for renewable energy generation technologies and incentives for energy storage technologies. The first type aims to increase the share of renewable energies in the electricity system while the second type aims the development of systems which use clean electricity to replace fossil fuels in other sectors of an energy system such as the transportation, residential and industrial sector. The results of the analysis showed that replacing fossil fuel-based electricity generation with wind and solar power is a less expensive way for the energy consumer to reduce GHG emissions (60 and 92 CAD/ tonne CO_2e for wind and solar, respectively) compared to investing on energy storage technologies (225 and 317 CAD/ tonne CO_2e for Power-to-Gas and battery powered forklifts, respectively). However, considering the current Ontario's electricity mix, incentives for the Power-to-Gas and battery powered technologies are less expensive ways to reduce emissions compared to replacing the grid with wind and solar power technologies (1479 and 2418 CAD/ tonne CO_2e for wind and solar, respectively). Our analysis also shows that battery storage and hydrogen storage are complementary technologies for reducing GHG emissions in Ontario.     

Mitigation measures to reduce greenhouse gas emissions and enhance carbon capture and storage in Saudi Arabia

The main causes of global warming are now attributed to the burning of fossil fuels. Saudi Arabia is the world's largest producer and exporter of total petroleum liquids, and one of the largest consumers of total primary energy. The activities which are mainly responsible for significant greenhouse gas emissions are consistently in the upslope. The electricity generation, the solid waste management, and the agricultural sectors are responsible for the highest share of emissions of CO₂, CH₄, and N₂O, respectively. The results of current research provided the initial justifications for the renewable energy sources such as solar and wind energy conversion, and hybrid systems. The Master Gas Collection System of Saudi Aramco can be considered as a remarkable step forward in lowering CH₄ emissions from the oil and gas fields. The integrated efforts of the public and private sectors are essential for development and implementation of appropriate strategies to reduce greenhouse gas emissions. The study provides an overview of Saudi initiatives related to policy, plan, program, and/or project towards the reduction of greenhouse gases and enhancement of carbon capture and storage.     

Status of thermal power generation in India—Perspectives on capacity,generation and carbon dioxide emissions

India’s reliance on fossil-fuel based electricity generation has aggravated the problem of high carbon dioxide (CO₂) emissions from combustion of fossil fuels, primarily coal, in the country’s energy sector. The objective of this paper is to analyze thermal power generation in India for a four-year period and determine the net generation from thermal power stations and the total and specific CO₂ emissions. The installed generating capacity, net generation and CO₂ emissions figures for the plants have been compared and large generators, large emitters, fuel types and also plant vintage have been identified. Specific emissions and dates of commissioning of plants have been taken into account for assessing whether specific plants need to be modernized. The focus is to find out areas and stations which are contributing more to the total emissions from all thermal power generating stations in the country and identify the overall trends that are emerging.     

Modeling China’s energy dilemma: conflicts among energy saving, energy security, and CO2 mitigation

This study analyzes China’s future energy scenarios stretching until 2050 under different policy portfolios of energy security (e.g., oil import dependency) and CO₂ emissions control. Four scenarios, namely, ① business as usual, ② strong oil import dependency (OID) control, ③ strong CO₂ emissions control, and ④ twofold emphasis on OID and CO₂ emissions control, are designed. The results reveal the existence of conflicts among China’s multiple objectives, particularly energy saving, energy security, and CO₂ mitigation. Based on the analysis, an improvement in China’s efficiency in fossil energy conversion and the promotion of the utilization of non-fossil energy such as nuclear, wind, and hydro energy are recommended. The over-development of coal-derived fuels should also be avoided because of incremental coal consumption and CO₂ emissions. Furthermore, research on and development of carbon capture and storage technologies should be promoted, while the energy efficiency loss caused by integrating these technologies into energy systems should be reduced in view of the high possibility of stricter standards for CO₂ emissions in the future.     

Scaling up carbon dioxide capture and storage: From megatons to gigatons

Carbon dioxide (CO₂) capture and storage (CCS) is the only technology that can reduce CO₂ emissions substantially while allowing fossil fuels to meet the world's pressing energy needs. Even though the technological components of CCS—separation of CO₂ from emissions, transport, and secure storage—are all in use somewhere in the economy, they do not currently function together in the manner required for large-scale CO₂ reduction. The challenge for CCS to be considered commercial is to integrate and scale up these components. Significant challenges remain in growing CCS from the megaton level where it is today to the gigaton level where it needs to be to help mitigate global climate change. These challenges, none of which are showstoppers, include lowering costs, developing needed infrastructure, reducing subsurface uncertainty, and addressing legal and regulatory issues. Progress will require a series of demonstration projects worldwide, an economically viable policy framework, and the evolution of a business model.     

Green hydrogen-based E-fuels (E-methane,E-methanol,E-ammonia) to support clean energy transition: A literature review

Renewable power-to-fuel (PtF) is a key technology for the transition towards fossil-free energy systems. The production of carbon neutral synthetic fuels is primarily driven by the need to decouple the energy sector from fossil fuels dependance which are the main source of environmental issues. Hydrogen (H₂) produced from water electrolysis powered by renewable electricity and direct carbon dioxide (CO₂) captured from the flue gas generated by power plants, industry, transportation, and biogas production from anaerobic digestion, are used to convert electricity into carbon-neutral synthetic fuels. These fuels function as effective energy carriers that can be stored, transported, and used in other energy sectors (transport and industry). In addition, the PtF concept is an energy transformation that is capable of providing services for the balancing of the electricity grid thanks to its adaptable operation and long-term storage capacities for renewable energy surplus. As a consequence, it helps to potentially decarbonize the energy sector by reducing the carbon footprint and GHG emissions. This paper gives an overview on recent advances of renewable PtF technology for the e-production of three main hydrogen-based synthetic fuels that could substitute fossil fuels such as power-to-methane (PtCH₄), power-to-methanol (PtCH₃OH) and power-to-ammonia (PtNH₃). The first objective is to thoroughly define in a clear manner the framework which includes the PtF technologies. Attention is given to green H₂ production by water electrolysis, carbon capture & storage (CCS), CO₂ hydrogenation, Sabatier, and Haber Bosch processes. The second objective is to gather and classify some existing projects which deal with this technology depending on the e-fuel produced (energy input, conversion process, efficiency, fuel produced, and application). Furthermore, the challenges and future prospects of achieving sustainable large-scale PtF applications are discussed.     

To sink or burn? A discussion of the potential contributions of forests to greenhouse gas balances through storing carbon or providing biofuels

Forests can affect net CO₂ emissions by increasing or decreasing the amount of stored carbon, or by supplying biofuels for power generation to substitute for fossil fuels. However, forests store the most carbon when they remain undisturbed and are allowed to grow to maturity, whereas using wood for bioenergy requires wood removal from forests, which reduces on-site carbon storage. Hence, it is difficult to manage a forest simultaneously for maximum carbon storage and supplying fuelwood.For developing optimal strategies for the use of vegetation sinks, it is necessary to consider the feedbacks via the inherent natural adjustments in the global carbon cycle. Increased atmospheric CO₂ currently provides a driving force for carbon uptake by natural carbon reservoirs, such as the world's oceans. When carbon is removed from the atmosphere and stored in biomass, it lowers the concentration gradient between the atmosphere and these other reservoirs. This reduces the subsequent inherent rate of CO₂ removal from the atmosphere. This means that transferring a quantity of CO₂ from the atmosphere to a biomass pool lowers the atmospheric concentration the most immediately after the initial removal, but subsequently, the atmospheric concentration trends back towards the values without biospheric removal.The optimal timing for the use of vegetation sinks therefore depends on a number of factors: the length of time over which forest growth can be maintained, whether biomass is used for energy generation and on the nature of the most detrimental aspects of climate-change impacts. Climate-change impacts related to the instantaneous effect of temperature are mitigated less by vegetation sinks than impacts that act via the cumulative effect of increased temperature. It also means that short-term carbon storage in temporary sinks is not generally beneficial in mitigating climate change.     

The environmental impact and risk assessment of CO2 capture, transport and storage - An evaluation of the knowledge base

In this study, we identify and characterize known and new environmental consequences associated with CO₂ capture from power plants, transport by pipeline and storage in geological formations. We have reviewed (analogous) environmental impact assessment procedures and scientific literature on carbon capture and storage (CCS) options. Analogues include the construction of new power plants, transport of natural gas by pipelines, underground natural gas storage (UGS), natural gas production and enhanced oil recovery (EOR) projects. It is investigated whether crucial knowledge on environmental impacts is lacking that may postpone the implementation of CCS projects. This review shows that the capture of CO₂ from power plants results in a change in the environmental profile of the power plant. This change encompasses both increase and reduction of key atmospheric emissions, being: NO_x, SO₂, NH₃, particulate matter, Hg, HF and HCl. The largest trade-offs are found for the emission of NO_x and NH₃ when equipping power plants with post-combustion capture. Synergy is expected for SO₂ emissions, which are low for all power plants with CO₂ capture. An increase in water consumption ranging between 32% and 93% and an increase in waste and by-product creation with tens of kilotonnes annually is expected for a large-scale power plant (1 GW_e), but exact flows and composition are uncertain. The cross-media effects of CO₂ capture are found to be uncertain and to a large extent not quantified. For the assessment of the safety of CO₂ transport by pipeline at high pressure an important knowledge gap is the absence of validated release and dispersion models for CO₂ releases. We also highlight factors that result in some (not major) uncertainties when estimating the failure rates for CO₂ pipelines. Furthermore, uniform CO₂ exposure thresholds, detailed dose-response models and specific CO₂ pipeline regulation are absent. Most gaps in environmental information regarding the CCS chain are identified and characterized for the risk assessment of the underground, non-engineered, part of the storage activity. This uncertainty is considered to be larger for aquifers than for hydrocarbon reservoirs. Failure rates are found to be heavily based on expert opinions and the dose-response models for ecosystems or target species are not yet developed. Integration and validation of various sub-models describing fate and transport of CO₂ in various compartments of the geosphere is at an infant stage. In conclusion, it is not possible to execute a quantitative risk assessment for the non-engineered part of the storage activity with high confidence.     

Potential for reduction of CO2 emissions and a low-carbon scenario for the Brazilian industrial sector

This study discusses the potential for reducing carbon dioxide (CO₂) emissions from energy use by the Brazilian industrial sector in a low-carbon scenario over a horizon until 2030. It evaluates the main mitigation measures, the quantities of this gas avoided and the respective abatement costs. In relation to a benchmark scenario projected for 2030, the reduction of CO₂ emissions estimated here can reach 43%, by adopting energy-efficiency measures, materials recycling and cogeneration, shifting from fossil fuels to renewables or less polluting energy sources and eliminating the use of biomass from deforestation. The set of measures studied here would bring emissions reductions of nearly 1.5 billion tCO₂ over a period of 20 years (2010–2030). This would require huge investments, but the majority of them would have significant economic return and negative abatement costs. However, in many cases there would be low economic attractiveness and higher abatement costs, thus requiring more effective incentives. Brazil is already carrying out various actions toward the mitigation measures proposed here, but there are still substantial barriers to realize this potential. Therefore, a collective effort from both the public and private sectors is needed for the country to achieve this low-carbon scenario.     

CO2 chemical conversion to useful products: An engineering insight to the latest advances toward sustainability

In the fossil‐fuel‐based economies, current remedies for the CO₂ reduction from large‐scale energy consumers (e.g. power stations and cement works) mainly rely on carbon capture and storage, having three proposed generic solutions: post‐combustion capture, pre‐combustion capture, and oxy fuel combustion. All the aforementioned approaches are based on various physical and chemical phenomena including absorption, adsorption, and cryogenic capture of CO₂. The purified carbon dioxide is sent for the physical storage options afterwards, using the earth as a gigantic reservoir with unknown long‐term environmental impacts as well as possible hazards associated with that. Consequently, the ultimate solution for the CO₂ sequestration is the chemical transformation of this stable molecule to useful products such as fuels (through, for example, Fischer–Tropsch chemistry) or polymers (through successive copolymerization and chain growth). This sustainably reduces carbon emissions, taking full advantage of CO₂‐derived chemical commodities, so‐called carbon capture and conversion. Nevertheless, the surface chemistry of CO₂ reduction is a challenge due to the presence of large energy barriers, requiring noticeable catalysis. This work aims to review the most recent advances in this concept selectively (CO₂ conversion to fuels and CO₂ copolymerization) with chemical engineering approach in terms of both materials and process design. Some of the most promising studies are expanded in detail, concluding with the necessity of subsidizing more research on CO₂ conversion technologies considering the growing global concerns on carbon management. Copyright © 2013 John Wiley & Sons, Ltd.     

Hydrogen production through sorption-enhanced steam methane reforming and membrane technology: A review

With the rapid development of industry, more and more waste gases are emitted into the atmosphere. In terms of total air emissions, CO₂ is emitted in the greatest amount, accounting for 99 wt% of the total air emissions, therefore contributing to global warming, the so-called “Greenhouse Effect”. The recovery and disposal of CO₂ from flue gas is currently the object of great international interest. Most of the CO₂ comes from the combustion of fossil fuels in power generation, industrial boilers, residential and commercial heating, and transportation sectors. Consequently, in the last years’ interest in hydrogen as an energy carrier has significantly increased both for vehicle fuelling and stationary energy production from fuel cells. The benefits of a hydrogen energy policy are the reduction of the greenhouse effect, principally due to the centralization of the emission sources. Moreover, an improvement to the environmental benefits can be achieved if hydrogen is produced from renewable sources, as biomass.