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Direct air capture (DAC) technology plays a crucial role in mitigating the effects of global warming by capturing carbon dioxide (CO 2) directly from the atmosphere. A significant technical challenge for DAC is its high thermal energy consumption, which results in an unacceptable overall cost (600 $ t CO 2 – 1). The combination of a high-temperature heat pump (HTHP) and DAC system offers a substantial reduction in thermal energy consumption, decreased reliance on renewable energy sources, and enhanced DAC system flexibility. This study presents three distinct thermal integration strategies that combine an HTHP with solid adsorbent-based DAC and verifies their effectiveness in reducing energy consumption and CO 2 emissions compared to a traditional DAC system. Among them, the deeply integrated DAC-HTHP system (I-DAC) exploits low-grade adsorption heat and waste heat, providing direct heating and cooling energy to the DAC system via refrigerant condensation and evaporation processes. Simulation results indicate that the I-DAC system achieves an extremely low operating energy consumption of 2.77 GJ t CO 2 – 1 , representing a 69.5% reduction than traditional DAC under the same conditions. Consequently, the I-DAC offers a cost-effective (32.0–46.2 $ t CO 2 – 1) negative emission solution. We also demonstrate that the I-DAC is promising for wide application in cities to recycle waste heat and remove CO 2 from the air. The comprehensive implementation of the I-DAC in 105 cities could yield a net annual productivity of 980 MtCO 2. • Proposed a deeply thermal integrated DAC system (I-DAC) with waste heat recovery heat pump. • I-DAC achieved a 69.5% reduction in specific energy consumption compared to base-DAC. • I-DAC offers a cost-effective and scalable negative emission solution for climate change mitigation. • Successful implementation of I-DAC in 105 cities could yield a net annual capture capacity of 980 MtCO 2 by 2050. • Highlights the potential of I-DAC to recycle waste heat and remove CO 2 from the air, with policy implications [ABSTRACT FROM AUTHOR]

Achieving net zero emissions is a crucial challenge in the global climate change policy. It requires a substantial reduction in unabated fossil fuel use, the deployment of renewable energy sources, and the development of carbon capture, utilisation and storage technologies. The aim of this study was to investigate and compare two CO 2 capture retrofits for natural gas combined cycle (NGCC). First one, amine absorption, is already mature and characterised as commercial technology, whereas second one, calcium looping is a promising method but still under pilot studies. Energy required for capture process yields net efficiency penalty, which in conducted research totalled 8.4% points for amine unit and 7.4–15.5% points in calcium-looping units. The economic evaluation was performed to analyse the impact of both concepts on their profitability. Moreover, the climate change mitigation potential was assessed and indicated that carbon capture can lower the emissivity of a conventional power plant by 82–87% or even contribute to achieving negative emissions when biofuels are used. Carbon dioxide capture is one of the key elements of ongoing energy transition and its integration with NGCC power units could be determined as essential for maintaining energy security with net zero emissions. • The work provides the comparison between amine scrubbing and calcium-looping CO 2 capture for Natural Gas Combined Cycle. • CCS retrofit causes a net efficiency penalty between 7.4 and 15.5%p for analysed configurations. • Calcium-looping retrofit placed after the gas turbine yield lower SPECCA and higher unit power due to new steam cycle. • Using biogas as a feedstock to calciner of calcium-looping unit leads to negative CO 2 emissions. • Amine scrubbing retrofit has much lower CAPEX and OPEX than CaL units, yet they reach higher ΔNPV within 25 years. [ABSTRACT FROM AUTHOR]

Abstract The Paris Agreement brings countries together in a combined effort to combat climate change and its effects. A key target is the reduction of energy related greenhouse gas emissions. Providing biogas from biomass is one option to provide renewable and less carbon intensive fuels. When upgraded to biomethane it may be a substitute for natural gas and thus may have many application pathways. Recognising this potential many European countries installed governmental support programmes to stimulate market growth over the last decade. However, most of the installed schemes in Europe are time-limited. Besides being time-limited most of the schemes include a degression of compensation over time, resulting in many having limited success over longer time frames. This study questions the feasibility of near-term business cases for biomethane plants and analyses options for making them less dependent on governmental support programmes. Currently a market potential is seen in the utilization of process carbon dioxide in carbon capture and utilization or carbon capture and storage pathways, because it is a widely available side product from biogas upgrading. Therefore, we examined three business cases for its utilization in across sectors. To answer the research question we use a previously developed biomethane market simulation model and added an extension for new business cases. Results indicate that there are specific business options in the field of 2160 m³ h−1 to 20,840 m³ h−1 that are economical feasible under certain circumstances. Highlights • Use of CO2 in the chemical industry was not economically feasible even under optimistic conditions. • Utilization of carbon dioxide from biogas upgrading offers new business options. • Production of bio-LNG is a promising business option. [ABSTRACT FROM AUTHOR]

In addition to carbon capture and storage, efforts are also being focussed on using captured CO 2 , both directly as a working fluid and in chemical conversion processes, as a key strategy for mitigating climate change and achieving resource efficiency. These processes require large amounts of energy, which should come from sustainable and, ideally, renewable sources. A strong value chain is required to support the production of valuable products from CO 2 . A value chain is a network of technologies and infrastructures (such as conversion, transportation, storage) along with its associated activities (such as sourcing raw materials, processing, logistics, inventory management, waste management) required to convert low-value resources to high-value products and energy services, and deliver them to customers. A CO 2 value chain involves production of CO 2 (involving capture and purification), technologies that convert CO 2 and other materials into valuable products, sourcing of low-carbon energy to drive all of the transformation processes required to convert CO 2 to products (including production of hydrogen, syngas, methane etc.), transport of energy and materials to where they are needed, managing inventory levels of resources, and delivering the products to customers, all in order to create value (economic, environmental, social etc.). Technologies underpinning future CO 2 value chains were examined. CO 2 conversion technologies, such as urea production, Sabatier synthesis, Fischer-Tropsch synthesis, hydrogenation to methanol, dry reforming, hydrogenation to formic acid and electrochemical reduction, were assessed and compared based on key performance indicators such as: CAPEX, OPEX, electricity consumption, TRL, product price, net CO 2 consumption etc. Technologies for transport and storage of key resources are also discussed. This work lays the foundation for a comprehensive whole-system value chain analysis, modelling and optimisation. [ABSTRACT FROM AUTHOR]

With the growing literature related to climate change mitigation measures and policy interventions, a systematic review of the application of computable general equilibrium (CGE) model is inevitable. Therefore, this article aims to characterise the relevant studies, define a comparative framework to identify the current state-of-the-art and the gaps in applied general equilibrium models. Firstly, the systematic review found a total of 301 research articles from Scopus and Web of Science databases and finally analysed 154 articles based on inclusion and exclusion criteria from 67 refereed journals. The review analysis found that application of CGE model is very vital in addressing climate change mitigation issues at the national, regional and global levels. However, China attracted the most substantial research interests followed by the USA, India and Australia, among others, which are in line with their share of greenhouse gas emissions in the world. Most of the research themes focus on the carbon tax, emission reduction target, emission trading, renewable energy, energy efficiency, and carbon capture and storage as primary drivers of low carbon economy. Nevertheless, there is a trend of employing more static CGE model compared to the dynamic CGE, although application of the latter has a limitation of providing right inputs to the macroeconomic policy. Finally, research directions and gaps envision other complementary models such as dynamic stochastic general equilibrium (DSGE) and agent-based model (ABM) for proper policy interventions. [ABSTRACT FROM AUTHOR]

Renewable energy can play an important role in India's climate change mitigation, as India has great potential for renewables, especially solar and wind. This paper analyses the role of renewables to meet India's possible 2050 climate change mitigation targets using a multi-region global energy system model called TIAM-UCL, where India is explicitly represented as a separate region. TIAM-UCL is a cost optimisation model. The climate policy is applied to all regions in the model based on equal per capita emissions of 1.3 tCO 2 by 2050. Analysis shows that renewable energy can play an important role to decarbonise the economy, especially the power sector. Two low-carbon scenarios are explored, the first allowing for carbon capture and storage (CCS) technology deployment and the second excluding this technology. In the first low-carbon scenario (LC1), the most critical renewable energy technologies in the power sector are biomass with CCS, solar and wind. In the second low-carbon scenario (LC2), without CCS, there is an even greater role for solar and wind. Over the whole Indian economy, by 2050 renewables contribute 57% of the total CO 2 reductions in LC1 (relative to a reference scenario with no CO 2 target) and 63% of the CO 2 reductions in LC2. [ABSTRACT FROM AUTHOR]

Abstract: Biomass from the forest sector can be an important source of renewable energy and can contribute to climate change mitigation and bioenergy development. However, the removal of biomass from forests has significant impacts on the forest ecosystem. For instance, it modifies soil litter which is particularly important to preserve soil characteristics and to sustain a diversity of organisms. Our aim is to analyze alternatives of sustainable forest management and compare how they perform in terms of carbon savings in order to assess the role of the sector in a regional emission reduction plan. The analysis is performed applying CO2FIX, a well-known carbon accounting model to the forests of the Italian region of Emilia-Romagna. The behavior of the most important forest macro-categories is investigated under common management alternatives: no harvest activities, maintenance of a constant stock, different rotation lengths, and maximization of harvested biomass. We evaluate their impact at landscape level on the regional carbon budget, thus estimating the maximum potential contribution from the forest sector. [Copyright &y& Elsevier]

Abstract: Gases like CH4, CO2 and H2 may play a key role in establishing a sustainable energy system: CH4 is the least carbon-intensive fossil energy resource; CO2 capture and storage can significantly reduce the climate footprint of especially fossil-based electricity generation; and the use of H2 as energy carrier could enable carbon-free automotive transportation. Yet the construction of large pipeline infrastructures usually constitutes a major and time-consuming undertaking, because of safety and environmental issues, legal and (geo)political siting arguments, technically un-trivial installation processes, and/or high investment cost requirements. In this article we focus on the latter and present an overview of both the total costs and cost components of the distribution of these three gases via pipelines. Possible intricacies and external factors that strongly influence these costs, like the choice of location and terrain, are also included in our analysis. Our distribution cost breakdown estimates are based on transportation data for CH4, which we adjust for CO2 and H2 in order to account for the specific additional characteristics of these two gases. The overall trend is that pipeline construction is no longer subject to significant cost reductions. For the purpose of designing energy and climate policy we therefore know in principle with reasonable certainty what the minimum distribution cost components of future energy systems are that rely on pipelining these gases. We describe the reasons why we observe limited learning-by-doing and explain why negligible construction cost reductions for future CH4, CO2 and H2 pipeline projects can be expected. Cost data of individual pipeline projects may strongly deviate from the global average because of national or regional effects related to the type of terrain, but also to varying costs of labor and fluctuating market prices of components like steel. [Copyright &y& Elsevier]

Abstract: A means of assessing the relative impact of different renewable energy technologies on global warming has been developed. All power plants emit thermal energy to the atmosphere. Fossil fuel power plants also emit CO2 which accumulates in the atmosphere and provides an indirect increase in global warming via the greenhouse effect. A fossil fuel power plant may operate for some time before the global warming due to its CO2 emission exceeds the warming due to its direct heat emission. When a renewable energy power plant is deployed instead of a fossil fuel power plant there may be a significant time delay before the direct global warming effect is less than the combined direct and indirect global warming effect from an equivalent output coal fired plant – the “business as usual” case. Simple expressions are derived to calculate global temperature change as a function of ground reflectance and conversion efficiency for various types of fossil fuelled and renewable energy power plants. These expressions are used to assess the global warming mitigation potential of some proposed Australian renewable energy projects. The application of the expressions is extended to evaluate the deployment in Australia of current and new geo-engineering and carbon sequestration solutions to mitigate global warming. Principal findings are that warming mitigation depends strongly on the solar to electric conversion efficiency of renewable technologies, geo-engineering projects may offer more economic mitigation than renewable energy projects and the mitigation potential of reforestation projects depends strongly on the location of the projects. [ABSTRACT FROM AUTHOR]

Abstract: The present study aims at shedding light into the interaction of fluctuating renewables and the operational flexibility of postcombustion capture plants in the framework of a long-term model. We developed a model of the electricity sector taking into account both long-term investment time scales to represent plant fleet development under economic and climate constraints as well as short time scales to consider fluctuations of demand and renewable energy sources. The LIMES model allows us to determine the respective roles of renewables and CCS in climate change mitigation efforts within the electricity sector. Furthermore, we assess the influence of natural gas prices on fuel choice and investigate the shares of competing CCS approaches in the technology mix. We find that the optimal technology mix includes large shares of renewables and simultaneously different competing CCS technologies, depending on emission constraints and fuel prices. [Copyright &y& Elsevier]