Chapter 9 : CO2 Use

This report on carbon capture, use, and storage (CCUS) answers the Secretary of Energy's request for advice on the actions needed to deploy CCUS technologies at scale in the United States. The report concludes that at-scale deployment requires strong collaboration between industry and government; improved policies, financial incentives, and regulations; broad-based innovation and technology development; and increased understanding and confidence in CCUS–to create a roadmap for achieving at-scale deployment over the next 25 year

Closing carbon cycles : Evaluating the performance of multi-product CO2 utilisation and storage configurations in a refinery

Carbon capture and utilisation (CCU) has the potential to provide business cases as CO2 waste streams are turned into feedstock for the synthesis of marketable products. Although CCU could reduce fossil resource demand, its capability as a climate change mitigation option is under debate. In contrast to single-product CCU, this prospective study explores the techno-economic and environmental feasibility of novel systems that include more than one CO2 utilisation product. The combination of multi-product CCU with CO2 storage is also investigated. Two configurations have been designed, in which CO2 is captured in a refinery and converted into dimethyl ether (DME) and polyols, simultaneously (parallel configuration) or in two consecutive cycles (cascade configuration). Compared to a reference system without capture, results show that the largest direct CO2 emission reductions are achieved with CCS without utilisation (−70%) but at the expenses of higher total costs (+7%). Multi-product CCU systems show lower fossil depletion and costs than the reference without capture (−10% and −9%, respectively) because of feedstock replacement by the CO2 utilised. Combination of multi-product CCU with storage turns to be the best alternative for reduced climate change potential (−18% relative to the reference) while still been economically feasible. In addition to lower upstream emissions due to fossil feedstock replacement by utilising CO2, process direct emissions diminish owing to storage. No significant differences were found between the cascade and the parallel configurations. The extra effort to recycle CO2 in the cascade configurations is neither penalised nor rewarded

Closing carbon cycles: Evaluating the performance of multi-product CO2 utilisation and storage configurations in a refinery

Carbon capture and utilisation (CCU) has the potential to provide business cases as CO2 waste streams are turned into feedstock for the synthesis of marketable products. Although CCU could reduce fossil resource demand, its capability as a climate change mitigation option is under debate. In contrast to single-product CCU, this prospective study explores the techno-economic and environmental feasibility of novel systems that include more than one CO2 utilisation product. The combination of multi-product CCU with CO2 storage is also investigated. Two configurations have been designed, in which CO2 is captured in a refinery and converted into dimethyl ether (DME) and polyols, simultaneously (parallel configuration) or in two consecutive cycles (cascade configuration). Compared to a reference system without capture, results show that the largest direct CO2 emission reductions are achieved with CCS without utilisation (−70%) but at the expenses of higher total costs (+7%). Multi-product CCU systems show lower fossil depletion and costs than the reference without capture (−10% and −9%, respectively) because of feedstock replacement by the CO2 utilised. Combination of multi-product CCU with storage turns to be the best alternative for reduced climate change potential (−18% relative to the reference) while still been economically feasible. In addition to lower upstream emissions due to fossil feedstock replacement by utilising CO2, process direct emissions diminish owing to storage. No significant differences were found between the cascade and the parallel configurations. The extra effort to recycle CO2 in the cascade configurations is neither penalised nor rewarded

New indicator for comparing the energy performance of CO2 utilization concepts

CO2 utilization is increasingly considered a greenhouse gas abatement strategy alternatively to CO2 storage. Existing indicators that assess the performance of CO2 utilization options often provide an incomplete perspective and are unsuitable to compare different utilization options with different functionality (e.g. plastics and fuels). This study introduces a new performance indicator for CO2 utilization options: Specific Primary Energy Consumption per unit of Fossil feedstock Replaced (SPECFER). This indicator, expressed in MJ/MJ, provides a proxy for the energy efficiency of which CO2 conversion options can replace fossil feedstock required in conventional processes. Three CO2 utilization case studies (CO2 based methanol, polyols and dimethyl ether) are used to show the application and effectiveness of the SPECFER indicator. Among the case studies, only CO2 conversion into polyol appears particularly efficient (SPECFER of 0.05 MJ/MJ), while the other options are not (SPECFER of > 1 MJ/MJ). The paper shows that the SPECFER indicator adds key insights compared to conventional indicators to the effectiveness of CO2 utilization options and is a promising indicator complementary to CO2 emissions reduction or life cycle greenhouse gas reduction potential. The SPECFER thus improves the understanding of the performance of CO2 utilization and enables the possibility to distinctly compare different CO2 converting utilization technologies

Potential and challenges of low-carbon energy options : Comparative assessment of alternative fuels for the transport sector

The deployment of low-emission alternative fuels is crucial to decarbonise the transport sector. A number of alternatives like hydrogen or dimethyl ether/methanol synthesised using CO2 as feedstock for fuel production (hereafter refer to “CO2-based fuels”) have been proposed to combat climate change. However, the decarbonisation potential of CO2-based fuels is under debate because CO2 is re-emitted to the atmosphere when the fuel is combusted; and the majority of hydrogen still relies on fossil resources, which makes its prospects of being a low-carbon fuel dependent on its manufacturing process. First, this paper investigates the relative economic and environmental performance of hydrogen (produced from conventional steam methane reforming and produced via electrolysis using renewable energy), and CO2-based fuels (dimethyl ether and methanol), considering the full carbon cycle. The results reveal that hydrogen produced from steam methane reforming is the most economical option and that hydrogen produced via electrolysis using renewables has the best environmental profile. Whereas the idea of CO2-based fuels has recently gained much interest, it has for the foreseeable future rather limited practical relevance since there is no favourable combination of cost and environmental performance. This will only change in the long run and requires that CO2 is of non-fossil origin, i.e. from biomass combustion or captured from air. Second, this paper address unresolved methodological issues in the assessment of CO2-based fuels, such as the possible allocation of emissions to the different sectors involved. The outcomes indicate that implementing different allocation approaches substantially influences the carbon footprint of CO2-based fuels. To avoid allocation issues, expanding the boundaries including the entire system and is therefore recommended

Potential and challenges of low-carbon energy options: Comparative assessment of alternative fuels for the transport sector

The deployment of low-emission alternative fuels is crucial to decarbonise the transport sector. A number of alternatives like hydrogen or dimethyl ether/methanol synthesised using CO2 as feedstock for fuel production (hereafter refer to “CO2-based fuels”) have been proposed to combat climate change. However, the decarbonisation potential of CO2-based fuels is under debate because CO2 is re-emitted to the atmosphere when the fuel is combusted; and the majority of hydrogen still relies on fossil resources, which makes its prospects of being a low-carbon fuel dependent on its manufacturing process. First, this paper investigates the relative economic and environmental performance of hydrogen (produced from conventional steam methane reforming and produced via electrolysis using renewable energy), and CO2-based fuels (dimethyl ether and methanol), considering the full carbon cycle. The results reveal that hydrogen produced from steam methane reforming is the most economical option and that hydrogen produced via electrolysis using renewables has the best environmental profile. Whereas the idea of CO2-based fuels has recently gained much interest, it has for the foreseeable future rather limited practical relevance since there is no favourable combination of cost and environmental performance. This will only change in the long run and requires that CO2 is of non-fossil origin, i.e. from biomass combustion or captured from air. Second, this paper address unresolved methodological issues in the assessment of CO2-based fuels, such as the possible allocation of emissions to the different sectors involved. The outcomes indicate that implementing different allocation approaches substantially influences the carbon footprint of CO2-based fuels. To avoid allocation issues, expanding the boundaries including the entire system and is therefore recommended.Energy & Industr

Prospective techno-economic and environmental assessment of carbon capture at a refinery and CO2 utilisation in polyol synthesis

CO2 utilisation is gaining interest as a potential element towards a sustainable economy. CO2 can be used as feedstock in the synthesis of fuels, chemicals and polymers. This study presents a prospective assessment of carbon capture from a hydrogen unit at a refinery, where the CO2 is either stored, or partly stored and partly utilised for polyols production. A methodology integrating technical, economic and environmental models with uncertainty analysis is used to assess the performance of carbon capture and storage or utilisation at the refinery. Results show that only 10% of the CO2 captured from an industrial hydrogen unit can be utilised in a commercial-scale polyol plant. This option has limited potential for large scale CO2 mitigation from industrial sources. However, CO2 capture from a hydrogen unit and its utilisation for the synthesis of polyols provides an interesting alternative from an economic perspective. The costs of CO2-based polyol are estimated at 1200 €/t polyol, 16% lower than those of conventional polyol. Furthermore, the costs of storing the remaining CO2 are offset by the benefits of cheaper polyol production. Therefore, the combination of CO2 capture and partial utilisation provides an improved business case over capture and storage alone. The environmental assessment shows that the climate change potential of this CO2 utilisation system is 23% lower compared to a reference case in which no CO2 is captured at the refinery. Five other environmental impact categories included in this study present slightly better performance for the utilisation case than for the reference case

Prospective techno-economic and environmental assessment of carbon capture at a refinery and CO₂ utilisation in polyol synthesis

<p>CO₂ utilisation is gaining interest as a potential element towards a sustainable economy. CO₂ can be used as feedstock in the synthesis of fuels, chemicals and polymers. This study presents a prospective assessment of carbon capture from a hydrogen unit at a refinery, where the CO₂ is either stored, or partly stored and partly utilised for polyols production. A methodology integrating technical, economic and environmental models with uncertainty analysis is used to assess the performance of carbon capture and storage or utilisation at the refinery. Results show that only 10% of the CO₂ captured from an industrial hydrogen unit can be utilised in a commercial-scale polyol plant. This option has limited potential for large scale CO₂ mitigation from industrial sources. However, CO₂ capture from a hydrogen unit and its utilisation for the synthesis of polyols provides an interesting alternative from an economic perspective. The costs of CO₂-based polyol are estimated at 1200 €/t polyol, 16% lower than those of conventional polyol. Furthermore, the costs of storing the remaining CO₂ are offset by the benefits of cheaper polyol production. Therefore, the combination of CO₂ capture and partial utilisation provides an improved business case over capture and storage alone. The environmental assessment shows that the climate change potential of this CO₂ utilisation system is 23% lower compared to a reference case in which no CO₂ is captured at the refinery. Five other environmental impact categories included in this study present slightly better performance for the utilisation case than for the reference case.</p