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.

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Calcium looping CO₂ capture is a promising technology to reduce CO₂ emissions from cement production. Coal has been seen as a logical choice of fuel to drive the calcium looping process as coal is already the primary fuel used to produce cement. This study assesses the impact of using different fuels, namely coal, natural gas, woody biomass and a fuel mix (50% coal, 25% biomass and 25% animal meal), on the environmental performance of tail-end calcium looping applied to the clinker production at a cement plant in North-western Europe. Process modelling was applied to determine the impact of the different fuels on the mass and energy balance of the process which were subsequently used to carry out a life cycle assessment to evaluate the environmental performance of the different systems. Using natural gas, biomass or a fuel mix instead of coal in a tail-end calcium looping process can improve the efficiency of the process, as it decreases fuel, limestone and electricity consumption. Consequently, while coal-fired calcium looping can reduce the global warming potential (life cycle CO₂ emissions) of clinker production by 75%, the use of natural gas further decreases these emissions (reduction of 86%) and biomass use could results in an almost carbon neutral (reduction of 95% in the fuel mix case) or net negative process (−104% reduction in the biomass case). Furthermore, replacing coal with natural gas or biomass reduces most other environmental impact categories as well, mostly due to avoided impacts from coal production. The level of improvement strongly depends on whether spent sorbent can be utilized in clinker production, and to what extent sequestered biogenic CO₂ can reduce global warming potential. Overall, the results illustrate the potential of using alternative fuels to improve the environmental performance of tail-end calcium looping in the cement industry.

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Calcium looping CO2 capture is a promising technology to reduce CO2 emissions from cement production. Coal is generally considered the fuel used to drive the calcium looping process as coal is already used as feedstock for cement production. This study assesses the impact of different fuels (coal, natural gas and woody biomass) on the technological and environmental performance of post-combustion calcium looping at a cement plant in North-western Europe. Process modelling is used to determine the impact of the different fuels on the mass and energy balance of the process. Life cycle assessment is carried out to evaluate the environmental performance of the different systems. Results indicate that firing natural gas or biomass instead of coal in an add-on calcium looping process can improve the efficiency of the process, as it decreases the fuel, limestone and electricity consumption. Consequently, while coal fired calcium looping can reduce life cycle climate change potential by 92%, the use of natural gas or biomass can make the process carbon neutral (reduction of 100%) or negative (-169%), respectively. Further research is required to complete the environmental perspective of using alternative fuels, but these results already illustrate a potential low-hanging fruit to improve the environmental performance of post combustion calcium looping in the cement industry.@en

CO 2 utilization is increasingly considered a greenhouse gas abatement strategy alternatively to CO 2 storage. Existing indicators that assess the performance of CO 2 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 CO 2 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 CO 2 conversion options can replace fossil feedstock required in conventional processes. Three CO 2 utilization case studies (CO 2 based methanol, polyols and dimethyl ether) are used to show the application and effectiveness of the SPECFER indicator. Among the case studies, only CO 2 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 conventi onal indicators to the effectiveness of CO 2 utilization options and is a promising indicator complementary to CO 2 emissions reduction or life cycle greenhouse gas reduction potential. The SPECFER thus improves the understanding of the performance of CO 2 utilization and enables the possibility to distinctly compare different CO 2 converting utilization technologies.@en

Equipping power plants with carbon capture technologies increases the (cooling) water demand of these plants. This study explores the potential impact of such increase in water demand on the regional water scarcity in Europe. A database with key characteristics of 458 of the largest European power plants is developed and the water use of these power plants is estimated. The water use of the power plants are spatially linked to current water stress index levels. Several prospective scenarios are developed accounting for variations in the future configuration of Europe's electricity generation and different penetration rates of carbon capture technology. Regional water stress index levels are calculated to compare the potential impact of applying carbon capture technologies on the water stress. Preliminary results indicate that the increase of water use due to carbon capture technology is partly expected to be compensated by the deployment of more efficient energy conversion methods which require less cooling water. As such, no significant increase in water stress is expected in the short term (2030), as the carbon capture penetration level in European power plants is expected to be quite low. However, on the long term (2050), large scale instalment of carbon capture technologies in power plants might significantly increase the water stress throughout Europe.

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