The conclusions of these studies are thus qualitatively very different: CO 2-based methanol could either even be a carbon sink over its life cycle or emits much more CO 2 than fossil-based methanol. For example, for CO 2-based methanol, LCA studies in the literature reported cradle-to-gate carbon footprints between −1.7 and +9.7 kg of CO 2, eq per kg of methanol. In particular, the supply of electricity or hydrogen has been shown to vary largely between various LCA studies such that conclusions even change qualitatively ( Artz et al., 2018). Even if functional units and system boundaries are comparable, LCA results often show significant variation for identical technologies, because different processes are selected for the production of feedstocks or utilities. As a result, LCA studies on CCU technologies are often not comparable, e.g., because of differences in functional units, i.e., the relative basis for which environmental impacts are assessed, or system boundaries.
#HOW TO GET NAVIGATION OPTIONS IN OPENLCA ISO#
A method for environmental assessment with broad acceptance among academic and industrial practitioners is Life Cycle Assessment (LCA).Įven though, LCA has been standardized in ISO 14040/14044 ( European Committee for Standardisation, 2009, 2018), the standard leaves methodological choices, e.g., for selecting the functional unit, system boundaries, background processes, or environmental impact assessment methods ( European Commission, 2018). Thus, whether CCU technologies reduce environmental impacts can only be concluded from a detailed environmental assessment. The production of these high energetic co-reactants, however, is associated with high environmental impacts. However, the reduction of environmental impacts cannot be taken for granted: high energetic co-reactants such as hydrogen ( Sternberg and Bardow, 2016) or epoxide are often needed to activate the chemically inert CO 2 ( von der Assen and Bardow, 2014). By converting CO 2 into valuable products, CCU aims to improve economic benefits while also reducing environmental impacts such as the impact on climate change or fossil resource depletion ( Al-Mamoori et al., 2017). Consequently, research funds and time can be allocated more efficiently for the development of technologies for climate change mitigation and negative emissions.Ĭarbon capture and utilization (CCU) involves the capture of the greenhouse gas CO 2 from point sources or ambient air and its subsequent conversion into valuable products ( Baena-Moreno et al., 2019).
Improved comparability should help to strengthen knowledge-based decision-making. Transparency is increased through interpretation and reporting guidance.
The presented guidelines should improve comparability of LCA studies through clear methodological guidance and predefined assumptions on feedstock and utilities. The guideline has been development in a collaborative process involving over 40 experts and builds upon existing LCA standards and guidelines. In this work, we therefore present a comprehensive guideline for LCA of CCU technologies. Applying LCA to CCU technologies leads to further specific methodological issues, e.g., due to the double role of CO 2 as emission and feedstock. The resulting LCA studies show large variability which limits their value for decision support. However, even though LCA is a standardized method, current LCA practice differs widely in methodological choices.
These potential benefits need to be assessed by the holistic method of Life Cycle Assessment (LCA) that accounts for multiple environmental impact categories over the entire life cycle of products or services.