Carbon Capture, Utilisation, and Storage (CCUS) and its methodological challenges in LCA
Carbon Capture, Use and Storage
WeLOOP collaborated with CyVi and ScoreLCA on a project focusing on carbon capture techniques and its utilisation or storage (Carbon Capture, Use and Storage), as well as the methodological challenges these techniques pose in Life Cycle Assessment (LCA), both for policymakers and for companies and LCA practitioners.
Interviews were conducted with 10 experts on CCUS from various countries and sectors (industry, research, public institutions…) to gain a comprehensive understanding of CCUS as it is practised today.
What is CCUS?
CCUS refers to the set of techniques that prevent CO2 emissions or remove CO2 from the atmosphere, followed by the utilisation or storage of carbon in various forms. CCUS will be essential to achieving carbon neutrality. After maximising the reduction of greenhouse gas emissions, residual emissions will need to be stored.
Only natural capture is currently used on a large scale through afforestation and reforestation, but the current global trend is towards deforestation. This trend still needs to be reversed to achieve a net sink effect.
Many barriers still need to be overcome before the large-scale implementation of CCUS technologies, but it is important to start considering their deployment now, as solutions already exist.
Missions for ScoreLCA
This is a pioneering effort, as these technologies are still not widely available on the market, and LCA practitioners lack experience in this area. LCA is especially crucial in this field because studies often focus solely on greenhouse gas (GHG) emissions, increasing the risk of impact transfer to other categories (e.g., mineral resource use, water use, ecotoxicity).
We have conducted a state-of-the-art review of the available solutions currently, from capture to storage or utilisation of CO2, and developed a classification system. Capture is distinguished into two categories.
- Natural capture: It does not require energy input and generates complex molecules, such as cellulose, for example.
- Technological capture: It requires an energy input and produces CO2 in a pure form.
The diagram above presents the summary of our work on the classification of CCU/S technologies, with the storage timelines for the different outcomes of carbon.
They cover all potential applications or forms in which carbon is stored (for example, the "living biomass" category includes annual plants and trees that can live for over 100 years). The gradients indicate the potential variability in storage duration.
Methodological challenges
The major challenges for the LCA of CCU/S are the valuation of storage temporality and the allocation of impacts between the actors capturing CO2 and those using it.
How can wood wool, which stores wood for 50 years, be rewarded when wood energy releases CO2 directly? Who should benefit from the credits associated with the use of CO2? Other questions remain, particularly regarding how to handle the status of carbon and how to classify the flows.
Handling multifunctionality
We have proposed a new hybrid method to allocate impacts between the producer and the user of CO2.
The proposed "Offer/Demand" hybrid method aims to be fair, easy to implement, and designed to encourage the adoption of the most effective solutions, while freeing itself from dependence on fossil fuels.
The impacts and benefits of capture are calculated through a system boundary extension with the substitution of the process generating CO2, and then they are allocated between the main product and CO2 based on a politically determined allocation factor to align with the carbon neutrality agenda.
Temporality
We compared the calculation results between different products using four methodologies and standards: ILCD, PEF, EN15804 A2, and ISO14040/14044.
The case studies were conducted on second-generation biodiesel (produced from wood and straw), wood pellets, wood wool (with two possible end-of-life scenarios, incineration or landfill), to compare the storage associated with different uses, and finally, on various types of cement to compare the geological storage of the same product.
Three different types of cement were used: CEM I cement, modelled in Ecoinvent, and two cements where carbon is captured and then stored. The difference between the two is that one uses Solid Recovered Fuels (SRF, biogenic carbon status), while the other uses a fossil fuel for clinker production.
Pellets serve as the reference here since there is no storage effect. ILCD encourages the longest possible storage, with landfill valorisation. For PEF and EN15804, there is almost no variation between the different products, as storage is not considered. ISO14040 allows for the consideration of permanent storage, without dynamic effects, which leads to a result equal to that of pellets for incinerated wood wool, and negative for landfill.
For ILCD, the results for fossil cement and SRF are equal because SRF has waste status and therefore no benefit associated with captured biogenic carbon. For PEF, the use of SRF is valued, but the total impact is higher than that of CEM I because storage is not allowed, and thus the additional effort required for capture is not rewarded. EN15804 allows for the storage of fossil carbon but not biogenic carbon, leading to higher impacts for CSR cement. For ISO, the results are equal to ILCD because there is no effect of temporary use.
The need for harmonisation between methodologies, identified at the level of the European Commission, is crucial for CCU/S studies, and it will become increasingly important.
The work carried out for ScoreLCA has provided us with a unique expertise in conducting CCU/S studies.
Learn more
Would you like to learn more about our work on CCU/S?
Send us an email: info@weloop.org