Carbon capture and storage (CCUS) and its methodological challenges in LCA
Carbon Capture, Use and Storage
WeLOOP has completed a project with CyVi and ScoreLCA on the carbon capture techniques and its use or storage (Carbon Capture, Use and Storage) and methodological challenges they pose in Life Cycle Assessment (LCA), for politics and for companies and LCA practitioners.
Some interviews were carried out with 10 experts on CCUS, from different countries and different sectors (industry, research, public institutions...) to get an overview of CCUS in practice today.
What are the CCUS?
The CCUS are all techniques for avoiding emissions of CO2 or remove it from the atmosphere, and then use or store the carbon in various forms. CCUS will be needed to achieve the carbon neutrality. Once GHG emissions have been reduced as much as possible, residual emissions need to be stored.
Only the natural capture is used on a large scale today via afforestation and reforestation, but the current worldwide trend is deforestation. The trend has yet to be reversed to speak of a sink effect.
Many brakes have yet to be released before large-scale deployment of CCUS technologies, but it's important to start thinking now about their implementation, and solutions already exist.
Missions for ScoreLCA
This is a pioneering work, these technologies are still not widely available on the market, and LCA practitioners do not yet have any experience. LCA is all the more necessary in this field as studies generally focus on the greenhouse gas emissions (GHG), with an increased risk of impact transfer to other categories (use of mineral resources, water, ecotoxicity, etc.).
We have made a state-of-the-art of available solutions from capture to storage or utilisation of CO2and developed a nomenclature. The capture is divided into two categories.
- Natural capture : it requires no energy input, and generates complex molecules such as cellulose.
- Captage technologique : it requires energy input and produces CO2 in its pure form.
The schema above summarizes our work on the classification of CCUS/S technologies, with storage timeframes of the different carbon futures.
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 more than 100 years). The gradations indicate the potential variability of storage life.
Methodological challenges
The main difficulties for LCA of UCC/S are the valorisation of storage time and the impact distribution between players capturing CO2 and those using it.
How can you reward a wood wool product that stores wood for 50 years when wood energy directly releases CO2 ? Who should benefit from the credits associated with the utilisation of CO2 ? Other questions remain, such as how to deal with the status of carbon, and how to classify flows.
Handling multifunctionality
We have proposed a new hybrid method for allocate impacts between the producers and users of CO2.
The hybrid supply/demand method proposed is intended to be fair and simple to implement, and to encourage the implementation of the most efficient solutions possible, freeing us from dependence on fossil fuels.
The impacts and benefits of capture are calculated using an extending system boundaries with substitution of the process generating the CO2, then they are divided between the main product and CO2 based on a allocation factor set at political level to comply 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 carried out on 2nd generation (produced from wood and straw), wood pellets, wood wool (with two possible end-of-life, incinerated or landfilled) for compare storage associated with different uses and finally on different types of cement to compare the geological storage of the same product.
Three different cements were used CEM I cement, modelled in Ecoinvent, and two cements whose 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 fossil fuels to produce clinker.
The pellets are used as a reference here, as there is no storage effect. ILCD encourages storage for as long as possible, with recovery from landfill. For PEF et EN15804, there is almost no variation between the different products, as storage is not taken into account. ISO14040 allows permanent storage to be taken into account, without any dynamic effect, which results in a result equal to pellets for incinerated wood wool, and negative for landfill.
To ILCD, the results for fossil cement and CSR are equal, since CSR has the status of waste, and therefore has no benefit associated with the biogenic carbon captured. For PEF, CSR is used, but the total impact is greater than that of CEM I, since storage is not authorized, and so the extra effort required for capture is not rewarded. EN15804 allows the storage of fossil carbon, but not biogenic carbon, resulting in higher impacts for CSR cement. For ISO, the results are equal to ILCD, as there is no temporary use effect.
The need for harmonization between methodologies, identified at the Commission Européennelevel, is important for CCU/S studies, and will become increasingly so.
The work we have done for ScoreLCA has given us an unique expertise in CCU/S studies.
Learn more
You would like to find out more about our work for the CCU/S?
Send us an e-mail: info@weloop.org