Carbon neutrality is part of every political agenda. But what concrete solutions can help us achieve it? The acronym CDR for Carbon Dioxide Removal refers to a whole range of possible technologies (CCS, CCU, DAC, BECC) to actively reduce emissions and complement actions taken downstream as well as natural solutions. To clarify these concepts, we’ve interviewed Tilly Undi. Author of a doctoral thesis on CO₂ capture and storage, she began her international engineering career in the energy sector, then specialized in the development of renewable and low-carbon activities. Today, she is an expert in the energy sector, transition, and carbon neutrality.
The European Scientist: What are the carbon dioxide removal (CDR) solutions, and what role can they play in achieving carbon neutrality?
Tilly Undi: To achieve carbon neutrality, it is essential to review our production and consumption systems by systematically integrating environmental and social impacts. In terms of greenhouse gases, this involves implementing measures to avoid and reduce emissions, downstream of which there could still be “residual” emissions to be dealt with. For example, CO₂ would still be present in steel and cement plants streams, even after the implementation of efficiency measures and replacement of fossil fuels with electricity from renewable energies. Due to the difficulty of eliminating emissions in these sectors, as in aviation and maritime transportation, they are referred to as “hard-to-abate industries”. In addition, in order to tackle climate change, it is necessary to act on the reduction of past emissions that have been building up and keep accumulating in the atmosphere, at an accelerated pace since the industrial era.
Carbon dioxide removal (CDR) technologies are particularly necessary for eliminating residual or historical emissions.
These include natural solutions, such as the creation, preservation, and restoration of natural carbon sinks (forests, mangroves, soils, peatlands, ecosystems), as well as enhanced ocean alkalinization, enhanced weathering of rocks and biochar production through plant pyrolysis.
Given the limited and increasingly reduced natural potential due to climate change and consequent weakening of natural balances, technological solutions have also been developed:
- Carbon capture and sequestration (CCS), which involves capturing CO₂ before it reaches the atmosphere and permanently sequestering it in onshore or offshore geological reservoirs;
- Carbon capture and utilization (CCU), which involves reusing captured CO₂ in a circular way;
- Direct air capture (DAC), which aims at reducing the CO₂ present in the atmosphere by creating negative emissions to offset residual and historical emissions;
- Bioenergy with carbon capture and storage (BECCS), which recovers CO₂ from biomass combustion, making the process emissions-negative when associated with permanent geological sequestration (BECCS).
TES: What are the main technological limitations?
T.U.: For natural solutions, it is difficult to quantify and monitor the CO₂ sequestration potential. As a consequence, it can be challenging to assess and verify its effective contribution to climate objectives. For example, concerning trees’ mitigation in terms of CO2 impact, it can vary depending on the type, age, health, climatic conditions, and, generally, environmental factors. Currently, there is no common methodology that allows for empirical measurement of the amount CO₂ that is sequestered, the efficiency of its capture and duration over time. Therefore, a larger deployment of nature-based solutions depends on improving our understanding of sequestration mechanisms and how they interact with our changing environment.
On the other side, technological solutions still require significant energy, particularly for DAC. For this reason, this solution has been deployed in areas where renewable energies are abundant (such as Iceland, thanks to geothermal energy) or in countries that have implemented subsidies to mitigate the associatedsignificant costs (such as the USA, thanks to the Inflation Reduction Act). Costs remain a barrier for the deployment of CCU and CCS as well, especially as long as there is not a CO₂ price high enough to justify investments in this sector, or a financial valorization (premium) for products characterized by a reduced carbon footprint.
Economic models of projects that are currently under development are based on subsidized environments, as an alternative to a carbon tax, and often aim at decarbonizing industries that would otherwise be penalized, under the Paris Agreement, due to their residual emissions. Finally, all solutions consisting in permanently storing the CO₂ can be deployed if geological reservoirs, that prove to be suitable for this scope, are identified. Companies involved in sequestration projects are required to guarantee proper injection, dissolution (or mineralization) of CO₂, as well as no migration and leakage of the greenhouse gas, over several decades, based on a monitoring, reporting, and verification program agreed with the authorities.
TES: What are the current volumes injected worldwide, and what are the targets to achieve carbon neutrality by 2050?
T.U.: In its 2022 report, the IPCC indicates that, to limit global warming below 2°C, 5 to 16 billion tonnes of CO₂ per year need to be removed by the second half of the 21st century . The latest World Energy Outlook from the International Energy Agency (IEA) indicates a need for DAC and BECCS of 0.6 billion tonnes of CO₂ before 2035 and 1.7 billion tonnes of CO₂ before 2050. Additionally, the scenario that targets a 1.5°C temperature increase, assumes that approximately 10% of all bioenergy production systems will be equipped with BECCS. Regarding CCS, the IEA notes a recent increase of projects worldwide (now deployed in more than 45 countries). The number of projects has tripled in 2021 and doubled in January 2022, meaning over 100 projects have been developed since January 2022. However, only 5% of these have received financial approval. We are far from the objective of capturing 1 billion tonnes of CO₂ before 2030 and 6 billion tonnes of CO₂ per year before 2050 (90% of which are geologically sequestered). »
TES: Are there any existing or prospective CC(U)S projects in Europe today?
T.U.: As of the end of 2023, there were 101 commercial CCUS projects worldwide in operational phase, capturing 54 million tonnes of CO₂ per year. 663 projects are in the pipeline with an expected start up by 2032, capturing over 678 million tonnes of CO₂ per year, mainly in the United States and Europe and with a rapid increase in projects in the Asia Pacific region.
Northern Europe is among the pioneers of CCS. In Norway, Northern Lights is the first commercial CCS project, capitalizing on the experience gained through its earlier projects Sleipner (1996) and Snøhvit (2008). Its start-up is expected to take place in 2024, with an initial target of permanently storing its own emissions as well as CO2 from neighboring countries in the amount of 1.5 million tonnes per year (first phase) and a gradual increase to 5 or even 12 million tonnes per year (second phase) . The Netherlands has also been a forerunner. Like Norway, it is an oil and gas producer country, characterized by fields that are almost depleted and, as such,are good candidates for storing CO₂. Similarly, Denmark, with its Bifrost project, aims to become a key player in the decarbonization of European industry. Southern Europe, subject to the same regulatory constraints (and associated emissions restrictions) as the rest of Europe, is looking for suitable storage sites near its hubs (concentration of emitters) but faces more reluctance, both in terms of governmental support and in terms of societal acceptability. According to a report published in March, France could remove 76 million tonnes of CO₂ equivalent per year by 2050. Its CCUS strategy should be presented by the government before the summer, highlighting the need for development of transport and storage infrastructures by 2030 and 2050. Its final version should also integrate the concept of negative emissions. However, in November 2023, the High Council for Climate estimated that the use of BECCS and DAC “must for now be limited to its minimum necessary contribution” so that these technologies are considered “as a last resort solution to achieve carbon neutrality.”
Regarding CCU, according to CO₂ value Europe, this solution could contribute to Europe’s carbon neutrality ambition by 8% and reduce greenhouse gas emissions by at least 20%, by valorizing CO₂ for the chemical industry (11%), synthetic fuel production (7%), or integration into construction materials (2%). Several projects aim at contributing to the decarbonization of maritime transport and aviation, but the availability of low-carbon electricity, water demand, availability of minerals and non-renewable materials, as well as the lack of regulatory and economic incentives, still limit the deployment of CCU on a large scale.
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