Sabine Fuss is an economist and head of research department at the Potsdam Institute of Climate Research Impact.
To start, there are multiple ways to remove carbon dioxide (CO2) from the atmosphere, and several terms are often used: carbon dioxide removal (CDR), carbon capture utilisation and storage (CCUS), direct air capture (DAC), bioenergy combined with carbon capture and storage (BECCS), and carbon sinks. Could you briefly guide us through these?
Sabine Fuss: There are different ways in which we can manage carbon dioxide: we can capture CO2 from coal-fired power plants, for example, thereby preventing that CO2 enters the atmosphere. In this case we speak of Carbon Capture and Storage (CCS). Importantly, capturing CO2 and storing it geologically can also lead to a net removal of CO2 from the atmosphere, but only if it is biogenic CO2 (as in the case of bioenergy with CCS (BECCS), where planted biomass absorbs CO2 through photosynthesis and that CO2 is not released when the biomass is turned into bioenergy, but instead captured and stored) or atmospheric CO2, as in the case of direct air carbon capture and storage (DACCS), where CO2 gets filtered out of the ambient air by means of a chemical reaction and subsequently stored.
Similarly, using captured CO2 for the production of goods (CCUS) does not necessarily imply that CO2 has been removed from the atmosphere on a net basis: If the CO2 is not permanently bound in the product, as for example in the case of synthetic fuels, emissions may be avoided, but not removed.
Once carbon dioxide is captured or removed from the atmosphere, what happens to it next?
Sabine Fuss: After CO2 is captured, it needs to be stored. Obviously, the durability of this storage is very important. However, different methods of removing CO2 from the atmosphere have very different horizons of storage permanence: while properly selected and managed sites of geological storage are generally considered to store CO2 for thousands to millions of years, additionally grown trees may release their CO2 much sooner, if they fall victim to either deforestation or to increasing disturbances from climate change such as wildfires or pests.
While these technological approaches have the potential to reduce emissions, they are energy-intensive and depend on low-carbon energy that should not compete with other societal needs. How can these challenges be addressed?
Sabine Fuss: Scaling direct air carbon capture and storage obviously only makes sense based on a sufficiently decarbonised energy system, while bioenergy with CCS produces energy as a co-benefit of CO2 removal from the atmosphere.
It does need more land as a resource, however, as additional biomass must be grown as a feedstock, which may be in conflict with land needed for agriculture.
These examples clearly show that each method to manage or remove CO2 comes with its own trade-offs and synergies and there is no single silver bullet we can rely on. Rather, we need to explore portfolios of methods realising the required removal potentials at minimal risks. And insofar as externalities such as distributional consequences in the context of increased energy needs for direct air carbon capture and storage cannot be contained, an adequate governance architecture needs to deploy instruments compensating those affected.
What are the main barriers to scaling up technological carbon dioxide removal approaches in Europe today?
Sabine Fuss: While the emission of CO2 is being penalised by requiring facilities to surrender or buy permits for each ton emitted, the removal of CO2 from the atmosphere is currently not consistently rewarded. Appropriately incentivising removals is thus key to achieve scale, but there are also many obstacles in other domains, e.g. the legal situation of CO2 transport and storage in some EU countries, the low level of public acceptance that also differs across countries, high up-front costs in the face of investment uncertainty, etc.
What are the consequences if carbon capture and carbon dioxide removal technologies fail to scale?
Sabine Fuss: Without novel carbon dioxide removal technologies (i.e. the more novel methods of removal, often in connection with carbon capture storage), only conventional removals – such as through afforestation and reforestation – are left to compensate for residual emissions that cannot be reduced to zero quickly enough. We will also be deprived of one of our means to return from a temporary overshoot of the 1.5°C temperature limit that appears to be imminent.
Given that conventional removals are often much more vulnerable to reversal or may become less effective under climate change, this is a risky strategy, as adaptation will eventually also have its limits.
Carbon capture has often been promoted by the fossil fuel industry as a way to continue business as usual – burning natural gas, oil, and coal – while claiming climate responsibility. Do you see a risk that this framing delays a genuine transition away from fossil fuels?
Sabine Fuss: Emissions pathways consistent with the Paris climate goals clearly show that rapid and deep emissions reductions are a prerequisite to achieve those targets, so scarce carbon dioxide removal potentials should not be squandered on offsetting emissions that can be cost-effectively dealt with in other ways.
Recent research shows, however, that the oil and gas sectors’ plans to scale carbon dioxide removal remain rather vague, which is why it is important to scrutinise such claims of climate responsibility in detail. In particular, removals need to:
- be additional,
- take into account issues around permanence including the risk of reversal,
- be based on atmospheric or biogenic CO2,
- feature transparent, science-based, and third-party verified monitoring, reporting and verification,
- minimise leakage and,
- respect other dimensions of sustainability.
As both a scientist and a citizen, what do you think is the appropriate role for these technologies in Europe?
Sabine Fuss: With a strong profile in research and development and a responsibility in terms of having accumulated a significant portion of the emissions currently in the atmosphere, Europe would be well-placed to promote the advancement of novel carbon dioxide removal.
Arguments beyond these also include the prospects of technological leadership, avoided or reduced climate impacts during a hopefully lower and shorter period of overshoot, and more flexibility in the context of carbon management.