Exploring carbon dioxide removal strategies to help decarbonise Europe using high-resolution modelling

Abstract

The electrification of energy demand across sectors, powered by solar and wind generation, is the best strategy for achieving carbon neutrality. Carbon dioxide removal (CDR) strategies are also expected to play a crucial role by providing net-negative emissions that can offset residual CO2 emissions, including those from cement manufacturing. While previous studies have assessed the role of CDRs in Europe's decarbonisation, most either focus solely on combinations of biogenic point-source capture and direct air capture (DAC) coupled with underground sequestration, or consider multiple CDR strategies at low spatial and temporal resolution, thereby limiting the representation of linkages amongst technologies. In this study, the sector-coupled European energy system model PyPSA-Eur is extended to include afforestation, perennialisation, biochar, and enhanced rock weathering (ERW) as additional CDR strategies. Using this model with a 3-hourly resolution and a network comprising 90 nodes, results show that a climate-neutral energy system equipped with these CDR strategies is 9% less expensive. Afforestation, perennialisation, and ERW potentials are fully utilised across regions, whereas biochar is not selected due to limited solid biomass feedstock being allocated to other higher-value processes. Furthermore, when these CDR strategies are combined with underground sequestration and a continental CO2 transport network, DAC is no longer required to achieve climate neutrality in Europe.

Figures (42)

• Figure 1: CDRs potentials and usages across Europe. CDRs (A) potentials and (B) usages.
• Figure 2: Total cost and technology configuration of a climate-neutral European energy system. Compared with an energy system relying exclusively on underground sequestration (U only), total system costs are reduced by 9% when the additional CDR strategies are included (U+A+P+B+E). The availability of CDRs reduces the production of electrolytic H$_2$ by lowering the demand for synthetic oil through Fischer-Tropsch, which in turn decreases the required deployment of wind and solar generation capacities. Technologies with annual costs below 0.1 BEUR are omitted for readability.
• Figure 3: CO$_2$ capture across Europe. Afforestation is widely deployed across the continent as a key strategy for capturing emitted CO$_2$, particularly in the Northeastern and Southeastern regions. Perennialisation and ERW are also widely deployed, particularly in Central Europe, France, Italy, and Great Britain. Point-source CO$_2$ capture and especially DAC are extensively deployed in countries with access to low-cost energy (enabled by favourable renewable capacity factors) and substantial underground sequestration potential, notably Great Britain, Denmark, Italy, and Portugal. Capture from process emissions and gas combustion do not entail CO$_2$ removal. Each pie chart aggregates all nodes belonging to the respective modelled country.
• Figure 4: CO$_2$ conversion and sequestration across Europe. As a direct consequence of the adopted CO$_2$ capture strategy (Figure \ref{['figure_co2_capture_spatial_pattern']}), afforestation is widely deployed across the continent for sequestering captured CO$_2$, particularly in the Northeastern and Southeastern regions. Perennialisation and ERW are also widely deployed, particularly in Central Europe, France, Italy, and Great Britain. Underground sequestration is extensively deployed in countries that rely heavily on point-source capture and DAC to manage captured CO$_2$. Each pie chart aggregates all nodes belonging to the respective modelled country.
• Figure 5: Temporal CO$_2$ capture, conversion, and sequestration across Europe. CO$_2$ capture from point sources and DAC, as well as its conversion into synthetic fuels, exhibit a seasonal pattern, with higher activity in summer and lower activity in winter, reflecting the greater availability of low-cost electricity. Underground sequestration exhibits the opposite pattern, as less captured CO$_2$ is sequestered in summer when more is diverted to conversion processes. Due to model simplifications, afforestation exhibits no seasonal pattern and operates at a constant rate throughout the modelled year. Perennialisation also operates constantly but is restricted to the months from May to October, corresponding to the harvesting period of perennial crops. In contrast, ERW exhibits a seasonal pattern, with higher activity in summer driven by the availability of low-cost renewable electricity.