The research team examined four NETs that interact with the energy system because they require energy for CO₂ capture, transport, or storage: CO₂ removal via biomass pyrolysis to produce biochar (Biochar Carbon Removal, BCR), Bioenergy with Carbon Capture and Storage (BECCS), Waste-to-Energy Carbon Capture and Storage (WACCS), and Direct Air Carbon Capture and Storage (DACCS). Using the REMod energy system model developed by Fraunhofer ISE, two cost-optimal scenarios for climate neutrality by 2045 were calculated:  The “rapid” and “delayed” scenarios differ in terms of when and to what extent CO₂ infrastructure becomes available.

Technology mix and early infrastructure development necessary for climate protection goals

The results show that a broad mix of all four NETs is required in both scenarios. In 2045, these NETs will collectively remove between 39 and 51 million tons of CO₂. The need for NETs depends largely on assumptions regarding future residual, hard-to-avoid emissions from agriculture, waste management, industry, and, in particular, land use (and land-use change) and forestry.

A five-year delay in the ramp-up of CO₂ infrastructure (CO₂ transport and storage infrastructure as well as CO₂ capture) makes it more difficult to achieve climate targets. Even with ambitious annual growth rates for NETs of 35 percent, net emissions will be reduced by only 97 percent by 2045 compared to 1990. The remaining emissions would have to be offset by alternative or international CO₂ removal. In addition, the requirements for defossilization and electrification in the consumption sectors are increasing.

BCR plays a special role: Since the technology operates independently of CO₂ transport and storage infrastructure, its early and more extensive deployment can mitigate the risk of failing to meet climate targets if the rollout of CO₂ infrastructure is delayed: The share of BCR in negative emissions in 2045 therefore rises in the scenarios from 13 percent with rapid CO₂ infrastructure development to 37 percent with delayed CO₂ infrastructure development. In both scenarios, BECCS and BCR shape biomass use and district heating supply: They would consume 30 to 52 percent of the biomass used for energy, but at the same time provide 16 to 27 percent of greenhouse gas-neutral district heating. This makes it clear that NETs must be considered as an integrated part of energy system planning.

Based on these findings, Fraunhofer ISE makes the following recommendations: A broad mix of NETs should be established as a strategic goal; the early expansion of BCR should be carefully weighed; and an integrated strategy for the energy system, NET ramp-up, and sustainable biomass use should be developed. In addition, a legal framework is needed to enable the rapid expansion of NETs, CO₂ infrastructure, and CCS.

“Regardless of the ramp-up of NETs, our study has identified strong electrification of the consumption sectors and the rapid expansion of renewable energies as fundamental prerequisites for a successful transformation of the energy system,” explains project manager Markus Kaiser from Fraunhofer ISE.

The study was funded by a consortium comprising Carbonfuture GmbH, the German Association for Negative Emissions (Deutscher Verband für negative Emissionen e.V.), E.ON Energy Projects GmbH, German Biochar e.V., MVV Umwelt GmbH, and SYNCRAFT GmbH. The statements and conclusions presented in the study are the responsibility of the authors and do not necessarily reflect the views of the funding organizations.