Sewage Treatment for the Skies

The report argues that carbon dioxide removal (CDR) should be treated as a public service, similar to sewage treatment, because most CDR technologies do not generate independent revenue. It identifies a massive implementation gap between projected removal volumes and current policies, noting that while nature-based solutions are cheaper, they lack the permanence of technological options like Direct Air Carbon Capture and Storage (DACCS) and Bio-energy with carbon capture and storage (BECCS). The authors recommend a mix of public subsidies for research, design, development and demonstration (RDD&D), carbon pricing, and the use of Article 6 of the Paris Agreement to create a credible investment environment. It also highlights the role of voluntary private sector commitments, though it warns of a 'wild west' situation in the voluntary carbon market due to inconsistent monitoring, reporting and verification (MRV) standards.

• CDR is characterized as a public service for atmospheric cleanup because most approaches do not produce sellable goods or services, meaning they lack a valid business case without dedicated policy intervention.
• There is a significant trade-off between cost and permanence: nature-based CDR options are currently inexpensive but face permanence challenges, while technological options are expensive but offer high permanence.
• A substantial gap exists between the volumes of GHG removal projected by the IPCC to limit warming to 1.5°C and the actual policies in place, with some estimates suggesting a need for 100 to 1000 billion tCO2e of removals this century.
• The cost of Direct Air Carbon Capture and Storage (DACCS) shows extreme variance, with estimates ranging from USD 20 to USD 1000 per tCO2 depending on the source.
• Current public policy instruments for CDR are underdeveloped, with most existing funding focusing on either fossil-point-source CCS or nature-based solutions rather than dedicated CDR.
• The voluntary carbon market for CDR is described as a 'wild west' due to the use of diverse and inconsistent methodologies for calculating removals and monitoring, reporting and verification (MRV).
• International regulatory frameworks, such as the Convention on Biological Diversity (CBD) and the London Protocol, currently act as barriers to the deployment of large-scale CDR and transboundary CO2 transport.
• To achieve the necessary scale, CDR would require a consistent annual growth rate of nearly 30% to move from 1 Mt in 2020 to 1 Gt in 2050.

APA

Poralla, M., Honegger, M., Ahonen, H.-M., Michaelowa, A., & Weber, A.-K. (2021). Sewage Treatment for the Skies. Climate Strategies. https://climatestrategies.org/wp-content/uploads/2021/03/CS-NR_Mobilising-CDR-report-1.2.pdf

Chicago

Poralla, Matthias, Matthias Honegger, Hanna-Mari Ahonen, Axel Michaelowa, and Anne-Kathrin Weber. Sewage Treatment for the Skies. Climate Strategies, 2021. https://climatestrategies.org/wp-content/uploads/2021/03/CS-NR_Mobilising-CDR-report-1.2.pdf.

Wikipedia

{{cite report |last1=Poralla |first1=Matthias |last2=Honegger |first2=Matthias |last3=Ahonen |first3=Hanna-Mari |last4=Michaelowa |first4=Axel |last5=Weber |first5=Anne-Kathrin |title=Sewage Treatment for the Skies |publisher=Climate Strategies |date=March 2021 |url=https://climatestrategies.org/wp-content/uploads/2021/03/CS-NR_Mobilising-CDR-report-1.2.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{poralla2021sewage, author = {Poralla, Matthias and Honegger, Matthias and Ahonen, Hanna-Mari and Michaelowa, Axel and Weber, Anne-Kathrin}, title = {{Sewage Treatment for the Skies}}, institution = {Climate Strategies}, year = {2021}, month = mar, url = {https://climatestrategies.org/wp-content/uploads/2021/03/CS-NR_Mobilising-CDR-report-1.2.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }