From scientific foundations to proposals for cooperation on geological carbon
The initiative presented on this website forms part of an international discussion on responsibility for geological carbon, reducing dependence on fossil resources and durable sequestration. Its development brings together scientific contributions, professional exchanges and proposals advanced notably by Patrick Portolano and EOSYS.
This page traces the main stages of this process and acknowledges the contributions that have informed it. It distinguishes international scientific research from the proposals and Pact developed within this initiative.
Scientific foundations and producer responsibility
The work of Myles Allen and his colleagues has helped establish the relationship between cumulative CO₂ emissions and global warming, as well as the role of permanent geological storage in addressing fossil carbon. In 2009, Allen, Frame and Mason advocated mandatory sequestration in The Case for Mandatory Sequestration.
The work of Margriet Kuijper and her colleagues on the Carbon Takeback Obligation (CTBO) is another important reference: it explores extending producer responsibility to the management of CO₂ associated with fossil fuels.
2019–2021: early proposals
From 2019, Patrick Portolano, through EOSYS and discussions within the ACP Énergies association, explored ways to strengthen fossil carbon producer responsibility and support the transformation of energy industries.
Laurent Nicolas contributed to these discussions, notably through the concept of a Fossil Carbon Indicator. Together, Laurent Nicolas and Patrick Portolano wrote Towards Responsible Circular Fossil Carbon Industries: Upstream Proposals to Reduce Demand and Control Supply, a working paper dated May 2021 and revised on 1 September 2021.
In 2021, ahead of COP26, Patrick Portolano proposed an international agreement on geological carbon neutrality in “Geological Net Zero”: A Proposal for a Simple and Globally Effective International Agreement on Fossil Carbon. Exchanges with British geoscientist Hugh Richards helped shape the approach and the adoption of the term Geological Net Zero in their work.
2022: developing the proposals and public debate
Hugh Richards and Patrick Portolano continued this work in “Geological Net Zero” (Geological Carbon Neutrality) — How Could We Get There?, dated January 2022 and revised on 25 March 2022. The paper examines political and institutional implementation pathways, the CTBO and the prospects for an international agreement. It benefited notably from comments by Margriet Kuijper and observations by Paul Zakkour.
On 28 September 2022, at the ACP Énergies conference in Paris on energy decarbonization, Patrick Portolano publicly discussed producer responsibility and geological carbon neutrality with Myles Allen, alongside Margriet Kuijper and Hugh Richards.
The conclusions of that day informed the Six Recommendations for COP27 (in French), prepared for ACP Énergies by Patrick Portolano with support from its H₂ working group and dated 12 October 2022. They bring together producer–consumer chain responsibility, bioenergy, restoration of biogeochemical cycles and industrial transformation.
2019–2024: a collective framework for discussion
Discussions within ACP Énergies brought together professionals from the energy, geoscience and industrial sectors. They addressed fossil carbon responsibility and traceability, defossilization, geological storage and its financing. They informed contributions to COP26, COP27 and COP28, as well as discussions on French energy and climate strategy.
2024–2025: the scientific formulation of Geological Net Zero
Allen and his coauthors subsequently developed a scientific formulation of Geological Net Zero and the need to distinguish categories of carbon sinks in Geological Net Zero and the need for disaggregated accounting for carbon sinks. The article was published online on 18 November 2024 and appeared in volume 638 of Nature in 2025, pages 343–350.
This publication is a major scientific reference for understanding the geological carbon balance. The chronology presented here traces discussions and publications; it does not imply that these different works derive from one another.
Today: from the GNZ Principle to the GNZ Pact
Under Patrick Portolano’s leadership, EOSYS continues to develop the initiative presented on this website, drawing on its experience in geosciences and subsurface studies.
The GNZ Principle sets a balance target between geological carbon extracted and carbon durably sequestered. The GNZ Pact proposes organizing its implementation through reciprocal commitments among producers, industries, consumers, stakeholders in biological carbon cycles, sequestration operators and public authorities.
The current approach extends the discussion to all geological carbon used in industrial processes and to responsibilities throughout value chains. It brings together defossilization, durable sequestration, financing and international cooperation.
An open initiative and distinct contributions
References to researchers, authors and organizations acknowledge their respective contributions; they do not imply affiliation with or formal endorsement of the Pact presented on this website. The initiative welcomes critical assessments and scientific, industrial and institutional proposals.
Explore the foundational publications · Suggest a contribution or a historical clarification
Documentary references:
Six Recommendations for COP27 (in French);