Sustainable financing of permanent CO2 disposal through a Carbon Takeback Obligation

Unless there is immediate, unprecedented, reduction in global demand for carbon-intensive energy and products, then capture and permanent storage of billions of tonnes of carbon dioxide (CO2) annually will be needed before mid-century to meet Paris Agreement goals. Yet competition from cheaper, temporary, carbon storage means that permanent disposal remains starved of investment, currently representing about 0.1% of Energy and Industrial Process (EIP) emissions. This stored fraction must reach 100% to stop EIPs causing global warming. Here we show that a cost-effective transition can occur by mandating an increasing stored fraction through a progressive Carbon Takeback Obligation (CTO) on fossil fuel producers and importers. Projected costs of storage to the consumer are lower than pricing carbon emissions in conventional 1.5{\deg}C scenarios until the 2040s, and comparable or lower thereafter. A CTO combined with measures to reduce CO2 production would deliver the lowest-risk pathway to achieving net zero.