Over 260 researchers gathered in Milan to discuss scaling carbon dioxide removal (CDR) technology to combat climate change. CDR must increase from 2.2 billion tonnes of CO2 per year today to 8.8 billion tonnes by 2050 to meet the Paris Agreement’s 1.5°C goal.

Current State and Limitations

Currently, 99.9% of existing CDR relies on forest-based methods like tree-planting, which are cost-effective (sometimes under $10 per tonne of CO2) but face critical limitations. CDR excludes CO2 uptake not directly caused by human activities, but separating direct from indirect human effects requires models—meaning conventional land-based CDR cannot be fully tracked in national inventories.

Long-Term Reliability Concerns

Research using dynamic economic models showed that as forests grow, an increasing share of captured CO2 must compensate for carbon released during forest disturbances rather than offsetting human emissions. Additionally, tight land availability in regions like the EU restricts forest expansion. This means forests are not reliable long-term solutions and technological CDR will be needed to offset remaining hard-to-abate emissions.

Experts also highlighted large uncertainties in forest-based CDR calculations, with current methods having 20-30% error rates, plus concerns about carbon permanence and forest vulnerability to climate impacts like wildfires.

Diversifying CDR: Technological and Nature-Based Solutions

Because land-use constraints limit forest-based CDR, a diversified portfolio of CDR approaches is essential. Emerging technologies currently represent less than 0.1% of CDR but are growing rapidly.

Other CDR Methods Under Investigation

Policy and Governance

While 140 countries have net-zero targets implicitly including CDR, only the EU has adopted a binding removals target into law (310 million tonnes CO2 equivalent by 2030). Key barriers include lack of demand signals like binding targets and procurement incentives. Experts stress that CDR must be treated as a public good requiring government-created markets to reach necessary scales.

The IPCC will publish a CDR methodology report in 2027, though challenges exist: many CDR solutions don’t yet exist at scale, making standard removal factors difficult to establish.

Public Acceptance

Public support for CDR hinges on procedural fairness and benefit-sharing, according to surveys of 10,000+ people. Planning processes must include public and expert scrutiny. Critically, CDR requires active public desire—not just tolerance—for deployment at necessary scales.

Source: Why carbon removal needs a ‘major scale up’ to return warming to 1.5C https://www.carbonbrief.org/experts-why-carbon-removal-needs-a-major-scale-up-to-return-warming-to-1-5c/