A new study by researchers at the MIT Center for Sustainability Science and Strategy evaluated portfolios of five carbon dioxide removal (CDR) options to assess their capability to meet the 1.5 C global warming cap enshrined in the Paris Agreement:

• bioenergy with carbon capture and storage (BECCS)
• afforestation/reforestation
• direct air carbon capture and storage (DACCS)
• biochar
• enhanced weathering (EW)- spreading finely ground rock particles on land to accelerate storage of CO₂in soil and water

The research report details three key findings:

Firstly, the most cost-effective, low-impact strategy policymakers can adopt to achieve global net-zero emissions is to diversify their CDR portfolio, rather than rely on any single option. This approach minimises overall cropland and energy consumption, and negative impacts such as increased food insecurity and decreased energy supplies. Through diversification, the highest CDR deployment of around 31.5 gigatons of CO₂ per year is achieved in 2100.

The study identifies BECCS and biochar as most cost-competitive in removing CO₂ from the atmosphere, followed by EW. Due to its high capital and energy requirements, DACCS emerges as uncompetitive. While posing logistical and other challenges, biochar and EW have the potential to improve soil quality and productivity across 45 percent of all croplands by 2100.

The second key finding from the research is that there is no optimal CDR portfolio that will work well at global and national levels. Since the ideal CDR portfolio for a particular region will depend on local technological, economic, and geophysical conditions, what matters is enhancing knowledge about local conditions that favour some CDR options over others.

Thirdly, delaying large-scale deployment of CDR portfolios could be very costly, leading to considerably higher carbon prices across the globe. This would deter the required climate mitigation efforts. As such, financial incentives and near-term implementation of policy are recommended to fast-track progress.

Find the published report here.