Pathway
Minerals
Carbon removal potential: 2-4 GtCO2/year
)
Over millions of years, weathering has caused the rocks in our landscape to erode and during this process they sequester CO₂. Rain containing dissolved CO₂ reacts with rocks forming bicarbonate. Bicarbonates are carried into oceans where they remain dissolved for thousands of years or are stored securely on the seabed. These processes naturally sequester 0.5 billion tons of CO2 per year. Enhanced weathering aims to accelerate this natural process by exposing a maximum surface area of CO₂ reacting minerals to the air. Bicarbonates formed through mineral weathering may help counteract ocean acidification in the oceans or improve soil health and yields on land.
Like many other carbon removal strategies, enhanced weathering is still in its early stages and has its own challenges. Mining, grinding, and transporting the rocks uses energy and so it is important to account for the full lifecycle of weathering projects. Decarbonising the transport system will help unlock the full carbon sequestering potential of rock weathering. There is also a broad lack of understanding on the impacts of enhanced weathering when implemented at scale. How much arable land will reasonably be available and what are the effects on yields? What are the ecological effects of depositing large volumes of rocks into the oceans? How much carbon from the oceans will return back into the atmosphere? All these questions require more research.
)
Benefits:
Simple well understood chemistry will little technological risk
Residence time of bicarbonates in oceans is in the order of 100-1000 years?
Co-deployable with carbon capture processes
Not in competition for land used for food
Potential to reverse ocean acidification
Potential to boost crop yields if applied to soils3
Issues We Care About
Providing permanent carbon storage at low costs.
Optimising the mining, grinding, transport and dissolution of rocks to obtain maximum carbon sequestration potential.
Working with scientists to understand the effects of enhanced weathering on the global carbon cycle and the ecotoxicology to assist social approval.
Sources
1. Negative emissions -Part 2: Costs, potentials and side effects, Fuss et al. 2018
2. Assessing ocean alkalinity for carbon sequestration, Renforth and Henderson, 2017
3. Increased yield and CO2 sequestration potential with the C4 cereal sorghum bicolor cultivated in basaltic rock dust-amended agricultural soil. Kelland et al 2020
More pathways
)
){kind=icon}
)
)
)