All negative carbon solutions consist of two components: a means of capturing carbon from the atmosphere and a means of permanently storing it away from the atmosphere. The role of negative carbon in climate action can be understood through the analogy of stopping an overflowing bath. Carbon reduction can be thought of as turning off the taps while negative carbon is the equivalent to pulling the plug.1
Carbon Storage Methods
Capturing carbon can take different forms but is primarily done through either biological processes (photosynthesis in leaves) or chemical processes (reactions with solvents). Storage always involves some type of reservoir. There is either biological storage in biomass or geological storage by injecting carbon into secure reservoirs such as saline formations or depleted oil and gas wells. There are several ways to capture and store carbon from the atmosphere, but in this article, we will focus on two popular, proven methods: Direct Air Capture and Storage (DAC) and Natural Climate Solutions.
The Direct Air Capture and Storage method involves carbon being pulled directly from ambient air into a processing plant, separating the CO₂ through chemical processing, and storing the resulting CO₂ into deep geological formations (read more here). Planting trees and growing forests are popular examples of biological CCS. Simply put, trees and other plants naturally capture CO₂ from the atmosphere. By preserving that biomass, carbon can be successfully stored long-term. However, these two storage methods vary greatly in terms of risk of reversal.
Storage Pros and Cons
Biological storage has a higher risk of reversal. In theory, trees can last for hundreds of years, but fire, disease or intentional land-use changes can cause them to release their CO₂ much sooner. This storage method requires careful monitoring, maintenance, and renewal.
Geological storage has a lower risk of reversal, as CO₂ storage has been proven to have extremely low levels of leakage as long as best practices are followed.
“Overall, our findings indicate that geological storage of CO₂ is a secure, resilient and feasible option for climate mitigation even when applying pessimistic values for input parameters and in poorly regulated storage scenarios.2”
There are two main benefits of negative carbon solutions. For some industries it will be incredibly difficult to decarbonize by our global goal of 2050. Either because of high costs or because there is truly no viable solution for them. For example, CO₂ emissions from long flights currently appear to be extremely difficult to eliminate. Negative carbon solutions can offset those emissions by removing an equal or greater amount of It can give those industries more time to find better decarbonization solutions. Secondly, CO₂ concentrations in the atmosphere decline very slowly. Carbon removal can speed up this decline process; therefore, presenting a means for stabilizing the climate in the long term.
2. Juan Alcalde et al., ‘Estimating geological CO2 storage security to deliver on climate mitigation’, Nature Communications, June 2018, Volume 9, Number 2201, https://www.nature.com/articles/s41467-018-04423-1