Project Permanence

One of the primary things we need to think about when talking about these different carbon sequestration techniques is how permanent the storage is, because it wouldn’t really help to have the CO₂ return right back to the atmosphere.

We love Soils as a solution because of the other benefits they provide - they are low cost, understandable and are available now. But Soils might only store carbon for maybe 10 years or so, and there are lots of reasons they might stop storing carbon sooner, for example if someone decided to turn the land into a parking lot. Forests are similar - lots of reasons to plant them, but if we are lucky, trees can only store carbon for decades, likely not centuries and definitely not millenia. They are susceptible to wildfires, disease and destruction by humans.

Biochar is a much more permanent way to store biomass, and may last on the order of 1000 years. Mineralisation and Bio-oil are some of the most permanent ways to store carbon, but these methods are more costly, and we need much more deployment to get the costs to come down.

Permanence is one of the primary considerations when considering the quality of the removal aspect of a CDR project. For now, until we get more techniques to scale and get costs to come down, the more permanent options are usually the most expensive (though you only have to do them once!) Of course, the climate crisis is not the only crisis humanity is facing, so co-benefits, such as biodiversity support or increased food supply, should not be overlooked. And then there are other things to consider as well, such as how additional each project is, will the project cause damage to happen somewhere else, and can it be effectively monitored after to make sure the CO₂ is safely stored and ecological impacts are kept to a minimum.