Startups overhyped marine carbon dioxide removal – it may never happen - Many overestimate how close we are to scaling up carbon removal deployment, says leading oceanographer David Ho.

Marine CDR lumps together many different techniques. They all seek to remove excess carbon from the atmosphere by lowering surface ocean partial pressure of carbon dioxide, or pCO2.

Some techniques exploit photosynthesis, for example by adding nutrients like iron to the ocean, to increase phytoplankton productivity. The complication there: if you make something organic in the ocean, something else will want to eat it. If the phytoplankton get consumed before their bodies sink to the deep sea, that organic matter is quickly turned back into CO2. There are also potentially negative effects for ecosystems, such as decreasing oxygen levels in the ocean, which would be bad for organisms with gills.

Alternatively, there are geochemical techniques, such as increasing ocean alkalinity to shift CO2 into dissolved bicarbonates and carbonates. This allows the ocean to absorb more carbon dioxide from the air. People think that this additional CO2 store should last tens to hundreds of thousands of years, and may not be as disruptive as other methods.

The different techniques have different uncertainties, but I wouldn’t say any of them are ready, for lots of reasons. We don’t know how effective they would be, or whether they will have negative environmental impacts.

...

Startups have to sell carbon dioxide removal as a solution today in order to survive. In reality, we are so far from deploying these things that none of the startups that currently exist will be the ones removing carbon in 50 years. They are developing intellectual property to sell.

cross-posted from: https://slrpnk.net/post/40829147