Hacker News Reader

Comment by pcurve | Hacker News Reader

"For every single tonne of cork produced we are talking about 73 tonnes of CO2 that are captured... 392g (13.8oz) of carbon is sequestered by every cork stopper"

This might be an obvious point but it's not that cork material itself is carbon friendly, but having robust demand for cork ensures proliferation cork oaks that can sequester CO2.

View on HN

This might be a dumb question but

Tonne is a mass measurement... How can 1 tonne store 73 tonnes of CO2?

The source of that fact is here [0], but that is counting the forest that makes the cork. However they aren't growing a new forest for new cork, so that 73 tonnes of stored carbon is static. Each cork harvest lowers that 73:1 ratio.

https://www.amorimcork.com/en/media-center/news/research-hig...

The article makes it pretty clear (cork forests aren't cut down for harvesting):

> Planting forests is a commonly used approach to offset carbon emissions by polluting industries, but when the trees are harvested they are usually cut down and much of their stored carbon is released back into the atmosphere.

> But cork oaks are one of the few commercial forests not felled for harvesting. This means the cork tree's carbon storage capacity keeps increasing during the 200 or more years the trees can live.

> Most of the carbon remains locked in the tree as it continues to grow. Although cork products contain some of the absorbed carbon, they can have a long life after being cut from the tree. Cork can be recycled and is slow to break down even when discarded.

I believe the trees continue to grow over the intervening near-decade between harvests, sequestering CO2 not only in the part of the bark that is harvested (which sounds like it is potentially only a meter or two off the ground) but also as new growth along the rest of the tree. I suppose that that statement implies that, on average, they harvest 1/73rd of the growth that a tree has had since the previous harvest.

(Note I am not attempting to state whether that claim is true or not, merely offering one potential explanation of how the trees might sequester 73 tonnes CO2 for every tonne of cork harvested)

You don't need to store CO2. You need to store the carbon somewhere and get some O2 for free.

There's about 2.5g of oxygen per 1g of carbon in carbon dioxide, and carbon takes the lion's share of hydrocarbons' mass, so I wouldn't be surprised if just the cork itself would burn to twice its weight in CO2. Then you consider the growth of the tree itself over time. Oak is about 3-4x the density of cork, so I wouldn't be surprised if you got a few grams of wood per gram of cork.

That 70x multiplier is enormous and probably overinflated, but these are just two factors I could think of in a couple of minutes, so I can easily see how a tree, over its lifetime, might sink 10-20 tonnes of carbon per 1 tonne of cork produced.

Reply on news.ycombinator.com