Plastic bags - carbon sink

[Speranza]

Are plastic bags and other types of plastic waste types of carbon sink? Seeing that you throw them away, they end up in landfill (more often than not in the UK) and they take hundreds of years to degrade. Do they ever release the carbon they're made of into the atmosphere?

[Mercadante]

Strictly speaking, the term 'carbon sink' refers to things that remove carbon from the atmospheric carbon cycle. As the carbon in a plastic bag comes from fossil fuels, then at the very best, if we returned it all returned harmlessly to the ground, plastic bags would be 'carbon neutral', rather than carbon sinks. But unfortunately making and transporting plastic bags chucks quite a lot of carbon into the atmosphere. Even disposing of plastic in landfill helps create anaerobic conditions for the decay of organic matter, which produces methane - a worse greenhouse gas than CO2.

Different plastics degrade at different rates, with some effectively not degrading at all. The carbon in biodegradeable plastic does end up as CO2, which is obviously a drawback (though of course so does the carbon in other plastic, when it's incinerated). The reason for preferring biodegradeable plastic is to help reduce plastic litter, which gets in the food chain and has a serious impact on wildlife: Ocean plastic

[svenrufus]

Originally Posted by Speranza

Are plastic bags and other types of plastic waste types of carbon sink? Seeing that you throw them away, they end up in landfill (more often than not in the UK) and they take hundreds of years to degrade. Do they ever release the carbon they're made of into the atmosphere?

Stringent new limits on the amount of stuff that we are going to be able to landfill in the EU mean that other end destinations are being lined up for our domestic waste. In many cases, this will involve - as in my local area - an incinerator. Thus, the carbon in plastics will be adding to the atmospheric CO2 load, not stored away as you suggest. Other schemes such as waste to fuel plants will have a similar impact. All said and done, plastic is remains a toxic substance at every stage of its production and use, and even though it is so hard to avoid, we should all make every effort to cut it out of our lives.

[Cotham Marble]

Originally Posted by Mercadante

As the carbon in a plastic bag comes from fossil fuels, then at the very best, if we returned it all returned harmlessly to the ground, plastic bags would be 'carbon neutral', rather than carbon sinks.

Plastics can of course be manafactured from cultivated material, not just from geological sources. The definition of ' plastic' is perhaps not very precise but could be considered to include Rayon, which has been around for over a century is derived from wood pulp.

Nevertheless, even if a plastic did serve as an effective carbon sink material, it would be hugely wasteful to use it in that way given that reuse/recycling would almost certainly be more energy efficient.

CM