What's the Carbon Footprint of Recycling?

[Marina Schwarz + 1,576]

I want to tap the knowledge of people here on this question. I recycle. I don't mind it and I like reusable things. But: melting plastics and glass involves high temperatures, perhaps high enough for burning to occur. This means emissions. Is the carbon (and other gases) footprint of recycling lower than that of producing more plastics or are there already technologies eliminating it? I realize it's difficult to compare new plastics production with plastics recycling but I'm sure it's not impossible.

[Guillaume Albasini + 851]

Maybe you can find some answers in this swedish thesis from 2009...

http://publications.lib.chalmers.se/records/fulltext/136412.pdf

[Rodent + 1,424]

20 minutes ago, Marina Schwarz said:

I want to tap the knowledge of people here on this question. I recycle. I don't mind it and I like reusable things. But: melting plastics and glass involves high temperatures, perhaps high enough for burning to occur. This means emissions. Is the carbon (and other gases) footprint of recycling lower than that of producing more plastics or are there already technologies eliminating it? I realize it's difficult to compare new plastics production with plastics recycling but I'm sure it's not impossible.

I don't have data to answer you, but as someone who used to work in the single-use foam/plastics industry, I can say that there is a lot of steps involved in the manufacturing process that would lead me to believe that recycling is more favorable than landfilling it and using all virgin material.

That said, recycled material has to be blended with virgin material at a specific ratio--too much reclaim material and the product quality is degraded, and it is a real pain in the butt for manufacturers.  I like to think of it as making cut-out Christmas cookies. You roll out the dough, cut out the cookies, then take the scraps and mix it with new cookie dough and roll it out again. You can't do it again, though, because once you roll it out twice, it gets tough. Recycled material is the same way. Really hard to work with, and it just can't be used over again as-is--it must be mixed with virgin material.

[Jan van Eck + 7,558]

9 hours ago, Rodent said:

. You can't do it again, though, because once you roll it out twice, it gets tough. Recycled material is the same way. Really hard to work with, and it just can't be used over again as-is--it must be mixed with virgin material.

All true, but it also depends on what you end up doing with the material.  

Old plastics can be treated with a special plastic binder that allows for various grades to be passed through an extruder, the output material formed into plastic lumber.  There is a big market for plastic lumber in everything from home decks to beach boardwalks and nature preserve walkways. Old plastic can also be used in ship fenders, dock fenders, and as fillers inside hollow shapes, used as plastic beams.  The stuff is used where you want a rugged material that will be exposed to the outdoor elements. 

The energy unit in recycling plastics is trivial compared to that of virgin material.  It is on the order of magnitude of 500 to 1.  But as Rodent points out, there are concentration limits.  Figure no more than 30%  (and that is pushing it for injectable grades) and never more than two passes through the grinder and extruder, or the heat history destroys the material and makes it fracturable. 

Edited May 31, 2018 by Jan van Eck
scrivener error

[Jouhou + 24]

I actually think aluminum is the big one when it comes to materials that are most efficient for recycling. It's takes a lot less energy to melt down already processed aluminum metal than it takes to produce aluminum metal from ore. 

Aluminum smelting is so energy intensive, smelters need their own power plants, and on a very large scale.

[Guillaume Albasini + 851]

Recycling offers the benefit of a 95 % energy saving compared with the production of primary aluminium

75 % of all aluminium ever produced is still in use today.

In Europe the recycling rate for aluminium packaging is over 60% (87% in Germani, 92% in Switzerland and 96% in Norway)

https://www.recycling-magazine.com/2018/05/22/aluminium-packaging-recycling-of-course/