# Recycling

## Idea

Municipal recycling is the collection of end-products such as aluminium cans or processed paper which has been partially separated by consumers, further separating it at recycling centres and utlising these to create new product. This is either of the same kind, or downcycling to a lower “grade” when impurity removal is too energetically expensive. Intuitively recycling should be a good idea, but the key question is whether it really stacks up on a careful analysis.

## Some statistics

This chart show the percentage of energy used in producing product from recycled items as a percentage of the energy used in manufacture of virgin product by extracting raw materials from the environment (so that lower values are better).

(The steel figure is in average value.)

Further figures describe the amounts of various quantities saved in recycling 1 ton of material (so that higher is better).

MaterialkWhbarrels of oil$10^6$ Btu’s of energycubic yards of landfill
Aluminum14,0004023810
Newsprint6011.710.24.6
Office Paper4,1009543.3
Plastic5,77416.39830
Steel6421.810.94
Glass420.120.7142

This data is extracted from the references.

## Non-energy constraints

As with many other issues, the lower energy usage is only one aspect of these things. For instance, “recycling” glass to a substance called cullet is energetically favourable. However, only a limited percentage can be incorporated into the production of new glass. This is made even worse in countries where the glass containers are imported (in this case green wine bottles) are different to the natively manufactured containers (typically white glass jars). In this case there’s not enough “suitable users” for the volume of recycled content to put to, leading to either “downcycling” usages such as incorporation into road surfacing or placing into conventional landfill.

## Questions

Does recycling save energy? Apparently so for aluminium: this takes around 54 MJ/kg to produce from ore (cf. Wikipedia), while recycling takes roughly 20% of the energy. For comparison: coal provides around 28 MJ/kg (again, cf. Wikipedia).

What about glass? This page asserts a significant energy saving, although only quantified as 315kg of $CO_2$ is saved per tonne of glass melted and “Recycling two bottles saves enough energy to boil water for five cups of tea”.

What about other materials? Of course, there are other reasons why recycling might be a good thing: reducing pollution from landfills, needing fewer bleaching chemicals for paper and card, etc. However, it would be nice to assess it from a saved energy point of view. Unfortunately, it seems that many criticisms of recycling come from economists criticising it on the basis of a higher monetary cost than landfill, rather than on other more physical criteria.