It is too simple to say that commingling on its own leads to higher recycling rates. Analysis published by WRAP produced the best statistical explanation of the factors that affect the capture of dry recyclates. In order of priority they were:
- Socioeconomic factors - poorer areas tend to produce less recyclate.
- The number of materials targeted at the kerbside.
- The frequency of residual collections - fortnightly collections tend to perform better.
- Some regional variations.
- The effective volume capacity provided for recycling - a product of size of container and frequency of collection.
Other factors, which are not routinely measured but can be expected to affect the outcome, such as communications campaigns, could not be included in the analysis.
When councils change their systems, they typically make other changes at the same time: to increase the number of materials collected, perhaps move to fortnightly residual collections or improve food and garden waste services. They usually spend money on communications, which refreshes interest and gets all residents up to speed with the new arrangements.
All of these will affect yields, yet the increases are attributed to the move to commingling, but the same changes could be applied to a change to a dual- or multi-stream approach as well.
Three advantages are presented for commingling. The volume available through the use of a wheeled bin is important. Adequate volumes are also possible using boxes if they are collected weekly. Too many multi-stream services just do not provide the necessary capacity, yet they could.
Commingling is also said to be easier for residents, but the volume of non-target materials presented to MRFs and too often still included in the output suggests this easiness is really an invitation for them to be less careful in making the basic decision about what is recyclable.
Finally, commingling is said to be cheaper, yet that is not often tested in procurements. With the JR rumbling on, local authorities would be well advised to show they have fairly considered separate collection options and have not relied on quantity trumping quality for protection from challenge.
Phillip Ward, former WRAP local government director
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