Almost half of UK councils currently provide a comingled collection service, mainly based on the perception that this is convenient for householders, as well as cheaper for the local authority.

Last year, WRAP published its report, ‘Choosing the right recycling collection system’, indicating that these two perceptions have flaws. Once revenue from material sales is counted, along with gate fee costs for materials recovery facilities (MRFs), the overall issue of cost looks different.

When it comes to convenience, the matter is far from clear. From a behavioural point of view, the rationale is easy to follow: putting all approved recyclables in a recycling bag or bin is no more effort than treating them as waste.

Proponents also cite operational considerations as a point of convenience. “We could not operate a borough-wide kerbside sort because of problems of congestion, especially during the summer season,” comments Harry Briggs, Recycling and Waste Enforcement Officer for Scarborough Council, which currently recycles 39 per cent through its single-stream approach.

He adds: “Also, many dwellings do not have sufficient capacity for a number of different containers so it was crucial to have a single multi-purpose recycling receptacle.”

Paul Levett, Deputy Chief Executive of Veolia Environmental believes these considerations validate the approach: “The appropriate collection system varies by area, based on demographics, housing stock, road types and local preferences. Commingled collection is often appropriate and this is demonstrated by the trend in this direction.”

Now this one-size-does-not-fit-all argument will be familiar to followers of the debate. Even councils that separate recyclables at the kerbside accept the need to be flexible. For instance Bristol, which operates a source-separation service for most dwellings, has taken a different approach in some places. “There have been few difficulties in providing a service in high-density areas. There have been issues with storage of the required containers in some areas. As a result, Bristol City Council is providing communal recycling bins in some streets,” according to a spokesperson.

These mini-recycling centres provide bins for glass, paper and cans, but significantly still maintain each material in its own stream, which unambiguously is the key to minimising contamination. Despite taking a different approach to Scarborough, Bristol also currently recycles 39 per cent of its waste. Its comprehensive approach to recycling, including the separate collection of food waste, has seen the city’s household waste fall by 21,000 tonnes per annum (12 per cent) in four years, saving the city £25 million in avoided disposal costs.

However, it is not clear if Scarborough’s figure takes into account material rejected from its MRF due to contamination. Generally speaking, this has been a point of significant debate when it comes to which collection method is more effective. The Environment Agency works on a baseline assumption that typical MRFs reject 10.8 percent; a recent WRAP study concluded that even the best MRFs reject between 2.9 and 8.4 per cent. Despite this, many MRFs claim to reject nothing!

A major part of the issue appears to be the specification of materials required by reprocessors. Levett believes this to some extent drives the reject rate: “MRFs are capable of producing a range of different specifications – obviously the higher the specification the higher the price.”

Philip Ward, Head of Local Government Services at WRAP, feels that recycling participation and capture rates would improve if the industry could work with a wider specification: “Local authorities could do more to make it easier for people by addressing not just the question of, say, ‘Do you collect tin cans?’ but also ‘Do you have a whole set of rules about collecting tin cans? Do they need to be washed, squashed and have the labels taken off?’ The same goes for window envelopes or taking lids off plastic bottles. It’s the detailed rules about how to present the material that householders find difficult. Local authorities and reprocessors need to address this, because a common message would overcome a significant barrier.”

For their part the reprocessors, who have driven the debate about quality, have been motivated by rising costs associated with contaminated feedstock. Commingled collections have been at the heart of rising equipment failure and maintenance costs for the reprocessors. The issue partly revolves around who has to bear the costs, especially when dealing with a global commodity with hungry markets overseas.

Levett feels that commingling is here to stay and that reducing contamination is more a question of education than which collection method to use. He adds: “All MRFs will produce a percentage of rejected material because of residents including non-recyclable material in their bins.”

It would seem, then, that much of the issue could be appeased if residents were better educated about what can and cannot be put into their bins. “We can’t foresee completely standardised collections,” says Levett. “But at least collecting the same materials everywhere would reduce residents’ confusion.”

Ward thinks that a single-stream approach limits the potential to identify when the householder is making mistakes and in the process correct this behaviour. “Once the wrong material has been put in the bin, there’s nothing anyone can do about it and it has to be sorted at the MRF. There is enormous confusion in people’s minds about these things and it’s a significant barrier to them engaging with the recycling system.”

In an attempt to balance considerations of convenience and contamination, some local authorities, such as Charnwood, have opted to introduce two-stream collections. In the case of this Leicestershire district, glass is collected separately from other dry recyclables. In many instances, two-stream systems split containers from fibres.

While single-stream, two-stream and source separation systems are all finding favour with different local authorities, last year there was a greater appetite on the part of local authorities to introduce two-stream collections. In 2008/09, 22 per cent of councils in England opted for this approach, an increase of 11 per cent on the year before. At the same time, 51 per cent of local authorities were running source-separated collections – up from 44 per cent in 2007/08 – and 38 per cent were operating commingled collections – up from 35 percent. (NB: Some authorities run more than one type of collection).

All this indicates that the appetite for commingling is much more subdued than it was a few years ago. The signs are that collection systems with negligible contamination are now viewed as cost effective. Charnwood for its part claims to have a reject rate of 0.39 per cent, with residents reporting a greater to inclination to use the service, in the process recycling 42 per cent.

There is a long way to go in the debate about which approach to doorstep recycling is the right one, but signs are that, increasingly, reprocessor specification (domestic and foreign) may drive the market. Some flexibility may be required all round to make the task of recycling easier. For the foreseeable future the picture, if not the materials, remains mixed.