Mixed plastics: Are they worth it?

Kerbside collections for mixed plastics are in their infancy. But new research on this waste stream could overcome some practical difficulties. Maxine Perella reports

Collecting mixed plastics at the kerbside “is possible to do without breaking the bank”, according to a senior director at WRAP. Phillip Ward, director of local government services, was speaking at a dissemination event in London recently, where early findings from local authority mixed plastics collection trials were aired.

The study, which looked at a sample of LAs who were collecting mixed plastics from households, found wide variation in collection costs between councils. But it also found that those authorities collecting mixed plastics at the kerbside have below-average costs per household compared with their statistical neighbours.

“That’s below those who are not collecting mixed plastics,” explained Ward, who added: “Those that collect [mixed plastics] at bring sites tend to have higher costs. This does suggest it is possible to collect mixed plastics without breaking the bank.”

Hard to pinpoint costs

He did point out, however, that it was hard for those who were considering it to quantify the actual cost of introducing a mixed plastics collection because often they are bolted on to existing kerbside schemes making specific costs difficult to isolate.

“If you look at those local authorities who are currently collecting mixed plastics, there is no systematic difference between the two lots of costs, and in many cases their costs are below,” Ward said. He urged those LAs who are considering introducing a mixed plastics kerbside collection to come forward so WRAP can help work with them.

Ward noted that there was scepticism about the practicalities and cost of collecting mixed plastics, which was also true of plastic bottles. Demand for bottle plastic in the UK is outstripping supply as retailers look for higher recycled content and so looking ahead, Ward said there were moves to examine the sharing of costs across the industry.

With most councils now collecting plastic bottles, a cross-industry group has been set up involving key stakeholders including the British Retail Consortium, LARAC and the LGA to look at various cost-sharing options which could include either regulatory or voluntary action.

Ward concluded that with mixed plastics there was a need to establish operational good practice and to understand better the cost implications. While research so far suggests that costs are containable, there are funding questions surrounding the further expansion of collection schemes.

Following this, WRAP’s plastics technology manager Paul Davidson outlined findings from the programme’s research. He said that, of those LAs that were collecting mixed plastics, “quite a few were doing it by accident” and so there was little information available on cost, method and efficiencies. He called for greater engagement with councils to take this forward: “We need to disseminate good practice from those that are already doing it.”

Plastics ‘travel well’

Touching on the transport issue, Davidson said that plastics travel very well. “In terms of finance, the variable component with mileage is relatively small. Plastics tend to be higher-value materials – as more plants get established as the market grows, the catchment area will reduce.”

On the reprocessing side, he favoured integrated solutions for mixed plastics recycling – for example, with a MRF. A 40,000tpa mixed plastics facility looked economically viable, he added, as data suggests there will be no need for a gate fee and it might even be able to pay for mixed plastics feedstock.

Daniel Sage from St Edmundsbury Borough Council gave an LA perspective on matters, as his council collects mixed plastics from the kerbside. St Edmundsbury has one of the highest recycling rates in the country, serving about 45,000 households in its area.

The council operates a three-bin alternate weekly collection – a black bin for residual waste, a brown bin for compostable waste and a blue bin for dry recyclables including plastic bottles, tubs, pots and food trays. Sage said film was not collected in these bins as its light nature means, once the lift is lifted, it can blow out of the bin and down the street on a windy day.

Issues of space

The blue bin is co-mingled and goes onto a MRF where the plastics are separated via optical sorting. “All plastics that go through the MRF are sent to China,” said Sage, who added that plastics account for 16% of the blue bin waste composition by weight, but 60-65% by volume. “This is critical as it frees up the capacity of the residual waste bin,” he explained.

Sage said that, while capture rates for plastic bottles were very high, the rates for mixed plastics were lower. “Bottles are easily identifiable but, with margarine tubs and yoghurt pots, you are asking residents to clean them more … it makes them more difficult to capture.”

Outlining the pros and cons of mixed plastics collections, Sage said that, while they assist with diversion targets, free up capacity in the residual waste stream and increase overall recycling rates, it is difficult to achieve high capture levels and can also lead to increased gate fees at the MRF.

“Mixed plastics is only 50% biodegradable in terms of LATS, so, if cost is a big issue, you might want to concentrate on food waste,” he told delegates.

Challenges for the MRF

Bill Griffiths, national recycling manager for Viridor, spoke of the reprocessing challenges MRF operators face in dealing with mixed plastics. Viridor operates five MRFs across the country which take in co-mingled material.

“Most of our input specifications for local authorities are for bottles only, but these contain a proportion of mixed plastics anyway. We need to actively manage this contamination and turn it into a resource issue,” he advised.

“If we target mixed plastics, we will double our plastics collection rates but we need to secure a cost-effective long-term market for it. If we start collecting this material, we cannot turn it off – the public will expect it to continue.”

Griffiths warned that capacity was a problem: “It’s small additional tonnage for the MRF, but big additional volume – it would quadruple or more. This will affect the capacity of the MRF and hence the quality of the existing recycling operation. You could get cross-contamination of existing high-quality recyclate, for example food mixing with paper.”

He spoke of the need for tighter reprocessing specifications to deal with the different polymer types. And he also questioned newer plastic packaging products coming onto the market, such as free-standing pouches for dishwasher tablets and dog food, which could present problems. “How are we going to sort and separate that out with existing MRF technology – is it a tetra-pak of the future?”

Maxine Perella is editor of LAWR

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