Source-separated recycling contamination low

Contamination of source-separated recycling streams in the UK is generally low, a report published by Zero Waste Scotland has claimed.

The report was commissioned by the Scottish Government to assess typical contamination levels in municipal and business recyclables streams which have been separated at the point of collection. It also aimed to address the lack of robust data available.

Contamination is defined in the report as any non-target material present in the dry recyclables stream when the load is accepted at the point of delivery, such as at a waste transfer station, a bulking station or a repressor.

For the purposes of the study, which began in November 2012, materials rejected at the kerbside by local authorities were excluded as were whole loads rejected at the point of delivery.

The study examined contamination levels in five key recyclable materials plastic, glass, metals, paper and card all of which must currently be source-separated by businesses in Scotland as part of the Waste (Scotland) Regulations 2012, which came into effect this year (see letsrecycle.com story).

The study, which aimed to devise a sampling framework for local authority and commercial waste collections, was conducted on a UK-wide level to yield sufficient data, according to Zero Waste Scotland. It took a total of 860 municipal samples from 59 sites, as well as 225 business recyclables samples across 18 sites.

Failures

However there were a number of statistical failures identified in the report, with the study unable to meet many of its local authority characteristic targets. Zero Waste Scotland was only able to find 13 of the 20 councils it hoped would collect five key recyclable materials separately, and just four of the 30 it figured would collect both business and household recyclables.

Conversely, the study was able to find more than double the projected councils that operated both a source-separated and commingled recycling scheme, with 46 local authorities identified despite a target of 20. Meanwhile, just five of the eligible authorities in Scotland were sampled compared to 43 in England.

The research found that the metals stream was the most heavily contaminated material analysed in municipal samples, with a median of 6.2% contamination by weight. This was followed by card (4.1%), plastics (2.9%), and brown glass (2.7%).

Metals

Meanwhile, metals was also the most contaminated stream in business material, with a median of 3.3% contamination, although paper and plastics were also high with contamination levels of 3.3% and 2.5% respectively.

Despite the findings, the study found that contamination levels in both source-separated municipal and business materials were generally low. But, the study also warned caution should be exercised in using the business recyclate figures due to the low sample size obtained.

The authors of the report blamed the small sample size on the failure to find a suitable list of pre-existing businesses that could be used in the sampling framework.

As a result, the study was unable to calculate robust estimates for business materials and so a consolidated estimate for recyclate from all sources, with the exception of card, could not be produced.

Separation

The report reads: Although contamination is generally low in source-separated recyclate streams, there are still improvements that can be made. Metals streams are the most

heavily contaminated, so work could be done with collection crews to ensure contamination is removed more effectively.

In particular, plastics appear to be a significant contaminant in many recyclate streams. People find it difficult to determine which plastics are recyclable due to the range of plastic polymers and differences between schemes. Further efforts should be made to educate waste producers both householders and businesses as to what is accepted in each stream.

In addition, the report recommends that the study should be repeated in a few years time when the Scottish regulations have had time to take effect. It urged that more time should be allowed for any future studies to ensure more robust data.

It added: In repeating this study, it will be important to give consideration to capturing and reporting weights of each contaminant separately. This will help differentiate contaminants that are problematic to reprocessors from those that are less problematic.

Gap

Commenting on the report, Iain Gulland, director of Zero Waste Scotland said: Poor quality of material has long been regarded as a key issue for the resource industry, with contamination playing a major part in this. To date we havent had any robust data on this, so its great to be able to address this gap.

Harnessing the maximum value from materials we collect for recycling is vital to achieving our zero waste goals and in helping us to move towards realising the environmental and economic benefits of becoming a more circular economy.

Welcoming publication of the findings, the Resource Association said the findings chimed with its own belief that source-separation tended to produce consistently better quality feedstock for UK reprocessors.

Resource Association chief executive, Ray Georgeson, said: We welcome this report at the end of what has been a lengthy and complex project. The Association has been pleased to have been involved in the Steering Group for the project and has welcomed the inclusive approach that colleagues at ZWS and WRAP have taken to this important piece of work.

Future

Zero Waste Scotland is to publish a separate report or briefing paper based on the data collected for the study on the factors that influence contamination, which is expected in summer 2014.

Mr Georgeson added: We note that the project work on factors that influence contamination will be completed and reported at a later date. We look forward to further engagement on this critical element of the project, as better insight into the variables at play here.