Contamination of source-separated recyclate ‘generally low’

Contamination levels in source-separated recyclate from both municipal and business streams are ‘generally low’, a new report from Zero Waste Scotland (ZWS) has found.

The ‘Contamination in source-separated municipal and business recyclate in the UK 2013’ report, designed and delivered by the Water Research Centre (WRc) and environmental consultancy RPS Ireland Limited (RPS), was commissioned by ZWS to ‘address the lack of robust data on the quality of source-separated dry recyclate’, specifically in regards to the five key recyclates (paper; card; glass; metals; and plastics) required for separation under the Waste (Scotland) Regulations, which came into effect in January of this year.

It found that of the 10 recyclate streams sampled (paper; card; mixed paper & card; clear glass; green glass; brown glass; mixed brown & green glass; mixed glass; metals; and plastics), none of the materials had a average contamination rate of more than 10 per cent.

Report details

Released yesterday (24 March), the report analysed 860 municipal recyclate samples from 59 sites across the UK, along with 225 business recyclate samples from 18 sites (focusing on just six recyclate streams: paper; card; mixed paper & card; mixed glass; metals; and plastics).

Although focused on informing Scottish policy, the scope was extended to sites across the UK as it was ‘recognised that sampling in Scotland alone would not yield enough data due to the relatively small number of source-separated collections there’.

Samples were taken from recyclate bulking sites between July and November 2013 with data collation and statistical analysis carried out in November and December 2013.

WRc and RPS found that in source-separated municipal recyclate streams, metals were most heavily contaminated (with contamination defined as any ‘non-target or non-recyclable material present in the recyclate stream’), with a median of 6.2 per cent, followed by card (4.1 per cent), plastics (2.9 per cent), and brown glass (2.7 per cent).

Contamination levels for the other streams were (in descending order):

  • Mixed brown & green glass (2.3 per cent);
  • Green glass (1.9 per cent);
  • Clear glass (1.2 per cent);
  • Paper (1.1 per cent); and
  • Mixed paper & card (0.9 per cent).

The stream with the least amount of contamination was mixed glass, with a median of just 0.4 per cent (however, the report highlights that ‘caution should be exercised in using these figures due to the low sample size obtained’).

Metals were also the most contaminated stream in the business recyclate samples, with a median of 3.3 per cent, tied with paper (3.3 per cent).

Following this, the most contaminated streams were:

  • Plastics (2.5 per cent);
  • Glass (1.5 per cent);
  • Mixed paper & card (1.0 per cent); and
  • Card (0.5 per cent).

The authors of the report highlight, however, that for both municipal and business recyclate, the level of contamination for each material stream includes contamination by similar physical materials (i.e. green glass in brown glass), and that some reprocessors may deem that ‘materials of the same physical composition…[are] not counted as contamination’.


The report concludes that although contamination is generally low in source-separated recyclate streams, ‘improvements can still be made’.

Specifically, the authors highlight that as metal streams are the most heavily contaminated, ‘work could be done with [waste collection] crews to ensure contamination is removed more effectively’.

Householders and businesses should also be educated on what materials contaminate the waste stream, especially in regards to plastics, the report adds. It reads: ‘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.’

The report concludes by adding that as the evidence shows that ‘local authorities are moving away from source-separated collections’ (despite the European Commission requiring EU members states to have in place separate collection for paper, metal, plastic and glass by 2015, where ‘technically, economically, and environmentally practicable (TEEP)), the study should be repeated in a ‘few years’ time, when the Scottish regulations have had time to take effect’.

In repeating this study, the authors add, consideration should be given to ‘capturing and reporting the weights of each type of contamination’, as this would allow a distinction to be made between ‘contaminants that are readily recyclable and normally accepted, and contaminants that are recyclable in theory but not normally accepted’. This data collection was reportedly ‘not possible’ in this project.

Analysis of the factors that influence contamination will be published in a separate report by Zero Waste Scotland later this year.

Iain Gulland, Director, 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 haven’t had any robust data on this, so it’s 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."

Gary Walker, Principal Policy Officer, at the Scottish Environment Protection Agency (SEPA) added: "The study provides important evidence on contamination levels and we will be considering the report findings in order to target our activities and priorities on material quality and ensure that contamination issues are addressed under the new Waste (Scotland) Regulations."

‘Results show just how supportive separate collections are to the development of a truly circular economy’

Speaking of the report, Ray Georgeson, Chief Executive of the Resource Association (RA, a member of the report’s steering group), 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.”

Project steering group member and RA member Peter Seggie of Smurfit Kappa Recycling said: “The report itself summarises: ‘contamination levels in source-separated municipal recyclate were generally low’. This chimes with the approach maintained by the association that, even recognising that materials come from all kinds of collections, our members still generally prefer source-separated materials as they have tended to produce consistently better quality feedstock for UK reprocessors. The report sets out the high bar on quality that must be achieved by those collection and sorting systems needing to demonstrate that they can conform to the separate collection requirements of the revised Waste Framework Directive as transposed into local legislation.”

“Taking into consideration that the report labels as ‘contaminants’ elements that relate to the same physical material as that targeted (i.e. paper in card, card in paper and glass of the wrong colour), the results show just how supportive separate collections are to the development of a truly circular economy. Maintaining the integrity of key materials remains a vital ingredient necessary for a healthy and viable reprocessing sector integral to the circular economy.”

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 – such as collection frequency, type of receptacles, socio-demographic and housing type and style and consistency of communication to households – could prove to be the most significant element of the project as they hold the key to so many of the issues of dysfunction in the recyclate supply chain that lead to lower and inconsistent quality and the problems this causes for UK reprocessors.

“As others draw their own conclusions from this project, I hope that the gap between publication of this report and the subsequent work on factors influencing contamination is not too long. The continuing debate about quality, collection and sorting will benefit from this further insight.”

Read the ‘Contamination in source-separated municipal and business recyclate in the UK 2013’ report.