Curbside Collection

Improving the Quality of Curbside Collected Recyclables

Considering how the focus in the UK waste management sector has shifted from tonnage to quality, and how to ensure feedstocks reach their end markets.

Dr. Nia Owen and Dr. Adam Read

UK municipal waste recycling rates have just hit 40 percent, but with new targets asking for 70 percent diversion through recycling and composting in Scotland and Wales, and with the EU Landfill Directive demanding a 75 percent reduction on 1995 levels of biodegradable municipal waste going to landfill, there is still a big push on for more collection of recyclables, whether it be through curbside programs, or through bring sites and segregation at the local tip.

We are experiencing the development of new Mechanical Biological Treatment (MBT), Materials Recycling Facility (MRF) and Mechanical Heat Treatment (MHT) systems to help segregate additional recyclable materials from the residual stream to improve recycling tonnage to ensure EU targets are met. However, the last two years has also seen a massive swing in local authority activity away from focusing purely on recycling tonnage (necessary to meet targets) to recycling quality, a reflection that we now have local collection schemes and processing facilities that are achieving 70 percent diversion, with the emphasis now more about securing markets and income generation—both of which are reliant on quality materials. This is in part a reaction to global trends in commodity prices, the increasing tonnage of recyclates within the UK market, and the filling of capacity of traditional market outlets, all of which have resulted in recycling loads being rejected at the paper mill or aluminum plant. But what is quality, how do we improve it and who is ultimately responsible for ensuring quality materials are segregated and delivered to end-users?

Making a Shift

Ultimately, quality materials are those that are provided in a form that an end market is prepared to accept, at a price that is more advantageous then alternative material steams—in particular raw resources. In the UK, with the prevalence of commingled collections and developed as a cheap means of collecting high tonnage rather than quality feedstock, there has been a key role for materials recycling facilities (MRFs) in taking these mixed recyclate streams and pulling out materials prior to sending them on to UK and wider afield markets. Over the last five years MRFs have been held up by parts of the UK waste sector and the national media as the ones responsible for producing low quality material, but the production of quality material from curbside recyclables needs to be more accurately considered as a supply chain providing materials to the end users—the markets. As such, the public is ultimately responsible for placing the correct materials into their recycling containers, and the waste collectors (recycling crews) are responsible for ensuring that only material of good quality is collected and delivered to the MRF. So, you can see there is inherent tension in the UK between curbside collection system design, with its historic focus on tonnage and its prioritization of commingled collections because of ease of public use and the end market users who want quality feedstock at an appropriate price.

Focusing on the Quality of Materials

This has put MRF operators in an uncompromising and difficult position, challenged by the demands of the end markets they supply, the feedstock they receive from the public and the local municipalities they serve. MRFs are essentially a manufacturing operation producing segregated recyclate from the material delivered to them. So, the old adage “rubbish-in rubbish–out” remains very true for MRF operators in the UK, as it is harder to produce a quality output (an output required to meet the specification of a glass bottle manufacturer or paper mill) when commingled collections are contaminated with unrequested materials such as food, diapers and some hard plastic packaging, etc. Therefore, focusing on the quality of materials presented at the curbside will not only improve the level of quality throughout the supply chain, but it will minimize the costs incurred at the MRF—disposal of residues, returned loads from end users, sorting streams for a second and third time, etc. This has become a key focus for municipal authorities over the last two years as local authority waste managers have begun to recognize that quality is becoming the limiting factor on service efficiency and value for money—something that is even more obvious in the current global recession with UK municipalities being asked to make cuts in budgets without impacting on service level. However, this has also led to many local tensions between operational staff and budget holders as addressing quality concerns at the curbside often involves targeted communication campaigns that educate and instruct households about what ‘not’ to put in their bin/box/bag. But as we all know, public communication funding is always the first to be hit during cuts in municipal budgets.

Non-Target and Target Materials

Non-target materials are defined by local conditions; that is collection infrastructure, MRF technology, and the material specifications required by the reprocessors. Thus, non-target materials at some MRFs may be target materials at others; for example, glass, Tetrapak, aerosols etc. Also, target material can become non-target materials (contaminants) when their property changes—for example, when paper or textiles include glass shards from broken bottles. Non target material levels vary widely in the UK with some authorities reporting less than 5 percent and other MRF operators claiming more than 30 percent—clearly it is an issue that needs addressing.

In a recent study with an MRF in the south of England, the single largest non-target material being delivered to their site was wet paper and card (60 percent of all contamination) which the plant equipment could not cope with and resulted in loads of mixed paper being frequently rejected on arrival. This has resulted in the MRF operator working with the local municipal authorities to develop a campaign that encourages paper to be stored in recycling boxes with the lid closed or in bins with the lid down; only time will tell how well the public take to this request.

It is essential for an MRF to monitor the presence of non-target materials and to identify the materials causing issues. This should be done in two complementary ways: by conducting composition analysis on the collected material when it arrives at the facility (this shows the level of reject materials that has made it through collection) and by recording the percentage of bins set out at the curbside containing non-target materials (this tells you what might have got through to the MRF if there was no quality monitoring by the crews). But it is important to note the differences that this data provides, in that compositional analysis provides information on the percentage by weight of each of the non-target materials, but does not provide any information on how widespread the problem is, i.e. is the contamination caused by a small number of people grossly misusing the scheme, or a large number of people getting it a little bit wrong?

It may be that contamination is linked to one housing estate or collection crew, and this would inform you plans to address contamination through a localized communications campaign or a crew training and monitoring program. While the ‘bin count’ methodology will tell you who is contaminating, it cannot accurately indicate the level of contamination. So, using both methods regularly will give you a clearer picture of what the contamination is and where it is coming from—only with this baseline data can you seriously expect to correct problems at the curbside.

Reducing Non-Target Materials

There are a number of tried and tested methods which can be used to reduce non-target material levels in commingled recycling collections. These can broadly be categorized as follows:

  • Scheme design

  • Operations

  • Communications

Aspects of scheme design which can impact the quality of recyclables collected include:

  • Container type—‘open bins or boxes’ can be compromised via littering from passers or will result in wet paper. To minimize this lids or lidded containers can be used, which may or may not be lockable.

  • Provision of free recycling bags, while black bags for residual waste must be purchased by the householder can lead to contamination of the recycling loads.

  • Use of transparent recycling sacks for easy identification of contamination at the point of collection by crews.

  • Border effects—the impact of a neighboring authority’s scheme which may encourage residents to put out non-target materials because their friends and relatives are recycling them, i.e. yogurt pots, etc.

  • Frequency of residual waste collection, which may encourage contamination of the recycling bins once the residual bin is full.

  • Range of recyclable materials collected, with a fuller coverage of materials resulting in less non-target materials ending up in the recycling stream.

  • Bin type—commingled collections that use wheelie bins are traditionally more contaminated than systems that use bags or boxes because they are easier to check at the curbside.

Studies completed in the UK suggest that the addition of new materials to the recycling service can reduce the presence of non-target materials, quite simply because the materials causing issues previously become target materials (glass, tetrapaks, plastics etc). However, this is dependent on whether the receiving MRF is able to process new materials such as mixed plastics or glass. Two authorities in the UK added plastic packaging and foil to their acceptable materials and reduced their contamination levels at the MRF from 8 percent to 1.4 percent and from 4.5 percent to 2 percent respectively.


However, the key operational factor that can impact the levels of non-target materials within commingled systems is crew training. This training can be focused on recognizing non-target materials in order to reject bins at the curbside, or training of the staff to more effectively engage with householders and encourage them to recycle correctly. The collection crews regularly come into contact with residents when collecting materials during the day and can help provide positive feedback about what can and can’t be recycled. A number of UK local authorities have undertaken crew training programs designed to address non-target materials and contamination and monitored the impact of the training provided to crews.

Portsmouth City Council found that providing crew training in the recognition of non-target materials reduced the levels from 11 percent to 5 percent for materials delivered to the local MRF. Similarly, one London borough has implemented a crew training program and found that the levels of non-target materials declined from 22 percent to 13 percent. So, clearly a small investment in crew support and local delivery can have significant benefits, and these are much easier to implement than whole-scale changes to the collection system or the containers in use.

Communication Campaigns

Not surprisingly, communication campaigns have been the most common approach used for positively influencing the levels of non-target materials. This is because many authorities use annual communication campaigns to remind residents about the scheme and plan for them to be associated with seasonal events, changes in service and the addition of new materials. Some of the best examples of communications campaigns that have been specifically targeted at the reduction of contamination at the curbside have resulted in falls in non-target material levels of 11.5 percent to 5.8 percent across Durham County, while in one Welsh Authority levels dropped from 17.5 percent to 8 percent when local officers monitored bins and visited offenders.

Communications campaigns can range from a series of leaflets and stickers on bins explaining what can and should not be recycled and why. It often helps to explain why materials are currently not being recycled and a reminder of the additional costs incurred in separating non-target materials or the rejection of whole loads of mixed recyclables at the MRF will often be powerful messages to residents who didn’t know what they were doing was wrong. In more problematic areas, the use of bin monitors checking for constant offenders and visits from recycling advisors to help challenge behavior and to help correct participation have also been very effective. Traditionally, a combination of communication activities are used in parallel, because as we all know different people will respond better to different messages and stimuli.

Everyone Plays a Part

Much work is underway in the UK to address curbside concerns around commingled recycling material quality. But quality must be a focus throughout the supply chain, in terms of educating the public as to which materials are being targeted in order to minimize contamination at source, working with crews to improve their recognition of target materials, encouraging them to leave behind contaminated bins and supporting their role as a recycling ambassador as they engage with residents, and by working with MRFs in rejecting poor quality loads at the gate and trying to process the rubbish they receive. If everyone plays their part and shares in the responsibility, then paper mills and reprocessors will not be able to turn away the materials delivered and recycling will continue to grow in terms of participation, diversion and sustainable cost-effective practices. However, you must continue to monitor which particular materials are causing the quality issues and from which locations the contamination is coming, so that any future communications can be targeted effectively and with an appropriate budget.

Dr. Adam Read is Global Practice Director for AEA’s Resource Efficiency and Waste Management Practice. He has had more than 17 years of operational experience both in the UK and overseas, the last 10 in consultancy. He was awarded an honorary professorship in 2002 for his pioneering work on waste communications and public engagement. He is a Fellow of the Royal Geographical Society and a Fellow of the Chartered Institution of Wastes Management. Adam leads a team of waste and resource management consultants at AEA specializing in resource efficiency, product design, clean technologies, waste management strategy, recycling service design, technology appraisal, procurement, training and behavior change. He is recognized as a leading waste management thinker with an extensive portfolio of research papers, conference articles and collaborative investigations both in the UK, U.S. and Europe. He can be reached at 07968 707 239 or e-mail [email protected].

Dr. Nia Owen is a specialist consultant in AEA’s Waste Management and Resource Efficiency Practice specializing in waste auditing, local authority recycling and treatment technologies particularly material recovery facilities, waste composition analysis and options appraisal. She was previously in the Waste Regulation Policy team within the Environment Agency. She can be reached at 07875 586 623 or e-mail [email protected].


Case Study

AEA is currently working with the Waste and Resources Action Programme (WRAP)—the UK Government’s delivery agent for support to local municipalities on waste management issues—on a project to improve the input quality of commingled recyclables to MRFs.  This project involved a literature review to assess what work had already been undertaken in this wide-ranging area, drawing on over a decade of UK based research and application. Many of the key findings from this have been reported in this article.

AEA was also responsible for developing a trial to use in Crawley Borough to help reduce the non-target materials reach their MRF, drawing on the best practice identified in the research. The authority has seen non-requested material levels rise from 4 percent to 16 percent over the last 18 months, with the problem materials being residual waste, textiles, wet paper and ice-cream tubs. The local authority and its waste contractor monitor the quality of material on a regular basis. The monitoring includes data on the number of recycling bins rejected at the curbside by the crews due to high levels of contamination, loads of collected material rejected at the MRF, as well as compositional analysis data on material accepted by the MRF.

As discussed in the article, communication and crew training are key factors in improving the quality of material, and as a result two parallel programs have been developed for use in Crawley—crew training (of one target) to help them recognise non-target materials and to empower them to leave behind contaminated loads as a reminder to residents about the contamination, and a bin sticker trial (in one crew area) to help reinforce messages about the materials accepted by the recycling scheme (all target households received a letter explaining this as well). This trial is currently underway, and the data will be available June 2011.