When you mention commercial and industrial (C&I) waste to anyone the issue of definition is one that inevitably arises. The wide range of sources coupled with the huge disparity of contents has contributed to many struggling to get an accurate picture of what a typical C&I waste stream comprises. Although this waste stream is proving more complex in its composition than municipal solid waste (MSW), consistent material patterns alongside appropriate processes for dealing with these materials, will result in recovery levels that surpass those possible with MSW.
The C&I waste stream has not particularly grown much in the last few years. Typically contracts for this type of waste were secured on the back of either sending all the material to landfill, or achieving a small level of recovery first, with the residue being landfilled. Now the scales have tipped firmly in favour of recovery, to such an extent that in some places contract prices are demanding recovery over landfill. A number of factors have given rise to this shift. One is the ongoing presence of legislation and the environmental commitments businesses are under, meaning they have to manage their waste more effectively. Coupled with this has been the increasing success in recovering material from the domestic waste stream, which is much more heavily contaminated. This has led many to evaluate just what recovery is possible should the correct technology be used for C&I waste. A third factor is the increasing demand for quality recyclates from countries such as China. The UK market for all recyclates, not just those from the C&I waste stream, is seeing challenges in trying to achieve the very high levels of purity now being demanded.
Although the composition of C&I waste varies significantly depending on the type of business it originates from, the materials it contains have exhibited stabilised price rises on the commodity markets in recent years. A typical composition of this stream is shown in figure 1, which represents a mean of samples taken from five C&I MRFs in the UK. Analysis across these locations has shown that many commonalities exist for the C&I waste stream regardless of the business from which it is sourced. These include:
- A high level of plastic film ranging in content from 6-13% and generally divided between 50-65% clear and 35-50% non-clear
- A high level of both paper and card with total contents ranging from 35-45%
- Wood shows a high diversity across samples with some as low as 1.5% and some as high as 9%
- Rigid plastics show a consistent 5-7% with plastic bottle content ranging from 1-3%
- Fines content is generally stable at 20-26% using a cut rate of 40mm
- Metals generally range from 2-5% with an 80:20 split between ferrous and non-ferrous
Having defined the waste stream and established the recoverable materials, the question of recovery techniques remains. In years past the typical process involved sending the material down a picking belt designed for skip waste and achieving 15-25% recovery at best, using a host of pickers. Recovery levels were low and throughput tonnages were significantly down on other waste streams as the C&I material was found to be much lower in density than other waste streams.
In the past three years we have seen an increase in the number of automated C&I MRFs. Many of the techniques for such MRFs have been adopted from those used in the processing of dry mixed recyclables and the MSW streams. The big difference is that recovery levels of +70% are being achieved, and the most modern plants are achieving material purity rates of 98% with no pickers whatsoever. While the process may differ from company to company, the plants generally include a bag opener that both opens bags and doses the virgin material to the plant at a consistent rate. Screening by trommel or screen then removes the fines and oversize material. Oversize material is then shredded and returned to the process. Correctly sized material then passes through a ballistic separator to separate the 2D material (>90% film and paper/card) from the 3D material (plastics, wood, metals, etc) and also catches any remaining fines in the mix. The 3D stream goes through a range of metal separation equipment to remove the ferrous and non-ferrous metals. Following this, both fractions are passed through a series of optical sorters to remove the paper and card, clear and non-clear films, rigid plastics, plastic bottles and wood.
In addition to the financial benefits of a fully automated C&I MRF, benefits include virtually eliminating the need for manual picking, thereby reducing labour costs, achieving higher throughputs, and doing this consistently on a 24-hour basis. The footprint for fully automated plants is generally similar or smaller than a manual plant and companies are seeing paybacks of only 12 months on the initial plant spend.
Since the first introduction of fully automated C&I processing in the UK, advances have been made in technology to address some of the more challenging aspects of C&I waste sorting. For example, while the removal of fibre has never been an issue, the quality of the removed product has, with several pickers, often required cleaning the removed fibre to an acceptable purity level. A two-step near infrared (NIR) approach is now used, whereby the fibre product is first aggressively removed and then passed through a second NIR for cleaning purposes. The same principle applies to film removal, with the difference being that all film is removed in the first step and clear film in the second. Through this two-step approach of hitting and cleaning using optical sorters, the throughput remains high while achieving high output purity levels.
The question of what to do with fines has still not been conclusively answered. Many equipment suppliers think they have found the solution and are carting around sample drying equipment and density separators throughout the UK for testing a small amount of material with a view to up-scaling this process for a larger plant. While many technologies are effectively able to remove lights from heavies or some other divide, many MRF operators understand that there is no point in splitting a single landfill product into two products, with both still going to landfill. NIR equipment providers can provide a viable solution to the issue of fines recovery but the capital cost is generally prohibitive. Many years ago the plastics division of the waste industry spun off into its own specialised industry, with several plants now in the UK solely dealing with this stream. Many think the fines market will go the same way with ‘Super Fines MRFs’ soon springing up around the UK, taking the fines from their own catchment area and investing in the technology to effectively sort this material.
One question that is often asked of an automated MRF is how well it can deal with input fluctuations. To illustrate, if a load of material that is 50% film came through a picking belt the pickers would know how to deal with it, but if such a fluctuation came through an automated MRF plant how would it be handled? The correct operation of a fully automated C&I plant does not include the blind loading of materials into a feed hopper; some amount of human interaction is required at the plant front-end. At normal operation, an automated C&I MRF may be operating at 14-35 tonnes per hour. Should material be loaded into the plant with a significant increase in one particular type of input material, the throughput rate of the plant (normally controlled at the bag splitter front-end) would need to be adjusted accordingly. In this way an automated C&I processing plant can successfully deal with input fluctuations.
Recently, the amount being recovered from the C&I waste stream has increased significantly due to the adaption of existing MRF processes and the success of NIR equipment. The future needs to balance the high levels of recovery being achieved with the increasing demands for quality outputs. There is no doubt however that the rates of both recovery and purity far surpass what was achievable through antiquated manual sorting methods.
C&I in practice: Devon Contract Waste
In 2012 Devon Contract Waste (DCW) in Exeter installed one of the first fully automated C&I plants in mainland UK. The plant was manufactured by McDonald International and incorporates TiTech sorting technology. The plant processes 75,000 per annum at a rate of 14 tonnes per hour. DCW operations director Trevor O’Malley said: “We were spending over £1m on landfill per year so decided to spend £2m to install a fully automated C&I waste processing plant. A total of three people operate the plant and we are achieving a 70% recovery rate of high quality materials. The plant has gone a long way toward achieving our zero to landfill target.”
The incoming MRF Code of Practice
Much of the emphasis on the incoming MRF Code of Practice appears to be on the inspection, sampling and testing of incoming materials to the MRF plant thereby passing much of the responsibility on to the customers of MRF operators. This will undoubtedly have the knock on effect of increasing the output quality of recyclates but, although it will implement a testing procedure for both incoming and outgoing materials, the Code of Practice will not be setting minimum quality standards for outputs. In many ways the market is self-regulating with regard to quality of output recyclates, in that should the contamination levels be exceedingly high the material will be rejected and only fit for re-preprocessing or landfill. The lack of regulation on MRF outputs in the MRF Code of Practice does beg the question: will the new Code be producing uniform MRF plants across the UK, or will it be giving MRF operators a stick they can use to beat their customers into ‘clean input’ submission?