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We're wasting value from C&D

The EU is calling for diversion of 70% of all C&D waste from landfill by 2020. Jonathan Clarke believes there has never been a better time to exploit the potential of this waste stream and introduce proven technologies

Construction and demolition (C&D) materials represent by far the largest proportion of the UK waste stream with more than 90 million tonnes of waste, according to the Environment Agency, generated annually from construction and demolition projects.  The EU Directive 2008/98/EC has set a 2020 recycling rate target of 70% (by weight) for reuse, recycling and other recovery of construction and demolition waste. This is an ambitious target and one that will only be met by exploring all the avenues to recover material from this complex waste stream.  

There are many factors at play here: EU legislation is driving recycling targets; ever-increasing landfill taxes are making disposal to landfill a very costly option, current treatment facilities are limited in their ability to sort C&D waste into recyclable fractions, and there is also continued demand from the UK’s construction sector for recycled materials for use in new projects. Taking all of these factors into consideration, it is high time that this sector of the waste management industry became aware of the opportunities – and benefits – that automated sorting can deliver.

Recovered inert fraction

Recovered inert fraction

The C&D sector should be applauded for the progress made over the past two decades in adopting a much more environmentally-aware approach.  A great example is the London 2012 Olympic Games where 99% of all construction and demolition waste was recycled and approximately 25% of all aggregates used were from recycled materials. Sadly, though, this is a unique example and throughout the UK, vast quantities of valuable recyclable materials from our construction projects still end up in landfill. But this need not be the case.

Whereas automated, or sensor-based sorting, has already been successfully adopted with exceptional results in other more complex waste streams such as MSW and C&I, the C&D sector remains a previously untapped source of recovery of valuable materials and diversion from landfill.

Perhaps the greatest challenge when approaching mixed C&D waste processing is the vast variations and complexity of the infeed material.  Materials commonly found within this waste stream include wood, paper, plastics, metals and insulation materials, as well as inert material such as stone, glass and ceramics.

It’s high time that this sector of the waste management industry became aware of the opportunities – and benefits – that automated sorting can deliver.

Manual sorting simply is not a suitable option for treating C&D waste because of the sheer volume of material to be processed and conventional sorting techniques are also limited in their ability to recover value. The current treatment process at UK C&D MRFs involves a combination of more traditional sorting techniques including shredders, screening machines, wind sifters, magnets and non-ferrous metal separators. Although material can be sorted by weight using this process, recovery by material type is more challenging and as a result, few materials other than aggregates are currently being recovered.

Automated or sensor-based sorting opens up opportunities for the treatment and recovery of C&D waste that would not be possible using conventional techniques. By applying the latest technology to mixed C&D waste, it is possible to recover inert materials, film, metals, wood, paper and cardboard and plastics. Polythene and wood can be recovered automatically, but the plastics and inert materials that form the largest proportion of C&D waste can also be sorted to extremely high purity levels, increasing their value.

Sensor-based sorting also enables the recovery of a fraction that can be used as refuse-derived fuel (RDF), with a typical calorific value in the order of 12,000kJ per kilogramme. By recovering this fraction, we would potentially make a significant contribution to another key target – generating 15% of the UK’s energy from renewables by 2020.

RDF fraction

RDF fraction

Commercially, it makes sense to recover these materials.  Not only will landfill reliance and the associated costs be reduced, but C&D MRF operators will be better placed to meet the high demand for these high value secondary materials. There is also a strong environmental argument in favour of recovery, as the use of recovered and recycled materials in construction projects is much more energy efficient than using virgin materials.

In recycling plants, sensor-based sorting technology is generally used after the metal extraction. Tomra Sorting´s Titech technology sorts according to material type and so generates marketable mono-fractions. Depending on the desired outputs, a combination of detection techniques can be applied. Techniques include near infrared (NIR), X-ray transmission, visual spectrometers (VIS), colour line cameras and metal sensors.

The technology is capable of detecting and sorting grain sizes in a bandwidth of 10 to 500 mm, preferably divided into grain size ranges. 

The Titech autosort, for example, uses an NIR sensor that detects the material-specific near infrared spectra of different objects with a high optical resolution.  Organic components such as wood and plastics can be detected and ejected.  The autosort can also generate RDF and separate PVC, paper and cardboard.  While the Titech x-tract can also – based on measurement of the atomic density – separate inert material from the input flow.  A residual metal fraction can be generated using the Titech finder.

There are many benefits associated with the use of sensor-based technology in the C&D waste stream.  These include consistent high purity (up to 98%) at a high throughput rate, the removal of impurities, reduced disposal costs and consistent quality of end fractions.

There is no denying that the EU targets set for the diversion of C&D waste from landfill will prove challenging. However, there are clear and considerable commercial opportunities available for the taking.  Although the infrastructure for C&D waste treatment is still in its infancy here in the UK and also throughout Europe, there are a number of companies that are leading the way in their treatment of this complex waste stream.  It is now time for more companies operating in this sector to take action.

Our advice would be first to finding experts that can help with the planning, design and installation of automated technology.  It is also vital to truly understand your infeed material, to research the markets for recovered fractions, to visit reference sites, and to undertake trials.

The C&D sector in the UK needs to recognise the significant role that automation could play in achieving the 2020 target.

Jonathan Clarke is global sales director for TOMRA Sorting Recycling.

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