H W Martin Waste Ltd has significantly expanded the volume of mixed recyclable materials it receives from council clients, due to an increase in volume from our existing clients and a growth in the number of new local authority contracts won by the company. Among the materials to be sorted by the company on behalf of the councils are mixed plastics, made up of drinks bottles, milk containers, detergent bottles, yogurt pots, food trays and so on. In order to sort the plastics into their separate polymer types ready for sending to recyclers, the mixed plastics go through the company’s existing plastics sorting plant.
The company’s plastics sorting plant, co-located with its Materials Recycling Facility (MRF) in Leeds, is routinely operated near full capacity due to existing recycling sorting contracts. The company needed to increase its plastics sorting capacity and it was clear the expansion could be better catered for at its Alfreton Recycling Centre (“ARC”) – the company’s MRF in Derbyshire.
As a result, the company committed to investing in a new plastics sorting line at ARC, that included sorting capability for multiple plastic polymers. This to be installed in addition to the existing MRF layout, enabling the new equipment to be part of the overall MRF process, but with the option to use it in isolation.
Procurement commenced in June 2020, a supplier was selected in August 2020 and the installation and commissioning was undertaken during September 2020.
H W Martin Waste Ltd’s Activity
The company selected a design that included the use of several Near-Infrared (NIR) sorters. This facilitates the extraction of two polymers per unit and can be changed to identify whichever polymers the company requires to be extracted.
The company can produce several polymer outputs, including PET, HDPE, PP, PS, etc. Whichever operating options are chosen depends on the mix of the input material and the requirements of the end recyclers and manufacturers to which the sorted polymers are sent.
It was imperative that the installation and commissioning of the new equipment would cause as little disruption as possible to the normal running of the MRF. The project manager was challenged with installing and commissioning the equipment during three consecutive weekends. This was successfully achieved, with the main equipment installation – steel framework, NIR sorters, conveyor belts, etc – undertaken during the first two weekends. During the third weekend, cabling and telecoms were completed and the equipment was tested and commissioned.
Once the new section of the MRF went on-line it was immediately apparent from the quality of the output that the equipment worked well. Each bay into which the sorted materials are deposited contains distinct polymers. Sorting is highly efficient, with good quality outputs of separated HDPE containers, PET bottles, etc.
- The quality of the mixed input material delivered by client councils can determine the efficiency of the NIR sorters.
- If PET drinks bottles still contain a lot of liquid in them, they can be too heavy for the sorters to fire them out of the mix.
- Squashed drinks bottles are preferred to bottles that are still round, in order to prevent the bottles from rolling on the conveyors, which can prevent the NIR working effectively.
Issues such as these are influenced by the behaviour of client councils’ residents and the quality of the material they leave out for kerbside collections. This kind of knowledge-sharing is continuously undertaken between the company and its client councils so that we continue to work in partnership with them to maintain high levels of recycling.