Waste MRFs Defined and Explained
What Happens Inside a Materials Recovery Facility
Materials Recovery (or Recycling) Facility
In many towns and cities these days, each householder is provided with at least two bins, maybe more, for recycling. When you deposit materials into your green wheeled bin, they are collected by the refuse/recycling collections crews and taken to the MRF (Materials Recycling Facility) in some districts the rubbish placed in your black bin/bin liner goes direct to the landfill.
The MRF is a large shed or several industrial buildings in a complex, where waste with several types of recyclable wastes (co-mingled as sorted by the householder) is sorted further, bulked up into load sizes suitable for transport, made ready for collection and transportation, sold, stored, and shipped to the buyers including some of the original manufacturers.
However, more and more waste disposal authorities nowadays also process the residual or mixed waste bins (ie black plastic bag waste), as is required in Europe for example to achieve the high recycling rates required by the Waste Framework Directive and the Landfill Directive.
When a MRF deals with only the bags (dry solid waste) which have been pre-segregated by the householders it is called a "Clean" MRF, but when the facility also breaks the mixed or "residual" waste bags or accepts mixed waste from commercial premises the MRF is called a "Dirty" MRF.
The Materials Recycling Facility is made up of a series of conveyor belts and a mix of manual and automatic procedures to separate the materials and remove the items that we don't need.
Sorting in a MRF
Mixed and segregated recycled material is sorted as it passes through an MRF, where a combination of mechanical, optical and hand sorting techniques are employed to separate out different materials ready for recycling.
A separating and sorting plant operator drives a loading shovel and loads the mixed material into a bag splitter where the material is allowed to discharge onto a conveyor system. Sorting and treatment follows, using mechanical processes so that recyclate, Refuse Derived Fuel (if included at the plant), and soil conditioner streams, as well as the rejected fraction of residual waste, are produced.
A trommel and screen separating process is very common as a first stage in these plants, and then the remaining mixed fraction is conveyed through a picking station for final sorting (by another team of waste operatives), and thence into various skips. The paper trommel usually traps about 70 per cent of paper and cardboard (and any large contaminants) which are are usually moved directly to a paper sorting line, and baled for dispatch.
Baling machines are used to compress the large volume otherwise needed for the transport of cans and plastic bottles. Some MRF operators use an Eddy Current Separator for sorting out the aluminium cans. Electromagnets are the obvious choice for extracting steel cans.
After sorting and baling plastic, glass, and metal containers, and processing paper and cardboard, the MRF operator, sells them to manufacturers who use the baled material as feedstock in manufacturing various products.
The larger particles of aggregate are used mostly for road-making, for making hard standing areas and for general infill systems. Crushed glass can make excellent aggregate for roads and colourful aggregate for stylish patio designs.
Development of soil recycling areas within the boundary of the landfill site to provide soil for land restoration from the soil entering the facility when segregated plus use of the dust fraction for soil making, may also also an option at some locations.
Different MRF's operate in slightly different ways, but this gives you an idea of the sorting processes involved. Fully-Automated MRF's with fully automated systems are available which are said to offer higher throughputs, reduced operating and sorting costs, and consistently higher recovery levels.
Household and Municipal Waste
Municipal waste includes all wastes collected by the Waste Collection Authorities (WCAs), or their agents, such as all household waste, street litter, municipal parks and gardens waste, council office waste and some commercial and industrial waste. A total of about 30 million tonnes of this waste is collected from households in the UK each year. That's about 500 kg or half a tonne of household waste per person. Some households may not be within easy walking distance of a recycling bank and you may be forced to use a car, requiring energy and resources and cancelling out many of the environmental benefits of recycling. Most UK WCAs are in the process of building additional recycling facilities to provide more local reception points and a greater range of collection containers for improved segregation at each.
Whilst it is difficult to monitor reduction and reuse schemes across all nations, councils and waste management companies do collect figures allowing us to note how much of collected waste is intended for recycling (or recovery) and how much for final disposal through landfill, and the recycling rate is rising just about everywhere.
The tax imposed on waste disposal authorities and groups that dump household, industrial or commercial waste at landfill sites puts a commercial pressure on all businesses to minimise their waste.
The result is the collection of the following common materials that are sold and recycled in some way:-
- Paper and cardboard
- Plastic films and hard plastics
- Containers (plastics, aluminium and steel cans, glass)
- E-waste (computer and printers)
Garden and green waste is increasingly being composted, and food waste is dealt with in the most environmentally sensitive, and with the highest security against disease transmission if sent to Anaerobic Digestion Plants, where energy recovery can be achieved.
Energy recovery is being achieved by incineration of wastes, production of Refuse Derived Fuel (RDF) from wastes (usually in MBT plants) , and through the sue of Anaerobic Digestion Plants (also called Biogas Digesters).
Recycling is placed above energy recovery, in what is called the Waste Hierarchy (EU), with disposal being at the base of the hierarchy. However, the purpose of MRFs is that they provide a capability to sort, segregate and process the materials for off site recycling and recovery, assisting in the achievement of reducing the amount of waste going to landfill for disposal, and not to produce recovered energy. Where that is provided the plant is called an MBT (Mechanical Biological Treatment) plant.
Recycling centre employees sort the glass by colour -- green, brown, and clear. Practically all the glass is broken and hen used in the manufacture of new glass. This saves energy and reduce the consumption of raw materials.
Plastic bottles are sorted for recycling by a combination of hi-tech equipment and highly skilled people. Plastic bottles can be turned into fleece jumpers, children's toys or garden furniture to name but a few of the many uses for recycled plastics. Sophisticated 'autosorts' use light to identify the plastic bottles and remove other unwanted items such as yoghurt pots with jets of compressed air. To the human sorter it is important to identify the type of plastic, which the autosort does by the lightwave. They must recognise the clear, rigid and strong plastic which is known as PET, PETE, or #1 plastic, and is identified by a #1 in the symbol on the bottom of the bottle.
Plastic is made from oil products normally, it has a high calorific(heat) value when burned. It makes a lot of sense to burn it, in the cities where electricity is needed, and in combination with he high efficiency of Combined Heat and Power installations, and make new plastic from more oil.
Aluminium cans are separated by a small air current.
Aluminium has a very high energy demand in its refining and manufacture so recycling it has a big benefit in energy saving and through that in reduced carbon dioxide emissions.
Paper gets turned into new paper products such as newspapers. Your MRF processes glass bottles and jars, plastic containers (soda bottles, milk and water jugs, and detergent bottles), aluminum cans, steel cans, bi-metal cans, and newspaper from 155,000 residences in the County.
It is important that these are removed at source as far as possible as they are difficult to remove and recycle once in the waste.
It is important that the cardboard-related materials are placed out separate from other recyclables and not in blue boxes or other plastic containers as it has a much higher value for recycling when kept separate with a very low degree of contamination by other materials.
Paper bags, brown envelopes, paper egg cartons and light weight boxboard tubes can also be included with cardboard or boxboard for recycling. A baler is an important inclusion for cardboard otherwise transport costs a high per tonne transported due to the low density of this material.
Waste Electrical Goods
Dedicated skips for wood, and or cages for WEEE (Waste Electronic and Electrical Equipment) sorted from the waste, is an important facility at every MRF and MBT Plant
Society is now, for the first time ever, having to realise and cope with the fact that the non-biodegradable materials which comprise the largest proportion of our waste and of which the quantity continues to rise inexorably cannot be simply disposed of by throwing into holes in the ground, without very serious consequences.
The need to reduce landfilling is driving waste management strategies. Improving the recycling rate is an essential part of this task and huge amounts of material can be diverted away from landfill by doing this.
The following quotation is included below to emphasise this point:-
"More than a million tons of recyclable paper is thrown away in Massachusetts every year, at a disposal cost of more than $100 million," said Laurie Burt, Commissioner of the Massachusetts Department of Environmental Protection (MassDEP) at a recent news conference.
Throughout Europe, and many other nations, the driver for increased recycling and landfill diversion is not cost benfit or even sustainability or carbon emissions based. The Waste Regulations do not set out to ensure that the recycling which is done is done efficiently or in an environmentally sustainable manner. Instead, legally binding targets have been set which, regardless of sustainability or cost must be complied with. Of course, all those implementing the Waste Regulations do usually endeavour to ensure the cost value and best level of sustainability of their solutions. However, this is a secondary consideration to compliance with the targets.
Costs for waste disposal are therefore bound to continue to rise very substantially above present costs. The cost of collection and disposal of household waste is met through taxation which is a burden on every one of us. Unfortunately, these costs are set to rise for probably at least the next 10 years, in order that recycling facilities of all types can be brought into use, operated and maintained.
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- What Is a Dirty MRF | Waste Management Technology
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