The Rubbish Book

By James Piper

A Complete Guide to Recycling


What is a MRF?

Throughout this chapter we will explore the sorting process for each material, assuming waste is collected co-mingled. If waste needs sorting it will likely go to a MRF which stands for Materials Recovery Facility.

Recovering materials

A MRF is where recyclable materials are separated by both human sorting and automated machines. Once the materials have been sorted they will be sent to recyclers and manufacturers to create new products. A MRF ensures things are removed that cannot be recycled and helps provide quality material. This stops manufacturers needing to use new materials which can be damaging to the planet and wildlife.

Dirty MRFs

The MRFs in this chapter assume waste has been separated by the household. There is another type of MRF, known as a ‘dirty MRF’ where recycling goes that is still mixed in with rubbish. This can be sorted as well but will ultimately create lower quality recycling as the recycling will be contaminated with other waste.

Recycling Rule: A MRF is where co-mingled recycling will go after being collected, when it is ready to be sorted.

Paper and Card

There are a number of ways of sorting paper and cardboard. The most common is to use a giant sieve, called a trommel, which separates the large paper and cardboard from the smaller plastics, glass and metals.

Large and airy

A trommel is a steel drum with holes in just like the inside of a washing machine - but much longer.

Like your washing machine, it rotates, which sends the material being put in from one end to the other. Plastic, glass and metal fall through the holes and the paper and cardboard will not. This means at the other end of the machine you will get a clean stream of paper and cardboard.

As paper and cardboard is very light, jets of air are another way of sorting. The jets are positioned to send the paper and cardboard to another conveyor belt ready to be piled up and sent on to the recycler.

Cameras, which are used for other materials and use colour to sort, do not work on paper and cardboard as it will change colour when it gets wet.

Recycling Rule: A trommel will normally sort paper and card from other materials, using size to separate.


Glass jars and bottles are recycled and sorted in the same way. Ideally, they would be collected separately but the ones that are collected comingled and end up at a sorting facility need to be separated from other waste, first by material and then colour.

Cullet and colour

When glass is crushed it will break into small pieces. These pieces are known as cullet. This process will remove any metal caps left on the jars and bottles - these lids will be picked out with magnets. Hot air is blown over the glass to dry it and remove any glass dust and paper labels.

Cameras and air are then used to sort the glass by colour. Three colours are sorted: clear, brown and green. The glass passes through a lit-up section and cameras scan the image of the cullet and detect what colour the glass is. Air is used to push the glass into different locations, based on colour.

Lower quality glass can be used as ‘aggregate’, which means it will be crushed and used in road building. If the glass is destined to be aggregate it does not need to be sorted by colour. If it is going to become a jar or bottle again, this glass is called ‘remelt’.

Recycling Rule:

Glass needs to be cleaned and sorted by colour. There are two types of glass; ‘aggregate’, which is used in road building and ‘remelt’ which will become a bottle or jar again.


Two types of metal are used in the packaging industry; aluminium and steel. Sometimes it is difficult to tell which is which. Luckily, your collection is normally just described as metal so you don’t need to know the difference, however, they do need to be separated at sorting.

Attractive sorting

Just as there are two different types of metals, so there are two different types of magnet. Aluminium is not normally magnetic, whereas steel is. If you have a magnet in your house, try running it over a drinks can and a tin of soup or beans. The can may not be attracted to the magnet, as these are normally made of aluminium, whereas the tin probably will stick as these are usually made of steel.

So, when the conveyer belt passes under a strong magnet all the steel cans will get lifted away and everything else is left behind to carry on along the conveyer belt.

Aluminium cans are also separated with the aid of magnets, however, as they are not magnetic, ‘Eddy current separators’ are used. These use fast-spinning magnets to repel any metal on the belt. This causes aluminium to jump across a gap into a container, whilst everything else falls onto another conveyer belt.

Recycling Rule:

Complex magnetism is used to separate aluminium and steel, ready for recycling.


Plastic packaging comes in many forms and is marked with a code from 1-7 which tells you which plastic material it is. This also helps the recycler. Mixing plastic types will give a very low-quality product so it is important for plastics to be sorted based on their properties.

Before reading this section, it is worth familiarising yourself with the seven types of plastic found later on in this book.

Bottling it

There are three types of plastic a bottle can contain; PE, PET and PVC. X-rays (like the ones at hospitals) will identify the chlorine found in PVC, which is then moved to a different conveyer belt with an air blast. The left-over PE and PET can be shredded and separated by using a liquid. This is because one will float (PET) and the other sink (PE).

Everything else

Increasingly more and more plastics are able to be sorted, thanks to better technology. The sorting company can pass an infrared beam through the plastic, like the one found on some remote controls. This will compare the makeup of the plastic to what each type looks like and sort it into different streams, using jets of air.

Recycling Rule:

Seven types of plastic can be sorted with X-rays, flotation and infrared.

What happens after sorting?

After sorting, the recycling is ready to be sold to the recycler who will turn it back into material for the manufacturer to use for new packaging.

A lot of recycling needs to be collected to be sold in big batches. To save money, sorters have found ways of squeezing the packaging together.

Bale out

Paper, card, metal and plastic are usually squashed into cubes (“bales”) using a machine, predictably called a baler. This is very similar to hay bales you see in fields. Bales make the recycling simple to transport and worth more as there is more recycling in a smaller space for easier storage.

The recycling is put into the baler (a large metallic box) and turned on. A large plate of metal pushes down on the waste, from the top of the box. This pushes the recycling together, once it has come fully together and is squeezed as tight as possible it is tied up with wire or plastic banding.


Glass is not transported in a bale as it is in small pieces and will not stay in a shape. Glass will be transported to the recycler straight after being sorted.

Recycling Rule: Bales are used to ensure recycling is squashed into cubes.

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