Landfills are becoming large concentrations of materials like plastic, aluminum and other. What part of the process of mining landfills and processing the materials for new products, makes mining raw materials from the earth and processing them cheaper?
In: Economics
What your describing is landfill mining and they’re testing it in very specific situation’s.
Commodities analyst here. Basically, lots of processing methods could be economic on a large scale. It’s scaling up that is difficult. Take magnets for example. Most magnets are very small and they are all made of slightly different compositions. Then, they are often encased inside a sealed component, inside your product – such as inside an old school HDD.
We would need to first establish a system of collection to retrieve a large number of old PCs. Maybe encourage people to return them to a drop off point. And then extract the magnet before processing it and to a session it for its composition. It’s this labour intensive part where most of the cost is.
As we start to use much larger such batteries and magnets in wind turbines and EVs, it becomes much more attractive to recycle as the volumes are higher and the material within one magnet has a similar composition. It’s early days yet for these applications as they have a long life span but we will start to see recycling happen more and more in the coming decades. For smaller things like mobile phones, it’s not really worth it.
In movies and tv there will often be inmates on the side of the road picking up trash. I don’t know if this actually ever happens… but I always thought it would be a good idea to put them to work in a landfill instead to sort out the recyclables.
Extracting materials from the landfill is a tedious task. First you have to sort the materials, and because most products are not designed for disassembly, you have to go through a lot of processes to to extract the materials you need. Extracting gold from a circuit board, first demands that you are cutting out the right components. Then dissolving these components in chemicals to get to the gold alloys, then dissolve the alloy to make new chemical bonds that leaves the gold as leftover. Then purifying the gold. In the end it’s a very long and expensive process, and the cost benefit is low.
Scrap steel is selling for around $50 s ton right now. At least that’s what the scrapyards around here are paying.
20 years ago my father predicted that in the future landfills would be gold mines of things that still functioned or were now valuable enough to recycle properly.
It’s efficient to mine and know what you’re getting. In a titanium mine, you can go through the kroll process which is a well defined set of reactions to separate titanium.
Plastics are a byproduct of oil and gas refineries. When you take gas from the grown, the hydrocarbons you get are useful in making plastics.
When you recycle from a landfill, you’re going to have to sort out a lot of things you don’t know what they are. Even worse, chemical separations may be more difficult because separating titanium from dirt may be easy, but separating titanium from dirt, plastic, other metals, may not be as easy. Second, it can take a lot of energy to separate the wanted items from the unwanted items. Recycling polyethylene is doable but recycling polystyrene is not cost effective.
Also, materials can be degraded in a landfill. Cardboard soaked with grease can’t be recycled into paper. Leaked gas could make things flammable where not expected.
One more reason, is that recycled plastics are of worse quality than new plastic. Recycled plastics go through wear and tear. If you bend a plastic like a mechanical pencil clip, it’ll turn white due to stresses on the material. That’s can’t easily be rearranged. Second is that melting a plastic can lead to undesirable cross links that make the polymer less valuable. A lot of purposes will require new plastics rather than recycled
Good aluminum or iron ore deposits are about 40-60% metal, with the remainder being oxygen atoms and maybe a bit of other simple minerals.
Municipal solid waste is about 9% metals, and that 9% is a mix of aluminum, steel, zinc, copper, tin, etc. It’s mixed in with huge amounts of organic matter, plus lots of other contaminants. And the metals aren’t pure metals: they’re usually alloys with a wide range of added elements.
The chemistry needed to separate such tiny amounts of metal from such a complex molecular stew would be really difficult.
It’s much easier to separate out the metal before it gets mixed into the trash, which is what recycling is all about.
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The difficulty with landfill is that you have no idea what’s in it. There may be a host of heavy metals and organic chemical which pose an unknown hazard to anyone handling the material.
There have been many cases where people have been caught tipping materials which have not been authorised in landfill, so there will be many more who never got caught.
Mining landfills for aluminum is already becoming cost effective, someday this may be true for other materials.
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