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
Mining engineer here. The reason it is cheaper to mine directly from the Earth is because sorting Mineral X from a bunch of rock is a fairly straightforward process. Rock has a set of properties and Mineral X has completely different set of properties. So you can use the differences to extract what you want. For example, magnets and density separation could remove iron from rock.
If you were to mine from a landfill, you would have to sort out countless different types of material. All these materials act differently, so you would have to individually process for each type of material. It is possible, but there would be so much contamination and the process would be very expensive.
In the future, landfills will be mines, but right now it’s too expensive.
Think of it this way – we have been mining natural resources for ages and have established methods and equipment. Depending upon the type of landfill, mining out usable materials can be done, but each facility can differ and there is no set method to implement. That increases labor and possibly requires additional equipment, both of which increase the costs.
Also, modern landfill methods tend to diminish oxygen needed to rot organic material. Add to that the fact that post 1950 landfills are packed with unusable plastics that will need to be separated and that newer facilities have everything wrapped in plastic bags, the work necessary to get recoverable material is very costly.
The optimal thing on this topic would be to mine the oldest landfills that have practically composted the waste first. Then, if technology catches up move on to newer facilities.
It’s cheaper to mine material and create new material than to go through garbage to recycle. Even the stuff in recycling rarely get recycled (about 1/3rd depending on where you live), it’s just too expensive and more and more countries refuse recycling because they get too much garbage mixed in it and it’s just not worth it.
Mining landfills for aluminum is already becoming cost effective, someday this may be true for other materials.
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.
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
What your describing is landfill mining and they’re testing it in very specific situation’s.
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