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Is it really worth mining a landfill?

Landfill mining has the allure of a funfair jackpot: the promise of bright lights and a top prize.

Unfortunately, as in a funfair game of luck, the odds are higher that you will walk away with a worthless souvenir. How to change the odds? Perhaps change the game: swap pot-luck for poker. And this is what a network of landfill prospectors are trying to do.

In theory, a landfill site is full of valuable materials that could be dug up and recycled. A Cranfield University study estimated that around £256m-worth of valuable metals across four UK landfill sites was present in the soil alone. Its report, Rare Earth Elements And Critical Metal Content Of Extracted Landfilled Material And Potential Recovery Opportunities, measured the metals that had been washed into the soil by leachate from metal items within the landfill.

Scientists drilled 26m down into the landfill to gather samples; large items such as plastics and metal were removed and the soil extracted. Therefore it is reasonable to assume that the metal value in the landfills sampled was much higher if you include the larger pieces. Dr Stuart Wagland, lecturer in renewable energy from waste at Cranfield, and one of the study’s authors, says: “The £256m was based only on small bits in the soil – not including large bits of metal such as aluminium cans – so you are getting the tip of the iceberg.”

However, the cost of removing materials is very high and, despite concepts such as the circular economy becoming mainstream, landfill mining for the sake of the materials alone is not currently economically viable. Research for Zero Waste Scotland carried out by Ricardo AEA suggests that landfill mining projects so far have taken place for myriad reasons.

These reasons might include having to move a site – for example to make way for major infrastructure such as a road – or repairing or stablising a site. It might be to make more room in the landfill and so extend its life. The removal and sale of materials has helped to fund the costs of projects like these, but the value of the recovered materials is not yet high enough to justify it alone. Dirty or contaminated materials are also not as valuable as ‘purer’ recyclates.

So true mining for the sake of the materials alone is not currently taking place. Prices for metals such as lithium and indium are going up and, in some cases, have doubled during the past 12 months. However, landfill miners will need to look at the gamut of materials to make a venture work.

“There is no single metal which is worth mining on its own – you also need paper and plastics. It will be a whole suite of resources to make the whole thing viable,” says Wagland.

Cranfield is about to embark on a European funded project, collaborating with other organisations across Europe, to look into landfills as a resource bank. This project will consider how to better quantify how much metal is in a landfill. Meanwhile Wagland is also trying to get funding for a project to develop equipment that can scan landfill sites and build up a 3D picture of the waste contained within.

Landfill mines

Working with a partner, Wagland’s idea is to use sonar equipment to measure the top 4m of a site. The scanning equipment would then be put down gas wells to take measurements. “It’s the sort of equipment used by archaeologists on Time Team,” says Wagland.

Another big challenge are environmental and health and safety factors. “What would be the environmental consequences of opening up a landfill?” asks Wagland. “It could release pollutants and gases. You might find asbestos or nuclear materials – although that’s less likely.

“Due to the cost of managing health and safety, a company that wants to look at landfill mining would need to be convinced there was a quantity of materials to make it worth the risk – it’s an emerging field. You also have to ask whether the Environment Agency would endorse such projects.”

Material prices going up and concerns about resource scarcity will inevitably help to make landfill mining more feasible, but there are other factors that could provide a boost.

Dr Adam Read, practice director, resource efficiency and waste management, at Ricardo- AEA, suggests that, in another decade, landfill mining for the sake of the materials alone should be closer: “Only a metre below the surface we have buried lots of plastics which potentially have refuse-derived fuel (RDF) and lot of valuable metals from electricals from the 1970s and 80s. This may be easier to mine than bauxite in Nigeria.”

But Read believes that freeing space may be a more pressing concern in countries such as the Netherlands. In the UK, he predicts that the first landfill mining projects will take place in the south-east, where land value is at a premium: “You are not going to get any new landfill sites in the south-east.”

Landfill operators may need to make more space because it is highly unlikely that new land will become available. There is even an argument that landfill sites will become prized possessions if they can be cleaned up and used to build on. A cleaned site will also mitigate the long-term costs of landfill maintenance, so this should add to the equation to make such projects economically viable. Read points to the Mucking landfill in Essex, which would be ideal for developers.

There are some anecdotal reports of large developers buying up closed landfill sites, speculating that in the future they can be cleaned up and the land value released.

While landfills are being increasingly looked at as resource banks, it is not simply a case of extracting the materials and recycling them in the usual way. Plastics buried in landfill become very brittle, almost like paper, and so have very little value as recyclate but do have calorific energy value for EfW, as does paper and card. Read argues that as recycling rates go up, councils may find it difficult to feed the large EfW projects. Landfill mining may be able to come to the rescue and provide the feedstock needed.

“You may well go for landfill mining because you need to free up space, and some of the costs can be offset by RDF and SRF,” he says. “Plants that need a constant throughput of material will be looking for fuel – we may run out of municipal solid waste so the demand for fuel and the resource value will work together.”

There is also a historical way of gaining a picture of what landfill is comprised of, argues Dr Richard Beaven, principle research fellow at Southampton University’s waste management research group: “The composition of waste has changed over the decades. Before the 1950s, there is probably not going to be a lot of interest in terms of materials with a commodity value.

“Much of the waste at that time was ash from people’s home hearth. They would burn coal and their own waste so there will be relatively little value in it. There might be some value for a low-grade engineering application.”

Beaven believes that, before the 1980s, there was a practice of landfill operators taking out materials that looked to be valuable for their own benefit rather than for a national recycling campaign. While this would not have had enormous impact, it is a consideration. But, he adds: “Waste deposited in the past five years, with the advent of recycling, has also seen a lot of the valuable commodities stripped out.”

He says it is also worth looking at available records because landfill sites have different licensing conditions, meaning that variable sorts of materials were allowed to be buried.

However, as Read says: “Ultimately, we are talking about landfill sites with mixed loads from different authorities and commercial waste, and there’s quite an uncertainty.” Until the odds increase or the game changes to one of skill, no one is putting their money on the table for the cash jackpot just yet.  

 

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