Digging out valuable material by landfill mining

Written by: Adrian Convery | Published:

Statistics on recycling and landfill use vary wildly from one country to the next.

In Europe, the amount of recyclable waste going to municipal landfill has steadily decreased as the member states strive to meet the EU’s target of 50% reduction in biodegradable municipal waste going to landfill by 2020.

It was reported that Sweden only sends 1% of its household waste to landfill, and their trash provides heating and fuels bus and taxi fleets. However, in 2018 we have seen the alarming reports that Singapore anticipates running out of package landfill space in 2035 as their society has experienced a huge rise in waste generation.

Usually, people think that once waste has gone to landfill, that’s the end of the story. Whatever has been buried there is lost forever in recycling shame. However, that doesn’t have to be the case given the new technology and methodology that reclaims lost resource from landfill and puts it to better use.

Landfill mining has been defined by EURELCO (European Enhanced Landfill Mining Consortium) as “the safe exploration, conditioning, excavation and integrated valorisation of (historic, present and/or future) landfilled waste streams as both materials (Waste-to-Material) and energy (Waste-to-Energy), using innovative transformation technologies and respecting the most stringent social and ecological criteria”.

On a practical, daily level, it also results in a significant reduction in the volume that remains in landfill; it also affects the associated environmental cost posed by potential leachates from dissolved or even suspended materials.

According to EURELCO there are an estimated 24,000 landfills in the UK. Back in 2015, Cranfield University carried out analysis and published a study on four UK landfill sites. It was estimated then that there could be as much as £360m of valuable metals in each of them.

It’s not just about metals, but a myriad of beneficial/important materials are recoverable from our municipal waste, from biodegradable waste to re-usable plastics. (Cranfield University is exploring the opportunities for recovering from waste plastics and turning them into high-value products such as liquid fuel.) With a little dedication, creative thinking and technology, so much more treasure can be re-used from buried trash.

This is equally true of more industrial materials, especially those which have been too difficult, or prohibitively expensive, to recover and recycle in the past. New solutions and approaches have meant that sorting, cleaning and recovery are more feasible than ever before.

Go with the flow

A key part of the message is that recovering reusable material from waste will have a significantly positive impact on the healthy future of our environment. We must, therefore, find more innovative ways of doing so. One of those ways is by landfill ‘mining’ which uses a mobile excavator, specially designed for the job.

When recovering materials from landfill the devil is really in the detail. It can be done if you have technology to wash and sort the re-usable materials from the unusable ones. We’ve developed technology (The G:FLO) which does just that and, furthermore, it’s mobile, so it can be taken to any site for material cleansing; it recycles up to 90% of the water used in the washing process.

Any grit that is recovered from the cleaning and sorting process can then be used in low-grade construction applications such as pipe bedding, road fill and landscaping. This reduces the need to further extract virgin resources (which through current practices may risk being lost to waste; and so, the cycle would continue in this unproductive fashion).

This kind of technology doesn’t just work for landfill reclamation, but also for cleaning of drilling muds, gully waste and environmental remediation. In all these activities, there is one thing in common – the necessity for cleaning and sorting of materials and water for re-use. When it comes to processing gully waste and drilling muds, there is significant reduction in operational, transport and disposal costs, which is a huge saving for drilling contractors, often burdened with waste slurry disposal.

Don’t write off the potential

Using technology makes financial sense because you can either divert waste materials from landfill or process waste products currently in landfill to make more space and extract valuable resources for re-use.If done correctly, sites can be remediated, and the waste separated to extract high-value materials. For example, sand and gravel can be recovered to use in a variety of re-use applications such as pipe bedding and cement production if the quality is assured.

Among the most valuable metals estimated to be languishing in landfill are tens of millions of pounds of palladium (used in automotive catalytic converters), copper, aluminium and lithium, even neodymium, which is used for high-strength magnets.

They all have the potential to re-enter the manufacturing chain. This is an issue of major concern for manufacturers who worry about the continued depletion of valuable minerals and metals that could negatively impact production in years to come.

Caution not fear

Although landfill mining has its risks, it also provides an opportunity to tackle the pollutants present in sites that breach current environmental standards.

Environmental remediation and landfill mining are not as commonplace as they could be due to concerns that opening up sites will expose the surrounding area and population to contamination. One of these risks is exposing and agitating asbestos. In the 1990s, Directive 1999/77/EC completely banned the use of asbestos due to its negative health impacts, but before the dangers were fully understood, waste asbestos would have been buried in landfill – out of sight, out of mind and deemed safe.

However, disturbing the material now would pose a large respiratory risk to the operatives and those further afield because the ultra-fine fibres that make up asbestos have the potential to travel long distances when carried by the wind. Conversely, the alternative is to leave the substance in situ where it could be doing long-term damage to the environment as some fibres escape into the soil.

Leaving certain substances in the ground can leach contaminants into groundwater and pose a greater risk to a larger area than removing it and remediating the land. Using experts to remove known accumulations of asbestos in landfill would mitigate risk and reveal an opportunity to explore landfill safely to reclaim the valuable materials within.

Because there is a general lack of understanding of the opportunities and trepidation about possible risks, there are few landfill mining projects anywhere in the world. However, awareness of its benefits is growing and intrepid companies willing to tackle the landfills around the world are fighting to gain ground – from Europe to Chile.

If you regard avoiding it as a missed opportunity, and landfills are not explored as a valuable resource, we risk missing the chance to reduce the danger of contamination, so that we can put our land to better use (once remediated). It provides saleable assets, therefore boosting the economy as well as the environment.

Adrian Convery is from waste recovery company CDEnviro


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