Some interesting articles on landfill mining and it’s potentials as well as the issues regarding SA’s landfill situation.
Mining News –
Closure, rehabilitation a major issue as SA’s landfills reach capacity
“With landfill space in South Africa at a premium, the controlled, planned, and systematic filling of landfill cells requires progressive closure and rehabilitation. This is a highly specialised endeavour that requires an integrated infrastructure delivery company like AECOM to drive it.
Landfills may need to be closed for various reasons, including unacceptable environmental impacts such as groundwater pollution, and/or unmanageable air pollution such as dust or odours. Geological issues include dolomitic ground conditions, which can result in water ingress and sinkhole formation. In many instances, improving landfill management and operations is a necessary first step, but if this proves unsuccessful, closure becomes necessary.
Landfills are usually designed with a specific lifespan, determined by the volume of waste that can be handled. Once filled to capacity, landfills must be closed and decommissioned, as stipulated in the Waste Management Licence. However, effective landfill remediation poses a challenge for both public and private entities.
Navigating the regulatory process, coordinating the different phases of the project, and establishing a long-term plan for post-closure reuse are only the beginning. Landfill site problems are often bigger than the eyesore created by the huge piles of waste. At one point or another, landfill sites will have to be closed.
“While this may seem like the end of the story, it is only the beginning of the next chapter in the life of the landfill,” comment Nicolas Vanhecke, Practice Lead: Remediation Services, and Soleil Jones, Environmental Scientist, at AECOM.
The process of landfill closure and remediation is legislated by the National Environmental Management Waste Act (NEMWA), the Water Act and the Waste Management Series, as promulgated by the Department of Water and Sanitation.
While it might seem that the closure process only commenced once the landfill has reached the end of its useful life, there are factors that can need to be attended to while the site is still operational. The slopes of the waste body must be resolved to ensure they lie at a safe angle.
This should be maintained throughout the operational phase, after which capping is carried out by means of an engineered liner. Furthermore, all stormwater run-off must be diverted away from the waste body so as to separate the clean and dirty water circuits, and to prevent leachate soaking into the waste body, which can result in subsequent groundwater pollution and odours.
The site must also be fully secured, and access-controlled, in order to prevent trespassers. For example, there could be an issue with people remining the waste body for recyclables, which presents a fire risk, as well as allowing rainwater to permeate the waste body.
“In the past, little to no consideration was given to the potential environmental impacts of landfills on human health and the larger environment, which is why today’s landfills are licenced, and with very specific engineering design,” Vanhecke and Jones highlight.
The remediation process depends on factors such as the type and classification of the waste, and the size of the landfill. Most of the time, the remediation process consists of waste reprofiling; capping, usually with topsoil such as clay or with a geotextile; revegetating, usually with indigenous grass; and, finally, closure. Once properly remediated, the landfill site could be used for anything from parkland to recreational infrastructure or even grassland, depending on the preference of the landfill owner, the surrounding community, and the regulatory authorities.
If the site is smaller, site reclamation can be conducted via an excavation-transfer-treatment process. A key element in site reclamation is the transformation of anaerobic to aerobic conditions in the landfilled waste. Depending on the waste accumulated in the landfill, a methane gas plant can be installed to recuperate methane for energy purposes.
Following closure and remediation, the landfill site is subject to a post-closure monitoring period, which is recommended for up to 30 years. This is in order to monitor the integrity of the capping, and the impact of the quality of the groundwater quality in and around the waste body.
There may also be a need for ongoing pumping and treatment of the leachate that gathers in the leachate collection system. The landfill will also most likely require a methane management system, whether that be done by landfill gas harvesting, or regular flaring, so as to prevent methane build-up, fire risk, and air pollution.
Adherence to legislation is key, and therefore a preliminary closure plan and end-use options for the landfill should be outlined from the outset of the project, and addressed ideally in the Environmental Impact Assessment phase. Financial provision must be made for these engineering works and materials, and a more detailed rehabilitation and closure plan must be developed as soon as landfill operations commence.
Some successful international examples of remediated landfills in urban areas include the London Olympic Stadium (2012), the Milan Universal Expo (2015), and the Confluence neighbourhood of Lyon in France, which is one of the biggest landfill rehabilitation projects in Europe.”
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Landfill mining: is this the next big thing in recycling? World Economic Forum
“For more than 100 years, the world has been discarding its unwanted waste in landfill sites. There are at least 500,000 of these sites in Europe alone, according to estimates by the European Enhanced Landfill Mining Consortium (EURELCO). Only some are still operational.
What concerns many experts is that a lot of these landfills are located in semi-urban environments. In Europe, fortunately, most of the still-operational landfills are so-called “sanitary” landfills, which are equipped with state-of-the-art environmental protection and gas-collection systems. It means that for these sites environmental pollution and release of greenhouse gas emissions from these landfills are avoided.
An environmental hazard
But this still leaves a good 90% in a “non-sanitary” condition. These landfills, which generally predate the EU’s Landfill Directive of 1999, have little or no protection technologies.
The situation is no better elsewhere in the world: the vast majority of landfills in regions such as Asia and Africa are downright “waste dumps”. These deposits could cause serious environmental problems, ranging from local pollution concerns (health, soil and water) and land-use restrictions to global impacts in terms of greenhouse-gas emissions.
Landfills are one of the major sources of methane emissions, a notoriously powerful greenhouse gas.
The “do nothing” scenario is not an option, as politicians and other stakeholders agreed at a landfill mining seminar organized by the European Parliament and EURELCO in 2015. For the thousands of waste dumps beyond Europe, the same conclusion can be drawn.
But remediation measures are pricey and environmentally risky. It costed Flanders’ public waste agency, OVAM, €80 million to excavate and move hazardous waste to state-of-the-art sanitary landfills between the years 1993 and 2001. For most of the EU member states – not to mention developing countries – costs like these are prohibitive.
Potential goldmines
However, by combining landfill remediation with resource recovery of the excavated waste, the net cost of the remediation activity can be drastically reduced. How? By generating recyclable goods and energy (carriers), all of which can provide much-needed revenue to counterbalance the cost of remediation.
In fact, if landfill mining followed the principles of the “enhanced landfill mining” approach, where higher added value outputs are targeted, the net economic balance of the combined remediation-landfill mining activity can even become positive, which is especially the case for larger landfills where economies of scale become relevant. As such, remediation combined with enhanced landfill mining can generate an income for public waste agencies, and this can then be used to cover the costs of remediating and mining smaller, less economic landfills that pose short-term environmental and health risks.
So, what exactly is enhanced landfill mining?
Officially defined as “the integrated valorization of landfilled waste streams as materials and energy”, enhanced mining extracts valuable materials from both landfilled industrial waste and municipal solid waste.
Industrial residues arise during the production of aluminium, zinc, copper or steel. In many cases these residues contain significant quantities of metals that are short in supply and that are central to the development of clean technologies, such as photovoltaic cells, e-cars or wind turbines.
Enhanced landfill mining is also relevant for municipal solid waste. In this case landfill mining separates waste into directly recyclable materials (glass, plastic, metals, aggregates) and a refuse-derived fuel fraction, which is further converted into high-added-value products. Using the new plasma gasification technology, it is possible to transform this refuse-derived fuel fraction into hydrogen and a mineral residue fraction that is then upcycled into a green, low-carbon cement.
The enhanced landfill mining approach is currently being demonstrated in two flagship projects funded by the European Commission’s Horizon 2020 Programme, ETN NEW-MINE (for municipal solid waste) and METGROW+ (for industrial waste).
This sort of mining can transform landfills, particularly those in urban environments, from a threat and a cost, into an opportunity for resource recovery. It closes the loop, injecting additional resource circularity and resilience into the economy.”
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