The microplastic pollution that turns up in landfill leachate has received much less attention than the stuff appearing in wastewater, and there seem to be far fewer studies exploring it. Envirotec comes across a recent summary of the situation.

The avenues by which microplastics find their way into landfills are obviously numerous, with the toxic load receiving a notable fillip from the events of 2020, and an estimated 129 billion face masks and 65 billion gloves finding their way into waste streams.

Certainly there’s a lot of it. According to the OECD, in 2019, 50% of the world’s plastic waste was landfilled, 19% was incinerated, 9% was recycled and 22% was mismanaged.¹

An article appearing in the Elsevier journal Desalination and Water Treatment in June² attempts a survey of the topic, and summarizes the current status of microplastics in landfill leachate, including aspects such as their source, abundance, characteristics (polymer types, shapes, and sizes), suitable remediation techniques, and environmental impacts.

Microplastics in landfill leachate are mainly produced from the fragmentation of larger plastic items, so its abundance will be determined by the various physical, chemical, biological, thermal and other processes occurring therein, and the environmental conditions (with plastics’ fragmentation hastened by the influence of UV radiation, for example).

The paper identifies a number of gaps in the research. For want of a standardized method of analysis for microplastics, it is impossible to compare landfill leachates from different places and different studies. So there is an urgent need to develop one.

A handful of studies focus on the size of MP occurring in leachates, but size estimates seem to vary widely, with particles generally occurring within the range of 1 µm-5000 µm.

The concentration of MPs also varies a great deal between landfill sites, it seems, and the authors cite a study in Hong Kong which found that MPs (> 100 µm) in raw landfill leachate from a landfill that had been in use since 1995 was 507.6 ± 37.3 items/L. The variation appears to track the wide variance between countries in terms of population levels, waste management strategies, living standards and consumption habits.

The age of a landfill is a good indicator of the type of plastic polymers that show up, with the authors noting a 2019 study showing that PE, PP, and PET occur more in young and medium-aged leachate, and less (or not at all) in old leachate. Cellophane MPs were also more a feature of younger leahate,

How good are landfill liners, when it comes to keeping the stuff in? High-density PE (HDPE) geomembranes are widely used in landfills and offer high resistance to chemicals and durability. But their long-term performance depends on exposure conditions and temperatures.

HDPE geomembranes in landfill have to weather the rigours of leachate comprising a wide range of contaminants. The authors cite a study by Zhang et al. (2024), which demonstrated that “HDPE-type MPs were not detected in the leachate of household food waste and that HDPE MPs constituted less than 1% of the residual waste leachate.” But, on the other hand, say the authors, the same study found a higher proportion of HDPE MPs (approx. 10 %) in the leachate of two different landfills, with one having been in operation for 16 years and the other for 8 years. Both had HDPE geomembranes.

The authors note: “Researchers have suggested that geomembranes may break with long-term storage and release MPs, leading to HDPE contamination in landfill leachate.”

Another important issue is remediation, and how best to remove microplastics from leachate. The paper looks at physical, biological and chemical treatment processes, and the use of wetlands. In terms of physical treatment, the authors give various reasons to consider sand filtration for leachate. Biological treatment is not suitable for old landfill sites.

Membrane processes are currently the best way of removing them from water, say the authors, so this looks like the most promising avenue to explore.

Notes
[1] “Microplastics in landfill leachate: Sources, abundance, characteristics, remediation approaches and future perspective”, Desalination and Water Treatment. https://doi.org/10.1016/j.dwt.2024.100445
[2] ibid

A provider of AI-powered sortation at scale for the waste and recycling industry, AMP Robotics is using its technology to extract mixed recyclables and organic material from municipal solid waste (MSW) for further processing at a facility owned by Recycling and Disposal Solutions (RDS) of Virginia (in the US).

This AI-powered MSW facility features an AMP ONE system and is an industry first, currently processing 150 tons per day of local MSW with over 90 percent uptime — described as “an unprecedented level of reliability for mixed waste sorting systems at a scale and footprint that was not previously feasible economically”. Designed to be co-located with landfills and transfer stations, the AMP ONE system separates bagged trash into its component parts of mixed recyclables, organics, and residue. Equipped with this technology, the RDS facility is capable of diverting more than 60 percent of landfill-bound material when paired with organics management and mixed recyclables sorting systems, whether incorporated into a project by AMP or built separately. MSW diversion meaningfully extends the life of landfills, reduces their environmental impact, and keeps disposal costs low.

“The economic and environmental opportunity in extracting value from the municipal solid waste stream is massive, and innovative sortation is key to unlocking this market,” said Matanya Horowitz, AMP founder and CEO. “To move the industry forward, we’ve designed technology that’s resilient to contamination and can more easily go after dirtier material streams. We see the success of the facility in Portsmouth as a blueprint for other municipalities looking to extend the life of their landfills and reach ambitious diversion targets. Given that recycling rates have been stagnant over the last decade, this presents a new opportunity to expand recycling—one that works for existing waste infrastructure assets.”

AMP offers the industry’s most sophisticated AI platform, which can be expanded to all types of material streams, including MSW. The company has a diverse set of sortation technology applications powered by this AI platform, including AMP Jet, which it can extend to sort in new ways to respond to design challenges or to enable new recycling and diversion pathways.

“At RDS, we’ve been early and enthusiastic adopters of advanced technologies to increase recovery and landfill diversion, drive down processing costs for local governments, and generate data for continuous facility improvement,” said Joe Benedetto, president of RDS. “AMP delivers best-in-class sorting solutions, and it was a natural fit to partner on this project and pioneer an economical way of capturing the value in our waste, especially as local communities close their recycling programs due to increasing costs.”

In 2023, RDS completed a new 33,000-square-foot building at its existing site in Portsmouth, which has provided local recycling services since 2005. RDS installed an AMP ONE system and began processing MSW in the facility in late 2023. This project demonstrated the AMP ONE system’s capacity for sorting MSW into salable commodities. AMP and RDS began working together in 2017; RDS also operates facilities in Roanoke, Virginia; Greenville, North Carolina; and Athens, Georgia.

Researchers analyzed solutions implemented in four very different Brazilian cities. Based on the results, they propose the creation of a national carbon credit fund to support sustainable waste management initiatives.

Some 20,000 metric tons of municipal solid waste (MSW) are produced every day in metropolitan São Paulo, with household trash accounting for 12,000 tons and street cleaning (mainly sweeping, open-air market refuse collection, pruning and grass cutting) for 8,000 tons. This amount of household trash corresponds to about 1 kg per inhabitant per day.

The national composition of MSW is 50% organic matter, 35% recyclables and 15% landfill refuse. Efficient MSW management, with processing of organic waste to produce fertilizer and biogas, effective recycling of recyclables, and creative solutions to use part of the landfill refuse, would reduce Brazil’s greenhouse gas emissions and serve as an additional source of revenue via the circular economy, which converts waste into resources. However, the rate of MSW reuse is still very low in Brazil (2.2%).

“Improvements such as implementation of technologies that integrate composting, recycling and use of methane from landfills to produce bioenergy could reduce the emissions from MSW management systems by 6%, as a highly conservative estimate, or 70% more optimistically,” said Michel Xocaira Paes, a researcher at Getúlio Vargas Foundation (FGV) in São Paulo. “That would correspond to between 4.9 million and 57.2 million metric tons of CO₂ equivalent, for annual economic benefits of USD 44 million to USD 687 million in carbon credits.”

He told the news agency Agência FAPESP: “We studied MSW management in six Brazilian cities, four of which we selected to exemplify different routes to innovation in this area: Harmonia, São Paulo, Ibertioga and Carauari. They are all very different in terms of geographical region, size, population and Human Development Index (HDI), among other criteria. Their MSW management systems are also different, but each one has at least one highly interesting innovation.”

Harmonia and Ibertioga have very high rates of waste reuse (56% and 67% respectively). Harmonia, which is located in the state of Rio Grande do Sul in the South region, also features domestic composting, and diverts almost half its organic waste from MSW collection and treatment systems. However, whereas MSW is managed by private enterprise in Harmonia, with a strong emphasis on environmental education and social participation in separating types of waste and in domestic composting for organic food production, MSW management in Ibertioga, Minas Gerais state, is entirely public. The researchers found the governance of its local MSW management system to be robust and noted significant support from the state government for the implementation of sorting and composting units across the state. The results have been very positive in both cases.

São Paulo, the capital of São Paulo state in the Southeast, and Carauari in Amazonas, a state in the North, are worlds apart. São Paulo is the fifth most populous metropolitan area in the world, and half its population lives in São Paulo city. Everything there is huge, including the problems and their solutions.

“Waste reuse in São Paulo is better than the national average but still very low at only 3%,” Paes said. “On the other hand, there are many innovations, such as strong participation by recycling collector co-ops, two material recovery facilities to separate recyclables, organic waste composting units, and power co-generation from landfill methane.”

São Paulo has three sanitary landfills. Two are privately owned, and a third operates as a state concession. The world’s third-largest sanitary landfill, in Caieiras, receives MSW from the northwestern area of the city, the CTL landfill receives MSW from the southeastern area, and the Pedreira landfill receives only street cleaning waste.

The Caieiras landfill has a biogas-fueled thermal power plant, where methane (CH₄) from decomposing organic matter drives electricity generators. CTL burns some of its CH₄ to produce CO₂ and steam (since CH₄ has 21 times the global warming potential of CO₂) and sends the rest to a thermal power plant with which it partners. In 2019, when the study was conducted, these two landfills had installed capacities of 8 megawatts (MW) and 29 MW respectively.

Another important innovation is the installation of 125 collection points across the city. These are known as “ecopoints” and receive not just recyclables (paper, cardboard, plastic, glass and metal) but also trimmings from household plants and trees, construction debris, and larger objects such as old furniture.

“The city also partners with associations of recyclable collectors, who do some separating and partial processing. In 2019, it had 24 co-ops with some 900 workers all told, as well as 1,400 self-employed collectors registered with the relevant municipal department,” Paes explained.

Besides the innovations mentioned in the article, new initiatives have appeared in the city. These are relatively small-scale but can be replicated. For example, Realixo is a firm set up by young university graduates to promote environmental conservation, the circular economy and sustainability. Customers pay a monthly subscription to have their organic and recyclable waste collected by the firm, which separates what it can send to partners for composting or recycling.

At the opposite extreme of the urban spectrum, Carauari has 28,000 inhabitants – 21,500 in the urban area and 6,500 in the rural area and forest. It is located on the Juruá River and is five days away by boat or two hours by plane from Manaus, the state capital. “These distances are misleading. I didn’t find an abandoned population there. On the contrary, they’re highly organized, empowered, and engaged in community management of natural resources, bioeconomy and circular economy initiatives, and sustainability policies. Local associations and groups do a great deal, in partnership with NGOs, universities, government and private enterprise,” Paes said.

A separate article on the study conducted in Carauari was published in Springer Nature’s journal Urban Sustainability, with detailed information on the activities of local communities, mainly Arapaima gigas fishery management and oilseed processing, all of which is integrated in a circular economy, so that waste from one activity becomes inputs for another instead of impacting the environment (read more at: agencia.fapesp.br/36780).

Oilseed hulls are composted, and almost all the arapaima (the giant fish also known as pirarucu) is used, with the viscera being ground up to make feed for turtles, the scales supplying material for jewelry, and the skin going into handcrafted bags, clothing and footwear.

“There’s no such thing as a magic wand to solve the waste problem, but in these four cities we found good practices that can be synthesized in a wide-ranging project with four pillars: local technical and political capacity; environmental education and social participation; collaboration among all three tiers of government [federal, state and municipal]; and local partnerships for innovation,” Paes said.

“From these pillars we derived the proposal to create a national carbon credit fund that would be managed by the federal government with participation by states and municipalities. This fund could be used to support waste reduction initiatives [via domestic composting, for example], conversion of waste into resources via the circular economy, and development and implementation of local technologies for composting, recycling and use of landfill biomethane. All this would help reduce greenhouse gas emissions and stimulate the low-carbon circular economy. It’s a model that can be used throughout Brazil and inspire similar solutions in the other BRICS and developing countries in Latin America, Africa and Asia.”

An article about the study has been published in the journal Habitat International.

The research was funded by FAPESP via a postdoctoral scholarship and via a project coordinated by José Antonio Puppim de Oliveira, a professor at FGV and supervisor of his postdoctoral research.

The earth has finite resources, and at some point, society will run low or even run out entirely of certain resources that it currently takes for granted. When that happens, materials discarded into landfills as waste are set to become a valuable commodity. That’s why the waste industry should be talking more about landfill mining, says Chris Williams, founder and CEO of ISB Global, a UK-based software and solutions provider for the global waste management and recycling sector. His views are presented here in an article authored by the firm.

“For too long, businesses and governments have acted as if the earth’s supply of certain material resources is inexhaustible,” said Williams. “We’ve chosen to bury these valuable materials in landfills when we think we’ve finished with them. But the world is about to realise we need those materials sooner than we think.

“Over the last few years, significant effort has gone in to reducing the amount of waste that ends up in landfills. We are making progress: in the UK in 2010, we sent 12.9 million tonnes of municipal waste to landfill. By 2020, that amount had fallen to 6.1 million tonnes.

“But not every country is reducing its landfill impact. In countries where the population is rising, economic development is taking place, and where knowledge and awareness of environmental issues are limited, landfill sites are growing, not shrinking.

“Landfill mining involves sifting through and extracting useful and valuable materials from landfills – such as glass, particular metals, plastics, textiles, brick, stone and cement – to be reused, recycled, refined and resold,” explained Williams. “It puts more ‘existing’ material back into the economy and creates valuable secondary markets while reducing the amount of dormant waste at landfill sites.”

But currently the main challenge for waste management companies considering landfill mining is to do it safely, efficiently and profitably. Many landfill sites are built with environmental safeguards in place. However, other sites don’t have these safety measures and contain a range of hazards, which if disturbed, affect people and communities living and working nearby by contaminating water supplies, releasing greenhouse gases into the atmosphere, and damaging soil.

“We’re going to need to return to our landfills and explore how to recover the valuable materials deposited in them – the challenge is, how to do so safely,” said Williams. “Over the next 10-20 years, expect to see an increase in businesses – including those already operating in the waste and recycling management space – set up safe, approved mining operations that become new income streams while also helping to drive a more circular economy.

“If we are to work with the planet rather than against it, we need to transition to a circular economy. Use recycled or pre-used materials instead of extracting or manufacturing entirely new ‘virgin’ materials from scratch is a central tenet of this transition,” he added.

“Done properly, landfill mining is a chance to create new jobs, reuse more materials, reduce landfill impact and work towards a more sustainable world. It’s already happening in different countries around the world. It’s only going to become more commonplace as business and industry looks for ways to move away from their dependence on the earth’s finite and increasingly depleted resources.”

General Atomics Electromagnetic Systems (GA-EMS) conducted live demonstrations of its industrial Supercritical Water Oxidation (iSCWO) system for destroying PFAS chemicals before a delegation of government, remediation, and waste management company representatives on 29 August.

It appeared to demonstrate the successful destruction of PFAS using an Aqueous Film Forming Foam (AFFF) waste feed in a series of back-to-back demonstrations of GA-EMS’ iSCWO system at the company’s dedicated, full-scale system test facility located in San Diego.

A variety of oxidation and other technologies are currently being explored in relation to the disposal of PFAS in substrates such as landfill leachate.

“PFAS chemicals have been used in products since the 1940s and communities today are grappling with the environmental and human health consequences caused by decades of exposure to these forever chemicals,” said Scott Forney, president of GA-EMS. “It’s time to end the cycle of PFAS contamination for good. We invited legislative and waste industry representatives to witness first-hand iSCWO’s effectiveness in eliminating PFAS, using our commercial technology that has been out of the lab and operational in the field for more than a decade.”

GA-EMS’ iSCWO system processes organic waste with water in an extremely high temperature (650°C) and high pressure (4000 psi) environment to efficiently destroy PFAS and PFAS waste containing other organic co-contaminants. The system is described as being safe to operate, environmentally sound, and cost-effective. There is no post-treatment required, no gas or liquid emissions to deal with, and no hazardous by-products to store, transport, or dispose of.

“We are working with remediation companies to develop plans to integrate our proven iSCWO systems into their waste treatment infrastructures and begin the process of eliminating PFAS from a wide range of waste sources, including landfill leachate, wastewater, biosolids, soils, and water filtration by-products,” continued Forney. “To date, our iSCWO systems have destroyed over 6 million gallons of hazardous and non-hazardous waste with a greater than 99.99% destruction efficiency.”

The EPA issued a detailed report documenting the first-ever test and verification of PFAS destruction efficiency greater than 99.99% using GA-EMS’ industrial-scale SCWO technology. In addition, GA-EMS’ iSCWO system has been successfully tested to destroy more than 200 different types of hazardous and non-hazardous liquids, solids, and slurry waste streams with the same 99.99% plus destruction results.

Envirotec struggles to find solid takeaways in the literature about PFAS contamination in landfills, and what might be done about it. As regulations tighten, the topic seems to be growing more urgent.

A contaminant whose importance appears to have grown significantly in recent years, poly- and perfluoroalkyl substances (PFAS) present a challenge to pollution management given their apparent toxicity – although a clear picture is still emerging – and persistence. The tag “forever chemicals” is clearly very appropriate for a class of synthetic compounds whose unusual molecular structure, including the carbon-fluorine (C-F) bond (considered one of the strongest found in organic chemistry), appears to offer little scope for any thermal or other degradation at all, so they endure permanently.

They make ideal surfactants, given their water- and oil-resistance, although this also contributes to their extreme mobility – problematic for those who might seek to constrain them.

These and other properties have made them an all-but-indispensable ingredient in a wide range of consumer and industrial products, and they have been used since the 1940s with applications including textiles and clothing, electroplating, fire-fighting foam, and ammunition.

And there are many of them (more than 4,000 on the global market). Most of the health studies and legislation have focused on the “long chain” PFAS compounds – whose molecular structure tends to feature 7 or more carbon atoms – and includes things like perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).

These compounds are known to accrete in human tissues, through consumption of contaminated food or water, and are not readily excreted. Efforts to phase out PFOS began in the US and Europe in the early 2000s, and these long-chain PFAS have gradually been substituted with short-chain replacement compounds, offering some of the same properties but presumed less toxic – an appraisal that seems to have been premature as these compounds are believed to raise similar health concerns.

The short-chain PFAS tend to feature 4 to 6 carbon atoms in their molecular structure, and include materials like perfluorobutanoic acid (PFBA) and GenX.

With their wide deployment and persistence, it’s no surprise PFAS collect in landfills – one of a number of acute pressure points in the environment where there is an elevated risk of their finding their way into soil, water and air. Numerous studies attest to their presence in landfills large and small, young and old, across diverse geographies and using different modes of operation. And they seem to appear in diverse landfill media, including solid waste, leachate, and the air at these sites.

Reliance on landfill is diminishing but it has served as the destination for more than 50% of the municipal solid wastes in the US, for example.¹

A January 2023 paper, appearing in the journal Waste Management, attempted to draw conclusions from the studies completed to date, looking at things like the occurrence and transformation of PFAS at these sites, factors affecting PFAS compounds’ release from waste, its effect on the liner system, and potential treatment technologies.²

Immediate weaknesses are apparent in the extant literature, however, and the authors, Zhang et al note that “the majority of current studies have targeted only a small fraction of PFAS (<200 out of > 4000 on the global market), which can lead to serious underestimation.”

Based on what’s been researched, a few nuggets of insight appear forthcoming about the types of PFAS prevalent at these sites. Shorter chain C4-C7 PFCAs, for example, appear the most abundant in landfill leachate in the US, Europe and Asia. Longer-chain PFAS such as PFOS and PFOS-precursors seem to dominate in landfill sediment.

With leachate, the short-chain predominance might be attributed to things like their higher solubility in water, the shift in global production towards these compounds in recent decades, and potential transformation mechanisms at landfill sites (where long chain compounds degrade into shorter chain ones).

“Mercurial” might be the term best applied to substances whose manifestations appear numerous and whose behaviour eludes easy categorisation.

Maybe the recent studies are the most trustworthy, as researchers get a better idea of what’s happening. A 2021 study by Liu et al, for example, seems to find PFAA precursors make up most of the “fresh liquid from waste collection vehicles”, while the leachate from the landfill where the same waste was left seems to be dominated by PFAAs, suggesting that a transformation is occurring at the landfill site.³

There has been lots of work attempting to correlate PFAS occurrence at landfills with factors like the type of waste, the age of the landfill, how it is operated and so on. No clear correlation with waste types seems apparent at this stage, but then only a small number of the most dominant PFAS have been studied. One study notes a higher prevalence of PFHxS in C&D leachate, likely due to its use in sealants and other building materials.

PFAS concentrations seem lower in older landfill sites, although this effect diminishes with those which closed more recently than 1993, and the growing prevalence of short-chain replacements like PFNA and PFBS over time reflects their greater usage as legislation changed. But PFAS might be expected to deplete over time in landfills because of things like desorption, leaching and decomposition.

Biological processes such as methanogenesis seem to encourage PFAS to release into leachate, and studies of bioreactor-style landfills seem to show more PFAS here than dry-tomb landfills.

These materials appear to be subject to a dizzying range of effects and dependencies over time, as landfill material passes through different phases of decomposition for example, and these in turn affect chemical properties like pH, which in turn affects things like adsorption and desorption. Zhang et al conclude that the release of PFAS from waste could be influenced by things like pH, dissolved organic matter (DOM) and electrical conductivity.

Do PFAS leak through landfill liners and geomembranes? Zhang et al conclude that “there is very limited data published to date” on the matter. One study of PFOA and PFOS onto a plastic geomembrane (LLDPE) seems to show that these PFAS have partitioning coefficients “at least two orders of magnitude lower than” other common hydrophobic (water repellent) compounds found in leachate (like benzene and PCBs). In other words, showing a greater propensity to leak. However, after 202 days of testing at different temperatures, the concentrations of these two PFAS remained below the detection limits in the receptor cells. So, no obvious leakage then.

Existing removal methods
When it comes to removing PFAS from leachate, there is a lot of data appraising activated carbon adsorption, ion exchange, biological treatment, and membrane separation.
Activated carbon has been more effective with longer-chain than short-chain compounds – a finding also apparent with groundwater, say Zhang et al. Its effectiveness depends on the adsorption rate of PFAS, which will be lower when it has to compete with other solutes in the leachate.

However, it doesn’t destroy PFAS, and disposing of the PFAS-laden media is costly as it involves expensive solvents like methanol (and subsequent disposal and handling) – and so very often this spent media is sent for incineration, which again is costly given the high temperature (over 900ºC) required to destroy PFAS.

Ion exchange removes PFAS, but like AC it doesn’t destroy them, presenting a need for costly regeneration or disposal of media.

Membrane separation methods like ultrafiltration and reverse osmosis (RO) have also been used to treat landfill leachate for many years, although ultrafiltration is ineffective. RO is “one of the most promising technologies” that has been used for leachate treatment but is energy-intensive, subject to membrane fouling if other materials or suspended solids are present, and – again – it doesn’t destroy PFAS so the RO concentrate has to be dealt with using methods that are all quite costly.

Emerging techniques to treat PFAS from leachate include foam fractionation, whereby gas bubbles are introduced, which are able to concentrate PFAS at the gas-liquid interface of the bubbles. Like RO, this concentrates PFAS in a form ready for removal and destruction.

In discussion of PFAS treatment and clean-up generally, Ian Ross – co-author of The Contaminant Handbook – has suggested solutions are likely to comprise “multiple technologies working in tandem”, and seems to anticipate a two-step process, where one of the aforementioned methods is used to remove PFAS from liquid media or water, and then this concentrated form is worked on by a destructive technology.⁴

Destructive methods
Hopes for a biological approach to remediate media such as soil and water have been suggested as “unlikely” by Ian Ross in a 2021 article.⁵ The somewhat alien chemistry of PFAS seems an obstacle, and he describes it as “a true xenobiotic” whose arrival on Earth, as it were, is a recent event.

Emerging chemical and physical possibilities for removal and destruction of PFAS in leachate include electrochemical oxidation, photocatalytic oxidation, and plasma-based treatment.

With electrochemical oxidation, Zhang et al cite a 2021 study demonstrating an average removal efficiency of 80% and 78% for PFOA and PFOS at a current density of 75 mA/cm2 after eight hours. And this could be increased to 100% with a higher current density, but with the formation of shorter chain PFAS. The method can also produce toxic halogens like perchlorate, presenting additional treatment demands. It seems expensive at present, with this study using boron-doped diamond (BDD) electrodes. There is also a high potential for electrode fouling when using real waste streams, suggest Zhang et al.

Photocatalytic oxidation, on the other hand, has successfully removed large proportions of PFAS from leachate relatively quickly (> 95% of 13 PFAS within 2 hours) in a 2021 study. It employs a novel electrode system (Fe-doped carbon-supported titanate nanotubes) to bind the PFAS prior to its destruction using UV light. However, this seems to lead to the creation of PFBA and PFPeA.

Plasma-based treatment also offers a way to destroy PFAS in leachate (or water). A 2021 study demonstrates a very high degree of PFAS removal after only 10 minutes (90% of PFOA and PFOS, >99.9 % of long-chain PFAAs, and 10–99.9 % of short-chain PFAAs). Problems so far include the generation of toxic halogen chemicals like chlorite, and challenges with scaling up – for example, making the plasma technology practical with a high flow rate of material.

Certainly, the need for reliable methods of treatment grows increasingly urgent. March 2023 saw a notable legislative landmark with the US EPA announcing the first enforceable drinking water limits for six PFAS with adverse health effects: PFOA, PFOS, and mixtures containing the shorter-chain compounds PFBS, PFHxS, PFNA, and GenX. Compliance will require monitoring down to miniscule levels, including 4ng/L for both PFOA and PFOS. As Ian Ross points out on the website of US firm CDM Smith, “Some studies have shown that rainfall in parts of the US has exceeded these levels.”

References
[1] “Poly- and Perfluoroalkyl Substances (PFAS) in Landfills: Occurrence,
Transformation and Treatment”, Zhang et al, Waste Management 155 (2023) 162-178.
[2] ibid
[3] ibid
[4] “An enduring threat to water”, Envirotec magazine, May 2021

The EA’s PFAS Risk Screening Project will undertake assessments which may inform future regulatory measures, and it has appointed professional services firm GHD to help with the associated research.

As part of Phase 4 of the project, GHD will work with the EA to help assess and characterise the risks of per- and polyfluoroalkyl substances (PFAS), persistent organic pollutants (POPs) and other hazardous substances in UK landfill emissions (leachate and gases). The objective of the work is to improve overall understanding of the scale and extent of such substances from landfill emissions and their potential migration pathways and impact on the terrestrial and marine environments.

Through monitoring at select landfills and wastewater treatment plants across England, GHD will test various media for the presence and magnitude of PFAS and POPs contaminants, and then interpret the data for emissions characterisation and look at the effectiveness of leachate treatment plants and associated wastewater treatment works in contaminant removal. The information gathered will be used by the EA to develop regulatory tools to ensure guidance for environmental monitoring at landfill sites is fit for purpose.

GHD wil work with its partners Enitial, a specialist monitoring firm with experience at landfill and water treatment sites.

Statistics published on 27 September by the Scottish Environment Protection Agency (SEPA) reveal some of the impact of COVID-19 polcies on recycling. The figures provide detail on household waste collected across all local authorities during 2021, as well as waste landfilled and incinerated in Scotland in 2021.

Standout findings include:

• Scottish 2021 household waste figures reflect the reality of easing pandemic restrictions
• Scotland generated 2.48 million tonnes of household waste (0.45 tonnes per person) in 2021
• Overall household recycling rate was (42.7%) up slightly on 2020
• Recycling of household wood and construction wastes increased after lockdowns
• Carbon impact of Scotland’s waste increased by 53,000 tonnes CO2 equivalent (CO2e) in 2021, but is down 860,000 tonnes CO2e since 2011

Waste from all sources landfilled and incinerated in Scotland 2021

• Waste from all sources landfilled in Scotland in 2021 increased 22.4% largely due to more soils and sorting residues being landfilled
• Waste from all sources incinerated in Scotland in 2021 increased by 7.4%, also mainly due to an increase in sorting residues incinerated

The figures, when compared to 2020, reflect the impact the pandemic had on Scotland’s waste. An increase in both the amount of waste generated and amount recycled are likely due to a bounce back after lockdowns and other restrictions were lifted.

Increases in waste wood and construction waste are likely due to people restarting of home improvement projects.

SCOTTISH HOUSEHOLD WASTE STATISTICS 2021
Scottish households generated the equivalent of 0.45 tonnes of waste per person in 2021, with 0.19 tonnes recycled, 0.12 tonnes sent to landfill and 0.14 tonnes diverted through other means, such as incineration.

The total amount of household waste generated was 2.48 million tonnes in 2021, an increase of 55,000 tonnes (2.3%) from 2020. Of this, 1.06 million tonnes (42.7%) was recycled, a 0.7 percentage point increase from 2020.

Data for every one of Scotland’s 32 local authorities are available on SEPA’s website.

Carbon impact of Scottish household waste
The Scottish carbon metric measures the whole-life impact of resources. A measure of national performance, the metric takes a holistic view, from resource extraction and manufacturing emissions, through to waste management emissions. This is measured in carbon dioxide equivalent (CO2e).

The carbon impact of Scottish household waste generated and managed in 2021 was 5.9 million tonnes of carbon dioxide equivalent, which equates to 1.08 tonnes of CO2e per person. This was an increase of 0.9% (53,000 tonnes CO2e) from 2020, largely due to more waste being generated.

While the amount of waste generated by Scottish households in 2021 was 4.7% below 2011 levels, the carbon impact of Scottish household waste generated and managed was 12.8% (0.86 million tonnes CO2e) below the 2011 level.

Amount of recyclables collected at the kerbside continues to rise
The amount of segregated recyclate collected via kerbside collections in 2021 was 721,000 tonnes, an increase of 5,400 tonnes (0.7%) from 2020. The change was more pronounced for rural authorities (up 4,700 tonnes, 1.6%) compared to urban authorities (up 600 tonnes, 0.1%).

These increases continue the overall trend since 2013 when 578,096 tonnes was collected, an overall increase of 24.8%.

Less than half as much waste sent to landfill as in 2011
2021 was the first time in 10 years there was no decrease in household waste sent to landfill – though the amount was more than half what was disposed of in 2011.

The increase of 4,000 tonnes to 664,000 tonnes, was a 0.6% increase from 2020, but 54.4% less than 2011. While there was an increase in the amount of waste landfilled, there was a slight decrease in the percentage sent to landfill (down 0.4 percentage points).

Waste recycled and diverted from landfill
The 2021, Scottish household waste recycling rate was 42.7%, up 0.7 percentage points from 2020. The amount of household waste recycled between in 2020 and 2021 increased by 41,000 tonnes (4.0%) to 1.06 million tonnes.

The majority was recycled or reused (677,000 tonnes, 63.8%), composting contributing the remaining 384,000 (36.2%).

The increase in waste recycled between 2020 and 2021 is likely due to a bounce back from the impact of the COVID-19 lockdown and other restrictions in 2020, which resulted in the amount of waste recycled and the waste recycling rate falling to the lowest levels since 2013.

The amount of household waste managed by other diversion from landfill was 758,000 tonnes, an increase of 10,000 tonnes (1.4%) from 2020. Most was managed by incineration (612,000 tonnes, 80.7%), which was also the case in 2020, although the proportion of the total was higher (81.9%) in 2020.

Wood and construction wastes largest changes in materials recycled
Of the seven material categories that were the most recycled or reused in 2021, wood wastes showed the largest change compared with 2020 (increase of 10,000 tonnes, 14.7%). These were followed by construction and soils waste (increase of 8,000 tonnes, 9.0%).

The increase in the recycling or reuse of these two wastes in 2021 follows a 21.5% reduction for each in 2020. This decrease is likely due in part to a reduction in the number and scale of home improvement projects, resulting from pandemic factors, such as lockdown and the inability to source raw materials.

WASTE FROM ALL SOURCES LANDFILLED AND INCINERATED IN SCOTLAND 2021
Also published today were statistics providing the details of waste landfilled and incinerated in Scotland for calendar year 2021. The corresponding data set for all waste generated and recycled in Scotland during 2021 will be published in March 2023.

Total waste landfilled in Scotland
The total quantity of waste landfilled in Scotland in 2021 was 3.2 million tonnes, an increase of 587,000 tonnes (22.4%) from 2020.

The increase was largely due to more soils (increased 297,000 tonnes, 35.7%) and sorting residues (increased 221,000 tonnes, 32.1%) being landfilled from 2020. These increases are likely due to a resumption of construction activity in Scotland following extended lockdowns and other pandemic restrictions in the previous reporting period.

The waste landfilled in Scotland statistics are available on SEPA’s website.

Waste incinerated in Scotland
The total quantity of waste incinerated in Scotland in 2021 was 1.35 million tonnes, an increase of 93,000 tonnes (7.4%) from 2020. Sorting residues made up a third (33.3%) of all waste incinerated (450,000 tonnes, up 74,000 tonnes – 19.5%). This increase is likely to due to a resumption of construction activity in Scotland after pandemic restrictions and an increase in treatment of residual waste, which was delayed in 2020 due to pandemic lockdowns at local authority recycling centres.

Hazardous waste comprised 0.2% (2,000 tonnes) of waste incinerated in 2021 and was solely composed of hazardous health care and biological wastes.

The waste incinerated in Scotland statistics are available on SEPA’s website.

Gary Walker, Waste and Landfill Tax Manager at SEPA, said:

“The latest official statistics reflect the reality of the easing of COVID pandemic restrictions, as household waste recycling centres re-opened. While Scotland has seen a reduction in the amount of waste generated in the last decade, the latest figures are a timely reminder of the need for a continued focus on recycling by us all.

“Recycling is a simple daily step everyone can take to build a more sustainable Scotland. We can all make choices to reduce the amount of waste we generate and keep products and materials in use for as long as possible through re-use and recycling to help Scotland tackle the climate emergency.”

Commenting on the figures, Iain Gulland, Chief Executive, Zero Waste Scotland, said:

“It is encouraging to see recycling rates recover slightly from 2020, when they were significantly affected by the Covid-19 pandemic. Recycling is a fantastic force for good, helping to keep materials in use for longer and evolve a more circular economy for Scotland.

“The latest data makes clear however that, as a society, we need to do more to curb our consumption. Around 80% of Scotland’s carbon footprint comes from the products and materials we make, use, and throw away – often before the end of their useable life. It’s a moral and environmental imperative that we change that.

“We need to transform our throwaway culture to one in which products and materials are valued and made to last if we’re serious about tackling climate change.”

A radical rethink of recycling and waste policy is required to put the UK on a more sustainable path, according to a new report from the Institution of Mechanical Engineers (IMechE). “Waste as a Resource: A sustainable Way Forward” advocates an approach that prioritises waste streams according to their usefulness to materials and emissions reduction, and to their utility to the wider energy system.

The original concept of a ‘Waste Hierarchy’ was adopted by the UK Government in the 1990s but viewed and still views waste as a problem rather than as a resource and thus does not fully deliver on the targets for which it was designed.

In the report, the IMechE recommends that the Government:

• Replace the Waste Hierarchy to drive prevention of waste at source, climate change mitigation and the recovery of energy and materials – valuable resources which will reduce imports and boost the UK’s economy. The primary premise of its replacement must acknowledge that reducing or preventing waste of all types is paramount. Not producing the waste in the first place has by far the most beneficial effect on the environment.
• Deal effectively with all waste streams. Rather than the almost exclusive focus on the small proportion of total waste arisings which are ‘household’ waste, develop more effective strategies for dealing with commercial, industrial, construction, demolition, and agricultural waste.
• Adopt a long-term zero-to-landfill approach and publish independently audited, transparent data on the recovery and destination markets of all materials and energy (heat, transport, and electricity).

Lead author, Professor Ian Arbon said:

“We need to stop seeing waste as a problem and to start seeing it as a valuable resource and use it to maximum advantage. Our proposed modification to the Waste Hierarchy, which reduces it to four tiers, removes the unhelpful competition between ‘recycling’ and ‘recovery’ and helps to focus attention on minimising landfill.”

Head of the IMechE’s Engineering Policy Unit, Matt Rooney said:

“The UK could and should be making much better use of our waste streams. The recent cost-of-energy crisis has emphasised how important affordable domestic supplies of energy can be. The fact that so much waste heat from many of our power stations, for example, is simply lost to the atmosphere is something we need to change to build a more sustainable energy system.”

The full report can be downloaded here.

Scotland’s pledge to ban the landfilling of biodegradeable waste by January 2021 always appeared ambitious, and was regarded as world-leading when the Waste (Scotland) Regulations 2012 first appeared, supporting the laudable aim of reducing the most significant contributor to the country’s waste sector’s greenhouse gas (GHG) emissions.

Then, there was the September 2019 decision to delay the deadline of the ban, until 31 December 2025, which seemed to indicate a mismatch between ambition and practical reality, that the country’s recycling “eyes”, as it were, had outsized its recycling “belly”. But in truth, it was always going to be an ambitious proposal.

Now, three years on from this decision, there is still a shortfall between the residual waste the country is producing and its capacity to handle it, an eventuality that has been long anticipated. A 2019 review by Eunomia noted that the extent of this gap would depend on the level of recycling that could be achieved in the interim.

An independent review of the role of incineration in Scotland (titled “Stop, Sort, Burn, Bury?”) – published in May – predicted a short-term capacity gap in 2025, but that options existed for plugging it, such as exporting waste to landfill in England, or exporting it as RDF. But there are serious drawbacks to such options, and some uncertainty over how “temporary” this capacity gap looks likely to be.

Ground-level success

The move away from landfilling in recent years is hailed by SEPA as a Scottish success story. As the regulator points out, in 2005 the country was burying over 7 million tonnes of its waste in 129 active landfills, a figure that by 2020 had been reduced to only 2.6 million tonnes, at 41 active landfills. At least three quarters of the decline is attributable to waste prevention and increased recycling, but some of it has also been possible because of the building of new EfW facilities.

Incineration has been a bête noire of circular economy champions, and often eyed with suspicion. It has helped reduce emissions – having historically held the edge over landfill in this respect – while introducing new problems, and arguably reducing the political and commercial impetus for achieving circularity. As zero waste expert Paul Connett has noted, “Energy generation and the promise of less climate impact don’t change the fact that when you burn resources they have to be replaced, which wastes more energy and creates more global warming than the marginal saving from reduced landfilling.”

“Marginal” seems not to be the definitive appraisal. A 2021 report from Zero Waste Scotland, for instance, cited results showing that incinerating waste is 27% less CO2-emitting than landfill. Numerous factors have a bearing on this, such as the composition of the waste. The independent review noted that progress towards avoiding and recycling organic waste, and decarbonising other sources of energy, will likely alter the balance further, “and it may well flip at some point”.

But the least carbon-intense option of all is obviously to recycle. As circular economy minister Lorna Slater noted in May, incineration “has a role to play
in managing Scotland’s unrecyclable waste in a safe way”, but she added that “that role is
inevitably limited”.

“As we transition to a circular economy, Scotland will need significantly less incineration capacity than is currently projected.”

This echoed the findings of the “Stop Sort, Burn, Bury?” review, and presaged a moratorium on the building of new EfW plants, announced by the Scottish government in June.

How big a gap?

The independent review modelled various scenarios and concluded that, where Scotland meets its policy targets, “there would not be an expected capacity gap from 2024”.

However, where policy targets aren’t met, it said, “there is likely to be insufficient residual waste treatment capacity in Scotland in 2025 by 590-680 kt”.

Analysis by SEPA, cited in the report, stated that around 1.05 Mt of waste that would be captured by the Ban was landfilled in 2020, resulting in an anticipated capacity gap of around 500 kt in 2025.

The Scottish Environmental Services Association (SESA) also clearly anticipates a lack of treatment capacity, according to comments made to the ENDS Report in August, while the UK Without Incineration Network (UKWIN) anticipates considerable overcapacity.

The review also predicted that, if all the planned EfW facilities that are currently “fully consented” are actually built, then there is likely to be overcapacity from 2027 no matter what else happens.

There seem to be enormous complexities involved in achieving this sweet spot between not building enough EFW plants (and having to export waste) and building too many – and undermining the future roadmap for circularity.

In its response to a Scottish government consultation on incineration, which closed in February, Zero Waste Scotland attempted to illustrate the choices facing Scotland. Both Slovenia and Lithuania also relied upon landfill in the early years of the last decade, and have since become champion recyclers (Slovenia being the top performing EU member state in 2019). If Scotland aspires to 60%+ recycling levels, then it could emulate these nations’ strenuous push for waste prevention, and things like source segregation and composting. But if incineration is used to replace current landfill use, then there is a danger that it might follow the trend recently reported in Finland, where recycling seems to have plateaued.

Many local authorities still seem unprepared for the ban, and have little room for manoeuvre at this point. Members of Clackmannanshire council appeared in reluctant agreement in August that it would have to move ahead with seeking a 10-15-year EfW contract. A local branch of the trade union Unison lamented that “there is no real political ambition to turn the tide on global warming.”

Two public consultations recently concluded on new proposals from Holyrood that might address the shortfall in recycling. A possible “Circular Economy Bill” has been seeking views on measures such as banning the destruction of unsold goods, improving household recycling (including a possible kerbside collection of textiles), and measures to tackle single-use items.

The government was also seeking views on “a Route Map to 2025 and Beyond”, looking at how to achieve things like food waste reductions from households, and embedding circular practices within the construction industry.

At present, little detail is available on how these measures will plug the gap. The other question mark is over how temporary any predicted gap is likely to be. Commenting in the ENDS Report in August, SESA said it didn’t share the government’s enthusiasm about the gap being short term.