The carbon cure: how to cut our waste emissions
Image credit: Dreamstime
Emissions from waste treatment have fallen dramatically, but official figures hide the true impact of our rubbish and the considerable savings to be made from reducing, reusing and recycling more of it.
Greenhouse gas emissions from waste management plummeted 73 per cent between 1990 and 2020, according to the UK government’s latest data. The waste management sector is now responsible for around 4 per cent of the country’s emissions (17.6MtCO2e of 404.5MtCO2e) compared to 8.5 per cent in 2000.
The progress is impressive, with landfill tax driving waste out of holes in the ground – a treatment that sits at the bottom of the ‘waste hierarchy’ and produces the potent global warming gas methane. But where has all this waste gone, with its accompanying emissions?
There have been improvements in the standards of landfilling, changes to the types of waste going to landfill (such as reducing the amount of biodegradable waste), and an increase in the amount of landfill gas being used for energy. More rubbish is now recycled, and food waste has been reduced, with more of what is left ending up at anaerobic digestion plants to create energy.
Yet a lot of residual waste historically landfilled now ends up in energy-from-waste (EfW) facilities. According to government figures, these accounted for just 0.3 megatonnes of carbon dioxide equivalent (MtCO2e), which is 1.7 per cent of waste treatment emissions in 2020. Meanwhile, landfill accounted for 17.6MtCO2e. That is not the full picture –it is only a tiny part of it, as 95 per cent of the emissions from EfW are not included in waste sector emissions, they are listed within ‘energy’ instead. That 0.3MtCO2e is only from incinerators that do not create energy.
It is a quirk of the accounting system used by the UN Framework Convention on Climate Change (UNFCCC), and followed by the UK Department for Environment, Food and Rural Affairs (Defra). This skews what is going on, as emissions are reported under the waste category, rather than the effect our managing waste has on climate change. The approach sends the wrong message to people dealing with waste, according to Dominic Hogg, founder of consultancy Equanimator, which recently published a report on the topic (‘Problems in the reporting of GHG emissions from ‘waste’’). It almost invites the waste sector to be indifferent as to where rubbish goes as long as it’s not a landfill, he explains.
So why does this matter? What is the full emissions footprint of managing our waste, and what is being is done to reduce it?
Between 1990 and 2019, emissions related to incineration ballooned from 1.66MtCO2e to 5.6MtCO2e. Most of the increase has been since 2010. Still, waste emissions, including EfW, landfill, as well as other limited sources like composting and anaerobic digestion, have fallen from 90MtCO2e in 1990 to 32MtCO2e in 2019. Good news – but not quite as good as the figures in the opening line of this article suggest.
Burning waste is, by and large, better for the environment than burying it. How much better is hotly debated. A 200kgCO2e saving per tonne of waste is often cited, but that was in a 2014 report by the Green Investment Bank using data from just three plants. Tolvik Consulting, in its annual statistical release on EfW in 2020, reckoned the figure was closer to 50kg, with EfW and landfill creating 0.27tCO2e and 0.32tCO2e per tonne of waste, respectively.
So EfW wins. Yes, but only over landfill. “Modern plants are far from the polluting monstrosities of the past,” wrote Colin Church, CEO at the Institute of Materials, Minerals and Mining (IOM3) recently, but “burning waste also produces carbon dioxide [...] so allowing it to be freely emitted in the long term is incompatible with Scotland’s desire to reach net-zero carbon emissions”.
Church has just finished an independent review of whether Scotland’s approach to residual waste management aligns with its carbon reduction ambitions, concluding that it does not. He recommends the country gives no further planning permission to incineration infrastructure as there will be overcapacity from 2026/27. Wales introduced a moratorium on EfW builds last year.
The UK’s Climate Change Committee (CCC) is now including the “increasing importance” of EfW emissions in its assessments and benchmarking of the waste sector within national carbon budgets. The committee cannot afford to “hide” EfW emissions in the energy sector, explains Professor Chris Hilson, an expert in environmental law at the University of Reading. “Otherwise their advice might be to just build more EfW to solve waste emissions. The waste sector might look rosy using that accounting, but falsely so,” he adds.
Church recommended Scotland follow suit. Defra, meanwhile, is mindful of the carbon implications of simply shifting waste out of landfill and into incinerators in the long term, but ministers are not yet worried enough, say campaigners. As Church noted at the launch of his report, EfW is less damaging in climate change terms than landfill now, but “over time that will change and that’s why it’s important now to be thinking how to [...] avoid that balance becoming unsustainably bad”.
There are three ways to do this: make the process more efficient, capture more CO2 (which the CCC has also recommended), and ensure less waste from fossil sources is burned. “Every facility can reduce its carbon impact by removing plastic before it gets burned. It is a bit of a no-brainer,” says Church.
Speak to the waste companies that run EfW plants and they say they don’t want to be burning plastic. They – and the public – could do more to separate recyclable waste out first. Twenty-five per cent of residual waste is easily recyclable, according to Defra, which is launching a raft of policies to ensure more materials are recyclable and recycled. This could have considerable carbon benefits.
Take plastic, which is being billed as ‘the new coal’ by some NGOs. Too much plastic is being produced, used once, then burned. “By 2050, the production and disposal of plastic could generate 56 gigatons of emissions, as much as 14 per cent of the Earth’s entire remaining carbon budget,” wrote the Centre for International Environmental Law in 2019. Plans to expand production could make limiting temperature rises to below 1.5°C “impossible”.
Recycling more is no silver bullet, as discussed below, but it will certainly help: for every tonne of polymer recycled in a ‘closed loop’ rather than incinerated, around 4tCO2e are saved. Yet these savings are also hidden in waste emissions accounting. “Recycling tends to show up in the waste sector only by its absence, in that it leads to lower landfill and EfW emissions,” explains Hilson.
Recycling also has a positive impact that comes from other sectors not using virgin materials. “A lot of the benefits of how you manage your waste system are around ‘avoided emissions’,” explains Lorna Pannett, associate director at consultancy Ricardo. These can’t be counted when reporting waste sector emissions (it would constitute double-counting) but they shouldn’t be forgotten – as many suggested they were at the COP26 climate talks.
Pannett has been working with the Environmental Services Association (ESA) on a net-zero plan for the waste management sector. For the first time, they have calculated the emissions impact of all services provided by the recycling and waste management sector. Their final figure was 35.8MtCO2e, or 8 per cent of all UK emissions (double Defra’s figure of 4 per cent, but in line with CCC’s). Recycling processes account for the biggest chunk of these emissions, followed by landfill, then EfW and transport.
The ESA has now produced a plan to achieve net-zero by 2040, with three decarbonisation priorities: a transition to zero-emission vehicles and fuels, removal of organics from landfill and plastics from EfW (ensuring carbon capture, use and storage), plus investment in new, efficient recycling infrastructure that will help meet the government’s 65 per cent municipal recycling target.
Ricardo also estimated the avoided emissions: all 49.9MtCO2e of them, of which 44.8MtCO2e are from recycling. This swallows the sector’s entire Scope 1 and 2 emissions (those arising from its own operations and from energy purchased). As Ricardo noted in its technical report, there is a “very compelling narrative here for the waste and recycling sector to convey” in relation to the UK’s net-zero aspirations.
David Wilson, an independent consultant and visiting professor in waste management at Imperial College, London, has been researching this topic in detail. “If we focus mitigation measures just on the waste sector doing its thing better, we’re completely missing the point of the contribution it could make,” he says. How big this carbon contribution could be is unclear. Whether it is 5 or 40 per cent, it is certainly significant.
New recycling technologies may also play their part. The UK government estimates that up to 31 per cent of waste currently landfilled or burned could be recyclable in the future. For example, there is a lot of attention around ‘advanced’ or ‘chemical recycling’ to tackle hard-to-recycle plastic that traditional mechanical recycling cannot deal with. The term covers a broad church of approaches, including solvent purification, chemical depolymerisation and thermal depolymerisation, but there is limited transparency of these processes and their impacts.
Critics argue that some are incineration by another name because they are “carbon intensive and toxic”. Supporters say it’s an essential technology to help recycle more of what’s currently burned. Some technologies “have promise”, Eunomia consultants concluded in a ‘state of play’ report in 2020, but evidence available demonstrates “possibility rather than viability”.
Expect further debate too around the carbon pros and cons of chemical recycling as businesses attempt to scale their approaches. A March 2022 report by consultancy CE Delft, for the Dutch Minister of Environment, showed mechanical recycling of mono-materials and solvent-based purification/depolymerisation saved similar amounts of carbon when compared to incineration. These also had far higher plastic-to-plastic yields than pyrolysis and gasification (it shouldn’t be forgotten either that to produce one tonne of recycled plastic by mechanical recycling, you need 1.4 tonnes of plastic input). If you try to recycle mixed plastics, emissions savings start to fall, data showed.
Technology isn’t the only factor in emissions that can be avoided by recycling. Materials easily and efficiently recycled many times are far better than those that are downcycled once before dropping into the two bottom rungs of the hierarchy (think of crisp packets turned into traffic cones). Of course, the best kinds of materials are the ones you don’t need at all, notes IOM3’s Church.
The role of resource efficiency in reducing emissions and achieving net-zero is often lost in the hype around recycling. Recent global polling shows people still consider recycling the most effective action they can take to reduce emissions. It isn’t, by a long chalk (please don’t stop recycling though). Policymakers have focused almost exclusively on recycling when it comes to waste. When it comes to carbon, policies home in on operational emissions (reducing energy and vehicles emissions). This has left resource efficiency as the Cinderella of carbon reduction strategies.
Research by Green Alliance shows that improving the use of resources in the construction, vehicles, food and drink, electronics and appliances, and clothing and textiles sectors, could save nearly 200MtCO2e between 2023 and 2032. Some 79.1MtCO2e of those could come in construction through design to reduce material inputs, increased reuse of materials, and switching from high- to low-carbon materials. An 80 per cent reduction in avoidable household food waste could bring another 17.3MtCO2e, while a rise in reuse of electronics to 32 per cent offers 10.2MtCO2e.
How to achieve those is something that continues to vex ministers and officials.
Between 2013 and 2019, government actions prevented just 17,200 tonnes of waste in England per year. For context, the latest waste figure for England was 187.3 million tonnes, so actions taken had “virtually no material impact”, noted Green Alliance. The next waste prevention plan is due to be published soon, but proposals, which rely heavily on voluntary agreements, have been widely criticised.
Defra is also consulting on long-term resource efficiency and waste reduction targets, which should see focus on the top of the waste hierarchy. The plan is to cut residual waste by 50 per cent by 2042, but this excludes ‘major mineral wastes’ – inert wastes from construction, demolition, excavation, and mining activities. These are hard to tackle, but offer considerable carbon savings potential: construction, demolition and excavation created 137.8 million tonnes of waste in the UK in 2018, five times that from households.
Continued use of weight as a metric in resource policies also appears outdated in a world focused on net-zero. Consider Scotland, for example, which has been measuring lifecycle impacts of its household waste since 2011. Data from this year’s report shows where we are on waste emissions and how far we must go. Landfill emitted 244,300tCO2e and incineration 171,300tCO2e (the highest recorded), while recycling ‘offset’ waste carbon impacts by 538,100tCO2e. However, at 5.97MtCO2e, embodied carbon impacts from material production are by far the greatest contributor.
That is the “untold story” here, says Jamie Warmington, principal consultant at Anthesis. Millions of tonnes of waste is lost and reproduced every year because we are not recycling it back into the system, reusing or reducing it in the first place. This is linear winning out over circular thinking and it is about much more than diverting waste from landfill.
As Professor Wilson suggests, we need to find ways to convey the bigger picture.
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