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Burning waste to generate heat and electricity was deemed the UK’s “dirtiest form of power” in a BBC investigation in October 2024, after the country’s last coal plant closed the month before.
The energy from waste sector has more drawbacks than just its contribution to climate change. Its incinerators are often built in deprived areas, where they emit harmful pollution. There are also allegations of malpractice against particular plants.
The government has given planning permission for 41 new incinerators of household and commercial rubbish to supplement England’s existing 50. Is there a case for it, or is this form of waste management overwhelmingly negative?
Landfill tax, levied on private or local authority handlers of black bin waste, has risen from £7 a tonne in 1999 to £48 in 2010 and £102 a tonne in 2023.
In 2000, the year after the landfill tax escalator began, nearly 80 million tonnes of waste went to landfill. In 2023, it was 35 million tonnes, of which 22 million tonnes was classed as “inert” with limited effect on the environment.
While we burn fossil fuels to generate electricity, all methods of treating waste will produce planet-warming greenhouse gases, including plastic, metal and glass recycling which requires heat. Of course, recycling is far better than landfill as it keeps mined material in circulation rather than releasing it to the air or burying it underground.
Food and other biodegradable waste decomposes in landfill to form biomethane, a gas composed of around 65% methane and 35% CO₂. Methane is around 23 times more effective at warming the atmosphere than CO₂, albeit it dissipates much more quickly.
But how much do landfills emit compared with incinerators? Comparisons are difficult as each incinerator and landfill is different. Assessments have to account for the emissions avoided by using one form of waste treatment over another. However, Fichtner Consulting Engineers estimated that burning general waste for electricity produces the equivalent of around 200 kg less CO₂ per tonne than letting it decompose in landfill. Carbon assessments accepted in support of incinerator planning applications show a range of 150–250 kg CO₂.
These figures may change as the UK’s electrical grid is decarbonised, and are sensitive to efforts to collect landfill gas and the composition of waste sent to landfill.
But if the Fichtner estimate is accurate, the UK’s incinerators may have saved 15 billion kg of CO₂ from being emitted by landfills between 2018 and 2023.
Not straightforward to recycle
Recycling rates in the UK in 2022 (44%) were almost the same as they were in 2015. Some recycling plants are closing, despite declining plastic exports and calls for more plastic sorting capacity.
Regulations which were intended to reduce the number of bins on doorsteps have meant more recycling bins in which cans, bottles and glass are mixed together. Contamination of recycling, whether deliberate or not, costs waste processors a fortune and in the case of plastic bottle recycling, produces discoloured or cloudy recycled plastic that drinks companies are less likely to use.
Local authorities that cut funding for educational programmes about recycling saw less recycling overall and higher contamination. A survey of schools in five European cities suggested that teachers who wanted to instruct pupils about the importance of separating waste for recycling were prevented by a lack of space in the curricula.
It’s a wicked problem. Waste processors need uncontaminated recycling, UK recycling infrastructure must expand to increase recycling volumes (but facilities are closing) and funding is being cut from educational programmes.
Necessary for now?
Energy from waste extracts some value from contaminated or otherwise unrecyclable waste. Recycling facilities are excellent at separating waste into processable materials. But they cannot continue to deal with all the different types of rubbish people put in their general waste bin all at the same time for long periods.
There are two options for the leftovers from general waste sorting. Landfill, where a fraction of the waste biodegrades into methane which can be recovered and burned for heat and electricity, but plastic and other non-biodegradable waste remains in the ground for decades. Or an incinerator that quickly reduces the volume of the waste while generating heat and electricity far more efficiently than landfill can.
Incinerators must monitor more than 30 pollutants (from heavy metals to sulphur dioxide) on a half-hourly basis and have strict daily emission limits. Each year, 97% of half-hourly averages must be below the permit conditions. It is up to the Environment Agency to decide where monitoring systems are installed onsite and air process techniques are used to neutralise acidic gases and adsorb toxic metals in exhaust fumes.
Even the ashes from burning waste can absorb CO₂ after being moistened and cooled. Adding carbon capture technology to incinerators to reduce CO₂ emissions while better recycling solutions are discovered is, I would argue, worthwhile.
Microbial technology offers one useful recycling alternative. Anaerobic digestion, based on the human gut, can cut waste volumes by turning sewage or food waste into biomethane using a series of microbes. Biomethane is burned for electricity and heat, as with landfills, while solids left over from digestion are composted.
Small digestion plants are already found on farms, while larger ones operate at sewage works. Perhaps with more investment it might be possible to design a greater range of microbes capable of digesting general waste more effectively, potentially even storing the carbon from waste in the products.
We will always need a disposal option for contaminated unrecyclable waste. That makes energy from waste, for better or worse, necessary for now.
Edward Randviir receives funding from Innovate UK and the Royal Society. He has previously consulted on waste management sites, including anaerobic digestion, in-vessel composting, and energy from waste plants on behalf of Viridor-Laing, a waste and construction consortium.
