Resource Use

Incinerator bottom ash reuse ‘insidiously hazardous’, says Zero Waste Europe

Research recently published by Zero Waste Europe (ZWE) has identified ‘at least 15’ concerns for public and health safety in relation to the reuse of waste incinerator bottom ash.

IncineratorThe report, entitled ‘Toxic Fallout: Waste Incinerator Bottom Ash in a Circular Economy’, describes the material as ‘insidiously hazardous and underregulated’. ZWE asserts that testing methods for its use as a building material are ‘outdated’, stating that they are ‘not based on current science and underrepresent real conditions’. The group consequently labels industry support for its use within a circular economy as ‘premature’, calling for all ongoing usage to cease.

Bottom ash is fallout from the grate of mass-burn waste incinerators. The material is typically produced in large quantities, with the residue having a negative value. According to ZWE, the material’s visible proportions of sand, glass, and stones make it appear as ‘low-hanging fruit’ for use in a circular economy. The report warns, however, that the material also contains ‘appreciable quantities of toxic ‘high level of concern’ elements and persistent organic pollutants’.

A secondary ‘fallout’ occurs when these substances leach from bottom ash into its surroundings across a range of conditions and timescales, something that, ZWE asserts, ‘the waste incineration industry fails to mention… when advertising [the material] as a ‘green’ building material’.

The findings, ZWE adds, raise concerns about the operational compliance of waste incinerators with the Industrial Emissions Directive, and consequently the efficacy of waste incinerator monitoring and policing. Also flagged was the capacity of incinerators to ‘produce benign bottom ash when fed with municipal solid waste (MSW)’.

The report outlines the initial uses of leftover ash – commonly repurposed during the 1800s as a sub-base for paths and carriageways. However, ZWE notes, modern incinerator bottom ash is ‘markedly different’ from this material, containing ‘ubiquitous quantities of plastics and their additives, along with plastic/metal composites and other petrochemical coated substances’.

According to the report’s findings, microplastics are not destroyed by the incineration process, with up to 565 microplastic particles accumulating per kg of bottom ash. Further polluting substances, such as PCDD/Fs, PBDE, PCBs, and PFASs, ZWE states, are overlooked by European countries when qualifying bottom ash for use in building aggregate. The report further notes that the bottom ash treatment industry is ‘still at a fledgling stage’ and is currently incapable of removing all metals.

ZWE’s findings were derived from a literature review, with papers selected for the research only if they contained results drawn from empirical research and referred to datasets that used samples of bottom ash produced by the incineration of MSW, excluding reports on special ‘hazardous waste’ incinerators. Also excluded were publications either directly commissioned by industry, co-authored by, or co-funded by industrial sponsors.