Treatment and Disposal of Air Pollution Control Residue

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Courtesy of Tetronics (International) Limited

What is APCr?

Thermal waste management using Energy Recovery Facilities (ERFs) is now a well-managed and mature technology that is subject to environmental monitoring by a range of competent international bodies. These ERFs have been established as a means of diverting waste away from landfill disposal and for valorising the material and energy content of the waste. Counter to historic operation of incinerators, modern ERF technology is now typically only applied to residual waste, i.e. municipal waste following the removal of recyclates, and is part of an integrated waste management infrastructure that spans the entire waste hierarchy, i.e. it complements recycling and recovery.

It is now estimated (2015 EA statistics) in England and Wales that 10.4 million tonnes of residual waste is incinerated per year, which equates to approximately 5.4% of our overall waste generated and with more capacity in the pipeline at various levels of development. Extensive pollution abatement techniques are applied to modern ERFs, but a consequence of using these techniques is a concentrated secondary hazardous waste called Air Pollution Control residue (APCr). APCr is a fine voluminous highly alkaline grey powder loaded with persistent organic pollutants, heavy metals and hazardous inorganic species, which is becoming more concentrated with time owing to the good stewardship of the UK Environment Agency. This makes the disposal of APCr a complicated and potentially hazardous process to implement which commands diligence.

Disposal of APCr is filling up landfills

Currently 282,000 tpy of APCr is generated in the UK which is equal to over 100 Olympic sized swimming pools. The amount of APCr is estimated to drastically rise, growing to600,000 tpy by 2020, as a greater proportion of the UK’s residual waste is treated via EfW facilities So, as residual waste incineration increases in the UK, the development of more sustainable methods for managing APCr is a key issue for the environmental industry. APCr is currently transported significant distances for ultimate landfill based disposal. These traditional disposal mechanisms are being increasingly challenged from availability, cost and compliance stand points and these pressures are magnified by the likely future escalation in the level of landfill based taxation.

Furthermore, UK landfill disposal of APCr currently occurs only within a 3xWaste Acceptance Criteria (WAC) by derogation; this is 3x the accepted European compliance standard. You can think of the leaching test for WAC compliance as an assessment of the environmental mobility of the pollutants within the APCr. Therefore, alternative sustainable treatment methods are urgently required to be implemented during any allocated transitional period and it is only right and just, based on the amount of resource and energy used to abate these sources of pollution originally, that the best possible method is used to manage this growing hazardous waste. And indeed, the National Policy Statement for Hazardous Waste released by the Department for Environment, Food and Rural Affairs (DEFRA) earlier this year (as referenced in their new guidelines for organisations within the UK dealing with hazardous wastes such as APCr), states that companies should be using the best available techniques to deliver the best overall environmental outcome.

Therefore, you may be surprised to learn that most APCr still goes to landfill after pre-treatment, most of which, counter to popular opinion, is non-hazardous landfill. Due to the regulatory structure the engineered environmental controls of non-hazardous landfills, are usually not as robust as hazardous waste landfill and instead pre-treatment of the APCr is meant to reduce its ultimate potential to cause pollution.

On the 7th February, Tetronics International were unfortunately informed that DEFRA Ministers have taken the decision, counter to industrial stakeholder opinion, not to remove the derogation that allows Air Pollution Control Residues (APCRs) that are three times above Landfill Directive waste acceptance criteria (3xWAC) to be landfilled. This is despite UK Government (via BIS) investing £1m pounds of taxpayers money in R&D grant work, match funded by Tetronics, to demonstrate the suitability of Plasma Vitrification to solve the problem and eliminate the need for this hazardous waste stream to be sent to landfill.

Products of APCr waste

On top of this dichotomy there are a number of products derived from APCr that are starting to appear on the market, although from the promotional material that surrounds these products it would not be obvious to the lay person that they contain diluted APCr derived ‘products’ that are only permitted for use in bound conditions. So how is this happening? Well, the UK Environment Agency have what is known as an end of waste panel, the role of which is to decide whether a treated material can end its life as a regulated waste and therefore become a material product. As one may anticipate, this is determined by a dossier of information presented by the applicant with a focus on engineering properties and environmental impacts of the material. The ultimate test is associated with a comparison of actual impact of the waste derived products with those of ‘virgin’ material products available from open sources. In other words, the waste-derived product is no worse than what is already available.

On first inspection, this would seem reasonable because as a product, these materials would be regulated more thoroughly under REACH (Registration, Evaluation, Authorisation and restriction of Chemicals) regulations. Unfortunately, although the Agency complies with the rules, there appears to be a loophole which means that because the products are shaped and most of their value is a result of them being shaped, they are regarded as ‘articles’ under REACH and are not as robustly regulated. Consequently, we have a situation where hazardous waste-derived products can be released into the community with limited controls and without ongoing monitoring of the product’s credentials. Most of these are associated with block manufacturing and the production of cement or gypsum based material building products.

Plasma solution for disposal of APCr

However, you will not be surprised to learn that there is an alternative solution to the disposal of APCr challenge: plasma technology. This technology is commercially attractive at the same unit costs as those achieved forlong terms contracts for landfill-based disposal alternatives. It is the challenging chemistry of APCr, significant centralised scale of annual arisings and the concentrated character of the APCr material’s chemistry that lends its treatment to plasma technology. In the plasma process, APCr is fluxed to encourage the formation of a rock-like product that has been termed Plasmarok®. Plasmarok® is qualified by the UK Environment Agency as a product by performing to inert WAC standards, i.e. no residual negative effect on the environment or human health, which is the gold standard and has permission for use as a secondary aggregate. In addition to Plasmarok®, the parts of the APCr that are volatile, in the main chlorine, formed from inhibited acid gas releases, are processed and captured as hydrochloric acid, which can then be sold back to industry.

The Plasmarok® and hydrochloric acid products in combination mean that the vast majority of the mass and chemical value of the original APCr is transformed into useful products, with only a relatively small amount of secondary waste remaining. The products off-setting environmental impacts associated with the use of virgin equivalents. Importantly, the hazardous organic fractions are destroyed and not merely packaged. Plasma is technologically advanced compared to the other solutions. It is robust and straight forward as a technology and the commercial comparison touched on earlier does take into account the energy consumption of the process, thereby addressing historical misconceptions that surround plasma. So, overall as the saying goes ‘you get what you pay for’.

Plasma is a truly sustainable means for the management of APCr waste, as an alternative to disposal. Tetronics currently anticipates plasma-based facilities coming into operation in the UK market within the foreseeable future. This APCr solution will be an essential part of future critical waste management infrastructure to close the waste management loop and promote the further development of circular economic models.

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