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Recycling vs Recovery of Construction Excavation Waste

Jul 9, 2024 | Waste Management

Managing Director Scott Brewster offers his view on how changing regulations and behaviours will hopefully drive more excavation waste up the waste hierarchy towards recycling:

The Scottish Environment Protection Agency recently consulted on its draft Integrated Authorisation Framework (IAF) which, on the back of Environmental Authorisations (Scotland) Regulations 2018 (EASR 2018), aims to provide a standardised, simplified, common framework for environmental authorisations in Scotland. Together with a devolved Scottish Aggregates Levy, I believe a new IAF represents a huge opportunity to drive more excavation waste up the waste hierarchy towards recycling (arguably ‘upcycling’ when washing technology is involved), creating an increase in the supply of recycled aggregates, and a move away from recovery and disposal.

Waste Hierarchy

SEPA has previously supplied guidance on the recovery and disposal of such waste in the back-filling of quarries. Within that guidance, the construction industry is reminded that the Waste Management Licensing (Scotland) Regulations 2011 define “Recovery” as “any operation the principal result of which is waste serving a useful purpose by replacing other materials which would otherwise have been used to fulfil a particular function, or waste being prepared to fulfil that function, in the plant or in the wider economy.”

  • Recycling” is defined as “any recovery operation by which waste materials are reprocessed into products, materials or substances whether for the original or other purposes. It includes the reprocessing of organic material but does not include energy recovery or reprocessing into materials that are to be used as fuels or for back-filling operations.”

 

  • Back-filling” is further defined as “any recovery operation where suitable non-hazardous waste is used for purposes of reclamation in excavated areas or for engineering purposes in landscaping. Waste used for backfilling must substitute non-waste materials, be suitable for the aforementioned purposes, and be limited to the amount strictly necessary to achieve those purposes.”

Recycled or Recovered?

Clearly from the above definitions, recovery/back-filling of excavation waste in restoration sites is not recycling, yet in SEPA’s own waste data reporting, absolutely zero waste soils are recorded as recovered. In fact, the definition of ‘recovered’ is conveniently redefined for reporting purposes and restricted to only include “waste inputs to co-incineration facilities and to incineration facilities which applied for and were demonstrated to meet the R1 energy recovery efficiency specified in the EU Waste Framework Directive.”

Omitting true recovery data and bundling all back-filling soil tonnages into the recycling column seems misleading and contradictory to SEPA’s own guidance. Given the tonnage of waste soils as a proportion of all waste stream arisings, this skews the overall recycling rate reported for the nation and presents a more favourable recycling story than reality.

Furthermore, SEPA’s waste data shows that approximately 25-35% of all soil waste generated over the last decade is still disposed of in landfill. If we use the Mineral Products Association (MPA) figure that approximately 17% (9.4/53.4mt) of excavation waste is recycled within the UK as an estimate, then over 50% of the waste stream is currently recovered. It will be interesting to see the impact of the impending ban of Biodegradable Municipal Waste from landfill on landfilled soil figures. If as predicted many landfills close as a result, then up to 1m tonnes of soils per year are going to have to either be rerouted to surviving landfills or be managed at recovery and recycling facilities.

 

 

The recycling rates of ‘hard’ Construction & Demolition Waste (aka rubble) vs ‘soft’ Excavation Waste (aka soil) are clearly distinguished by the Mineral Products Association

Lack of Supply?

The Mineral Products Association talks about the potential for increased recycled aggregate production within its latest ‘Nothing is wasted’ press release. To me, the ‘no more can be done’ conclusion is premature as the increased recycling of EW through wash plants offers significant growth opportunities in recycled aggregate production, as evidenced by the proliferation of such plants throughout the UK (estimated to now be 100 in number) in recent years.

During the Scottish Government’s Aggregates Levy consultation, the MPA and construction industry cited a lack of supply as a constraint to further use of recycled aggregates and moving beyond the estimate of 20% derived from waste sources referenced in SEPA’s guidance. I would question this in the Scottish Central Belt, where 50% of the nation’s construction activity occurs. This region has the densest network of wash plants in the UK (approx. a dozen in number).

Any supply constraint is likely due to a lack of feedstock and circular thinking on waste management by contractors (more on this below), rather than production capacity. If suitable waste material was mandated to be recycled, increasing the amount of feedstock for the production of recycled aggregates, then I am confident that Scotland could surpass the UK’s currently superior rate of approx. 30% from recycled sources.

Drumshoreland Plant

Lost Resource

Not all excavation waste (such as soils with high clay content) is suitable for recycling (washing/upcycling), but there is a substantial amount of material with high sand and gravel content being indiscriminately tipped into backfilling restoration sites. This is lost resource/value to the economy and is a missed opportunity for natural resource preservation. Developers, contractors and waste management firms that allow relatively granular excavation waste with high sand and gravel content to go directly to restoration sites without first extracting available resource are also not adhering to their duty of care:

Section 34 of the Environmental Protection Act 1990 (as amended) makes it the duty of everyone (with the exception of occupiers of domestic properties as respects the household waste produced at those properties) who produces, keeps or manages controlled waste, or as a broker or dealer has control of such waste, to:

  • “take all such measures available to that person as are reasonable in the circumstances to apply the waste hierarchy set out in Article 4(1) of the Waste Directive”.
  • “take all reasonable steps to ensure that the waste is managed in manner which promotes high-quality recycling”.

 

Site investigations

Developers already conduct site investigations for planning purposes, so they already hold information on subsoil/made ground composition and its suitability for recycling/washing before waste management decisions are made, but unfortunately, these reports are rarely used in an environmental/waste hierarchy context.

For the future, and as part of the IAF/Scottish Aggregates Levy proposals, there is an opportunity to drive more material up the waste hierarchy by mandating the use of site investigations in waste management plans and offsite treatment decisions (i.e. excavation waste of a certain sand and gravel content must be recycled first, in areas where such recycling facilities exist, while heavy clays and the residual silt/clay filter cake from washing non-haz excavation waste can go to backfilling restoration sites). Combined with the proposed new tiers of authorisation within the IAF, this would give SEPA greater clarity and enforcement control, improve waste data quality, generate true recycling rates thereby creating a more circular economy, and ultimately align the construction industry with legislation that has existed for nearly 35 years.

‘Dirty MRFs’ (Material Recycling Facilities), such as Viridor’s GRREC in Glasgow, extract resource such as metals, paper, plastics and glass from residual ‘black bin bag’ waste before incineration/recovery of the calorific value. If this is technologically possible and makes common sense for a mixed refuse waste stream then surely the same model should be applied to much less problematic excavation waste?

Increased recycling of this resource into recycled aggregates is low-hanging fruit and an easy win in the context of zero waste targets, natural resource preservation, and ultimately net zero aspirations.

 

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