Gaps in the market for gutter waste

Written by: Peter Hayes | Published:
Dewatered grit from a CDEnviro plant

Attitudes to resource management, and our abilities to recover and reuse material, have perhaps never been better, but there are still areas where we aren’t maximising our opportunities.

Growing awareness of environmental issues, along with legislative levers designed to move our society from a linear ‘extract, use and dispose’ culture to one that values resources and keeps them in use as long as possible through the ‘circular economy’, are having a dramatic impact on a number of industries, not least the waste management sector.

Less glamorous resources

Media headlines are often grabbed by changing attitudes to ‘big ticket’ items such as single-use plastics, but we are also beginning to see – and recover – the value in even unpromising materials, such as street sweepings.

However, a similar source material, gully waste, is still being largely overlooked here in the UK with a lack of processing facilities available to sort and recover the components trapped in gullies.

This is despite the Environment Agency, as far back as 2012, instructing all composters in England and Wales not to use street sweepings and gully waste residues to produce compost due to the contaminants that would be present with such treatment, which should have been a trigger for improved facilities.

Gully waste is collected from roads, car parks and airports and any areas where water won’t naturally drain away.

It’s fair to say that when faced with the collection of materials present in this waste – including glass, plastic and metal fragments, gravel, organic material, oil, heavy metals and other chemicals, along with sand, silt and stones – it can be hard to recognise the mess as a potential revenue source, but we need to ensure that view can be changed.

High water content needs to be removed before disposal, but that alone isn’t the best solution for gully waste. With disposal costs and resultant operating costs high, the incentives are clear for companies providing gully emptying services to ensure they maximise resource recovery and reduce the weight of any material.

There are obvious benefits to the environment too, both in terms of the reduction of material to be disposed of and the reuse of materials meaning less mining of virgin materials.

A weighty issue

The largest constituent of gully waste by some way is water; simply leaving the material to drain is time-consuming, ineffective and requires a sealed-drainage system.

The weight of the water contributes significantly to transport and disposal costs and to environmentally damaging emissions. The largely liquid nature of gully waste also means it is banned from landfill under the Landfill Directive 2002.

Even if operators took no other steps there would be a great benefit in investing in systems to ‘dewater’ the gully waste as close to source as possible.

However, an additional issue is that the potentially hazardous nature of gully waste often requires a number of transport, treatment and analysis operations that mean one solution won’t fit all.

Therefore it makes sense to go beyond dewatering and benefit from the collected resources. Specialist bespoke gully waste recycling systems separate, sort and dewater materials regardless of input quality or quantity. The best systems will also reduce contamination levels, allowing safe reuse. For example, we estimate that around 95% of a gully’s content is natural material that can be reclaimed for reuse.

This is often washed grit, clean sand or oversized stone for construction projects, organic material for composting, or energy from waste use.

New processing solutions include systems to screen and scrub material to ensure effective removal of contaminants, sand washing plant and water treatment systems.

Using a trommel at the start of the process can protect the system and removes oversized contaminants from the feed system. A decanter can also be used to maximise recycled water. With new advanced liquid/solid separation modules, and multi-stage chemical dosing systems, a very high quality of water is achieved.

Growing importance

As disposal costs will only continue to rise, recycling gully waste becomes even more relevant. Reducing the reliance on landfill as a disposal option not only reduces companies’ costs but also the environmental impacts.

In the past, all the material in gully waste would have eventually gone to landfill, incurring significant disposal costs, but top solutions can now successfully divert up to 99.7% of waste away from this destination.

Investing in the future

By investing in our recycling technology, operators are safeguarding their business for years to come.

One of our current customers, Irish Waste, for example, collects around 12,000 tonnes of street sweepings and gully waste material from around Northern Ireland every year which had been going to landfill. With the increasing cost of landfill, a solution was required that would significantly reduce the volume, and therefore cost, of disposal.

Thanks to the solution we developed for them – which encompasses a series of techniques including a two-stage density separation process, attrition and high-pressure wet processing – the vast majority of that waste material is now diverted from landfill.

Instead, thanks to the superior separation of lightweight and fine constituents, through a series of density separation techniques, the client achieves the highest quality end products.

For Irish Waste, these products are a 5-40mm aggregate, 0-4mm fine aggregate and an organic fraction which are being used in a variety of construction applications including trench fill, pipe bedding and non-structural concrete mixes.

Another customer, UBU Environmental, found that with ever increasing landfill costs and taxes, it was becoming unsustainable to keep taking this type of waste to landfill.

Instead, thanks to the solution we devised, it is now able to use the processed material for pipe bedding for utilities. The company has already used the products around its own site and the quantity of material being recovered means it plans to market the products externally as well.

They could even end up being used on the sites they were collected from in the first place; a truly circular approach to resource management!

Mind the gap

As well as the costs of landfill, gully waste can have other financial impacts. Keeping gullies clear is vital to ensure debris doesn’t build up, potentially damaging infrastructure, nearby buildings and passing vehicles.

Blocked gullies can also pose a flood risk, particularly after increasingly regular incidents of heavy rain or because people have poured inappropriate material, such as commercial waste – including sand and concrete – down them. Gully waste is also unsightly, negatively affecting the perception of an area.

However, with the solutions available to reduce landfill costs and provide an extra revenue source, gully waste does not have to be a burden any more.

Like other materials once considered solely as waste, the material in gullies needs to be recognised as a resource and increasingly collected, processed and diverted from landfill. Operators have the opportunity to close a gap in the waste management market while ensuring our gullies are kept open and free-flowing.

Peter Hayes works for waste design and manufacturer CD Enviro

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