Adding road waste to hydraulically bound mixtures and using it to fix roads could help Scotland meet its zero waste regulations. Allan Sandilands construction key account manager, Resource Efficient Scotland, reports
Digging up roads to install, maintain and fix water, gas, electricity and telecoms services creates around 680,000 tonnes of excavated material per year in Scotland. And the nature of utility trench arisings makes it ideal for almost full ‘closed loop’ recovery, by using the excavated material to reinstate trenches.
Yet currently Scotland only diverts 72% of this waste from landfill. In England, where the practice of stabilising excavated materials with hydraulic binders to create hydraulically bound mixtures (HBMs) is widespread, a massive 95% is diverted from landfill. The Scottish Government’s vision for zero waste means harnessing the value of all materials, helping to boost our economy, mitigating against rising landfill costs, and reducing reliance on finite resources.
Exploiting the use of HBMs and other alternative reinstatement materials (ARMs) could help the utilities industry move towards zero waste.
HBMs are versatile products which can offer benefits in the efficient use of materials; including the potential to increase the value of the material being recycled (up-cycling), and the ability to consume a wider range of feedstocks, including soils, aggregates and other industry by-products such as pulverised fly ash.
The main barrier to using HBMs in trench reinstatement in Scotland was found to be a lack of technical knowledge in the application of the materials and in the specification of when best to use them, resulting in a perceived lack of confidence. For this reason, Zero Waste Scotland carried out a project to raise awareness and build confidence through five practical placement demonstrations in Glasgow, East Dunbartonshire and Edinburgh, working with road authorities and utility companies and contractors.
Carrying out the demonstrations allowed local authorities and utility companies to see first-hand the practical advantages of using HBMs and to address perceived barriers and concerns.
The demonstrations consisted of two elements: a production demonstration by Doocey North East’s recycling facility at Rutherglen, Glasgow which featured the production and testing process, and five site-placement demonstrations which looked at the application of the material on roads of differing class. The details of the five demonstrations can be seen in the table.
Ensuring a high level of performance is obviously a key priority for the industry, not least because the quality of roads and pavements is now becoming a political hot potato. It is worth noting that Edinburgh City Council recently increased its inspection regime by 30% in response to public frustrations over poor quality road repairs.
The demonstrations showed in all cases that the HBM reinstatements were a quality controlled product which met all required standards. The material can be overlaid immediately and supports the pavement without creating hard spots. What’s more, no additional operational skills or techniques are required to switch to using HBMs, making this a relatively easy transition to make.
Environmental factors are also a concern for the industry, with tough requirements being increasingly set by contracting authorities, as well as by companies striving to meet their own internal targets. Critically, trench reinstatements can have a much lower carbon impact when an HBM is used instead of an asphalt base layer. In one of the site demonstrations a 15% reduction in carbon footprint was achieved.
Current practice involves transporting reinstatement waste between site and a waste facility. However, with HBMs the waste material can be offloaded and reinstatement material collected from the production plant, reducing empty vehicle movements so associated carbon emissions can be minimised further.
Kevin Skinner, Scottish Water’s New Roads and Street Works Act (NRSWA) technical leader, who partnered with Zero Waste Scotland on this project says: “I got involved in this study simply because it was the right thing to do for both the Scottish Water customer and the environment.
“Making the utility industry’s road footprint more sustainable by reusing our trench arisings is, by far, more responsible than continuing with our finite natural resources and disposal methods at present.
“Since the first usage, we have found that, by using the stabilised materials, there have been no reinstatement failures so far, Scottish Water’s landfill usage has dramatically been reduced and there has been an economic benefit also. It is not often that anyone can get involved in a project that ticks so many boxes and is for the greater good of everyone.”
Following the demonstrations, partners showed an increased awareness of HBMs, their application and quality control requirements. As this was identified as one of the greatest barriers to uptake of trench reinstatement, it is hoped that this increased confidence will lead to more partners moving to the use of HBMs and more companies setting up to supply the material.
Within the context of Scotland’s zero waste ambitions, it’s obvious that this is a significant waste stream which needs to be addressed. With multiple benefits including better road conditions, improved operational efficiency and environmental performance, there really is no reason why using HBMs to minimise waste should not become the norm in Scotland.
Zero Waste Scotland targets
- Divert 370,000 tonnes of waste from landfill every year
- Cut 1.1m tonnes of carbon emissions
- Save the Scottish economy £370m a year
- Avoid the use of 710,000 tonnes of primary resource
- Prevent 570,000 tonnes of waste
Zero Waste Scotland regulations
The Scottish Parliament passed the Waste (Scotland) Regulations in May last year and it will play a key role in Scotland achieving its target of recycling 70% of all waste by 2025. Research has shown that if this target is met it would benefit the Scottish economy by £175m. The regulations aim to help Scottish organisations and residents to see waste as a resource, avoid landfill tax as well as boost the economy by creating green jobs.
Household recycling rates have grown to over 40% yet household waste represents just over 16% of all waste produced in Scotland. The regulations do contain some requirements for local authorities but have a focus on businesses - and next January is a key date.
Local authorities will have to provide basic recycling services for all households by next January and a ban on landfilling materials collected for recycling also comes into force. A ban on municipal biodegradable waste going to landfill takes effect from 2021. By 2016 local authorities will have to offer a food waste recycling service in non-rural areas.
The regulations require that all businesses and organisations put out key materials (paper and card, glass, metals, and plastics) for recycling from January next year. Businesses in food retail, production or preparation, producing more than 50kg of food waste per week will have to have a separate food waste collection also from next January. Those businesses producing over 5kg of food waste per week will need to put it out as a separate collection from January 2016. On this date a ban on the use of macerators to discharge food waste into the public sewer will also come into effect.