The development of new treatment systems for waste from road sweepings and utility waste has grown quickly. Peter Craven of CDEnviro – a company involved in this sector – explains the potential they offer and how government agencies can support their development. CIWM Journal Online Exclusive
With increasing pressure on landfill space across Europe, the introduction of the Waste Framework Directive and the Landfill Directive has attempted to deal with the issue of waste reduction and encourage a greater awareness of the potential that exists for the recovery of materials previously sent to landfill.
What has emerged as this discussion has developed is that rather than activity in this area simply being a requirement of new EU legislation it actually offers everyone in the industry an opportunity to make their businesses much more efficient through the elimination of unnecessary waste disposal costs.
Across a wide range of materials from sewer grit to road sweepings and gulley waste there is a realisation that this material has the potential to be a valuable resource if the appropriate processing technologies are employed in its treatment.
CDEnviro has installed several recycling systems for sewer grit at various sewerage treatment works throughout the UK. These plants are processing sewer grit from the inlet works and in some instances are also acting as a central recycling facility for imported wet waste captured at other smaller treatment plants. As sewer grit is more than 90% mineral material there is significant potential for this material to be cleaned and dewatered and made suitable for further use. The treatment process involves a variety of processing phases including attrition, high frequency screening, efficient fines removal, dewatering and stockpiling.
While the initial purchase decision is made on the basis of a diversion of waste from landfill the ability of the system to produce a clean, dry grit and recycled aggregate product has been recognised by the major water utility companies. In response to this they have carried out considerable market research with local construction contractors in an effort to establish whether there is a commercial application for this material. The response to these approaches has been extremely positive with the general feeling being that contractors would be more than happy to use this material if all the required certifications were in place.
A similar situation applies in relation to road sweepings and gulley waste. Research has shown that this is a valuable resource with the potential to recover the 90% mineral material which makes up this waste stream. Typically 50% of this waste is sand, grit and small stones with another 40% being a larger mineral fraction with potential for use as a recycled aggregate.
Volumes Generated In The UK
Figures are hard to come by which give an accurate picture of the volumes of this waste currently generated in the UK but as a general rule of thumb each local authority in the UK sweeps roughly 20,000 to 25,000 tonnes of waste from the highways every year with a further 4,000 tonnes coming from road gulleys. With 27 County Councils in the UK with responsibility for waste disposal we can therefore estimate that between 648,000 tonnes and 783,000 tonnes of this material could be treated every year. With efficient recovery of the 90% mineral fraction this would mean somewhere between 583,000 and 705,000 tonnes of recycled grit and aggregates every year in the UK alone.
At present approximately 2 million tonnes of road grit is spread on the roads every winter in the UK so even at a conservative estimate we are in a position to reduce the pressure on the virgin materials currently used for this by 25%.
The opportunity that exists in the UK for the recycling of road sweepings and gulley waste is replicable across Europe so if we consider the potential across the EU member states we can immediately see the potential to reintroduce several million tonnes of recycled road sweepings and gulley waste into local construction applications if all the required certifications are in place.
It is here that the system appears to break down. At present the Environment Agency in the UK has issued a ‘Guidance on low risk waste activities’ which deals with both sewer grit and road sweepings. Currently this guidance allows for these recycled materials only to be used in a very limited field of application and this restriction is stifling the development of this industry.
In the absence of the certification allowing for the more widespread use of these recycled materials the full potential of these new processing technologies to reduce the volumes of this material going to landfill will not be realised.
Both equipment manufacturers and the industry as a whole have demonstrated a commitment to tackling waste reduction and maximising the value of the recycled products. Unfortunately, the Environment Agency has not demonstrated the sense of urgency that is required if we are to fully exploit the opportunity that is presented by sewer grit, road sweepings and gulley waste.
