In 1994, targets to increase the use of secondary materials as aggregates in England from 32 million tonnes in 1992 to 40 million in 2001 and 55 million by 2006 were set in a planning guidance note on aggregates provision, MPG6 (ENDS Report 231, pp 40-41 ). The Department of the Environment, Transport and the Regions (DETR) intends to consult on a review of MPG6 later this year.
Planning Minister Richard Caborn told a conference in May that more could be done to increase the use of recycled aggregates. "I do not think we are yet at, or even near, the limits of the tonnages we can recycle," he said.
Recent research suggests there has been an upward trend in the amount of construction and demolition (C&D) waste used as aggregate, with current levels estimated at 25 million tonnes in England - double the 1990 estimate. When secondary materials such as fuel ash, furnace ash and other mineral wastes are added, the DETR believes the MPG6 target for 2001 may already have been exceeded. Reclaimed material now accounts for 20-25% all aggregate used in England.
The exact position is uncertain because current aggregates data are heavily biased in favour of primary material. In April, the DETR issued a report examining ways of collecting data on arisings and destinations of mineral and construction wastes which could be used as aggregates.1 One recommendation is for legislative change to enable the Environment Agency to monitor waste inputs to sites exempt from the waste licensing regime. Some have been attracting growing quantities of C&D waste since the landfill tax was introduced.
In May, the DETR held a conference to promote the Aggregates Advisory Service (AAS), a Government-sponsored service set up in 1996 and run by consultants Symonds Travers Morgan. The scheme is due to end this year, and the DETR is seeking industry views on whether it should continue and, if so, whether it should be operated and funded publicly or privately.
At the meeting, a number of potential barriers to recycled aggregates were identified:
Risk of poor performance or pollution: Anecdotal evidence suggests that potential users perceive an extra risk in using recycled aggregates. But AAS Project Director Richard Smith contends that this "is not really the issue it is made out to be." Construction insurers and insurance brokers often initially believe it to be a problem, but no client has actually raised the use of reclaimed materials as a problem with the AAS.
Despite the lack of evidence to suggest that the performance of reclaimed materials may be inadequate, designers may have a greater exposure to legal action, Mr Smith suggested. This is because the lack of information about practical experience with secondary materials could make it difficult for a designer to demonstrate that he had exercised skill and judgement appropriate to the "state of the art" - as a defence against a liability claim would require.
"Scheme promoters, and their financiers and insurers, might well be prepared to consider the use of secondary and recycled aggregate materials, but very few designers and specifiers are proposing this," Mr Smith told delegates.
Clauses in collateral warranties and other forms of contract barring the use of "deleterious materials" or requiring "new" and "best" products effectively preclude the use of reclaimed materials, he added.
The British Standards Institution is waiting for its European counterpart, CEN, to complete a standard on aggregates. Work on this began ten years ago but the standard is unlikely to be agreed before 2003, and may not even take account of recycled aggregates.
Despite these barriers, quarrying firms are looking to increase sales of recycled products. "While the need for primary aggregate in high-specification applications will be ongoing," said ARC Southern's Project Manager Steve Cole, "it is inevitable that recycled products will continue to take an increasing share of the overall construction aggregate market at the expense of primary products." Reflecting this trend, ARC's parent company, Hanson, recently acquired a Kent-based producer of recycled aggregates, Pinden Plant and Processing.
Tarmac Quarry Products, which set up its first recycling operations three years ago, recently signed a deal to take up to 250,000 tonnes of construction waste per year from Liverpool City Council, in an agreement the authority believes to be the first of its kind. According to the council's General Manager of Engineering Services, Eric Simm, the projected net savings to Liverpool "are significant and accrue from reduced waste disposal costs and reduced procurement costs for aggregates."
Under the agreement, Liverpool is providing a site and building for crushing and regrading operations. A new highways maintenance depot on the same site is being built with private finance. Construction of the facility should begin in July, with the recycling operation starting up in the autumn.
Tarmac is providing mechanical equipment, expertise and marketing of the recycled aggregates. The site will be open to third parties and Tarmac already has outline agreements with other councils to process their inert wastes.
The company is also negotiating with several large foundries for supplies of green foundry sand to use in asphalt manufacture. Tarmac already uses around 10,000 tonnes per year of greensand from Precision Disc Castings in Poole.
On the C&D waste recycling front, however, the UK's record remains poorer than in some neighbouring countries. In the Netherlands the utilisation rate is 91%, with 11.8 million tonnes of C&D waste recycled in 1996 to produce a 13% saving in consumption of primary construction materials. Up to 21% of total demand could be met if all available secondary raw materials were reclaimed.
Since 1996, Dutch demolition contractors have been required to recover all C&D waste and to segregate materials such as concrete rubble, masonry and wood. A voluntary agreement has been set up between the demolition contractors association, a glass recycling firm and an umbrella body for the aluminium building products sector to separate and collect those materials.
Almost all of the "stony" fraction of the C&D waste is used in road building. But a large house-building project is under way in Delft in which prefabricated concrete blocks containing 100% recycled aggregate are being used.
In Denmark, three million tonnes of C&D waste was recycled in 1996, giving a recycling rate of 89%.