Wednesday, 23 January 2013

Secondary vs. Primary

The left pile: secondary aggregate - a by-product from china clay (kaolin) operations dumped for over 250 years as waste in huge amounts across Cornwall and Devon; the right pile: primary aggregate - a finite virgin resource sitting under Straitgate Farm. Two different materials we are told; different properties - physically, chemically, economically.

Whilst DCC in its Local Aggregate Assessment said "Devon has the capacity to support increased production of secondary... aggregates", it also said that "limited spatial occurrence" and "technical requirements" may constrain their use.

In evidence to the Competition Commission, however, Aggregate Industries said that whilst "in Cornwall and Devon alone there was about 600 million tonnes of secondary aggregates already available with about 40 million tonnes more being generated a year", its customers were "increasingly able, willing and prepared to use secondary and recycled aggregates". AI added "secondary and recycled aggregates now accounted for between 25 and 30 per cent of the current market and were a substitute for primary aggregates in the vast majority of cases. AI used secondary aggregates in its own production of [ready mix concrete] and other products."

The aggregates levy, currently £2 per tonne, was introduced by the government in 2002 not only to "address the environmental costs associated with quarrying" but also to support "the use of alternative materials such as recycled materials and certain waste products". Encouraging local use of secondary aggregate would have the advantage of extending reserves of sand and gravel whilst also reducing the 'mountains' of tipped waste across Cornwall and Devon. Is Devon's Mineral Planning Authority doing enough to achieve this?

Admittedly, not all china clay waste is suitable - nine tonnes of waste are generated for every tonne of china clay produced - but for the right quality of granite fraction (stent) there has been a "long history of satisfactory use in ready mixed concrete over much of Cornwall and Devon". In addition "An assessment of the specifications and standards available demonstrates that there are a significant number of applications available for the use of China Clay waste derived aggregates. While many secondary materials are used in low value applications such as fill, China Clay waste derived aggregates are suitable for a number of higher value applications including use in concrete and bitumen bound products."

Furthermore, it's now finding applications elsewhere. In 2006 the construction of One Coleman Street, a prestigious commercial building in London, was "the first major use of china clay stent coarse aggregate outside the locality of its production in the South-West" and "demonstrated the feasibility of using 100% secondary coarse aggregates in a large scale project remote from the source of aggregate". The stent aggregate concrete "cost a little more" due to the "transportation and testing costs" but this was partially offset by the stent being "exempt from the UK aggregates levy" and "if used more often for future projects there would be less need for extensive testing". The project won the 2007 Concrete Centre Award for Sustainability. AI will know about it since it supplied the aggregate. It will also know about the construction of the Olympic Park, where it supplied "secondary aggregates arising from the production of China Clay".

So, if the economics can work supplying London, why not Devon?

With existing supply agreements coming to an end, "IMERYS Minerals Ltd are actively developing the growth of their secondary aggregates (china clay waste) products from Cornwall and are currently seeking partners to realise the full potential of the materials in the markets they serve". With its new Minerals Plan, maybe DCC should work with Cornwall to facilitate and encourage this. And how about Devon's own levy too, on primary aggregate extracted from the Budleigh Salterton Pebble Beds?!