Monday, 19 May 2014

Secondary aggregates

Cllr Claire Wright asked the following question at Devon County Council's Annual Meeting last week:
Does the Chairman of the Development Management Committee consider that sufficient use is made of secondary aggregates in Devon? Would he indicate what measures Devon County Council has been taking to maximise sustainable use of mineral resources?
This was Cllr Brook's written response:
Annual sales of secondary aggregates, derived from waste from china clay and other minerals, have been in the region of 400,000 tonnes over the past five years. Together with an estimated 1.2 million tonnes of recycled aggregates (from construction and demolition waste) each year, these materials have made a significant contribution to meeting Devon’s needs for construction aggregates. While a higher level of sales of secondary and recycled aggregates would be welcomed in reducing reliance on quarried aggregates (which amount to around 2.7 million tonnes), their use is dependent to a large extent on the procurement decisions made by developers together with fiscal measures such as the Aggregates Levy. 
In its role as mineral planning authority, Devon County Council’s emerging Minerals Plan will pursue a sustainable approach to aggregates supply that places emphasis on the need to reduce the use of aggregates, and then to use secondary and recycled materials in preference to quarried aggregates. The Plan will therefore view favourably proposals to increase the output of secondary and recycled aggregates. However, the need for aggregates to meet high-specification uses, together with the uneven distribution of secondary aggregate resources, mean that Devon will continue to require a supply of quarried aggregates as part of a sustainable solution.

In highway maintenance, emphasis is placed on long term durability, reducing the overall need for aggregates, while recycled materials and secondary aggregates are utilised whenever possible (although in the south west of England this is not always the most cost effective option with primary sources nearby). Examples of works that encourage recycling and secondary aggregates include specifying a minimum content of 10% recycled road planings in new asphalt materials and in-situ recycling of road materials for large schemes.
A report prepared for Imerys in 2005, Feasibility of China Clay secondary aggregate use, is one of the most thorough we have seen on the subject. Here are a few lines from it:
The objective of the study was to consider the feasibility of moving large quantities of secondary China Clay waste materials from their existing locations to new markets outside the current local market area.
The use of China Clay wastes from the existing tips offers the opportunity for significant improvement in both the existing landform and for creating or recreating biodiversity habitats.
With a kaolin mining history of around 250 years there is now a significant mining legacy of surface tips covering a large amount of the 26 square mile clay working area in Cornwall. There are similar surface tips associated with the clay working areas in South Devon and Dorset.
It is evident from the research that recycled and secondary aggregates are still not used to their full potential, often used for general fill when in fact many secondary aggregates, China Clay waste included, is capable of much higher value applications. As a consequence of this the potential market for secondary aggregates is currently not being realised and there exists further potential in the secondary aggregates market in terms of tonnage and performance.
It does seem perverse that more cannot be made of this waste material within the region that it already blights, either transporting by rail or ship to local wharves and quays.