Urban mining for sand and gravel

'During a UNEP study of coastal erosion in Jamaica we heard in a village how their traditional beach was destroyed in a matter of days when an armed group arrived, mined the sand and carted it off in lorries,' says Professor Pascal Peduzzi. 'I wondered if this was a more widespread phenomenon. When this was confirmed in a French news story in 2013, I decided it was time to look into it properly.' Peduzzi is director of GRID-Geneva, one of the group of environmental information centres, the Global Resource Information Database, run by UN Environment (UNEP). He is also the lead author of a provocative article published in 2014 in which UNEP warns about a growing worldwide scarcity of sand and gravel as building materials and the widespread use of unsustainable mining practices.

 

Pascal Peduzzi (GRID-Geneva):

"A whole new approach is needed, a shift from a linear to a circular materials chain."

 

The 40 billion tonnes of sand and gravel aggregates extracted worldwide, or 68-85% of the total, make them by far the most important minerals. Traditionally these aggregates have been extracted in and around rivers, but the growing shortages in these locations have led to increasing extraction from the seabed. The rate of extraction now far exceeds the rate at which these resources are being replenished by natural processes of erosion. Although empirical impact studies are few and far between, the UNEP discovered that extraction causes major local ecological, geological and hydrological damage. The resulting biodiversity loss in turn impacts on fisheries and food chains. Damage to river basins, coasts and water tables endangers drinking water supplies and environmental safety, and the carbon footprint of transporting these aggregates over increasingly long distances is considerable. One of the possible ways to reverse the growing impacts of aggregates extraction is urban mining: recovering and reusing building materials.

Growing awareness

In 2014 the UNEP complained that policymakers and scien-tists had largely failed to recognise the problem. What is the situation today? 'Both worse and better,' concludes Peduzzi. 'There are still no records on how much is being extracted, but from global production figures for cement and asbestos we can be fairly certain that since 2014 extraction has increased by 5%. Luckily the media and politicians have woken up to the problem. I have already given dozens of interviews. The US media are highly interested and the European Parliament is also aware of the issue. Hopefully this will stimulate researchers to throw more light on the situation.'

 

This is already starting to happen, observes Peduzzi. 'A recent study in Cambodia describes the consequences for certain fisheries, and we ourselves are working on this topic with organisations like Wetlands International and research institutes such as Utrecht University. In a few months' time, UNEP will publish a full report on global aggregates extraction.'

What options does Peduzzi see to resolve this problem? 'First, the relevant governments must set up a good monitoring system to keep track of extraction volumes and impacts on ecosystems. Statistical data like these are needed to inform national and international measures. Second, policies must be adopted that effectively reduce the rate of extraction. Apart from a few EU countries, such policies exist almost nowhere. Exceptions are Spain, which has in principle banned extraction in coastal waters, and the United Kingdom, which is the only country that levies a tax on the extraction itself rather than the end products. International environmental conventions either only touch briefly on aggregates ex-traction (OSPAR) or ignore it entirely (Barcelona Convention).'

 

Peduzzi: 'More generally, though, a whole new approach is needed: a shift from a linear to a circular materials chain. Alternatives have to be found, both by limiting the use of raw materials, for example through new construction methods such as adaptable building, and through urban mining, as in the Netherlands where part of the construction and demolition waste stream, as well as bottom ash from waste-to-energy plants and certain fly ashes, are recycled into reusable secondary building materials.'

The Netherlands has built up valuable know-how in other areas as well, according to Peduzzi, 'such as more sustainable methods for the extraction of sand and gravel, and for "building with nature" for coastal protection. For many developing countries such alternatives to hard, hi-tech defences can be excellent 'no regret' options that are cheaper, less resource intensive and have ecological added value.'