Can marine minerals boost supply of UK aggregates?

Every year, Britain uses around 250m tonnes of construction aggregates. That's roughly four tonnes per person – enough to fill a small truck for each person in the UK. Together, these materials support a construction industry worth nearly £180bn.

About 20% of England and Wales's sand and gravel requirements don't come from quarries on land, but from the seabed. Marine sources represent about 25% of Britain's sand and gravel production and 10% of demand in England and Wales for primary construction aggregates.

Marine aggregates are dredged from the seabed. The extraction process involves the dredger moving slowly, at about 1.5 knots, over identified geological deposits, while dragging a suction pipe along the seabed, removing the sand and gravel in thin layers.

Using purpose-built ships, companies extract these materials from licensed areas around the coast of England and Wales, bringing them into ports to be used in construction. Dredging is carefully managed by conditions on marine licences to minimise ecological impacts, such as avoiding harm to benthic organisms or during fish spawning and bird breeding seasons.

In 2023 alone, 14m tonnes of marine aggregates were landed in England and Wales, supplying more than half of London's demand for primary aggregates and 90% of South Wales's need for construction sand.

Without marine minerals, the UK's busiest cities and infrastructure projects would grind to a halt.

Think back to the London 2012 Olympics. Without marine minerals, we could not have built the stadiums, the velodrome, the aquatics centre, and the athletes' village in just four years. Half the aggregates used in London during that time came from the sea, as they do now.

Other iconic projects being built using marine minerals at the same time included:

• Crossrail – Europe's largest construction project at the time (now the Elizabeth line)
• The Shard – the UK's tallest skyscraper.

More recently, Thames Tideway, the super sewer beneath the Thames, and HS2 have both been built using marine minerals.

The Principality Stadium in Cardiff, Southampton's St Mary's Stadium, the AMEX Community Stadium in Brighton, along with countless other housing projects and infrastructure schemes, were all built using marine minerals.

Even flood defences and beach replenishment projects rely on marine resources to protect coastal communities from rising seas and storm surges. More than 30m tonnes of marine aggregates have been used for this purpose since the mid-1990s.

As demands increase for more housing, greater energy resilience, improvements to health, the expansion of waste water treatment systems, and tackling climate change, how will the UK source its construction materials to underpin this order book?

At the same time, the Marine Management Organisation (MMO) oversees the regulatory licensing process in English waters under the Marine and Coastal Access Act 2009, Natural Resources Wales is responsible in Wales and the Marine Directorate in Scotland.

As with planning permissions for land-based mineral extraction, MMO dredging licences are temporary, typically lasting 15 years. Where commercially viable resources remain, areas may be relicensed to extend their working life, with some licence areas having been dredged for more than 40 years.

Locations close to Special Protection Areas and Special Areas of Conservation under the EU Habitats Directive require further Habitats Regulation Assessments as part of the overall licensing process.

Where marine aggregates are landed, there's also the issue of housing developments springing up near wharves and railheads, creating conflicts over neighbouring land uses and logistics. As soon as a housing scheme is built close to a wharf, port or harbour, that location's sustainability can be compromised.

Current planning policy around the safeguarding of such wharves, which is intended to protect this important infrastructure, needs to be more rigorously applied when considering future housing needs.

But are there alternatives? The dredging of marine minerals replaces the need for an additional 50 land-based quarries or so in Britain. They contribute to demand for construction aggregates that come from a range of other sources, typically crushed rock quarries, sand and gravel quarries, recycled construction and demolition waste and secondary aggregates.

No one source can fulfil the nation's demand. Ensuring this demand can be met is a careful balance of recognising each source, understanding regional needs and constraints, and ensuring there are sufficient resources.

However, marine aggregate resources are perfectly placed to:

• help fill some of the gap left by declining land-based quarries. Marine minerals are already replacing land-won quarries in the south east of England as land-based sources become depleted. Economies of scale provide the ability for marine sources to supply large volumes into coastal urban areas, often close to the point of demand
• support government priorities such as housebuilding and infrastructure. Where such locations are coastal or within reach of a marine wharf or port, marine minerals can often help support this growth. Many wharves are also rail-linked, further increasing the ability of marine to fulfil demand, while also reducing lorry miles
• protect coastlines with stronger flood defences. Self-discharging vessels can supply direct to a coastal defence scheme without the need for secondary logistics via a wharf or port
• enable renewable energy expansion, providing material for ports and offshore wind turbine foundations
• boost exports to Europe, where rivers are running short of suitable sand and gravel.