Shell-covered breakwater, CO2-absorbing bricks among $22m PUB-funded projects to fight rising seas

SINGAPORE – Concrete waste is getting a new lease of life, as a local firm and Nanyang Technological University (NTU) are turning it into carbon dioxide-absorbing bricks for seawalls and other coastal protection measures.

A submerged breakwater covered with shells could also become a reality, with two institutes at the National University of Singapore (NUS) and a consultancy firm developing the structure, which could weaken waves and serve as a new habitat for marine life.

These are two of 14 projects involving companies and academics that have received a total of $22 million in a grant from national water agency PUB to develop innovative solutions for tackling rising seas and floods.

Announcing the grant recipients on Sept 17, Senior Parliamentary Secretary for Sustainability and the Environment Goh Hanyan said: “Our R&D investments will shape Singapore’s technical capabilities in coastal protection, developing home-grown expertise within our industry and research community.

“This enables us to develop more innovative and cost-effective solutions that address our distinct coastal challenges... Singapore’s urban space constraints and unique wave conditions mean we cannot simply adopt off-the-shelf solutions.”

She was speaking at the Coastal Protection and Flood Resilience Institute’s (CFI) symposium at NUS.

CFI and the new applied research projects are part of a growing pool of sea level-related research efforts under PUB’s $125 million Coastal Protection and Flood Management Research Programme.

The project involving concrete waste is led by low-carbon concrete leader Pan-United Corporation. The waste will be processed to become pebble-like aggregates, into which industrial carbon dioxide, or CO2, is injected and converted into a mineral.

The CO2 used is captured and liquified from that emitted by manufacturing, chemical and petroleum companies. One tonne of the aggregates could sequester up to 100kg of CO2.

The resulting novel concrete is 15 per cent lighter than the ordinary kind.

“This tackles two problems at once by upcycling waste and reducing carbon emissions,” said Pan-United Corporation.

“Due the lightweight property, the aggregates can be used to make lighter but strong concrete for coastal structures, like seawalls.”

The lighter concrete could also be a suitable material to top up existing coastal defences like shoreline slopes, raising the height without overloading the original structure.

Pan-United is currently working with NTU to develop prototypes of its novel concrete. The next step will be to embark on a field trial.

The 14 new projects were assessed based on how practical the solutions will be in Singapore’s context, and whether they have the potential to be monetised and installed along the coastlines in the near term, said PUB.

The projects cover five themes: using waste materials in coastal solutions; smart ways to monitor the health of coastal infrastructure; innovative engineering solutions; better ways to monitor the movement of sediments; and creating a framework to shape future solutions.

The project on the submerged breakwater is led by the Technology Centre for Offshore and Marine, Singapore (TCOMS) in NUS, which will work with Surbana Jurong and the NUS Tropical Marine Science Institute.

Instead of using boulders and concrete, the bund will be formed using soil and marine clay. The sea-facing side of the breakwater will be layered with discarded oyster or mussel shells.

“This shell-covered surface not only helps break waves but also creates a textured habitat where marine life can settle and thrive,” said Dr Lim Kian Yew, acting director of operations at TCOMS.

Over time, the calmer waters behind the bund may encourage sediment to build up naturally, gradually raising the seabed as sea levels rise, he added.

If the bund is submerged near a mangrove habitat, the complex roots of mangroves can capture more sediments and raise the forest floor, helping it keep up with sea-level rise. Mangrove habitats are living coastal defences that will flood more often without such support.

Ms Goh said: “Envision living shorelines that grow resilient with time, fortified by our native ecosystems and species.”

Dr Lim added that the underwater breakwaters will be suitable for coastlines with moderate waves, or near beaches where such hidden structures will not mar the landscape.

This three-year project will involve engineering the shell-covered bund, running simulations, testing the structure in the field, and studying if tiny marine animals make homes in the shells.

In her speech, Ms Goh highlighted the need for companies to trial new solutions in the field and establish a track record in the emerging coastal protection sector.

“This is particularly important as we seek to build a robust ecosystem of solutions providers who understand Singapore’s unique challenges and requirements,” she said.

In 2023, CFI was set up to bring together expertise from various universities to strengthen core research in areas such as coastal science, forecasting extreme weather and nature-based solutions.

There are 17 ongoing research projects, and the symposium gave updates on some of them.

A team led by Assistant Professor Pearl Li Yuzhu from the NUS Department of Civil and Environmental Engineering is building virtual models to help conservationists restore mangroves and seagrass meadows more optimally by understanding how sediments shape those habitats.

One model simulates how sediments move within complex root systems, using field data from Rhizophora mangroves in South-east Asia. Early findings show that sediments can both erode and settle within mangrove roots, with saplings more vulnerable to scour.

“Commonly, people think mangroves attract sediments, but they can also be eroded by them. If the roots are not deep enough, the trees need to be protected,” said Prof Li.

In another project, Professor Chu Jian from NTU’s School of Civil and Environmental Engineering is creating tube-like barriers made of natural materials such as plant fibres, sand and soya bean powder.

These barriers will shield the beach from strong waves. Over time, sand and soil can slowly accumulate and raise the shores, turning the beachfront into a natural “sea wall” of sorts.

Prof Chu is now working with Surbana Jurong and engineering firm HSL Constructor to test these barriers at Tanah Merah beach – a sandy shore prone to erosion and strong currents – and the muddy shores near Yishun dam.

The fieldwork is expected to begin in early 2026. Over the first two years, beams that are 100m-long and 50cm in height will line the coastlines of both sites.

Through the 17 projects, CFI has so far trained more than 90 researchers and students to grow Singapore’s pool of coastal protection and flood management specialists.

Source: The Straits Times © SPH Media Limited. Permission required for reproduction

Discover how to enjoy other premium articles here