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Getting to the Bottom: Coral, Steel, and Carbon

Counting Coral's first sculptural gene bank off of Nacula Island, Fiji grows climate-resilient coral on 137 marine grade stainless-steel substrates. The steel is polished, etched, and scuffed to allow seaweed, algae, and sponges to attach to its surface in order to provide the food source and shelter for growing coral and the coral ecosystem. But why steel? What is its environmental impact? And will they continue to be made from steel? Let's take a closer look at the impact and decision-making behind steel substrates for coral conservation. 1. Corals and Steel To successfully build up coral, the choice of substrate on which it grows is critical. Main Characteristics of a Successful Coral Growing Substrate:

  • Provides a rough surface for coral fragments to adhere

  • Large and secure enough and to provide stability: they must reduce movement in severe storms

  • Allows for coral to fuse to the substrate and grow like they would on a natural reef

  • Long-lasting: substrates cannot degrade too readily before corals can adhere

  • Provides a safe shelter and habitat for the fish and invertebrates that take part in forming a healthy coral reef ecosystem

  • Non-toxic

  • Structurally diverse to deliver the needs of the other organisms in the ecosystem

Steel substrates can meet all of these qualities to nurture successful coral reefs. The scuffed steel structures in Fiji have shown to have strong coral adhesion. The marine grade stainless steel is even more durable than mild steel with its higher nickel and chromium percentage to resist corrosion. The sculptures have a life expectancy of 200 years and is resistant against storms. The sculptures and mounting are stable in storms and because of its modularity, during severe storms, can be taken out of the water for its duration to avoid destruction and bleaching events. The steel sculptures do not release microplastics nor leech any toxicity into the corals or water. The material also offers the ability for different designs to create structurally diverse habitats for the growing coral reef ecosystem. So, while steel is a good choice looking at a coral growth point of view, is it the best choice on the environment at large?


2. Current Impact of Steel Production on the Environment


Currently, steel is largely made in coal-fired furnaces which contributes to its high carbon emissions, making it a high GWP (global warming potential) material. The carbon associated with the energy process it takes to produce steel is the main driver of its high emissions because high temperature furnaces are required to reduce the iron ore to a usable form and to heat up the metal to be malleable.


Because the issue lies with its process emissions, shifting away from coal as the energy source for steel production has great opportunity to make steel instead a low-carbon material. Emissions from steel must be reduced by 50% by 2050 and continue to fall to meet world climate goals (IEA), and fortunately, efforts in the industry are already underway.


3. Transitioning with Green Steel


By moving away from coal as the main energy source for the high-temperature furnaces, the "embodied carbon" of steel is drastically reduced. Hydrogen or electric powered furnaces have been growingly increasing in the industry with about 30% of steel makers transitioning instead to using "green hydrogen" technology.

Green hydrogen is hydrogen produced using electrolysis and water powered by renewable electricity (such as from solar, wind, biogas, hydro). Burning this hydrogen allows for the furnaces to reach the high-temperatures necessary for steel production with its only emittance: water.


The technology is tested and viable, with the only bottleneck now being its availability. It takes infrastructural changes to produce green hydrogen and with it being a relatively new approach, it requires high costs for manufacturers to transition their operations. However, as countries are transitioning to renewable energy generation and steel makers must reduce their emissions to meet policy, the transition is anticipatory of what is to come.


4. How We Wish To Improve Low embodied carbon steel is coming, although not yet the industry standard in many parts of the world. Counting Coral is constantly seeking to improve our methods and contribute to the greenest ways in which we can conserve our coral, our oceans, and fight climate change. We are looking at ways to improve the embodied carbon of our sculptures through:

  1. Sourcing upcycled steel: using materials of opportunity so no new materials are produced to make our sculptures.

  2. Sourcing highly recycled steel: recycled steel cut out a huge part of its embodied carbon, reducing emissions.

  3. Target our transition to green steel and partnering with green steel manufacturers to support the industry transition.

  4. Investigate a possible hybrid material approach to achieve the lowest possible embodied carbon in our work.

If you would like to take part in helping us make this transition, please reach out! We'd love to hear from you!


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