Carbon ‘seaquestration’: can kelp help combat climate change?

For many of us, the word ‘kelp’ conjures up dreamy images of fronded forests gently waving underwater. But don’t be distracted by its beauty – there’s much more to this wonderful ‘weed than that.

‘Kelp’ is actually the umbrella name we’ve given to a group of large, brown algae that grow in cold, coastal seawaters worldwide. Humans have used this nutritious seaweed for thousands of years – for everything from food and medicine to cosmetics. But more recently, as part of a growing interest in innovative, nature-based solutions, kelp is being considered for its fantastic potential in the fight against climate change.

So, can kelp really bolster our efforts to mitigate climate change?

Yes, we certainly think so (Carbon Kapture wouldn’t exist otherwise!). But don’t just take our word for it. Let’s wade into the science to understand exactly how kelp offers hope. According to current research, there are a variety of ways in which kelp (and other seaweeds) can be useful in the fight against climate change. These include, but aren’t limited to:

  1. Carbon sequestration: growing kelp to capture carbon, harvesting it and ensuring it doesn’t release its carbon back into the atmosphere.
  2. Reducing carbon emissions: by replacing carbon-intensive (possibly fossil-fuel based) products with lower emission seaweed-based products.
  3. Avoiding carbon emissions: by using kelp or seaweed products in production processes to reduce greenhouse gas emissions.

Here at Carbon Kapture, we’re focused on the first point: farming kelp to capture carbon. So, let’s dive a little deeper into that.

How exactly does growing kelp reduce atmospheric carbon dioxide?

The ocean absorbs vast amounts of carbon dioxide from our atmosphere. Kelp takes up some of this carbon dioxide from the seawater during photosynthesis and locks it within its own tissues.

Once our kelp is fully grown, we harvest it and carefully dry it out. When it’s only 20% wet, it’s ready to be converted into beautiful biochar.

What is kelp biochar and why do we char our kelp?

Dark biochar in a white bag.

Kelp biochar is made by heating it up (alongside other organic matter) without oxygen until it breaks down into a lightweight black residue. When the dried kelp is biocharred, about 70-75% of the carbon in the original material remains and will resist degradation for hundreds – or even thousands – of years.

We can then take that biochar and give it to farmers to put in their soil. This means the carbon is locked away on a long-term basis.

Ok, that sounds promising. But what is kelp's carbon-capture ability compared to terrestrial plants like trees?

Kelp grows very quickly – in fact, some species of kelp can grow as fast as half a metre per day and ultimately reach 30 to 80 metres in length! Amazingly, this means seaweed can sequester carbon up to 30 times faster than terrestrial forests. So, it makes for a very effective carbon sink.

Other problems that threaten the efficacy and success of land-based carbon capture projects (like tree planting) include threats like increased wildfires and issues like thirst maintenance. Happily, kelp aquaculture doesn’t share these same concerns. Seaweed doesn’t require protection from fire, grazers like deer, trampling cattle and bark-stripping squirrels. It also doesn’t need regular applications of fresh water or synthetic fertilisers.

Does farming kelp for carbon capture offer any other benefits?

As well as hoovering up carbon, cultivating kelp also offers several other bonus benefits:

  1. De-acidification of the ocean: When the pH of seawater drops due to the ocean absorbing too much CO₂, we call this ‘ocean acidification’. Its impact on marine life can be devastating, as acidic seawater dissolves the calcium-based shells and skeletons of creatures like shellfish. Kelp can help counteract this locally – by consuming CO₂ in the water and producing oxygen in its place, preventing further acidification.
  2. Increased agricultural yields for farmers: adding biochar to agricultural soil can improve soil water retention, nutrient retention and uptake, boost microbial life and, consequently, improve crop yields.
  3. Ecological benefits: Kelp forests are vital marine habitats, providing a shelter and food source for a wide range of marine creatures, including fish, invertebrates, and marine mammals. Kelp also acts like a beautiful filtration device – ‘cleaning’ the water around it by absorbing unwanted toxins.
  4. Jobs for rural communities: Kelp farming has the potential to generate employment, particularly within rural coastal communities, which are typically the locations most affected by climate change. By investing in this sector, we hope to foster sustainable livelihoods and support the economies and communities local to our kelp farms.
Fronds of kelp waving underwater.

So, is kelp farming the future?

We’d like to think so. Of course, when it comes to a problem as huge as climate change, there is no silver bullet. We know, first and foremost, that we must dramatically and rapidly cut emissions. Nature-based solutions (such as kelp-based carbon capture) can’t replace emission reductions – but they are a very useful tool to have in our climate action toolkit.

Going forward, there are some challenges to overcome. Questions still remain around the costs, labour intensity and scalability of these kinds of projects. That’s why we’re working with our Scientific Advisory Board to overcome these challenges, test the science and results, and bolster the positive impact of kelp-based carbon capture for everyone.

If you’d like to learn more about Carbon Kapture’s endeavours and how you can get involved with our work, please reach out to our team. Or, if you’re inspired to directly contribute to our mission, consider sponsoring a rope of kelp (or two). Help us grow a better future!

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