Member Spotlight: Blue Carbon Services

Blue Carbon Services uses seaweed to draw down excessive atmospheric carbon dioxide. As the kelp sheds its organic matter, it drifts into the nearby deep ocean locking the carbon away for 100s to 1000s of years. 

We talk with Blue Carbon’s Team, Robert and Sandy Hickson, who explain how their not-for-profit will achieve the ambitious goal of developing an offshore deep-water kelp farm. As kelp progressively becomes a bigger player in carbon sequestration, we are excited to have welcomed Blue Carbon into our inaugural cohort!

This discussion sheds more light on the team’s motivation and purpose behind their innovative design and some recent research discoveries.  

1.Where did your interest in kelp carbon sequestration come from (especially since this is a relatively novel concept)?

So originally, we both read ‘Seaweed and Sunlight’ by the Climate Scientist, Tim Flannery and there was one paragraph that caught our attention the most - that if we covered 9% of the oceans in kelp then we would sequester enough carbon to offset the world’s emissions, produce enough biofuels to fuel the world’s energy needs and produce enough protein to feed the world!

Now, we certainly don’t plan on covering 9% of the world’s oceans with seaweed but it shows the potential and power of these aquaculture systems. And with more recent developments, the number is probably down to more like 4-5% of the world’s oceans so they are incredibly efficient systems and don’t use up prime productive land. 

The seaweed species that we’re interested in is a bit of a freak of nature and is the fastest-growing organism on earth - Giant Kelp (Macrocystis pyrifera). The speed that it grows determines how much dead kelp (organic matter) it releases into the ocean, and ultimately how much carbon dioxide is absorbed from the atmosphere.

2.How do your plans for an offshore deep-water kelp farm differ from ones closer to shore?

The main aim of kelp aquaculture is to get biomass into the deep ocean where that carbon can be sequestered for 100s - 1000s of years. When you have an inshore kelp farm, it’s less likely that the biomass shed by the kelp will get into the deep ocean. Whereas when you have a kelp farm located over a deep-water trench, you can get up to 30% of the biomass falling into these deep-water trenches and then carbon sequestered for 100s - 1000s of years. 

Essentially, the longer it takes for the dead organic kelp (biomass) to get from that active zone of the ocean (the surface layer) into the deep water, the more likely it is that it will be degraded back into carbon dioxide which will ultimately end up back in the atmosphere.

Logistically, the open ocean is a great place to have these large, highly productive aquaculture farms. Currently, there are vast amounts of the underutilised ocean, so we wouldn’t be in competition with other users. This also allows us to place the farms in locations ideal for carbon sequestration, such as a relatively shallow area (~200 metres deep) at the edge of a deep-ocean trench (which can be kilometres deep). In the best locations, currents take all that dead organic matter away from the kelp farm towards that deeper water, which will allow us to achieve very high rates of sequestration. 

3. Why do you hope to offer co-culturing mussels with kelp as an added element of the kelp lines?

Ultimately, we need some means to make kelp carbon capture financially viable, because kelp carbon sequestration is not yet recognised by the New Zealand Emission Trading Scheme (ETS). Growing kelp along mussels is not only an efficient green way of producing protein, but it's also a commercially viable way to capture large amounts of carbon. The synergy that this multi trophic aquaculture provides will essentially allow the mussels to grow quicker and support kelp to grow quicker, producing protein in a very efficient way.

There is quite a lot of symbiosis between mussels and kelp. If we can grow them together, we will be able to grow high-quality mussels, which will provide a steady income stream, and faster-growing kelp, which will capture more carbon. We can also harvest and sell some of the kelp. Giant Kelp grows so rapidly that in a year it will turn over its biomass about 10 or 12 times so harvesting the top metre or two occasionally for some revenue would only be capturing a very small percentage of the total primary production of that kelp. Therefore, harvesting some of the kelp is not greatly in conflict with carbon sequestration.  

The reality is that these systems need to be financially viable! For these concepts to be replicated and picked up around the world, it’s going to be important that the model generates revenue. We know mussel farms have a much higher cost of establishment and are commercially viable. There are also large-scale open ocean kelp farms being developed and making revenue, so co-culturing makes sense to us and fits well with our research. 

4. What data are you currently collecting and what have been some key discoveries to date?

At the moment, we are managing two research projects. First, we’re starting to get quite a bit of data on kelp and mussel co-culturing and the synergies when they grow together. The second is looking at kelp carbon sequestration and modelling how much carbon will be sequestered if we have a kelp farm in a certain location. 

For kelp mussel co-culture, a recent finding is that mussels can get up to 90% of their required diet just from kelp, so they can primarily consume kelp which is a promising finding. Another interesting thing is we found mussels don’t like fresh kelp, they actually like aged kelp and that’s because, in older kelp, the phlorotannins have broken down and are easier for mussels to digest. This finding will help inform harvesting cycles and the farm aquaculture design going forward. Different species of kelp also all have different levels of phlorotannins, affecting their palatability to fish, mussels and other bivalves that consume the kelp dead organic matter.

But then looking at it from a carbon sequestration perspective, high levels of phlorotannins found in fresh kelp are advantageous as the organic matter shed from kelp is less likely to be grazed or broken down and therefore more likely to reach deeper water. So, while high tannin levels make it less attractive for mussels growing right next to it, it makes it attractive from a carbon sequestration perspective and vice versa. 

The other thing that we have been finding over the past 3 years is that each summer we have been experiencing marine heatwaves. The North Island water temperature has been getting as high as 28-30 degrees which are normally unheard of. We have found that it is adversely affecting the growth of our transplant sporophytes. In one of the experiments, we attached Ecklonia sporophytes to vertical ropes and found that none of the sporophytes in the top 2-3 metres survived, but in the colder deeper water they were surviving well. In some ways, this feeds into our current interest where we’re looking at being able to control the depth at which we grow kelp.

5.What are you working on at the moment and what are the next steps you will take to ensure a successful pilot for your offshore aquaculture farm?

Right now, there are two main projects.

The first is our portable hatchery. The idea is that we will have an insulated trailer that we can drive around the countryside to collect kelp samples from a site, add the spore onto rope and use those ropes to seed kelp onto mussel lines in that area. And that’s good as then we can use the genetic diversity of a given region and the genomic material that has evolved in that region in each area, avoiding issues of genetic contamination. We’re currently in the process of developing this mobile hatchery and then you’ll see us driving around the countryside with our portable hatchery, seeding kelp everywhere we go!

We are also in conversations with a variety of traditional land owners, who are eager to work together to re-establish native seaweeds in Wellington harbour, particularly Giant Kelp. We will work with the National Institute of Water and Atmosphere (NIWA) who will provide technical support. We have agreed to collaborate all together and we’ll provide the mobile hatchery. This project is quite exciting as kelp is an essential part of the ecosystem around Wellington harbour. 

The second project is a new project and we’re just writing up the grant application to design a system to actually lower the kelp platform. This system has a few benefits, the first is that you can get the kelp out of the way of storms that come through and could potentially do a lot of damage and the other is you can keep it out of the heat, to temperature regulate the kelp. 

On top of that, there’s this effect where the first 50-100 metres of water is actually quite nutrient-depleted because all the photosynthetic organisms can thrive and survive from the sunlight so it is not a nutrient heavy environment but once you get down to the deeper water, it’s nutrient-rich. We are looking into regulating the system by moving the platform to deep water at night to irrigate the kelp in nutrient-rich waters and then during the day, move the kelp closer to the sun to get photons for photosynthesis. 

More generally, we’re going to start to prototype farm designs with our collaborators, prior to developing a larger open ocean farm in the Cook Strait. For this project, we will be working with a large number of research institutes and universities, specifically, our research will be looking at how to control the depth of these open ocean aquaculture platforms, to avoid storms, marine heatwaves and provide an abundance of nutrients to our kelp.

To find out more about Blue Carbon Services, check out their website: https://bluecarbon.co.nz