Elon Musk, a tweeter, stated that he would give $100 million to carbon-removal technologies. This sparked the imagination of entrepreneurs and researchers.
A few weeks later Arin Crumley (a filmmaker who developed electric skateboards) announced that a team was forming at Clubhouse, an audio app in Silicon Valley, to compete to win a share of Musk's XPrize.
There were artists, engineers, and designers who met there to discuss various technical and natural ways of sucking carbon dioxide from the atmosphere. The conversations continued, and a core group of people formed Pull To Refresh. They eventually settled on the idea of growing huge bladder kelp in water.
The venture's primary efforts have been to grow the seaweed in tanks and test their control systems on a small fishing vessel on a Northern California lake. It is encouraging companies to contact it if they are interested in purchasing tons sequestered CO2 as a way of balancing their greenhouse-gas emissions.
Crumley claims that large fleets of semi-autonomous vessels, which grow kelp, could absorb around a trillion tonnes of carbon dioxide. They would then store it in the ocean depths. This could reverse climate change. He believes that we can return to preindustrial levels of atmospheric CO2 with a little bit of ocean.
"No one knows"
Many studies have shown that the world needs to eliminate billions of tonnes of carbon dioxide per year by midcentury in order to stop dangerous levels of warming and bring the planet back to its pre-industrial state. More corporations are looking for carbon credits to offset their carbon emissions and make progress towards carbon neutrality.
This has prompted a growing number companies, investors and research groups, to investigate carbon removal methods that include planting trees, grinding up minerals, and building huge C02-sucking factories.
Because there is already a large industry that grows kelp, it has been a hot area for investment and inquiry. The theoretical carbon removal potential of kelp is substantial. The Energy Futures Initiative assembled an expert panel that estimated that kelp could remove between 1 billion and 10 billion tons of carbon dioxide each year.
Scientists are still trying to figure out the fundamentals of this method. How much kelp is possible to grow? How much kelp can we grow to ensure seaweed doesn't sink to the bottom? How much carbon will remain there for long enough to help the climate?
A further concern is that no one can predict the ecological consequences of dumping billions upon billions of tonnes of dead biomass on the seafloor.
Steven Davis, an associate professor at University of California Irvine, said that we have no experience in perturbing the ocean bottom with such a high level of carbon. He is currently analyzing the economics of various kelp uses. I don't think anyone has a good idea of what it means to actively interfere in the system at such a large scale.
However, some companies are still rushing to make bold claims and sell carbon credits despite the uncertainty. The practice of not sequestering as much carbon as it claims could lead to overstatement or slowing down progress on climate change. Companies that buy those credits continue to emit false promises that the oceans will balance out the pollution.
Holly Buck, an assistant professor at Buffalo University, is researching the social implications and economic impacts of ocean-based carbon reduction.
The lure of the sea
California's Monterey Bay is dotted with giant kelp columns that form swathes along the rocks. These columns provide habitat and hunting ground for rockfish, sea-otters and urchins. To grow as high as two feet per day, the brown macroalgae depends on sunlight, carbon dioxide, nutrients, and cool coastal waters. Waves and storms can cause the seaweed to fall off its fronds and blades.
Researchers at Monterey Bay Aquarium started a series experiments in the 1980s to find out where all the seaweed ends. They attached radio transmitters on large floating kelp rafts and used remote-operated submarines to scan the ocean depths.
A forest of underwater kelp off the coast California. GETTY
Scientists estimated that more than 130,000 tonnes of kelp was released each year from the forests. The majority of the kelp rafts washed up on the shore in just a few days. However, the team discovered seaweed bundles lining hundreds of meters beneath the surface of the Carmel Submarine Canyon.
Scientists have found similar remnants of Kelp in deep ocean floors and coastal areas around the globe. It is clear that some of the carbon in the biomass remains down for many millennia because of kelp, which is a well-known source of oil.
In a 2016 Nature Geoscience paper, it was estimated that seaweed could naturally store nearly 175,000,000 tons of carbon each year around the globe as it sinks in the deep seas or drifts into sub-sea canyons.
This means that Crumley's team and others will need to remove far less carbon dioxide annually than they currently do. Pull To Refresh, along with other companies, are looking for ways to dramatically increase the growth of kelp on offshore vessels and elsewhere.
The deep seas
How much carbon will be retained below the surface, and how long?
Some species of seaweeds, such as giant bladder kelp have tiny gas bladders attached to their blades. This allows the macroalgae more sunlight to fuel photosynthesis. The bladders can keep the rafts, or remnants, afloat for several days depending on which species. This allows currents to transport kelp from distant shores.
David Koweek, science director of Ocean Visions, a research group that works with universities like MIT, Stanford and the Monterey Bay Aquarium Research Institute, said that kelp carbon can be released to the atmosphere if it decomposes on the ground or becomes dissolved inorganic CO2 in shallow seawater. If the kelp is eaten by marine animals in the upper oceans, the carbon could also be released.
Some kelp also sinks into deep oceans. Bladders degrade. The seaweed is pushed down by storms so that they collapse. Some species are naturally nonbuoyant. Some of the water that escapes below the surface remains there, and can drift into deeper waters via underwater canyons like the one off Monterey.
Ocean circulation models indicate that much of the carbon in biomass reaching great depths of oceans could stay there for very long time because of slow overturning patterns that bring deep water toward the surface. According to Environmental Research Letters, below 2,100m, sequestration times would be greater than 750 years in major regions of the North Pacific.
This suggests that seaweed can be deliberately sucked down to store carbon for long enough to reduce the effects of climate change. It will still matter where it is done and how much effort is made to ensure that the most biomatter reaches deep seawater.
For-profit plans
Pull To Refreshs's goal is to create semi-autonomous craft equipped with floats and solar panels, cameras and satellite antennas. This will allow the crafts to adjust their speed and steering to reach designated locations in the open ocean.
These so-called Canaries will also tow an underwater trellis made from steel wire called the Tadpole. It ties together large vases in which enormous bladder kelp can be grown. The seaweed will be fed by the vessel through tubes using a tank of micronutrients.
Pull To Refresh tested its control systems in a fishing boat on a lake near Northern California. COURTESY OF PULL TO RENEW
Crumley believes that eventually, the kelp would die and fall off. Then, it would naturally sink to the bottom. The company believes that by putting the vessels away from the coast, they can reduce the chance of dead seaweed washing up on the shore.
Pull To Refresh is already in discussions with companies to purchase kelp tonnes of seaweed.
Crumley states that we need a business model which works immediately or in the near future. They are patient and understand that it is still in its infancy. We will tell you everything we know. We will continue to deploy these Canaries until there are enough tonnes for us to close your order.
Crumley stated in an email that Crumley will give the company two years to have the carbon accounting approved by a third party accreditor. This is part of any transition. Crumley stated that the company is pursuing internal environmental impact and has been in contact with at least one carbon removal registry. He also said that it plans to seek input from researchers outside of this field.
He wrote that we will never sell a tonne of metal that has not been verified by a third party because we don't want to be part of any scheme that might even sound suspicious.
Scale beyond all others
Other ventures are also taking additional steps to ensure the kelp sinks and to coordinate with scientists in the field.
Running Tide, an aquaculture business based in Portland Maine, is conducting field tests in the North Atlantic in order to determine which types of kelp thrive in different conditions. The company's main focus is on non-buoyant macroalgae species and has been working to develop biodegradable floating floats.
Although the company has not yet tested sinking, the idea is that the floating objects will eventually be dissolved as seaweed grows in oceans. The whole thing should sink to the bottom of ocean after six to nine months.
Marty Odlin is the chief executive officer of Running Tide. He stresses that Running Tide works with scientists to ensure that they are evaluating the carbon removal potential in kelp in rigorous, appropriate ways.
Ocean Visions established a scientific advisory group to help with the company's field trials. This team included researchers from the Monterey Bay Aquarium, UC Santa Barbara and other institutions. The company also coordinates with the Centre for Climate Repair at Cambridge to determine how much carbon oceans can absorb through these types of approaches.
Running Tide will conduct tests over a period of at least two-and-a-half years in order to compile robust data on the effects of these practices.
Odlin states that at this point, we might conclude that more data is needed or that it doesn't work or is ready to go.
The company is optimistic about what it can achieve. According to its website, "Growing kelp and securing it in deep sea are carbon sequestration solutions that can scale beyond all others."
Venrock, Lowercarbon Capital and other investors have provided millions to Running Tide. Stripe and Shopify, tech companies, have also provided funds. They purchased future carbon dioxide removal at high costs ($250 per ton in Stripes' case), to fund research and development.
Other companies and non-profits are also looking into ways to sequester seaweed carbon dioxide. The Climate Foundation is offering a $125 blockchain-secured "kelp coins" to help fund its wider research efforts to increase kelp supply for food and other purposes.
The risks
Many experts in carbon removal fear that the market could drive kelp-sinking forward, regardless of what research shows about its effectiveness and risks. It will be profitable for the companies and nonprofits that do it to sell credit. Investors will be looking to get their money back. The demand from corporations for carbon credits is on the rise. The offset registries make money by stamping approval for carbon credit programs. They have a clear stake.
Verra is a voluntary offset registry that is currently developing a protocol to remove carbon through seagrass cultivation. Verra is also actively monitoring the kelp space according to Yale Environment 360.
These pressures have already been seen with other approaches for offset credits, says Danny Cullenward (policy director at CarbonPlan), a non-profit that evaluates the scientific integrity and carbon removal efforts.
CarbonPlan and other research organizations have pointed out excessive crediting and other issues with programs that incentivize and measure carbon emissions and remove it through soil and forest management. The carbon credit markets are still growing as corporations and nations seek to offset their continuing emissions.
It is difficult to verify that carbon removal has actually occurred by sinking seaweed to bottom of ocean. It is much easier to measure trees than to track the carbon dioxide that has dissolved in deep seawater. Any carbon accounting system forkelp will heavily rely on models that calculate how much carbon should remain below the surface and how long, in particular circumstances. It is crucial to make the right assumptions in order to ensure the integrity of any offset program and any corporate carbon math that depends on them.
Researchers are also concerned about the ecological consequences of seaweed disappearing.
Wil Burns, a Northwestern University visiting professor who studies carbon removal and is a member the Running Tides advisory panel, says that to grow enough kelp for a billion tonnes of carbon removal would require millions of buoys in oceans.
These floating forests could block marine mammals' migration routes. These creatures could also be transported on the ships delivering them. This could allow for the introduction of invasive species to different regions. Burns also believes that kelp forests could be used to create huge new sushi bars. This could tip the balance in a way that is hard to predict.
The seafloor could be affected by the addition of carbon and biomatter to the ocean, which could also alter the biochemistry and have a ripple effect on marine life.
Burns states that if you're talking about an approach that could dramatically alter ocean ecosystems, would you prefer that it be in the hands the private sector?
Running Tides Odlin emphasizes that he is not interested in carbon removal methods that don't work or harm the oceans. He said that kelp sinking is the reason he began to investigate it. This was because he saw firsthand how climate change was affecting fish populations and marine ecosystems.
He says that he is trying to solve the problem. If this activity does not solve the problem, I'll move on to something else.
Scaling up
John Beardall, an Australian emeritus professor at Monash University, has spoken out to say that scaling up kelp-based carbon extraction from the hundreds of million of tons expected to occur naturally to the billions will present some logistical challenges. He is also familiar with the challenges and potential of seaweed cultivation.
One reason is that only a few parts of the globe are suitable for kelp. Most seaweed grows in shallow, cool, and nutrient-rich water along rocky coastlines.
Ocean Visions notes that expanding kelp cultivation close to shore will be limited by existing uses such as shipping, fishing, and indigenous territories in a state-of-technology assessment. It will be more difficult to move it offshore with rafts and buoys. This will also increase costs.
Companies may need to deal with legal issues if they are primarily interested in sinking kelp commercially. The London Convention and London Protocol, which regulate marine geoengineering and prevent dumped materials in open oceans, have complex and changing rules.
Burns states that commercial efforts to sink seaweed in some areas could face permitting requirements under the London Convention or be considered illegal if they proceed without environmental assessment.
Beardall wrote in an email that climate change is already destroying kelp forests in some parts of the globe. The kelp forests of California's coast have been decimated by rising sea levels and a surge in sea urchins, which eat seaweed. In recent years, the kelp forests of Tasmania have shrunk by 95%.
Beardall said that this does not mean we should overlook seaweed harvesting and aquaculture as a way to sequester CO2. However, I want to emphasize that this is not going to happen.
There are other, more effective uses
Another question is whether seaweed can be sucked into the ocean.
It is a vital food source and income source for many farmers in Asia. However, it is already facing increasing pressures from climate change. It is used in pharmaceuticals, animal feed, and food additives. It could also be used in bioplastics and biochar, which enrich soils with carbon.
A sustainable cultivation of seaweed is valuable and has a wide range of uses. Dorte KrauseJensen, a professor from Aarhus University in Denmark, stated in an email that kelp carbon sequestration can be achieved by sustainably farming seaweed. It would be a horrible waste to dump biomass into deep sea.
UC Irvines Davis is conducting a comparative economic analysis on various methods of putting kelp into use. This includes sinking it or converting it to carbon-neutral biofuels or using it for animal feed. Even if all costs were at the lowest end, seaweed sinking could cost around $200 per ton. This is more than twice the long-term, low cost estimates for carbon-sucking plants.
Davis believes that these costs will likely push kelp growers towards higher-economic value uses. He says that farmed kelp will not have the greatest climate benefits if it isn't sunk.
Do it!
Pull To Refreshs Crumley said that he and his crew hope to start testing a vessel in ocean waters this year. He says that if it proves successful, they will attach baby kelp on the Tadpole to make it go on its journey.
He refuted the idea that companies should not sell tons of carbon now in exchange for eventual carbon removal. He said that companies need the resources to scale up and develop these technologies and that grants from the government won't help them get there.
He says, "We've just decided that we want to do it." We will take full responsibility for any errors if we are wrong. We believe this is the right decision.
However, it is not clear how such a startup would be held responsible for any mistakes that may have been made if they cause harm to marine ecosystems. There are currently no mechanisms to hold companies responsible for overestimating carbon removal by kelp.
