WORKWEEK

Carbon removal is one of the hottest areas in climate tech right now. So much so that there’s a concern the energy, attention, and investment paid to it are misplaced. 

The world emits ~50 billion tonnes of CO2-equivalent greenhouse gasses annually. Shouldn’t the lion’s share of our efforts concentrate on reducing that number before we worry about removal? 

As David Ho, a scientist who studies carbon and ocean climate systems, wrote in the subhead of a recent opinion piece:

Drastically reduce emissions first, or carbon dioxide removal will be next to useless.

At the same time, most climate change mitigation pathways call for significant carbon removal capacity by the year 2050. One number many in the industry anchor to is 10 billion tonnes of carbon removal by 2050—a far cry from the hundreds of thousands of tonnes that will be removed this year. 

Still, even if 10B tonnes of carbon removal capacity existed today (and were paired with permanent storage or utilization), it would reduce global CO2-e emissions by ‘only’ 20%. Which speaks to Ho’s point. Absent deep emissions reductions, carbon removal is an insufficient palliative.

Things might look different by 2050. Hopefully, by then, emissions will be lower. At that point, significant carbon removal capacity could reduce atmospheric greenhouse gas concentrations, not just slow their seemingly inexorable rise. 

Given that setup, if you held all the purse strings, how would you allocate resources between carbon removal and emissions reduction technologies? 

Oh, you want to punt? That’s fair. It’s a bigger question than I’m keen to take on today, too. 

Still, the thought exercise sets the stage nicely for important considerations within carbon removal. Regardless of what level of resources the space receives, directing said resources toward the most scalable techniques and technologies makes sense.

From that perspective, leveraging natural systems, the most prominent existing capturers and sequesters of carbon seems attractive. The ocean, in particular, stands out. When I chatted with Ben Tarbell, the CEO of Ebb Carbon, an ocean-based carbon removal firm, he put it succinctly for us:

The ocean is the largest air capture membrane you could imagine. Starting with a natural process as the lever makes it easier to scale.

Ebb Carbon works on ocean-based carbon removal. This week, the firm announced a $20M Series A to preserve and restore the ocean’s capacity to remove carbon. The thrust of their work involves adding alkalinity back to the ocean to reverse ocean deacidification. 

Sound complicated? No worries, we’ll break things down and keep it all a bit more ~basic~. 

Deacidification for decarbonization

The ocean is one of the biggest sequesters of carbon in the world. To date, it has sequestered some ~40% of anthropogenic greenhouse gas emissions, i.e., the additional man-made emissions we’ve thrown at it and the atmosphere. How does this work? Here’s what I wrote eight months ago while covering another ocean deacidification and carbon removal firm:

At the highest level, the atmosphere and the ocean seek equilibrium. As more greenhouse gasses enter the atmosphere, some of it transfers to the ocean over time, seeking balance. Ocean alkalinity converts excess carbon entering the ocean into carbonates and bicarbonates, which sink deep below the ocean’s surface. Even though these processes take time, the ocean’s scale allows for significant carbon removal and sequestration. 

This carbon sequestration is not without consequences, however. And these consequences accelerate as more and more carbon accumulates in the ocean.

Present day me will now pick this up. As ocean alkalinity captures carbon and converts it to carbonates or bicarbonates, that alkalinity is ‘used up.’ 

There are natural mechanisms that add alkalinity back to the ocean. For instance, there’s rock weathering, during which acidity in rain corrodes rocks and washes alkalinity freed from said rocks into the sea. 

But as more and more carbon enters the ocean from man-made activities, the ocean loses alkalinity more quickly than natural systems replenish it, making it more acidic. Ocean acidification harms marine ecosystems (see coral reef bleaching) and the ocean’s carbon removal capacity.  

That’s where the idea of ocean alkalinity enhancement comes in. By adding extra alkalinity back into the ocean, people hope we can restore some of the ocean’s carbon removal capacity. 

That’s the crux of what Ebb Carbon wants to do. The core components of their ocean alkalinity enhancement process ‘tech’ stack are as follows:

• Waste feedstock: Ebb Carbon uses waste streams from industrial partners (e.g., brine from desalination plants) as an input to produce alkalinity with their electrochemical systems. 
• Membrane electrochemical systems: This is the technology Ebb Carbon uses to manufacture alkalinity onsite at coastal operations like desalination plants. The systems are powered by low-carbon electricity (to preserve the net negativity of the whole supply chain).
• Industrial waste streams: Co-location with industrial partners has another benefit: Ebb Carbon can use industrial partners’ infrastructure, which already includes ways to discharge waste into the ocean, as the delivery mechanism for the alkalinity into the ocean.
• And, of course, the ocean: The ocean is still the carbon remover and sequester here. Ebb adds alkalinity back to it, alkalinity the ocean then ‘uses’ to turn carbon into carbonates and bicarbonates. These (ideally) sink to the bottom of the ocean.

Notably, this ocean-based carbon removal and sequestration in one motion, which isn’t true of other carbon removal efforts (direct air capture firms typically partner with other firms to sequester carbon they’ve removed).

Judging by its presence in three of four bullets above, co-location is a significant component of the story here. Ben noted Ebb Carbon aims to use feedstocks from various partners, including industrial cooling operations, power plants, aquaculture operations, or desalination plants.

In most of these cases, they can add their alkalinity directly into existing, permitted outflows into the ocean these partners have in place. This keeps regulatory hurdles lower. 

Working with Ebb Carbon should also be a boon to the partners. All operations listed above face regulatory and consumer pressure to clean up their act. In the case of a desalination plant, for instance, Ebb Carbon helps clean up their brine by reducing its salinity. 

Ebb Carbon has operated their systems in the lab for a year and a half based on co-founder Matthew Eisaman’s decadal scientific study of ocean alkalinity enhancement dynamics. Currently, Ebb Carbon is working on a 100-tonne capacity deployment with a TBA industrial partner. 

Ben’s experience is in solar, so he and the team are sharply focused on modularizing Ebb’s system. As we wrote last weekend concerning Emrgy’s hydroelectric turbines for waterways, to scale fast, it makes sense to follow the playbook of photovoltaics.

Designing smaller, standardized components that can be manufactured by the thousands (or by the billions, in the case of PVs) is more scalable than building huge infrastructure. As Ben noted concerning the first 100-tonne capacity system:

Every time we build one, we’re going to get better.

I also asked Ben which components of the business strike him as most defensible (several other firms are working on similar approaches to ocean alkalinity enhancement). He noted much of it is on the electrochemistry side. But there’s also interesting IP on the measurement, reporting, and verification front. 

The devil is in the details (of MRV)

Beyond financing, improving technology, and scaling a new industry, carbon removal will sink or swim based on its ability to measure, report on, and verify how much carbon it removes from the atmosphere and reliably sequesters. 

In some cases, as in direct air capture, this is a bit easier. All of the carbon removal takes place within the engineered system, so it’s easier to keep track of what’s happening (or isn’t). 

For ocean-based carbon removal, it’s a lot harder to ‘see’ the carbon removal in action. There are robust models that predict carbon uptake rates based on alkalinity enhancement. But the ocean is also a tremendously complex system.

Here’s Ben again on Ebb’s MRV perspective:

We can say with a high degree of precision what the level of CO2 drawdown and sequestration is with existing models and sensors. And we’re collaborating across the industry to improve upon that. All of our MRV is inherently open; for it to be effective, it has to be scrutable.

Perhaps more critical is gesturing at the uncertainty that still exists in the models, however, which Ben also did:

There’s a level of uncertainty in the existing models, but we can quantify that uncertainty with a high degree of certainty.

Discussing certainty around uncertainty feels almost Rumsfeldian – a la “known unknowns and such” – but it’s a pivotal point. If you have a firm sense of your uncertainty bands, you can appropriately under-credit your carbon removal efforts and effectively overdeliver against your uncertainty. Which provides more certainty.

This also establishes a positive incentive for firms like Ebb Carbon to contribute to reducing modeling uncertainty over time; as uncertainty shrinks, their margin will expand.

To continue the business model conversation, basically, it’s all about carbon credits for now. Ebb Carbon has a paying customer (Stripe) willing to buy their carbon removal tonnage.

There may also be future opportunities to make money from industrial partners by helping them valorize their waste streams. But Ben noted more of their focus is on nourishing solid partnerships. The $20M they just raised should help maintain that perspective (and, of course, design the necessary electrochemical systems).

The net-net

As the ocean warms and loses its carbon-capturing capacity, interest in ocean-based climate tech is heating up. Propeller, a venture firm focused exclusively on ocean-based climate tech, launched late last year with its first $100M fund. 

Other carbon removal firms like Running Tide and Planetary have raised significant big rounds to accelerate ocean deacidification and have made progress on their measurement, reporting, and verification protocols. 

What matters for ocean-based carbon removal is whether firms like Ebb Carbon and others can scale to millions (and ideally, billions) of tonnes of capacity. Anything less is a drop in the proverbial ocean. 

Scaling carbon removal capacity 1,000 to 10,000x will obviously be no small feat. As it pertains to ocean-based approaches, challenges I’ll track include:

• The tech: Can more modular removal systems actually scale like solar? 
• MRV: How certain are we really about the many uncertainties inherent to ocean alkalinity enhancement? I’m not equipped to answer that, and it’s an ever-evolving field of study. 
• Externalities: What known unknowns or unknown unknowns might spook folks concerning alkalinity enhancement’s impact on marine ecosystems?

Ben noted that down the line, taking the size of the desalination industry alone, he sees a path to driving 1B tonnes of carbon removal annually. And he sees a “clear pathway to reducing costs to less than $100/tonne in less than five years.”

That’s good news for the optimists among us. Let’s hope it comes to fruition (and all help how we can).