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Carbon Pickling is Newest Idea to Remove Greenhouse Gas From Air

Shipwrecks can remain intact in saltwater for decades, and a startup is betting a similar idea can work for commercial carbon offsets.

When pictures of the wrecked ship Endurance emerged last week, most readers were told or reminded of the story of polar explorer Ernest Shackleton, who struggled for months in the hostile Antarctic environment after his ship sank and found a way to save every man in his crew.

But for environmental chemist Florentino De La Cruz, the ship is the perfect example of a new way to capture and store carbon. The remarkably pristine 107-year-old shipwreck shows how to preserve wood in salty water that’s devoid of light and in the presence of very little oxygen.

It’s also the idea that a startup called InterEarth has embraced. Instead of trying to sink wood to the bottom of the ocean, however, founders Howard Carr and Simon Avenell have been able to replicate the process on degraded land in the state of Western Australia.

These lands were home to hardy trees that grew despite low levels of salt in the soil. However, once European settlers began agriculture, it disturbed the water balance and supercharged the accumulation of salt. Some areas began going fallow in less than 30 years of crop cycles. Now the groundwater there can be five or 10 times more saline than seawater, says Tom Hatton, a consultant to InterEarth and an adjunct professor at the University of Western Australia.

Here’s how it works. First, InterEarth coppices trees, which is a sustainable timber technique that involves cutting trees in a way that allows them to grow back, found in areas near to the salty lands. Next, it digs pits about 6 meters deep where it places the wood and allows it to soak up salty groundwater. It then fills the pits with the dug-up soil and adds monitoring equipment.

In the absence of oxygen and in the presence of so much salt, not many microbes can eat up the wood and release carbon dioxide, as normally happens when trees die. There’s a small chance that methanogens — microbes that can live without oxygen and produce methane as a byproduct — can live in these environments. Though InterEarth hasn’t detected them yet, if they do detect release of methane then they can flood the pits with freshwater, which kills the microbes.

De La Cruz, who consults for a carbon-removal standards organization, has evaluated the carbon potential of burying wood. He himself has stored wood in labs where it’s not exposed to oxygen and found that more than 60% of the biomass is preserved over a period of nearly a decade. Salt can enhance the carbon storage process. “Waterlogged wood in salty and anaerobic conditions can stay undecomposed for hundreds of years,” he said. The sunken Endurance and many wooden shipwrecks around the world are proof.

InterEarth is a startup looking to sell carbon-removal credits, but what it’s doing is frontier science. While research has looked at what happens to wood under various conditions, it hasn’t focused on maximizing carbon storage. Thus, the startup will have to work hard to prove that its buried biomass (or at least a good fraction of it) can stay stored for a long time. “It will take at least four or five years of monitoring,” said Hatton.

Counteract, a U.K.-based company that funds carbon-removal startups at early stages, has invested $500,000. InterEarth has secured a further $400,000 in purchase commitments for its carbon-removal credits from a large insurance company, which Carr declined to name citing confidentiality. So far, InterEarth claims to have stored away enough wood to account for 80 tons of carbon dioxide in its pilot-scale operation. Carr and Avenell hope to raise as much as $30 million this year to scale up.

If it works, InterEarth says there’s enough salty land around the world to scale the technology to bury as much as 1 billion tons of carbon every year. Once its technology scales, InterEarth could be selling carbon-removal credits for less than $50 a ton given the relative simplicity of its idea compared to other startups that rely on more complex methods. For context, the European emissions trading system currently prices a ton of carbon dioxide at nearly $90 a ton. Bill Gates has even paid as much as $600 a ton for the highest-quality offsets.

The carbon-removal industry has been supercharged in recent years as companies look to offset emissions that are too expensive to cut. It’s been helped further by revelations that existing carbon offsets on the market are often of poor quality and involve projects that only avoid emissions, rather than removing it from the atmosphere.

The focus on carbon removal has led to an explosion of ideas, funded by private companies like Stripe Inc., Microsoft Corp. and Shopify Inc. The handful of startups that have received carbon-credit purchase commitments so far show that, with the right incentives, there are plenty of viable ideas that can help fight climate change. The domain of climate solutions is finally receiving the kind of attention it deserves.

Original source: Bloomberg


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