Carbon capture technology is held up as both an essential piece of our renewable energy transition and a last ditch effort of the fossil fuel industry to keep polluting. Regardless of which side of the debate you’re on, there’s been a lot of advancements in recent years. Most of the headlines come from direct air carbon capture technology, but there are some natural approaches starting to get attention that could not only sequester carbon from the atmosphere, but also improve our food production, reduce erosion, and many other benefits. Do we need to build giant machines to capture carbon or has nature already given us the technology we need? Let’s see if we can come to a decision on this.
My thoughts on this topic are nuanced, which usually doesn’t go over well on the internet. Coal and gas-fired power plants share about 58% of the carbon emissions coming from the energy sector.1 However, that massive amount of CO2 emissions is currently providing stable operation of the worldwide electrical grid, which hasn’t been possible with just renewables…yet. Simply eliminating fossil-fuelled power plants from our grid doesn’t solve our CO2 problem. Our atmosphere is full of carbon coming from different sectors, like transportation, industry, shipping, agriculture, and more. We also need to accelerate and help the ecosystem process and remove the excess CO2. Greenhouse gasses, like CO2, are a necessary piece of our climate, but it’s about restoring the balance.
That’s where carbon capture, utilization and storage (CCUS) technologies and direct air capture (DAC) come into the picture. They’ve been considered fundamental for achieving net-zero in the next few decades without compromising the stability of the electrical grid, but it’s not just about that. Captured carbon can be used for storing thermal energy, replacing water in cement curing, speeding up algae growth, and more.2 3 That algae can be used to create biodegradable plastics, liquid fuels, and as a food source.
While I did explore some of the approaches for direct air capture in a previous video, we’ve been seeing some companies around the globe exploring interesting natural alternatives to capturing carbon, such as biochar (biological charcoal) and enhanced weathering … that one was new to me. Before we jump into these more natural methods, let’s take a quick step back to understand the basics of CCUS and DAC.
CCUS involves the capture of carbon dioxide (CO2) emissions from industrial processes, such as steel and cement production, or from the burning of fossil fuels in power generation. Usually, solvent filters are installed in factory and power plant chimneys in order to capture the emitted CO2. The gas can then be routed to various sites for usage or storage. The majority of carbon dioxide will be pumped and then stored far underground in geological formations, although some portions can be utilized to produce polymers, cultivate greenhouse plants, even to carbonate beverages … if you like that kind of thing. 4 5 6
In addition to removing as much as 20% of carbon emissions from industrial processes and power facilities, a great pro of CCUS is that it can largely decrease the emissions of other pollutants like nitrogen oxide (NOx) and sulfur dioxide. However, CCUS also have several disadvantages and challenges, including the high cost of implementation, regulatory barriers, the risk of leak issues during transportation and uncertainties regarding storage capacity for CO2. The price of CCUS varies greatly from $50 to $100 per ton of captured CO2. 7 8 9
You can also capture CO2 that’s already in the air though DAC. This technology uses a fan to draw carbon dioxide from the atmosphere using a chemical process. When air passes over these substances, they react and trap CO2 while letting the other elements of the air pass through. That captured CO2 can be released from the solvent or sorbent when heat’s applied to it, which allows it to be used again to capture more CO2. The disadvantages of DAC are pretty similar to CCUS, and it’s also expensive, costing from $250 – $600 per ton of captured CO2.10 11
That brings us to the more natural approaches.
Biochar, which stands for Biological charcoal, is a natural carbon capture approach that’s been getting attention around the globe. It’s produced using a process called pyrolysis, in which organic material, such as wood chips, agricultural leftovers or switchgrass, are burnt at high temperatures with little to no oxygen in the chamber, which can produce oil and synthetic gas (called syngas), and a solid residue resembling charcoal. In some configurations, the syngas and oil can be used to power the pyrolysis reaction, basically making the system self-sufficient.
There are some big advantages to biochar. The first is its capacity to retain carbon in a stable form, which prevents organic matter’s CO2 from escaping into the atmosphere. Although further research is needed, burying biochar can increase crop yields in some soil types by enhancing water retention and reducing the soils pH. Adding biochar to animal feed can also improve the health and digestion of farm animals. Manure becomes more fluid and the biochar gets infused with more nutrients. 12 13 14
Because the process changes naturally decomposing organic matter into a stabilized form, it actually lowers atmospheric CO2 levels. You’re breaking a cycle. Normally, plants produce CO2 as they decompose, which other plants eventually absorb, and the cycle keeps going. Instead of letting that material decompose, you’re turning it into biochar and burying that stabilized CO2 in the ground where it can remain for hundreds or even thousands of years. 14 15
Although biochar does contain significant amounts of carbon, it’s still unclear how long that carbon will stay in the soil after being applied in a topical fashion. The feedstock and pyrolysis conditions determine the characteristics of the biochar that’s made, but they can also change with environmental factors like temperature and precipitation to determine how long biochar carbon is retained in the soil.16 17 It’s highly dependent on the specific soil conditions and makeup of the biochar used.1718
The California-based company, Pacific Biochar, is one of the companies trying to pave the road for the development of the biochar industry to lower carbon emissions. It collects organic materials and then distributes the biochar it creates to agricultural suppliers and compost yards. Pacific Biochar sells its biochar, unadulterated or enhanced, to farmers who want to benefit from this material. 19
A large portion of the surplus forest biomass is chipped and burned in biomass energy plants, so Pacific Biochar partners with these power plants to use their existing infrastructure. Although pyrolysis does occur in biomass furnaces, they need to be upgraded (they call it “modification light”) to make biochar correctly and not simply burn it.19 20
Its biochar product, called Blacklite Pure, is sold in two ways: loose, costing $60 per cubic yard or $305 per ton, and in bulk tote bags, costing $135 per tote. The company’s carbon dioxide removal projects can be incremental, achieved in steps of 10,000 to 50,000 tons of CO2 per year. 21 22
In a study, Pacific Biochar’s products boosted pinot noir grape yield by an average of 1.2 tons per acre over two years of harvest, with a payback period of only 1 year. With carbon credits to offset the cost, a larger portion of the farming community can apply biochar profitably. 23 19 The company’s technology also got on the radar of giant companies like Microsoft, which bought 1,500 metric tons of CO2 in carbon credits that will be third-party audited by the European Biochar Certification. 24
Although biochar looks promising, it still faces challenges. I had the chance to interview Josiah Hunt, the CEO of Pacific Biochar, and he gave me his thoughts on the challenges around this technology:
“We need to be deploying some significant capital and we need people willing to invest in taking some of these technologies to the next level. In 2008, there wasn’t really any available technologies. There are viable technologies right now, but a lot of them have only a little bit of deployment history. And there’s still a lot of dramatic improvements that could be done to make these machines… To scale up their manufacturer, like actually manufacturing the machines that we’re going to use, and then also their deployment, how we can efficiently deploy them cost-effectively…” – Josiah Hunt
Biochar isn’t the only natural approach to capturing carbon. Enhanced weathering is another interesting approach that’s being explored. This whole concept was new to me … and unlike the name implies, it has nothing to do with changing or enhancing “weather.” The weathering it’s referring to is a natural process in which rocks are eroded by human activity, rainwater or extreme temperatures. It’s a process that’s been going on for millions of years and is a significant carbon sink.
I had the chance to talk to Mel Murphy, a Research Lead at UNDO, a British company that’s been focusing on enhanced weathering, and she provided me with a nice high level explanation:
“…When rocks that contain lots of calcium and magnesium in them, such as basalt, break down they take carbon dioxide from the atmosphere, which dissolves into rainwater. That reaction actually sequesters carbon over the geologic time period. Enhanced weathering is simply speeding up this process through the addition of finely crushed and highly reactive basalt to forests and agricultural land…” – Mel Murphy
This process also forms bicarbonate, which might get into the oceans, where the carbon is trapped on the seafloor or preserved in soluble form for hundreds of thousands of years. However, we can speed up this natural process.25 26
Enhanced weathering demands the extraction, processing, and reaction of minerals, but more CO2 can be sequestered as a result of this than would normally occur. You’re probably asking yourself if mining rock might not cause more environmental damage and emissions than what you can sequester with using it for enhanced weathering. However, UNDO has been distributing the rock over agricultural areas in collaboration with partners using an approach that doesn’t consume additional energy or resources to generate crushed rock.
“…Annually, there are 50 billion tons of aggregate material produced globally. Of this, about 6% is the composition that we need. Then of that, probably about 20% is what we call off spec, which is four millimeters and down. So that’s quite a lot of material that is being produced that is not being used in aggregate industry. So we, at the moment, are not even looking into mining for purpose. We are using this quarry byproduct…” – Mel Murphy
UNDO is collaborating with climate experts and carbon authorities, and it’s also developing a model to forecast the rate of sequestering carbon, which will provide information that will serve as a benchmark for the sector. 27
Mel Murphy also pointed out that they’re conducting field trials to look at how basalt improves soil:
“…We’ve done some field trials, but more from a commercial perspective, where we’ve spread over a thousand tons on one farm, and this is at an application rate of 20 tons per hectare. What we’ve been doing is going back to this farm periodically and monitoring things like the soil pH, the alkalinity, which is a measure of how much carbon dioxide is present in a dissolved form, looking at the heavy metals and also other cations, such as calcium and magnesium…” – Mel Murphy
Enhanced weathering takes advantage of the fact that natural weathering of rocks is a surface effect. Rainwater can only penetrate and react with the surface of the rock. To speed up this process, the rocks are crushed, drastically increasing the surface area exposed to the weather.
Understanding the impacts this can have on the environment is important. Alkaline bicarbonate, which is washed into the ocean, can positively impact coral reefs and fisheries. Rock particles could be applied to open ocean regions or combined with agriculture with the additional benefit of enhancing crop yields and preventing soil erosion.
On the flip side, it also has the ability to negatively change the pH and chemical composition of the soil, impact ecosystems, and affect groundwater. In addition, the amount of basalt needed vs. CO2 captured can be around 3:1. For every billion tons of CO2 captured, you’d need 3 billion tons of basalt. Mel Murphy mentioned to me that they’re seeing slightly less than that, but to give it some perspective…
“So, we’re looking at about 0.26 tons of CO2 are sequestered per ton of basalt. If we’re spreading at an application density of about 20 tons per hectare, we’re looking at probably around four and half tons of CO2 are sequestered over the total lifetime of that project.” – Mel Murphy
There are constraints on how this natural process can change the course of nature. 28 25 When it comes to costs for enhanced weathering, it’s a bit uncertain and what my team and I found varies widely from $52 – $480 per ton of sequestered CO2. 29
One concern about using basalt is that it releases heavy metals such as nickel and chromium, but she explained how they’re trying to measure this problem:
“…We’re designing protocols to monitor that. So what we’re doing is we’re screening all of the basalts that we’re applying, and we have US EPA and European soil guideline values that we’re comparing our basalt to. So we’re ensuring that the application doses that we’re putting onto soils don’t exceed these agricultural limits. Then we’re also following that up with looking at field trials, to look at the uptake of these heavy metals into the plant tissue…” – Mel Murphy
She also had some thoughts on the challenges around enhanced weathering getting more traction:
“…At the moment, the biggest challenge is measuring the signature in the field. We’re looking at applying 20 tons per hectare. This is not a lot. So what does this look like in the field? It looks like a sprinkling over the top of the soil, and it’s really difficult to measure directly the carbon that’s being sequestered. Unlike technologies like DAC, where you can meter it, this is really challenging…We need more innovation and technology to help us to solve this. There are a lot of companies right now investing in sensor based technologies or neutron based technologies to measure infield variations in carbon…” – Mel Murphy
The transition to renewables and other technologies like EVs is a long road … and we’re only at the very beginning of it. I’ve said this before, but there’s no silver bullet here. We can’t buy an EV and call the problem solved. Simply cutting out fossil fuels won’t solve all the issues that need to be solved. Carbon capture is another tool in the tool chest that can help, but it doesn’t need to rely only on mechanical/electrochemical processes. Natural approaches like biochar and enhanced weathering could offer a win/win scenario for the environment, the land owner and farmers, as well as all of us. They can help with increasing crop yields, regulating pH, and helping our oceans to achieve better alkalinity levels.
CCUS and DAC have a longer history and more financial investment coming their way, which means more projects running around the globe. The more natural approaches are still at the earlier stage of development, with fewer resources and investments. They need further research, development and demonstration – not just across a range of crops and soil types, but also different climates and areas. Despite that, biochar and enhanced weathering can not only contribute to capturing CO2, but also to improving soil and crops … which benefits all of us in multiple ways.
- Why carbon capture technologies are important ↩
- CO2 Battery ↩
- These uses of CO2 could cut emissions — and make trillions of dollars ↩
- Carbon capture, utilisation and storage ↩
- Carbon Capture and Storage 101 ↩
- What is CCUS Technology? ↩
- Carbon Capture and Storage (CCS) Pros and Cons ↩
- CCUS Technologies – Can they mitigate climate change? ↩
- Widespread adoption of carbon capture, utilization and storage technologies in South East Asia remains highly unlikely ↩
- Post-Combustion Carbon Capture Research ↩
- Pre-Combustion Carbon Capture Research ↩
- Carbon Sequestration with Biochar ↩
- Carbo Culture Biochar: Stable CO2 Removal Technology ↩
- Refilling the Carbon Sink: Biochar’s Potential and Pitfalls ↩ ↩
- LAND CARBON SEQUESTRATION – BioCHAR ↩
- Biochar and Carbon Sequestration ↩
- What Is Biochar? – Uses, Advantages and Disadvantages ↩ ↩
- “The Effect of Biochar and Its Interaction with the Earthworm Pontoscolex corethrurus on Soil Microbial Community Structure in Tropical Soils” ↩
- Pacific Biochar is paving the way for the rapid growth of the biochar industry and the carbon sequestration needed to address climate change ↩ ↩ ↩
- How We Produce Biochar ↩
- Biochar Products ↩
- Pacific Biochar is paving the way for the rapid growth of the biochar industry and the carbon sequestration needed to address climate change ↩
- Microsoft Carbon Removal: An Update with Lessons Learned in Our Second Year – March 2022 ↩
- Enhanced Weathering for Carbon Capture ↩ ↩
- ENHANCED WEATHERING (TECHNOLOGY BRIEFING) ↩
- Enhanced Weathering ↩
- Guest post: How ‘enhanced weathering’ could slow climate change and boost crop yields ↩
- The potential of enhanced weathering in the UK ↩