As a part of my graduate program, I’m making a video game in which the player breeds and collects flowers on an alien world, then sells them to customers across the galaxy. Initially, it’s a fairly straightforward time management experience. Orders come in and the player directs drones to fill them before time runs out. Eventually, it becomes clear that all this horticultural activity has unintended consequences. The drones emit a substance that is slowly warming the planet, threatening its life (and the fledgling enterprise). Sound familiar?
The goal of this educational experience is to force the player to deal with the same dilemma we confront in our terrestrial battle with climate change. They can plow ahead with indifference, making as much money as possible before the temperature kills all the flowers. They can attempt to limit the impact on the environment, replacing their systems with those that do less (or no) harm. Yet another path is to invest in systems that will remove the already introduced carbon analog from the environment.
It is this final approach that I’ve been thinking about a lot lately. The real-world equivalent is referred to as negative emissions technology (NET), a blanket term for the tools (many of them unproven) that we hope will allow us to remove the carbon we’ve introduced to the atmosphere and store it (somewhere). The industrial technology behind NETs is fascinating, but the space is controversial because it distorts incentives.
NETs present an interesting game design challenge because they have a big impact on the way players operate. If I over incentivize them, the player might ignore emission reduction altogether. Why change the damaging way I “collect flowers” when I could just erase the negative consequences? If I under incentivize them, they don’t represent a “meaningful choice” in the language of game design, and the player will ignore them altogether. Figuring out the right balance for these emerging technologies is an area of intense focus and debate in the real world as well.
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Human activity typically adds about 51 billion tons of greenhouse gas to the atmosphere each year (79% of which is CO2). To meet the Paris Agreement target of 1.5 degrees of warming (and avoid some very bad outcomes), humanity has the unenviable task of bringing emissions down to net zero by 2050. The vast majority of the change needs to come from reducing, and eventually eliminating, our use of fossil fuels while transitioning energy consumption to renewable resources like solar and wind.
The “net” in net zero is important. Industries like aviation, marine shipping, steel, and cement manufacturing are extremely difficult (or impossible) to decarbonize at present. We will need a way to offset the emissions we can’t get rid of, so negative emissions technologies have become an increasingly important component of proposed climate policy. It may not even be possible to achieve our goals without them.
THE CARBON CYCLE.
One thing that was surprising to me at first, but obvious in retrospect, is that the planet has a closed carbon cycle. Carbon atoms naturally move from living things, soil, rocks, and oceans (so called “carbon sinks”), to the atmosphere in the form of CO2, then back again. We aren’t adding carbon to the system when we burn fossil fuels, we are shifting the balance from the planet to the atmosphere.
There are a dizzying variety of proposed negative emissions technologies and most take advantage of natural carbon cycle processes, shifting the balance away from atmospheric carbon. For example, reforestation is a proven, affordable, and broadly popular way of sequestering carbon. Trees consume carbon dioxide as they grow and hold it for decades. Similarly, restoring degraded coastal and marine habitats (referred to as coastal blue carbon) captures carbon in the soil and plants like mangrove trees.
Our ability to implement any of these strategies will be determined by a series of criteria, including cost, space needs, scalability, and energy requirements. We also need a plan for where to put the carbon once we capture it so that it doesn’t escape back into the atmosphere. Though far from ready for prime time, there are several promising approaches.
A note about the numbers below: Cost estimates for NETs vary wildly across sources, and are highly dependent on the assumptions made. I’ve done my best to find consensus values, but you’ll likely find different numbers when doing your own research.
DIRECT AIR CAPTURE.
One NET that has received a lot of attention recently is direct air capture (DAC), which leverages naturally occurring chemical reactions to remove carbon from the air. Proponents of DAC laud its space efficiency and geographic flexibility. A 1 million ton per year system (sitting on 7 square kilometers) could capture as much carbon as a forest spanning more than 400 square kilometers. Because carbon is captured from the open air, you can place a DAC plant anywhere (though this is somewhat limited by carbon storage and power needs).
The problem with DAC is that CO2 has a very low concentration in the air (.04%). This means that it is quite expensive to convert into something that can be sequestered, roughly $600 per ton at present. The cost would need to drop to around $100 per ton to be useful for achieving our climate goals.
Just this past month, Heirloom Technologies opened the first commercial DAC plant in the US. It is the second industrial-scale plant in the world – the other launched in Iceland in 2021. Heirloom’s process, which you can get a glimpse of in this video, is fairly simple. The key input is limestone, which is heated to nearly 900°C. This separates it into CO2 (which is stored temporarily in tanks) and calcium oxide, a substance that looks like flour. The calcium oxide is then placed in trays and exposed to the open air with large industrial fans. Over a few days, the powder turns back into limestone, which is returned to the furnace where the process starts again. The captured CO2 at this particular facility will be mixed into concrete or stored in underground wells. Heirloom’s plant is quite small and will only capture about 1000 tons of carbon per year – roughly the amount produced by 200 cars.
Sourcing energy for DAC is a key challenge. If it isn’t renewable, the process doesn’t create negative emissions. Heirloom paid a local utility to add more renewable electricity to the grid, but that begs an important question: Why use renewable energy to remove carbon from the atmosphere when you could use it to eliminate emissions in the first place?
My favorite frontier carbon capture technology is Sargassum drawdown. Sargassum is a hearty seaweed that grows in the open ocean, particularly in an area of the Eastern Atlantic called the Sargasso Sea, from which the plant takes its name. Heavy industrial fertilizer use (and subsequent runoff) has recently fueled excessive growth and made it a nuisance to many coastal communities. The brown leafy weed is bad for tourism – it ruins the pristine look of beaches and has a noxious smell.
The rapid growth that makes Sargassum such a nuisance also consumes large amounts of CO2, to fuel photosynthesis. This makes it a terrific carbon sink.
The idea of Sargassum drawdown is to farm the seaweed and prevent it from reaching coastal communities, then bale and sink the carbon-enriched bundles to the bottom of the ocean. This would effectively sequester the carbon permanently. Though in a research phase, the approach has two-birds-with-one-stone elegance to it that I find appealing.
Seafields, a startup in the space, charges roughly $250 per ton of carbon sequestered, a figure they subsidize. The actual cost is probably north of $1000. This is far too expensive for broad-scale adoption.
BIOENERGY WITH CARBON CAPTURE.
One of the more affordable approaches to negative emissions is bioenergy with carbon capture and sequestration (BECCS), which involves burning biomass (agricultural and forestry waste, or energy crops), then capturing and sequestering the carbon before it is released into the atmosphere. Similar carbon capture technology has existed for decades in coal and gas-fired plants, but changing the fuel source has huge implications. Biomass removes carbon from the atmosphere as it grows. When a BECCS plant processes sawgrass, for example, the carbon that the plant collected during its lifetime is sequestered, resulting in negative emissions. The energy produced by the plant is used to make things like ethanol or cement. Waste CO2 can be stored underground or converted into biochar, a soil additive in agriculture.
The idea of burning something and having it result in negative emissions is counterintuitive at first, but BECCS has gained traction since it was first proposed in a book on Sustainable Development in 1998. There are currently 5 BECCS facilities operating that capture 1.5 million tons of CO2 per year. Relative to some of the other NETs I’ve discussed above, it is affordable, with estimates ranging from $20-200 per ton captured.
Though promising, the technology still has significant challenges that prevent adoption. A big constraint is the availability of biomass, which requires significant land and water to produce. If not managed carefully, the facilities could create unhealthy competition with food production or exacerbate deforestation.
I recently heard a podcast ad from a company touting its investment in carbon capture. It has since been removed from the feed, but I managed to cache a copy here. I was surprised to hear that the advertiser was oil giant ExxonMobil, but have since learned that it is far from the only fossil fuel company investing in negative emissions. This gets at the heart of why many people are ambivalent about NETs, or don’t support them at all: NETs are increasingly popular with companies that have little economic interest in reducing our reliance on fossil fuels.
Occidental Oil recently broke ground on a new DAC facility in Ector County, Texas. The $1B plant will capture 500,000 tons of CO2 annually, dwarfing the Heirloom facility and making it the largest in the world. Occidental won’t be storing the recovered CO2 in concrete, however. The plan is to use most of the captured gas in enhanced oil recovery, a process for increasing oil production by injecting gas or other chemicals into a well site. Occidental argues that the injected carbon will offset the CO2 that will ultimately be released when the fuel is burned, making it a “carbon neutral” alternative for difficult to decarbonize industries.
This type of investment has alarmed environmental groups, who view such moves as an attempt to prolong reliance on fossil fuels. In a recent online interview, Occidental’s CEO said as much (at 21:50): “The fight against fossil fuels is wasting too much energy and too much time. We need to partner with those that want to kill fossil fuels and help them understand that what we really want to do is kill emissions.”
I mentioned earlier that incentives play a huge role in video game design. Getting the balance right is critical for encouraging the types of behavior you want from players. It strikes me that our climate policy is a different type of game, with very high stakes. Like me, policymakers must engineer the right balance, with the crucial disadvantage of not being able to control the laws of nature.
The Inflation Reduction Act adjusts incentives in several ways. It increases tax incentives for investment in DAC to $180 per ton. It also has incentives for capturing CO2 directly from polluting sources and the enhanced oil recovery process I described above. These credits are time limited, so companies like Occidental are moving quickly. It is certainly true that we need solutions for difficult to decarbonize industries, but I worry that such incentives hamper our efforts to reduce dependence on traditional oil and gas infrastructure. Have we unintentionally incentivized some players to delay necessary action?
The reality is that NETs alone cannot solve the climate problem. Capturing the 51 billion tons of greenhouse gas we currently produce would cost trillions (every year) and it's unclear who’d pay for it. We also don’t know how to safely and reliably store that much reclaimed carbon. Bill Gates lays out this challenge in How to Avoid a Climate Disaster, and estimates that it would take 50,000 DAC plants to manage the CO2 emissions we’re producing right now (and DAC doesn’t work on greenhouse gasses like methane and nitrous oxide). With so many unsolved problems in the NET space, we avoid tackling the underlying issue of carbon at our own peril.
- Climate change is such a massive problem that it can be easy to feel overwhelmed and powerless. When reading Electrify in the members' reading group recently, we learned that there are meaningful changes each of us can make, namely – get an electric car, use solar, and install a heat pump.
- If you’d like to go deeper on NETs, the National Academies of Sciences, Engineering and Medicine has written a detailed ebook on the topic, which is free online.
Thanks as always to Scope of Work’s Members and Supporters for making this newsletter possible. Thanks also to Aaron, Stu, Ed, Christina, and Hillary for playing prototypes and offering thoughtful feedback.