Swamp Thing is actually taking carbon out of the atmosphere.
When I started talking about this project with friends and mentioned Swamp Thing, the most common response I got was, “what’s Swamp Thing?” If it helps, you can replace all “Swamp Things” on this page with “Groot,” and you’d get the same basic idea.
His consciousness was literally blasted from his previous human-scientist form during an explosion, and he can now pull all types of nearby plant matter together into a humanoid form called Swamp Thing (I promise that sentence makes sense). Most of the time, Swamp Thing uses plant matter that can be found in… wait for it… swamps.
Plants are pretty cool. While we humans pump carbon dioxide into the atmosphere, plants draw it back out of the air — one of the many important life-support services they provide. But swamps are tricky. Because they’re warm and constantly soaked in water, they provide a perfect oxygen-poor environment for microbes to produce methane, an extremely potent greenhouse gas (28-36 times worse than carbon dioxide). To figure out Swamp Thing’s carbon footprint, we need to know how much methane he’s emitting and how much carbon dioxide he’s absorbing – what scientists call “carbon sequestration.”
I was surprised to discover how difficult it was to find reports on methane emissions from swamps. The best I was able to find was a report from 1990 that documented methane emissions from swamps in Quebec. The scientists found that swamps release around 4 grams of methane per square meter per year, which approximately equals 120 grams of carbon per square meter per year.
Figuring out how much carbon dioxide swamps pull out of the air was a little easier. Scientists working in various Florida swamps found that they can pull 22-98 grams of carbon per square meter per year out of the atmosphere. The largest carbon sequestration rate comes from bald cyprus or deep slough swamps, so we’ll start with that.
Now that we know the carbon sequestration and emissions rates per square meter, we need to know how big Swamp Thing is. The average man has a surface area of around 1.9 square meters. But Swamp Thing isn’t an average man. He’s huge. If we assume he has a similar body to that of famous wrestler Andre the Giant, we can estimate Swamp Thing’s surface area at around 3.7 square meters.
If we combine his surface area with the emissions and sequestration rates, we can calculate Swamp Thing’s carbon footprint:
Emissions = (120 g-CO2e m-2yr-1 – 98 g-CO2e m-2yr-1) * 3.7m2 = 81.4g = 0.18 lb CO2e
If you’ve read about the carbon footprints of the other superheroes, you’ll recognize that this is a tiny number.
While this result shows that Swamp Thing has by far the lowest/best carbon footprint of our superheroes, it also assumes that Swamp Thing spends all his time as a humanoid bald cyprus swamp. But the comics are clear that he can pass his sentience to any plant matter. So what if Swamp Thing spent his time in other ecosystems, like grasslands or tropical rainforests?
The first and most obvious change would be to Swamp Thing’s name.
The other big impact would be his carbon footprint. A few studies have shown that grasslands are actually great at absorbing and storing carbon. According to these studies, the best estimates suggest that grasslands sequester carbon at a rate of 195 grams of carbon per square meter per year. Unlike swamps, grasslands don’t emit methane. That means that our “Grass Thing” carbon footprint would be:
Emissions = -195 g-CO2e m-2yr-1 * 3.7m2 = 721 gyr-1 = -1.59 lb CO2e
This negative carbon footprint means that Swamp “Grass” Thing is actually pulling more carbon out of the air than he’s releasing. This is great! He’s helping regulate carbon dioxide. But we can do better.
What if Swamp Thing spent most of his time as a humanoid tropical rainforest?
Tropical rainforests sequester a huge amount of carbon. Scientists at the University of Leeds showed that rainforests sequester 269.9 grams of carbon per square meter per year. When we apply this to all of our tropical forestland, it means that our rainforests sequester around 4.8 billion metric tonnes of CO2e per year. While that might sound great (it is), human carbon emissions from only agriculture, forestry, and land use were over 8 billion metric tonnes. So we’ve got a ways to go.
Back to Swamp Thing. If he spent his time as a tropical rainforest, his carbon footprint would be:
Emissions = -269.9 g-CO2e m-2yr-1 * 3.7 m2 = -997.5 g yr-1 = -2.20 lb CO2e
This is the best we can do for a single Swamp Thing.
The Final Analysis
Swamp Thing is definitely a candidate for the best superhero, at least in terms of carbon emissions. In fact, he’s the only superhero we’ve analyzed with a potentially negative carbon footprint:
Swamp Thing = -2.20 – 0.18 lb CO2e
This analysis definitively proves that superheroes benefit humans by helping regulate carbon in our atmosphere. Yet even under ideal circumstances, it would take just over 20,000 Swamp Things spending every hour as a tropical rainforest to remove the carbon emissions from just one average American every year. This would be enough Swamp Things to cover 60 football fields.
To remove the carbon emissions from every US citizen, it would require a forest of Swamp Things covering 70% the land area on planet Earth.