How Carbon Farming will Save the World (A Love Letter in 4 parts)
Have you heard all the talk about Carbon Farming??
Well, me neither. But don't worry, up until a few weeks ago I had no idea what it was, and now I’m totally obsessed. It’s serious folks- it’s going to save our planet from catastrophic climate change. Yes, a real solution, within reach- we have the tools and we know it works.
Just let that settle in: Climate Change, that huge, hulking beast of a problem, so unwieldy, scary and complex, it feels inevitable it will be our demise….we can start to reverse it…in five years!!
The cool thing is that the answer to reversing global climate change is: PLANTS! And what is IN THE SOIL, in the very Earth itself. But we must first accept the mighty challenge to step up and heal her.
Part 1, The Issue:
Can we all agree that excess greenhouse gas emissions are being pumped into the atmosphere by human activity? The planet has always had these gases (mainly carbon dioxide and methane) that have been released into the atmosphere by things like animal respiration, and swamp off-gassing; however, Industry, deforestation, the burning of fossil fuels and other fun activities have put the system waaaay out of balance, we are releasing too many greenhouse gasses, trapping too much radiation and warming the planet way too much.
Some scary numbers:
For the majority of the time humans have been on this planet, carbon dioxide (CO2) has accounted for about 0.03% of our atmosphere, or 280 parts per million (ppm) of it. Today, carbon dioxide is up to 400 ppm, with scientists at NASA saying we need to get back to at least 350 ppm to avoid “catastrophic” climate change consequences. Let’s not go there shall we?
So, where did all this excess carbon in the CO2 come from in the first place? Well, it came from the ground, where can it go back again. And what magical beings will do this for us you ask? Well, plants will! In tandem with my favorite microscopic friends- soil biota. (To read my other post about the link between soil biology and the human microbiome click HERE)
Agriculture is responsible for 30% of annual global GHG emissions- imagine if we could harness this carbon pump and turn it into a carbon sink?
Part 2, The Solution:
I'm going to delve deeper into the relationship between plants and soil microorganisms, and it may seem complicated, but stay with me- this is really the key to the whole thing. So get comfortable, grab some snacks, and prepare your brain for some new synapses.
...So, plants are autotrophs, meaning they make their own food. To do this, plants use a process called photosynthesis (a word you totally know- this isn't too hard right?) where they absorb sunlight through the chlorophyll in their leaves and absorb water (H2O) through their roots. They use this energy from the sun to break apart the water molecules, and release the oxygen into the air. The leftover hydrogen then binds with CO2 drawn from the air to create simple sugars and carbohydrates (aka plant food.)
So far so good! Plants draw CO2 from the air, that's the first part- then what?
Well, plants use these sugars and carbs to grow cells and flourish, but something else happens, they start to leak some of it out of their roots as 'root exudates.' You may wonder why plants would do this, since it seems to be wasting precious resources, but it's actually a savvy way to access critical nutrients and hydration that is out of their reach. Think of the obvious limiting factor that plants cannot move and therefore cannot always access all the nutrients from the soil that they need to grow and thrive.
So they need little helpers to go get things for them. It's a little bit like how I used to get my little sister to get snacks for me from the fridge...Plants are constantly getting other organisms to help them out, delegating important aspects of their survival to those that can move around for them.
(Think about the majority of flowering plants, and how they have suckered all sorts of insects into helping them spread their pollen to reproduce. They do it by luring them with beautiful attractive flowers, and giving them a treat of nectar. We are familiar with this dance of pollination that happens above ground, but did you know that something similar is also happening below ground? )
We know a healthy soil is alive with microbes (bacteria, fungi, nematodes and others) that cycle organic matter and process minerals, all which plants need. (Read my post about Soil Biology Here) So to get better access to those minerals, plants do something that attracts these biota to their root zone. They leak these exudates, this liquid carbon, in the form of simple sugars and carbohydrates (“cake and cookies” as the soil scientist Elaine Ingram calls them) so that the microbes start to colonize the root zone and effectively carry minerals and moisture closer to the plant. Mycorrizal fungi has very long and delicate hyphae, which spreads through the soil, attaching to plant roots on one end and demineralizing rocks on the other. Bacteria also breaks down chunky organic matter into nutrients that plants can absorb.
And you thought the only symbiotic relationships were above ground!
Ok, so the carbon dioxide from the air has been drawn down by plants, and some of it has leaked out of their roots as sugars and carbohydrates for microbes to consume. So let's keep going- after consuming these exudates, the microbes secrete substances also, one of which is a glycoprotein called glomalin. Glomalin is super sticky, and it binds soil particles together into larger aggregates, creating the holy grail of soil structure- something that has large enough pore space to hold air and water, but will also drain well. These aggregates hold large amounts of stable carbon inside of them, carbon that is protected and won’t just be cycled by microbes; it will remain stable as sequestered carbon.
This is it folks- this is the carbon sink; this is the easy peasy scientific solution.
To recap: Plants take carbon dioxide from the air during photosynthesis to create their food, some of which they leak out of their roots in the form of liquid carbon to attract microbes in the soil to their root zone. In exchange for giving these ‘cake and cookies,’ plants get access to precious nutrients and moisture that the microbes can reach. From this process, microbes secrete glomalin, which binds soil particles to create larger soil aggregates. These soil aggregates are safe-houses for carbon, which can be held in the soil for very long periods of time if not disturbed.
Voila! CO2 from the air into the ground!
Part 3, The How:
Regenerative Organic Agriculture- a term coined by The Rodale Institute refers to "working with nature to utilize photosynthesis and healthy soil microbiology to draw down greenhouse gasses.” Much of the literature is geared towards agriculture (I plan to do my own research and use these principles on the gardening level) but for now, here are some of the basic management strategies of ROA:
Always make sure soil is covered with plants- plants are the vehicle by which this whole system operates, and bare soil just exposes organic matter to oxygen where the microbes quickly devour it. Exposed carbon molecules bind with oxygen and are released into the atmosphere. (Basically the opposite thing we want to have happening!) Instead of leaving soil bare or "fallow" between crop rotations, cover cropping is recommended. These are living plants used as 'green manures' and 'living mulches' that help build soil fertility. And instead of monocultures of these cover crops, like a large expanse of crimson clover or winter rye, polyculture ‘cocktail’ mixes are in vogue, with a diversity of plants with diverse root systems to attract a diversity of microbes. Crops are even seeded directly into cut or ‘crimped’ cover crops, so residues are not taken away and the soil remains covered.
Don't till- Tilling is just not good- it breaks up all the fungal hyphae and the soil aggregates that hold the stable carbon; it also exposes organic matter to oxygen. And it kills larger organisms like earth worms that pull crop residues from the surface deep into the soil.
No synthetic chemicals- This basically sterilizes the biological activity in the soil and carbon cannot be sequestered. Without their beneficial soil microbes, plants don’t grow well, with less root mass and nutrient availability they become susceptible to pests and diseases.
Perennial crops best- this is mainly talking about pasture for grazing animals, but is the most exciting thing for the home gardener- that meadow you are fantasizing about is the best carbon sink ever!
Part 4, Shooting for the Stars:
Now remember in the beginning how I said we could start to reverse climate change in five years? Well here is how (this includes more numbers, but I know you can handle it ;)
In one part per million of carbon dioxide that is in the air, there is 2.125 Gigatons of carbon in it. If we are currently at 400 ppm and scientists are warning us to get back to at least 350 ppm, that means we need to restore 50 ppm, or 106.25 Gt (2.125 x 50) of carbon into the soil. If all the world’s 8.3 billion acres of grassland (that can on average sequester 2.6 tons of carbon per acre) and all the world’s 3.8 billion acres of cropland (that can sequester on average .55 tons of carbon per acre) were managed using these regenerative organic practices, we could sequester 23.7 Gigatons per year. So we could reach our goal of cutting back to 350 ppm in less than 5 years! After that, we could literally reverse the threat of the ‘catastrophic’ climate change I mentioned earlier.
And we can’t just ‘Stop all emissions’ and think that we will be safe- the extra CO2 that is in the atmosphere now needs a place to go, otherwise it will continue to heat the planet for generations.
Imagine clean air, clean water, healthy soil and healthy plants producing nutrient dense food for healthy people all over the world. We don’t have to wait for some big sci-fi solution to save us- we can start right now.
The answer is right under our feet; You'll never look at bare soil the same again.
The Rodale Institute, "Regenerative Organic Agriculture and Climate Change."
Jack Kittredge, NOFA- Mass Policy director, "Soil Carbon Restoration: Can Biology do the Job?"
Adrian Ayres Fisher, "Why Not Start Today? Backyard Carbon Sequestration is Something Nearly Everyone Can Do."