The dirt on dirt
A meander through composting and soil-based carbon sequestration
Every few nights after dinner, I, my dad, a rusty shovel, and a jangling silver pail will take to the backyard. The journey is never easy; I stomp after him in shoes that are too big with a flashlight that barely cuts through Houston’s damp air. After what feels like millennia, we’ll reach a wooden plank wedged into the ground. A hole quickly opens to meet the odds and ends of napa cabbage, orange peels, and scallions. Dirt turns over it, which frees us to scurry back to the glow of the climate-controlled house. I’m never sure if the hurriedness is in response to the chill or some vague superstition.
Such is the odd chore that comes with visiting home. There, composting teaches the principle of making the most of what you have.
My roommates and I recently started composting. Here, I’ve managed to romanticize it to the point that it’s a source of joy. For example, I would describe the ritual of clawing expended coffee grounds out of my french press as one I approach with an odd sense of relish, as they are rough and aromatic and frankly as close to soil as I can get in this greenery-forsaken part of town (Manhattan). For another, every Wednesday at 11:45 am, when I walk my food scraps to the drop-off location (and make sure everyone on Instagram knows), I whisper to myself that I’m returning to the earth what modern agriculture and supply chains borrowed.
Composting pulls the reduction lever toward a climate-proof future
Humor aside, it turns out that there is some truth to this notion of “returning to earth.” When we choose to compost our food scraps, we choose to keep them out of landfills, where they would have anaerobically decomposed to produce methane. This is no small matter. I was surprised to learn that landfills are the third-largest source of human-caused, or anthropogenic, methane emissions globally.
The plot thickens: methane is estimated to have caused ~30% of the current rise in global temperature (EPA, IEA). This seemingly disproportionate impact is due to its high global warming potential (GWP), a measure of a greenhouse gas’ warming effect over one hundred years relative to that of carbon dioxide.
These observations alone suggest that diverting food waste from landfills could meaningfully reduce near-term warming. It also appears to be the least controversial and most ready of the top three methane-reducing levers; I imagine that acting on agriculture and energy would largely consist of adopting plant-based or cultivated meat diets, refining then deploying methane-reducing cattle feed additives, and converting energy sources to renewables or nuclear power.
In America, the diversion of food waste from landfills is a work in progress. In 2018, 56% of food waste went to landfill. In contrast, only 4.1% of American food waste was composted.
What I found interesting was the “Other Food Management” and “Combustion with Energy Recovery” categories. Digging deeper yields a more granular breakdown of the management pathways:
It is not clear which of these pathways are considered preferable to composting. However, they all still require the systematic separation of food waste from trash and recycling.
One policy that could help us get to this future is the Recycling and Composting Accountability Act, which will task the EPA with studying and planning a national composting strategy. I’d also like to see more city-level programs. Cities like San Francisco and Seattle lead by requiring the separation of compostable waste in several streams for curbside pick-up, and others like New York City are experimenting with pilot programs right now.
All that said, as a perhaps obvious reminder, zero food waste upfront is better than 100% diverted food waste. These optimizations can happen close to the source, as Misfits Market does, or even at your local bakery, thanks to Too Good To Go.
Soil is an underrated removal mechanism
I’m currently taking a course about carbon removal, and composting sounds like it could also help pull a major carbon removal lever: soil carbon sequestration.
Healthy soil is a complex ecosystem rich with carbon. Carbon is a building block of the organic matter, microbes, and minerals that make the land so productive to grow on. Unfortunately, according to Dr. David Montgomery, a geomorphologist studying land evolution and MacArthur Fellow, agricultural soil around the world has lost 50% of its carbon since the Industrial Revolution.
What changed? Not just the scale of industrial agriculture, but the way in which it is done. Consider the popular practice of heavy tilling: this relentless turning of the soil (in hopes of discouraging weeds and distributing fertilizer) breaks up its structure, accelerating erosion and the decomposition of organic matter. It was actually heavy tilling, in combination with drought conditions, that set America up for the Dust Bowl of the 1930s. And as with the dust bowl, soil degradation impacts both the climate and our food—one-third of agricultural land has already been taken out of commission (Nori).
Slowly, farmers are making the shift to practices that support farmlands as an ecosystem, rather than take from it as an agricultural input. This philosophy is not new; it can be traced back to Indigenous communities. Tactically, Dr. Montgomery encourages the concurrent adoption of these three practices:
No / low-till—preserves soil organic matter; weeds are instead handled by cover crops
Cover crops—small plants like legumes planted in between seasons rather than leaving fields bare; discourages weeds and erosion and improves soil quality
Crop rotation—planting crops in “unpredictable” patterns; discourages pest and disease cycles and improves soil quality
These are celebrated as win-win solutions for farmers and the climate; healthier soil, higher yields, fewer costly inputs like fertilizer, and higher carbon content. Compost, as a soil amendment, further reduces reliance on fertilizers and increases water-holding capacity. The greatest technical challenge facing soil carbon sequestration would probably be the verification of soil carbon. Perennial is the poster child here.
Go touch grass
I recently came across some reading notes by Nan Ransohoff, a leader in the climate space I admire, about the act of aspiring:
You can’t really know what a value really means or feels like until the end of the journey. Definitionally, aspiring is a leap of faith.
To take that leap requires work:
In pursuing these values, our attitude is not merely a hope or wish that we will one day come to appreciate them. We work to appreciate them… In these cases, the full justification of what we are doing can come only at the end of the story.
Aspiring, by Agnes Callard
When I started composting, I didn’t know how much I would come to value the closed-loop nature of earth’s ecosystems. If you’re looking to deepen your appreciation for what this planet offers us, I’d encourage you to give composting a try as well. A quick search of “composting near me” should do the job—you’ll likely find a city website with a list of options like drop-offs at farmers’ markets, supermarkets, community gardens, etc. If you have an outdoor space, you can even try backyard composting. Appliance lovers can consider Mill or Lomi.
I’ll end with three simple tips to get addicted to composting:
“Stack” the drop-off time and location to and near an existing habit, like grocery shopping
Store food scraps in Tupperware in the freezer to slow decomposition and reduce waste
Tell someone about it, like everyone you know on Instagram
Housekeeping note: I’m resetting my publishing cadence to monthly. Look out for my next piece in February!