What Happens to your Food Waste in a Landfill?

It’s Worse Than You Think

Most of us don't think much about what happens after the garbage truck pulls away. The bag goes in the can, the can goes to the curb, and the truck takes it somewhere else. Problem solved.

But "somewhere else" is a real place. And what happens to your food waste once it gets there is worth understanding, because it's a much bigger problem (and more solvable!) than most people realize.

The 40% Problem

The EPA estimates that food is the single most common material in American landfills, making up about 24% of everything that gets buried. When you add yard trimmings, wood waste, and paper products, the compostable share of the waste stream climbs significantly higher. In 2019 alone, 66 million tons of food waste was generated in the retail, food service, and residential sectors, and about 60% of it went straight to landfills.

Globally, it’s estimated that 40% of waste gets sent to the landfill! And the largest single category of material in our landfills is something that never needed to be there.

What Happens Underground

When organic material ends up in a landfill, it doesn't just harmlessly decompose. A landfill isn't a compost pile. It's the opposite of one.

Composting requires oxygen. The microbes that break down food scraps and yard waste into soil need air to do their work. In a well-managed composting facility, organic material gets turned regularly, exposed to airflow, and broken down aerobically: cleanly, efficiently, and with minimal harmful byproducts.

A landfill has no oxygen. Waste is compacted and buried. The organic material still breaks down, but it does so anaerobically (without air). And anaerobic decomposition produces methane.

Methane has more than 80 times the warming power of carbon dioxide over the first 20 years after it reaches the atmosphere, according to the Environmental Defense Fund, drawing on findings from the IPCC's Sixth Assessment Report. It doesn't linger as long as CO2, but while it's there, it traps heat with extraordinary efficiency. Landfills are the third-largest source of human-caused methane emissions in the United States, accounting for approximately 14.4% of all U.S. methane emissions in 2022.

Food waste in the landfill isn't just sitting there, or harmlessly breaking down. It's producing methane for years. And an estimated 58% of the fugitive methane emissions from landfills come specifically from food waste, because food decays faster than any other landfilled material.

The Leachate Problem

Methane isn't the only issue. When food waste breaks down in a landfill, it produces leachate, better known as “garbage juice”: a toxic liquid that forms when rainwater seeps through the layers of garbage, picking up chemicals, heavy metals, and biological contaminants. Modern landfills have liner systems designed to capture leachate, but no liner lasts forever. Over decades, leachate can migrate into groundwater and surrounding soil.

In a valley like Missoula's, where the Clark Fork runs through the center of town and groundwater feeds wells throughout the county, this isn't an abstract concern. It's local infrastructure interacting with local geography affecting the health of Missoula residents and Missoula soil. And we’re running out of time: Missoula’s landfill is expected to be full by 2080.

The Nutrient Problem

Here's the part that doesn't get talked about enough: food waste in a landfill isn't just a pollution problem. It's a resource problem.

Every pound of food scraps buried in a landfill is a pound of organic matter that could have been returned to the soil. The nutrients in your kitchen scraps — nitrogen, phosphorus, potassium, carbon, and dozens of micronutrients — are the same nutrients that soil needs to grow food. When we landfill organic waste, we're mining nutrients from the food system and burying them permanently.

Meanwhile, we spend money on synthetic fertilizers to replace the nutrients we just threw away. It's a loop that runs in exactly the wrong direction.

What Composting Actually Does Differently

Composting reverses every one of these problems.

When organic waste goes to a composting facility instead of a landfill, it breaks down aerobically, with oxygen. No methane. No leachate. No buried nutrients. The end product is finished compost: a stable, nutrient-rich soil amendment that goes right back into the ground to grow food, support gardens, and build healthier soil.

The difference between the two outcomes is entirely about infrastructure. A landfill is designed to store waste. A composting facility is designed to transform it. Same banana peel, same coffee grounds, same plate scrapings — but one path produces a greenhouse gas and toxic runoff, and the other produces black gold (soil).

Diverting 75% of U.S. food waste from landfills to composting or anaerobic digestion would reduce emissions by 80–90% over the waste's lifetime, according to the Rocky Mountain Institute using EPA's Waste Reduction Model. That's not a marginal improvement. It's a near-total elimination of the problem.

Why This Matters Locally

Missoula has committed to its Zero by Fifty plan: a goal to reduce landfill waste by 90% by 2050. Composting is one of the single biggest levers in that plan, because organic waste represents such a large share of what currently gets landfilled.

The infrastructure already exists here. The composting facility exists. Curbside pickup exists. Over 1,000 households and 100+ businesses in Missoula are already diverting their organic waste from the landfill. The gap isn't technology or access — it's awareness and habit.

And building that habit makes a big difference: every household that composts pulls anywhere from 8–32 pounds of organic material out of the waste stream per month! Over a year, that's roughly 100–400 pounds per household that becomes soil instead of methane.

The Bigger Picture

The food waste problem isn't unique to Missoula. It's a national infrastructure failure.

The fix isn't complicated. It's composting. It's been composting for thousands of years. The only thing that's changed is scale: industrial composting facilities can now process the volumes that modern communities generate, and curbside collection makes it as easy as taking out the trash.

The question isn't whether composting works. It's whether we build the systems and the habits to use it.

Same food scraps. Two completely different outcomes. The only variable is which bin it goes in.

If you're not a customer and curious about how curbside composting works in Missoula or want to see the full list of what's accepted in the compost stream, we've written guides for both.

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Missoula Compost Collection is a locally owned, family-operated company partnering with Garden City Compost and the City of Missoula to keep organic waste out of the landfill and return it to the soil. Need composting service? Start residential pickup at $19.21/month, explore commercial pickup for your business, or set up event composting for your next gathering.