Composting Glossary

The A-to-Z Guide to Composting: A Comprehensive (and Approachable) Glossary

Welcome to the world of compost, where food scraps are your friend, humus isn’t dip, and piles are sources of pride. 

Real talk: Composting can be intimidating! There’s dirt, different types of bins, and chemical terms, not to mention worms. But composting is actually pretty straightforward once you get into a groove — and that starts with learning the lingo. 

Below we’ve put together a glossary of terms to give you the scoop on all things compost, whether you’re just starting out, looking to deepen your understanding of the practice, or feel like dropping a fancy compost term in your next conversation. (Our favorite lately? Wigglers.) 

Of course, you don’t need to know all these words to start composting, but it can help you feel more empowered. Even though we’ve been composting for over a decade and have a business that revolves around sustainable packaging, we still come across new terms and tools within the composting community — and that’s part of what we love about it. 

So keep scrolling to see the definitions of everything from browns and greens to sheet composting and vermicomposting. Some of these terms explain the science behind composting, others describe different methods. But all of them will help you feel more “in the know” when it comes to composting. Let’s talk dirt! 


From Aerobic to Vermicompost: Essential Composting Terms to Know 

Aerobic: A method of composting that requires oxygen to support the decomposition process. This type of compost often involves stirring the compost regularly or putting compost in a bin with holes around it to promote air circulation. 

  • Pros: It’s common for at-home and small-scale composting because it keeps odors to a minimum 
  • Cons: Can be on the labor-intensive side 

Anaerobic: Unlike aerobic, anaerobic composting is the method of composting without oxygen. 

  • Pros: No need for stirring
  • Cons: Takes longer and tends to get smelly

Browns: One of the most important terms on this list, browns are compostable, carbon-rich materials — like leaves, twigs, sawdust, wood chips, paper, and cardboard. Browns will likely make up a big chunk of your compost pile. 

  • Heads up: All brown things aren’t necessarily considered “browns.” For example, coffee grounds are in the “greens” category (definition below). 

Cold Pile: This is a compost pile with a higher carbon-to-nitrogen ratio that doesn’t involve turning and stirring the pile. Although a cold pile decomposes slower than a hot pile (definition below), it’s a good place to start and can be great as long as you have the patience to keep at it. 

  • Tip: If you have access to a backyard, it’s common to keep a small cold pile in a kitchen, and transfer it weekly to a larger hot pile outside. 

Composting: A (very effective and empowering!) method of decomposition, where organic matter breaks down in a climate-positive way. The result? A nutrient-dense material that returns back to the earth rather than filling a landfill elsewhere. Composting significantly cuts back on food waste AND it turns the waste you do have into a material that replenishes the soil. Win, win.

  • Why we love it: When the world can feel increasingly uncertain and chaotic, composting puts a sense of power back in our own hands. Plus, it’s very satisfying to see the process from start to finish right before your own eyes. 

C/N Ratio (Carbon-Nitrogen Ratio): This is the balance of carbon-rich “browns” and nitrogen-rich “greens” in a compost pile. 

  • Tip: Finding a good C/N Ratio takes practice. We suggest starting with about 3 parts brown for every 1 part greens and adjusting as you go. But don’t overthink it! Composting is not about perfection and you can always change your ratio as you go. 

Decomposition: The process of organic matter breaking down. The longer you compost, the more organic matter decomposes.

Fertilizer: Fertilizer is used to supply plants with nutrients. Nitrogen, potassium and phosphate are generally the most common sources of nutrients in mineral fertilizers. 

  • Keep in mind: Although compost is often used as a fertilizer to nourish soil, they’re not interchangeable. 

Greens: While browns are carbon-rich materials, greens are the nitrogen component in the composting process. Greens include coffee grounds, grass/flower clippings, egg shells, and other food waste. 

  • Tip: If possible, add greens and browns to your compost in alternating layers. 

Hot Pile: If you have a pile of compost, and you mix it — that’s’ a hot pile. It’s the process of bringing together different materials (food scraps, leaves, coffee grounds, etc), stirring them, and potentially adding some water. 

  • Keep in mind: It’s ok if your compost isn’t heating up as you’d expect. Hot piles take time (however, once they get going they decompose quicker than cold piles) and as long as your compost is breaking down — that’s what matters. 

Humus: This refers to the natural decay of material (like leaves) in the soil’s top layer. It’s dark earth that’s very nourishing for soil health and plant growth. 

  • Compost vs humus? While compost is intentionally created by humans, humus is naturally occurring from decay over time. 

Mulch: A material that you use to cover the soil surface. It’s used for a wide range of purposes, from improving moisture and the visual aesthetics of a backyard to helping with weed maintenance. 

  • Tip: Organic mulch can be a very useful ingredient to compost, but make sure it’s not dyed. 

Pile: This is a word you’ll likely see a lot in the compost community. A pile (sometimes referred to as heap) refers to the living and “breathing” compost you maintain. 

  • Tip: Learn to love your pile! With some TLC and patience, your compost pile may be a part of your life for years or even decades. It’s what you may or may not show on a house tour to your fellow eco-conscious friends, neighbors, in-laws, you name it. At least we do!

Sheet Composting: This type of composting is when a thin layer of organic material is put over a large area, such as a garden bed. So instead of creating a pile, you’re creating a sheet. 

  • Why sheet compost? It is often used to turn a lawn into a garden or replenish a garden that’s in need of a little extra love and nutrients. 

Red Wigglers: These are the most common type of composting worm, and they’re some of the best worms for compost out there.  

  • Tip: Other names for red wigglers are tiger worms, manure worms, composting words, and trout worms. 

Windrow System: Usually used for large-scale composting, this method uses long, open-air piles that are roughly twice as wide as they are high. These are aerated naturally or mechanically, often by turning the piles with a machine or by forced aeration.

  • Fun fact: Windrows are the most common method of composting in the United States. Learn more here.

Vermicomposting: This composting involves a specific composting worm (usually red 

wigglers) to eat up the organic matter, so it turns into nutrient-rich material. 

  • Fun fact: Some say a composting worm can eat the equivalent of its own weight each day.  


Did we miss a composting term you think is important? Let us know!

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