Compost Basics: How to Balance Greens and Browns

Composting is like yoga: Balance is crucial, and (mental) flexibility is helpful. Nitrogen-rich materials (often called “greens”) must be properly balanced with carbon-rich materials (“browns”) to ensure proper decomposition. However, this ratio isn’t always exact. Beginner composters must be willing to adapt to changing seasonality and input availability. 

Fortunately, this isn’t as difficult as it sounds. It is easy to separate greens from browns and guestimate their amounts. No complicated math equations or scientific experimentation is needed. A compost pile with the wrong ratios can quickly go awry, sometimes causing an unbearable stench, the growth of disease-causing organisms, or a failure to break down into a usable garden amendment. 

However, a properly balanced pile can yield incredibly rich compost that is far cheaper and of higher quality than store-bought equivalents. Every garden will have slightly different requirements based on the inputs you want to compost, but these basic ratio-balancing rules can help you quickly master this craft!

What is the Ideal Ratio of Browns to Greens in Compost?

The officially recommended ratio for home composters ranges from 2:1 to 4:1 ratio of browns to greens. This means you should always aim for at least twice as much brown material as green material. In most settings, three or four times more carbon-rich ingredients are ideal for balancing out the high-nitrogen content of food scraps, grass clippings, and animal manure.

11 Ways to Balance Greens & Browns in Compost

Composting can feel like a mystical blend of confusing science, art, and microbial magic, but there is still a straightforward strategy for home gardeners. While composting requires specific environmental factors, like proper aeration, temperature, and moisture, it is also quite forgiving:

Due to the wide variation in compost methods and inputs, backyard composting requires trial and error for most gardeners. Luckily, these tried-and-true science-backed steps will make this process much easier. There is no need to agonize over complex mathematical equations!

Whether you’re using a three-bin system or a compost tumbler, here are 11 simple ways to balance the ratios of browns and greens.

These compost ingredients are essential for fueling beneficial microbes that catalyze the breakdown of a compost pile. They provide nitrogen, enzymes, moisture, and minerals to help the pile heat up. However, if your pile is too green, you can end up with a slimy, stinky mess! These ingredients must be balanced out by sufficient amounts of carbon. 

On the flip side, too little nitrogen can create a pile that never heats up or lacks nutrients. If you want to make quality compost that enriches your garden soil with fertility, green ingredients are essential. As these materials break down, they’ll provide the rich naturally-occurring fertilizer to yield strong, healthy plants.

Storage

Green materials are best added to the compost pile immediately. If you gather biodegradable scraps from your kitchen, it’s natural to empty your countertop bin every few days so you can avoid unwanted smells or gnats. Prunings or fresh clippings from the garden can wait a bit longer before they start to break down. 

For gardeners using animal manure or grass clippings, mix brown materials with these ingredients ASAP to prevent anaerobic (low-oxygen) breakdown. Anaerobic microbes are often the source of that unbearable stench emitted from piles of pure manure or grass clippings.

Stockpile Your Browns

Browns are carbon-rich materials with semi-woody or woody texture. They tend to be brown because they have been dead for longer than green materials. You usually need a higher volume of browns than greens because these materials provide essential carbon. 

The carbon adds structure and airflow to the pile while absorbing excess moisture from the greens. It also feeds beneficial microorganisms like fungi that break down materials into a desirable soil amendment.

Common brown inputs include:

Too little carbon can cause a wet, smelly, rotten pile. It is essential to keep enough browns handy to absorb the moist leachate from nitrogen-rich materials like grass clippings or manure. 

However, a pile with too much brown material can take a very long time to break down because it relies mostly on slow fungal decomposition. When there isn’t enough nitrogen to fuel fast-growing bacteria, fungi take over. While fungi are mostly beneficial to the soil, they take a long time to decompose woody materials.

Storage

Browns are one of the most important things to stockpile in the garden! If you use leaves or straw as mulch, then you have even more reason to keep these materials on hand. In the autumn, rake as many fallen deciduous leaves as possible and keep them in an easily accessible pile near your compost bin. 

It’s important to keep your browns as dry as possible. Build a small awning over your leaf storage area. For a cheaper, quicker option, lay a tarp over the leaves and weigh down with rocks.

Sourcing Leaves

Check if your city has a leaf delivery program! Many municipalities gather roadside leaves throughout the fall and look for easy places to dump them. Residents can register online to receive piles of leaves in their driveway. Lay out a tarp and have wheelbarrows ready to transfer the leaves to your backyard or side yard for long-term storage.

Sourcing Wood Chips

Ask local arborists to deliver piles of ramial wood chips. Ramial is a type of mulch made from small branches from deciduous trees. This carbon-rich material breaks down more quickly than wood chips from large limbs or fallen trees. Ramial wood chips are awesome for compost, but standard wood chips are better for mulching pathways and perennial beds.

Sourcing Paper

If you want to compost household paper products, these should also be kept in a separate bucket or bin. Shredded paper and non-glossy newspaper are excellent brown sources for smaller compost piles and vermicompost bins. Large cardboard pieces are also beneficial, but you must first remove the tape and shred them into smaller pieces. It is easier to gather pre-shredded paper from offices or local businesses and keep it in boxes in your garden shed.

Eyeball Your Measurements With a Shovel or Bucket

When considering the proper balance of browns to greens, it’s easiest to think of the ratio in terms of buckets. If you have one full bucket of greens (like kitchen scraps), you will need three to four buckets of browns (like leaves). Similarly, if you add one shovel scoop of manure, you will need three or four shovel-fulls of straw.

You don’t necessarily need an actual bucket or shovel (though they help tremendously), but this visual is useful for making measurements. This method ensures that you can raise or lower the amount without changing the overall ratio. Whether you use a one-gallon bucket or a five-gallon bucket, the results will be the same as long as you stick to approximately a 4:1 ratio of browns to greens.

Composting is not like baking; you don’t need precisely measured cups and tablespoons of ingredients. Eyeballing the measurements is fine as long as you have a good mental picture of the volume you are adding to the pile.

Use Layering

Mixing your browns and greens together doesn’t need to be a laborious chore. Instead, add the ingredients in layers like lasagna. Alternating the greens and browns will more evenly distribute the organic material. This allows more oxygen to flow through the pile, facilitating faster breakdown. It also helps reduce the amount of shoveling and turning that you must do.

The layering method ensures a balance of beneficial microorganisms. In general, bacteria are the first to break down materials high in nitrogen. Fungi prefer carbon-rich materials, like woody and dense browns. By layering the ingredients, you can create the ideal environment for balancing beneficial organisms, ultimately yielding a loamy microbiome-boosting amendment for the soil. 

Maintain Airflow

Oxygenation is the difference between a healthy compost mound and a nasty rotten heap. Airflow between materials is absolutely crucial for yielding a quality microbially-rich amendment. In organic systems, the soil microbiome is arguably the most important part of your garden. The billions of beneficial microorganisms in the soil include healthy bacteria, fungi, nematodes, and protozoa. 

These microbes work together in a symbiotic food web that breaks down dead materials and rocks so they can make mineral nutrients available to plants. They also act as a defense army for your plants, preventing disease-causing organisms from taking hold.

Aerobic vs. Anaerobic Organisms

Most beneficial soil organisms require oxygen to thrive. Oxygenated or aerobic environments promote “good guy” microbes, while non-oxygenated or anaerobic environments welcome the “bad guy” microbes. This is why compacted and overwatered soil makes plants prone to root rot. 

Compressed soil particles create a lack of airflow in the root zone. When water oversaturates the area, the soil becomes even soggier, leaving little space between particles for oxygen to flow through. As a result, anaerobic root-rot-causing fungi grow easily, while the “good guy” microbes suffer. 

These same principles apply to compost, and their effects are even more magnified. If your compost pile does not have sufficient airflow, it can quickly go anaerobic. You will know if this happens because it will smell absolutely terrible! 

Properly balanced compost tremendously enhances a healthy soil food web. But if the compost goes anaerobic (without oxygen), you could be exposing your soil and plants to more disease-causing pathogens.

How to Aerate

It’s nice to understand the value of airflow in theory, but how do we apply this in a practical way? Grab your pitchfork or shovel! 

You may have heard of “turning” your pile. If you have a compost tumbler or other device, this process is easy to do with a handle. But if you have a standard mound or a three-bin composting system, you will need to manually flip and turn the materials to incorporate oxygen.

The easiest way to turn your compost is to scoop the outer layer of the existing pile and put it on the ground next to it. This essentially creates a new “flipped” mound. Continue the process until the outer layer is on the inside and the innermost hottest layer is on the outside. Oxygen will flow into the layers as you turn them, reinvigorating the microbes for another round of decomposition. 

How Often to Turn

In the early stages of composting, it’s important to turn the material every few days. Before decomposition is complete, you should turn it at least five times. Oxygenation usually enhances the speed and heat of decomposition. This is when the balance of your brown-to-green ratio becomes the most obvious!

If you’ve balanced the browns to greens at around 4:1, the mound should heat up fairly quickly. If it is not heating up, you may need to add more greens so that the carbon-to-nitrogen ratio is closer to 2:1. If it appears soupy, sludgy, or excessively stinky, then you need to add more browns.

You should notice visible steam coming from a hot compost bin. However, a long thermometer is also useful for gauging the temperature at the center of the mound. The goal is to heat your compost to at least 131°F (55°C) for 10-15 consecutive days. This temperature kills off harmful pathogens as well as weed seeds.

Keep Multiple Piles

It is a very common mistake to continuously add to one compost pile. This doesn’t necessarily ruin your compost, but it drastically lengthens the amount of time it takes to make finished compost. Backyard composters often forget that a compost pile is sort of like a cake. Once it’s in the oven, you don’t want to take it out and add more flour or eggs! 

So, once you start heating and turning a pile, do not add any more ingredients. Use new inputs to start a separate mound. There is no harm in keeping several mounds (or bins) at one time. You may have a reserve of leaves, an “in-progress” bin, and a heap of aging compost. 

A three-bin wooden pallet system can help keep these stages separate and tidy. If you don’t have room for several heaps, consider alternating between two different barrel tumblers.

Ensure Proper Moisture

Soggy compost is a slimy, smelly, rotten mess. But overly dry material won’t ever break down. Just like soil, compost requires a happy medium of moisture. An inadequate ratio of inputs can dramatically affect the moisture, but the weather can also shift the water balance. 

The best way to moderate moisture is to keep your compost in a covered area. A simple metal roof over wooden posts can provide protection from the rain and shade from extra-hot days. A top layer of browns is another line of defense if you don’t want to create an entire structure. You can add an outer “crust” of leaves or straw to moderate moisture inside the pile.

If It’s Too Wet or Smelly, Add Brown

The sour smell of rotten eggs or any foul odor is a sure sign that your bin is lacking oxygen. Anaerobic decomposition is caused by bacteria that thrive in low-oxygen conditions, creating a long-lasting odor that attracts even more “bad guys” like bugs and critters. 

Thankfully, all of these problems can be solved with one simple task: Add more brown material! An imbalanced ratio of too few browns and too many greens typically causes the compost to go anaerobic. 

Dry leaves, shredded paper, or straw are all quick fixes for a wet, smelly mound. These materials soak up excess moisture from the greens and simultaneously add texture (more air pockets) to enhance airflow. When you mix the browns in, the aeration starts to fix the putrid smell.

Key Caveat: Adding excessive fat, oil, meats, or dairy to your compost can also cause a nasty smell. While they are biodegradable, it’s usually best to keep these items out of a home compost bin.

If It’s Too Dry or Cold, Add Green

On the opposite end of the problem spectrum, we have a pile that is cold, dull, and dehydrated. These mounds usually break down very slowly because there is little microbial activity. Beneficial microbes are a lot like people; they need oxygen, water, food, and habitat in order to thrive. A bone-dry mound of material is not the ideal home for the bacteria and fungi we need to break down inputs.

The solution to this problem is exactly the opposite of the above: Add more greens! Increasing the nitrogen ratio is like jumpstarting the browns to start decomposing again. 

In very hot, dry climates, you may also need to spray the decomposing material with a hose a few times per week. To help retain moisture, you can use a tarp or a layer of straw.

Greens will speed up the microbial breakdown, and your compost should start heating up within a few days.

Check the Temperature

It is OK to leave a heap of biodegradable material to decay on its own, but this won’t yield a consistent, loamy compost. For the best end product possible, you must monitor the temperatures. A long thermometer is essential for monitoring your bin. The thermometer should be at least 12-18 inches so it can reach the center of the decomposition action. 

Beneficial decomposition bacteria reproduce rapidly between 110°F and 160°F (43-71°C). Once your pile is “cooking,” it should put off steam and feel hot when you hover your hand near the outside. Don’t worry; the external layers are not usually hot enough to burn you, but always approach with caution. 

The warmth is worth celebrating—this means your carbon-to-nitrogen ratio is in the proper balance! 

Stick the thermometer in the center and wait a few days for it to rise to 140°F (60°C). This ensures that parasites, eggs, flies, cysts, pathogens, and weed seeds are killed. Once the temperature rises above 140°F (60°C), it is safe to flip the compost to incorporate more air and help it cool down. The temperature will cool down and then rise again.

Turn actively decomposing compost every three to four days. Tumblers should be turned about twice per week.

If the pile is still not heating up, you may need more greens, such as grass clippings or veggie scraps. But if it skyrockets in temperature, it can get too hot. You don’t want the compost to combust! In this rare scenario, you may need to add more quick-breakdown browns, such as shredded newspaper.

Recognize Signs of Off-Balance Ratios

If your browns to greens ratio is off, your compost will tell you! It’s very important to pay attention to the signs of imbalance. This chart is a helpful cheat sheet: