The Carbon-Nitrogen Ratio Explained Simply

For composting to work quickly, cleanly, and without odors, one thing is essential: the right balance between carbon (C) and nitrogen (N).

These two elements are the “staple food” for the microorganisms in the compost. They are what break down organic waste and convert it into valuable humus.

Why is nitrogen so important?

Microorganisms need nitrogen to reproduce. It is a key component of their cell structure—especially for protein compounds. Only when sufficient nitrogen is available can microorganisms develop rapidly and function effectively.

If there is a lack of nitrogen, the entire composting process slows down significantly. Decomposition stalls, and the material remains unchanged for a long time.

Why is carbon important?

Carbon provides energy for microorganisms while also adding structure to the compost. Materials with a high carbon content—such as leaves, paper, or wood—loosen up the compost and improve aeration.

Good compost therefore always needs both: nitrogen for activity and growth—and carbon for structure and energy.

What happens if the ratio is incorrect?

An unbalanced C/N ratio is one of the most common causes of problems with composting:

Too little nitrogen (too much carbon): The compost decomposes very slowly. This is typically caused by a high proportion of dry material such as wood, leaves, or cardboard. The microorganisms are, in a sense, “starving,” and the decomposition process is slowed down.

Too much nitrogen (too little carbon): This results in a nitrogen surplus. Under these conditions, ammonia—a gaseous substance with a pungent odor—can form. This leads to the loss of important nutrients and can cause unpleasant odors.

Carbon, Nitrogen, and Nature's Helpers

Kitchen waste has what is known as a nitrogen surplus, which should be balanced out with carbon-rich materials—such as woody components like napkins, paper bags, leaves, or dry grass.

For composting to work, you need three key "helpers":

Compost Organisms Billions of microorganisms are at work in compost—up to 1 billion per cubic meter. These include bacteria, fungi, and compost worms. They break down organic material and turn it into valuable humus.

Valuable compost worms, in particular, benefit from this. They thrive on the paper scraps added to the mix and play a key role in turning it into high-quality compost. Worm castings are considered particularly nutrient-rich and high-quality.

Water Without moisture, there is no life in the compost. The material should always be moist, but not wet—similar to a wrung-out sponge.

Air, air, air… that’s all there is to composting

The concerns people had about compost 20–30 years ago—odors, flies, or “vermin”—are not unfounded. These issues always arise when there isn’t enough air in the compost.

Without enough oxygen, the organic matter will rot rather than decompose properly. With enough air, however, composting becomes easy: the microorganisms work at their best, organic waste breaks down properly—and composting becomes a breeze.

When composting is done properly with oxygen, there are no negative effects; on the contrary, it creates a stable, sustainable cycle of humus and nutrients—the foundation for fertile soil and successful gardening.

Why this works SUPERCOMP well in SUPERCOMP

Thanks to its integrated support system and vertical aeration (chimney effect), the SUPERCOMP that oxygen reaches the very center of the compost pile. This maintains optimal conditions at all times—without the need for turning and without unpleasant odors. Thanks to continuous vertical aeration (chimney effect) and the integrated support system, the compost material remains loose and optimally supplied with oxygen. This allows microorganisms to work actively throughout the entire volume—even if the mixing ratio isn’t perfect.

The result: a stable, fast, and odor-free composting process.

Recognizing the C/N ratio in everyday life

In everyday life, there’s no need to calculate the exact ratio. It’s much more important to consider the material itself: moist, green, and fresh waste usually contains a lot of nitrogen. Dry, brown, and woody materials mainly contain carbon.

An ideal mixture consists of kitchen scraps, fresh grass clippings, or vegetable scraps, supplemented regularly with paper, cardboard, leaves, small pieces of wood, or dry grass. This keeps the material loose and provides good conditions for the composting organisms.

Typical examples of nitrogen-rich materials

Fresh kitchen scraps, fruit and vegetable scraps, coffee grounds, fresh grass clippings, and young plant matter are particularly rich in nitrogen. They provide moisture and nutrients for the microorganisms, but if used in excessive amounts, they can quickly make the compost too dense and too wet.

Typical examples of carbon-rich materials

Dry leaves, small pieces of wood, paper, napkins, paper bags, cardboard, and dry plant stems are all high in carbon. These materials provide structure, retain moisture, and help keep oxygen in the compost.

If the compost seems too wet or too dry

If the compost feels wet, heavy, or smells unpleasant, it usually lacks structure. In that case, adding dry, carbon-rich materials can help. If the compost feels very dry and shows little change, it usually lacks moisture and fresh, nitrogen-rich ingredients.

The SUPERCOMP an imperfect mixing ratio because vertical aeration brings oxygen all the way to the core. Nevertheless, a diverse mix of materials remains the best foundation for high-quality compost.

FAQ on the Carbon-Nitrogen Ratio

What is the ideal C/N ratio?

Simply put, an ideal mixture is achieved when approximately 60 to 70% fresh, green, moist, nutrient-rich compost material is mixed with 30 to 40% brown, dry, nutrient-poor, and carbon-rich materials. In everyday practice, however, you don’t need to calculate this exactly—what’s important is a balanced mix of moist and dry materials.

How can I tell if a relationship is unhealthy?

If the compost smells bad or becomes slimy, it usually means there is too much nitrogen. If the material remains unchanged and dry for a long time, it usually means there is not enough nitrogen.

What can I do if there's a smell?

Simply add carbon-rich materials: paper, cardboard, dry leaves, or small pieces of wood. These absorb moisture and balance out the excess nitrogen. SUPERCOMP the material from the harvest chamber at SUPERCOMP .

What should you do if the compost isn't breaking down?

Add more nitrogen-rich waste, such as kitchen scraps or fresh grass clippings, and mix gently (for conventional composters).

Are paper and cardboard really a good choice?

Yes, absolutely. Unprinted or lightly printed paper is an ideal source of carbon and is easily broken down by microorganisms and compost worms.

Do I have to follow the ratio exactly?

No. With traditional composting, experience SUPERCOMP . With SUPERCOMP , the optimal

The oxygen supply balances out many factors, so even minor imbalances are easily tolerated.

How important is water in composting?

Water is essential. Without moisture, there is no microbial life—and therefore no composting. The material should always be moist, but not wet. Rule of thumb: like a wrung-out sponge.