Composting is the natural process of recycling organic matter like food scraps, leaves, and paper into a valuable soil amendment called compost. Compost adds nutrients and improves soil structure, helping plants grow stronger. While composting is simple, getting the right balance of ingredients leads to more efficient composting. The key is balancing carbon-rich “brown” materials with nitrogen-rich “green” materials. Read on to learn the ideal ratios and practices for fast, effective composting.
What is Compost?
Compost is the dark, crumbly, earthy-smelling result of the natural decomposition process. When microorganisms like bacteria and fungi break down organic materials, complex compounds get simplified into basic minerals and nutrients that plants need.
Finished compost looks and smells like rich soil. It contains macro and micronutrients that are slowly released as plants grow. Compost also contains beneficial microbes that help suppress disease and improve soil structure. The organic matter in compost helps soil better retain moisture and nutrients.
Adding compost to garden beds, lawns, and potted plants improves fertility and plant health in a natural, sustainable way. Composting recycles waste that would otherwise go to landfills, reducing waste and methane production. It’s a simple way to create a valuable product while shrinking your environmental footprint.
Greens – The Nitrogen Source
The microbes that drive decomposition need carbon for energy and nitrogen to build proteins. Greens provide the nitrogen and tend to be:
- Moist and dense
- Quick to decay
- High in nitrogen
Greens include:
- Fruit and vegetable scraps
- Fresh grass clippings
- Manure from chickens, rabbits, etc.
- Coffee grounds and tea leaves
- Fresh garden trimmings
- Green uncooked plant matter
Too many greens make compost wet, compact, and smelly. But the right amount provides nitrogen to balance browns.
Browns – The Carbon Source
Browns provide carbon as food for microbes and tend to be:
- Dry, bulky, and airy
- Slow to decay
- High in carbon
Browns include:
- Dried leaves and twigs
- Straw
- Wood chips
- Sawdust
- Shredded paper/cardboard
- Dried grass or hay
- Woody garden trimmings
Too much brown material can make compost dry and slow to decompose. But the right amount provides energy to microbes and air pockets for proper aeration.
The Ideal Carbon to Nitrogen Ratio
Microbes need approximately 30 parts carbon for each part nitrogen. This ideal C:N ratio allows them to work at peak efficiency to break down waste and produce compost. Materials high in carbon tend to have a C:N ratio over 100:1, while nitrogen-rich greens are around 15:1.
By balancing high-carbon browns with nitrogenous greens, you can achieve the right C:N ratio.
Easy Green to Brown Ratios
While scientists suggest an exact 30:1 ratio, home composters need simpler guidelines. Some common green to brown ratios are:
- 2-3 parts browns to 1 part greens (by volume)
- 50% browns, 50% greens
- Alternating 6-8 inch layers
Mixing equal volumes provides a good starting point when building new piles. Simply add available materials in roughly equal proportions by volume or weight.
The 2:1 or 3:1 brown to green ratio gives more browns since they break down slowly. For example, mix 3 buckets of browns like dry leaves to 1 bucket of greens like veggie scraps.
Layering also ensures a blend of materials. Simply alternate brown and green layers of roughly 6-8 inches.
What Happens With Too Many Greens?
Excess nitrogen from too many greens causes problems:
- Bad smells from ammonia gas
- Compaction and matting
- Lack of air circulation
- Overheating and burning
The decomposition process slows down without adequate carbon. Microbes use up available carbon rapidly without browns to balance the nitrogen.
If your pile gets too green and smelly, remix it adding a lot of browns like dried leaves or wood chips to soak up moisture and balance the ratio.
What Happens With Too Many Browns?
Too many browns also causes issues:
- Slow decomposition
- Lack of moisture and nitrogen
- Materials take longer to break down
Without adequate nitrogen, microbes can’t build proteins needed to function, reproduce, and decay the waste.
Remix overly brown piles using fresh grass clippings, green plant trimmings, and food waste to provide more nitrogen. Also check the moisture level, as browns are dry.
Adjusting Ratios Through Composting Stages
The ideal ratios change during the composting process:
Early Stage: High nitrogen fuels rapid breakdown. Use a 1:1 ratio or even more greens.
Middle Stage: Shift to a higher proportion of browns as materials decompose. Aim for 2:1 or 3:1 browns to greens.
Final Stage: Further increase browns to absorb moisture as compost matures. Use 4:1 or higher ratios.
If you continuously add new materials, maintain a 2:1 or 3:1 ratio long-term. For batch composting, adjust ratios to suit the stage.
Finding the Right Balance
Getting the perfect C:N ratio takes practice. Don’t worry about being exact. Watch your pile and make adjustments as needed.
Signs it needs more browns:
- Ammonia smell
- Wet and compacted
- Lack of air pockets
**Fix: ** Remix adding more browns like dry leaves, wood chips, sawdust or cardboard.
Signs it needs more greens:
- Decomposition slows down
- Materials pile up unchanged
- Lack of nitrogen odor
Fix: Add fresh grass clippings, fruit and vegetable scraps, or other nitrogen sources.
A balanced compost pile should:
- Have a pleasant, earthy smell
- Feel moist but not wet
- Heat up from microbe activity
- Show a darkening and shrinking of materials
Use your senses along with the green/brown balance to monitor conditions and actively manage your pile. With practice, you’ll get a feel for the ideal ratios needed for efficient composting.
Helpful Strategies for Balancing Browns and Greens
Here are some useful tips for maintaining the ideal carbon and nitrogen balance:
- Collect browns throughout the year as they become available. Stockpile leaves, wood chips, straw, and paper to balance greens later.
- Chop or shred large pieces into smaller bits to decompose faster.
- Avoid thick layers or large piles of any single material, mix it up.
- Use a variety of different browns and greens for diversity.
- Loosen and aerate materials regularly for airflow. Turn or stir the pile to remix.
- Check moisture weekly, adding water or dry browns as needed. Compost should feel like a wrung-out sponge.
- Adjust recipes over time based on your results. Take notes to improve your process.
- If in doubt, add more browns. Excess carbon causes fewer problems than too much nitrogen.
Typical Browns for Composting
Here are some common carbon materials to stockpile for balancing compost piles:
Fall Leaves
Dry, crinkly leaves are the classic brown ingredient available in autumn. Oak and maple leaves break down slower than softer varieties. Shred them first with a mower for faster composting. Stockpile leaves in bags or wire bins to keep them dry.
Wood Chips
Arborists often chip up wood debris, providing free carbon-rich mulch. Avoid painted or treated wood. Chips take longer to decompose than leaves unless shredded first.
Sawdust
Sawdust from untreated wood is excellent for compost, absorbing odors and moisture. Let it age for faster composting. Use sparingly to avoid compacting piles.
Straw
Dry straw makes great passive aeration and balances wet grass clippings. Get straw from a feed store or farm. Avoid hay, which has too many seeds.
Shredded Paper
Shred junk mail, newspapers, cardboard and office paper. Avoid glossy/coated paper. Soak shredded paper first or it will blow around. Paper decomposes faster if torn or chopped into small bits.
Pine Needles
Pine needles are acidic so use sparingly, mixing with other browns. Chop them to break down faster.
Dried Grass
Save extra clippings to dry in the sun, then store in bags for winter composting. Or let your lawn go to seed and mow/collect dried grass.
Corn Cobs & Stalks
Chopped corncobs and husks provide stable carbon but break down slowly. Best shredded before adding.
Cotton Burrs & Lint
Natural cotton byproducts add carbon without chemicals. Sticky burrs take longer to decompose than soft lint.
Peanut Shells
Crushed peanut shells decompose faster than whole shells. They are drier than most green ingredients, adding valuable carbon.
Coffee Grounds
Used coffee grounds are a mild green but low moisture makes them useful browns. They contain nitrogen but act more like a carbon material.
Tea Leaves/Filters
Dry used tea leaves and paper tea bags provide carbon and aeration similar to coffee grounds when composting.
Nutshells
Crushed or ground shells from walnuts, pecans, almonds, hazelnuts, etc. all make good high-carbon browns but break down slowly.
Eggshells
Ground eggshells are a mild source of calcium carbonate and carbon. They decompose very slowly so are just a supplemental brown.
Wood Ash
Wood ash adds potassium and trace minerals, balancing the carbon in acid pine needles. Use sparingly to avoid salt buildup.
Typical Greens for Composting
Here are some nitrogen-rich materials to balance carbon:
Grass Clippings
Fresh-cut green grass clippings are the classic high-nitrogen green ingredient. Mix with dry leaves or let dry before composting.
Food Scraps
Fruit and vegetable kitchen scraps provide nitrogen and moisture. Bury them in layers to discourage pests. Avoid meat, oils and large amounts.
Manure
Chicken, rabbit, horse, cow, sheep, goat and other herbivore manures all provide nitrogen, micronutrients and beneficial microbes. Age manure first or compost thoroughly.
Garden Trimmings
Green leaves and plant debris from pruning add nitrogen. Chop or shred branches for faster breakdown. Use herbicide-free trimmings only.
Seaweed & Algae
Dried seaweed from the beach makes excellent nitrogen and micronutrient source. Rinse salt first.
Coffee Filters
Paper coffee filters provide carbon but also contain residual coffee oils that add nitrogen.
Tea Bags
Soiled tea bags contain traces of nitrogen from the tea leaves. Compost used bags for a mild combined green/brown ingredient.
Nutrient Meals
Alfalfa, soybean, canola and other plant-based nutrient meals from making vegetable oil provide balanced greens.
Fresh Hay
Green hay with seeds provides balanced carbon and nitrogen. Let age a bit since fresh hay can get hot. Avoid hay fed to unknown livestock.
Feathers
Feathers are high in nitrogen but take a long time to break down. Chop or shred into small bits first.
Hair & Fur or pet hair is slow to decompose but provides nitrogen. Chop and mix in thin layers with other greens.
Cotton Rags & Denim
Chopped or shredded cotton clothing scraps are a source of cellulose and nitrogen.
Barnyard Bedding
Mix used horse, chicken, rabbit, or other herbivore bedding provides nitrogen once solids are sifted.
Conclusion
Balancing greens and browns is crucial to efficient composting. Shoot for a 25-30:1 ratio of carbon-rich browns to nitrogenous greens as a starting point. Adjust proportions over time based on results. Stockpile browns in advance and mix materials thoroughly for the ideal composting recipe. With practice, you can create finished compost to nourish your garden using nature’s recycling system.