Compost 101: What Is Compost and How Do You Get Started?

Imagine being able to reduce your environmental impact by transforming everyday organic waste into a nutrient-rich soil amendment that benefits your garden for years to come. That's exactly what composting makes possible.

Composting is both a science and an art. It is the natural process of transforming once-living organic materials into a rich, nutrient-dense soil conditioner through decomposition. This guide focuses on practical composting methods that you can easily start at home.

What Is Compost?

Compost is the nutrient-rich material produced through the natural decomposition of organic matter. Composting, meanwhile, is nature's recycling system.

Leaves, fruit and vegetable scraps, coffee grounds, and other organic materials naturally break down over time. Composting accelerates this process by creating the ideal conditions for bacteria, fungi, earthworms, and other beneficial organisms that convert organic waste into healthy, fertile compost.

The finished product resembles dark, crumbly soil and is often referred to as “black gold” by gardeners and farmers because of its value. Rich in essential nutrients and organic matter, compost improves soil health and supports healthier plant growth in gardens, farms, and landscapes.

Organic waste can be composted at many different scales—from industrial composting facilities to community composting programs and simple home compost bins.

Why Is Composting Important?

Reduces Organic Waste

Composting is one of the simplest and most effective ways to reduce household waste.

According to the United Nations Environment Programme (UNEP), food waste accounts for a significant share of municipal solid waste worldwide. ⁽¹⁾ Instead of sending food scraps and garden waste to landfill, composting keeps these valuable organic materials in circulation and returns their nutrients to the soil.

For households, this means less waste sent to disposal facilities while producing a free, nutrient-rich resource for gardens and plants.

Helps Reduce Methane Emissions

Food waste has a surprisingly large climate impact.

When organic waste ends up in landfills, it decomposes without oxygen, producing methane, a greenhouse gas that is significantly more powerful than carbon dioxide over the short term.

According to the IPCC, methane has approximately 80 times the warming potential of carbon dioxide over a 20-year period. ⁽²⁾ Although it remains in the atmosphere for a shorter time than CO₂, reducing methane emissions is considered one of the fastest ways to slow the rate of global warming. ⁽³⁾

By composting organic waste instead of sending it to landfill, decomposition occurs in the presence of oxygen, greatly reducing methane emissions while returning valuable nutrients to the soil.

Improves Soil Health

Rather than discarding food scraps and garden waste, composting transforms them into an organic soil amendment that supports healthier, more productive soils.

Compost naturally contains essential plant nutrients—including nitrogen, phosphorus, and potassium—while also adding valuable organic matter to the soil. ⁽⁴⁾

Beyond nutrient content, compost improves soil structure, increases microbial activity, and enhances the soil's ability to retain both nutrients and moisture. ⁽⁵⁾

Healthier soils are more resilient to environmental stress, better able to support plant growth, and can contribute to improved yields in gardens, farms, and landscapes.

Supports Water Conservation

One of compost's most valuable environmental benefits is its ability to improve the soil's water-holding capacity.

Soils enriched with organic matter absorb water more efficiently and retain moisture for longer periods, reducing the need for frequent irrigation. This is especially valuable in regions experiencing increasing drought and water scarcity.

Healthier soils also allow rainwater to infiltrate more effectively, reducing runoff and helping recharge groundwater resources.

Helps Prevent Soil Erosion

Dry, compacted soils are far more vulnerable to erosion caused by wind and rain.

Adding compost increases the organic matter within the soil, improving its structure and helping soil particles bind together more effectively. This creates more stable soils that are better able to resist erosion while supporting healthy root development.

According to the US Composting Council, compost can also help reduce surface runoff by improving water infiltration, allowing rainfall to soak into the soil instead of washing valuable topsoil away. ⁽⁶⁾

Protecting soils from erosion also contributes to cleaner waterways, healthier ecosystems, and more productive agricultural land.

Supports a More Circular Economy

Composting demonstrates how organic waste can become a valuable resource instead of a disposal problem.

Rather than extracting new resources to produce soil amendments, composting returns nutrients to the environment through a natural cycle. This circular approach reduces waste, supports healthier ecosystems, and encourages more sustainable consumption habits.

Whether practiced at home or at an industrial scale, composting is a practical way to turn everyday organic waste into long-term environmental value.

How Composting Works: The Essential Components

Successful composting depends on creating the right environment for naturally occurring microorganisms to break down organic materials. To thrive, these organisms require four essential elements: nitrogen, carbon, oxygen, and water.

While all compostable materials contain carbon, they contain varying amounts of nitrogen. The key to effective composting is maintaining a balanced mix of these materials while ensuring adequate airflow and moisture throughout the compost pile.

A commonly recommended carbon-to-nitrogen ratio is approximately 25–30 parts carbon to 1 part nitrogen. ⁽⁷⁾

When there is too much carbon, decomposition slows down. Too much nitrogen, on the other hand, can create a wet, compacted pile with unpleasant odors. Fortunately, these imbalances are easy to correct by adding more carbon-rich or nitrogen-rich materials as needed.

“Green” Materials: Nitrogen Sources

Nitrogen fuels the growth and reproduction of the microorganisms responsible for decomposition. Fresh organic materials generally contain higher levels of nitrogen and are commonly referred to as green materials.

Examples include:

• Fresh grass clippings
• Fruit and vegetable scraps
• Coffee grounds and paper coffee filters
• Tea leaves and tea bags
• Fresh garden trimmings
• Plant-based kitchen scraps

“Brown” Materials: Carbon Sources

Carbon serves as the primary energy source for decomposer organisms. Dry, woody, or fibrous materials are typically rich in carbon and are known as brown materials.

Examples include:

• Dry leaves
• Small twigs and branches
• Straw
• Shredded cardboard
• Newspaper
• Untreated sawdust and wood chips

A healthy compost pile should contain a balanced combination of both green and brown materials.

Oxygen and Moisture

Like all living organisms, compost microorganisms need both oxygen and water to survive.

Maintaining good airflow allows aerobic microorganisms to thrive, speeding up decomposition while minimizing unpleasant odors.

Moisture is equally important. An ideal compost pile should feel like a wrung-out sponge—damp but not dripping wet.

If the pile becomes too dry, decomposition slows significantly. If it becomes too wet, oxygen levels decrease, encouraging anaerobic conditions that produce foul odors and slow the composting process.

Temperature

Temperature is a good indicator of microbial activity.

In hot composting systems, microorganisms naturally generate heat as they break down organic matter. Under ideal conditions, internal temperatures typically range between 54–60°C (130–140°F), helping accelerate decomposition while reducing weed seeds and many plant pathogens.

Maintaining the proper balance of green materials, brown materials, oxygen, and moisture allows these beneficial organisms to remain active throughout the composting process.

Turning the Compost

Regularly turning the compost pile introduces fresh oxygen and helps maintain consistent decomposition.

As a general guideline:

• Turn the pile about once a week during warmer months.
• During colder weather, turning every three to four weeks is usually sufficient.

Some compost bins also use ventilation pipes or passive airflow systems to improve oxygen circulation.

Maintaining the Right Moisture

Checking moisture regularly is one of the easiest ways to keep compost healthy.

If the compost becomes too dry, lightly add water while turning the pile.

If it becomes too wet, mix in additional brown materials such as dry leaves, shredded cardboard, or straw to absorb excess moisture and restore airflow.

Maintaining balanced moisture levels keeps decomposition efficient and minimizes odors.

Choosing the Right Size

For home composting, a pile or compost bin measuring approximately 1 cubic meter (about 3 × 3 × 3 feet) provides enough mass to retain heat while remaining easy to manage.

Breaking larger materials into smaller pieces before adding them also speeds up decomposition by increasing the surface area available to microorganisms.

As a general rule, avoid adding branches or materials thicker than a finger unless they have been shredded first.

Choosing the Right Location

Location plays an important role in maintaining a healthy compost pile.

Choose a location that is:

• Shaded or partially shaded
• Well-drained
• Easily accessible throughout the year
• Close enough for convenient disposal of kitchen and garden waste

In very wet climates, avoid areas where rainwater collects. In hot, dry climates, partial shade helps prevent the compost from drying out too quickly.

Building and Maintaining a Compost Pile

Getting started is straightforward.

Begin by alternating thin layers of green and brown materials, finishing with a brown layer on top.

As you continue adding organic waste over time, lightly moisten the pile whenever necessary to maintain the texture of a wrung-out sponge.

Allow the pile to sit undisturbed for several days so microbial activity can begin. Afterwards, monitor moisture levels regularly and turn the pile periodically to maintain airflow.

With the right balance of materials, oxygen, and moisture, the compost will gradually transform into a dark, crumbly material with a rich, earthy smell.

What Can You Compost?

Most plant-based organic materials can be composted successfully, including:

• Grass clippings
• Dry leaves
• Small twigs and branches
• Straw
• Fruit and vegetable scraps
• Coffee grounds, filters, tea leaves, and tea bags
• Shredded cardboard and paper towel rolls
• Wood shavings and untreated sawdust
• Fireplace ash from untreated wood
• Houseplant trimmings
• Nut shells
• Shredded newspaper
• Natural fabrics made from cotton or wool

What Shouldn't Be Composted?

Some materials should be kept out of home compost systems because they can attract pests, spread disease, or slow decomposition.

Avoid composting:

• Meat, fish, and bones
• Dairy products
• Cooking oils and fats
• Pet waste
• Diseased or pest-infested plants
• Plants treated with persistent pesticides or herbicides
• Coal or charcoal ash
• Black walnut leaves or branches, which contain compounds that inhibit the growth of some plants

Removing these materials helps maintain a healthy compost system while reducing odors and minimizing the risk of contamination.

Whether you're managing a small compost bin on a balcony or a larger backyard compost pile, composting is one of the simplest ways to reduce waste while improving soil health. Every compost pile keeps valuable organic matter in circulation, helping build healthier soils and supporting a more sustainable future.

---

References

1. United Nations Environment Programme (UNEP). Food Waste Index Report 2024
2. Intergovernmental Panel on Climate Change (IPCC). AR6 Synthesis Report (2023)
3. United Nations Environment Programme (UNEP). Global Methane Assessment (2021)
4. Food and Agriculture Organization of the United Nations (FAO). Global Soil Partnership
5. U.S. Department of Agriculture (USDA NRCS). Soil Health
6. U.S. Composting Council. Benefits of Compost
7. U.S. Environmental Protection Agency (EPA). Composting at Home