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What Do Commercial Composters Use in Their Compost?

January 23, 2025

Composting on a commercial scale is a fascinating blend of science and sustainability. While many of us are familiar with backyard composting, the processes and ingredients used in large-scale commercial composting are designed to handle significant volumes of waste efficiently and sustainably. Here’s an inside look at what typically goes into commercial compost and how it’s managed.

The Building Blocks of Commercial Compost

To produce nutrient-rich compost, commercial facilities rely on a combination of ingredients categorized as green materials (high in nitrogen) and brown materials (high in carbon). Maintaining the right balance between these two types of materials is critical for efficient decomposition.

1. Green Materials (Nitrogen-Rich)

Green materials provide the nitrogen needed to fuel microbial activity during the composting process. Common green materials include:

  • Food Scraps: Residential food waste, along with scraps from restaurants, grocery stores, and food processing facilities, forms a significant portion of the inputs.
  • Garden Waste: Grass clippings, green leaves, and non-woody plant trimmings.
  • Agricultural Waste: Crop residues and plant trimmings from farms.
  • Manure: Animal manure, particularly from cows, chickens, or horses, is a valuable source of nitrogen and microbes.

2. Brown Materials (Carbon-Rich)

Brown materials help to balance the nitrogen content, creating the ideal carbon-to-nitrogen ratio (25:1 to 30:1) for effective composting. These materials include:

  • Yard Waste: Dried leaves, straw, and woody branches (often chipped).
  • Paper Products: Cardboard, shredded paper, and newspaper, typically sourced from recycling programs.
  • Sawdust and Wood Shavings: Often from untreated lumber or woodworking facilities.
  • Compostable Packaging: Certified compostable bags, utensils, and other packaging materials.
contents of commercial compost
Commercial compost is made with a mix of recyclable materials

Understanding the 25:1 to 30:1 Ratio

The carbon-to-nitrogen ratio (25:1 to 30:1) refers to the balance of carbon (browns) to nitrogen (greens) needed for optimal decomposition. This ratio is based on the chemical composition of the materials, not a strict volume or weight measurement. For example:

  • High-carbon materials like dried leaves may require equal or greater amounts of nitrogen-rich materials like grass clippings by volume to achieve the correct balance.
  • A pile with too much carbon (browns) decomposes slowly, while too much nitrogen (greens) can cause odors.

How to Gauge Ratios by Volume

In practice, many composters estimate the ratio by volume using the general properties of materials. For example:

  • Two to three parts browns to one part greens by volume is a common guideline. For every bucket of greens like food scraps, you’d add two to three buckets of browns like shredded leaves.
  • This is an approximation, as materials vary in density and composition. Adjustments can be made based on the pile’s performance (e.g., odors or slow decomposition).

When planning compost, it’s helpful to think of the ratio in terms of the materials’ properties, ensuring a mix that supports efficient microbial activity.

3. Moisture and Aeration

In addition to green and brown materials, commercial composting facilities manage two critical factors: moisture and aeration. These are achieved through:

  • Water: Moisture levels are carefully monitored and adjusted to stay within the optimal range of 40-60%.
  • Bulking Agents: Larger materials like wood chips or shredded branches help create airflow within the piles, preventing compaction and encouraging aerobic decomposition.

Optional Additives for Enhanced Decomposition

Commercial composters may also use additives to enhance the composting process or tailor the final product:

  • Soil or Finished Compost: Adding small amounts of soil or mature compost introduces beneficial microbes to jumpstart decomposition.
  • Lime or Gypsum: These can be added to balance pH levels or reduce odors.
  • Biochar: Sometimes incorporated to increase carbon content and improve nutrient retention.

Controlled Inputs for Quality and Safety

Commercial composters have the capability to process materials that would typically be excluded from backyard composting:

  • Meat, Dairy, and Fats: These materials are often included in industrial composting systems, which reach the high temperatures needed to break them down safely.
  • Compostable Plastics: Only certified compostable plastics are accepted, as they require specific conditions to decompose.

However, some materials are strictly excluded to ensure the safety and quality of the final compost. These include:

  • Plastics (non-compostable).
  • Treated or painted wood.
  • Persistent herbicides or pesticides.
  • Inorganic materials like glass or metal.

The Science of Commercial Composting

Large-scale composting facilities rely on precise processes to manage decomposition effectively. By maintaining optimal moisture levels, aerating compost piles, and controlling temperatures, they produce compost that is free of pathogens and rich in nutrients. The process is designed to:

  • Minimize odors and pests.
  • Reduce greenhouse gas emissions.
  • Produce high-quality compost for use in agriculture, landscaping, and gardening.

The Benefits of Commercial Composting

By turning organic waste into compost, commercial facilities provide a sustainable solution to waste management. The compost they produce helps:

  • Improve soil health by adding organic matter and nutrients.
  • Reduce the need for chemical fertilizers.
  • Lower landfill contributions by diverting biodegradable materials.

Commercial composting showcases the potential of organic waste to create something valuable for the environment and agriculture. By understanding the materials and methods used in this process, we can better appreciate the benefits of large-scale composting—and perhaps even take inspiration for our own composting efforts at home.


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