Composting 101

What is Composting?

Composting, as defined by the EPA,  is “... the managed, aerobic (oxygen-required) biological decomposition of organic materials by microorganisms.” In layman's terms, it's aiding the natural process of oxygenated decomposition.”

By composting we can help the earth restore nutrients and strength in the soil to foster new growth, build a stable foundation, and look into a prosperous future.

Methods of Composting

There are different types of composting to accommodate different types of materials, environmental conditions, available space, and time constraints. Each method is designed to optimize the decomposition of organic matter under specific circumstances.

Industrial Composting

Industrial composting is large-scale composting for municipal or agricultural waste. It relies on high temperatures (thermophilic composting) to break down large volumes of organic material quickly. Industrial composting is strictly monitored to meet heat, time, and ratio requirements. This allows the community to safely compost meat, dairy, and bio-plastics.

Industrial composting is ideal for people with limited time or resources. It is a simpler, low-maintenance method to reduce waste and recover resources.

Garden City Compost uses the Windrow composting method.

Backyard Composting

Backyard composting relies on heat to accelerate the decomposition process. Temperature varies between 131–170°F during composting. Regular turning and monitoring are required to obtain proper oxygen and moisture levels.

Backyard composting is ideal for people with the time and interest in maintaining the pile. Backyard composting is not meant for meat or dairy products; bioplastics are not recommended. 

Other types of at-home compost include vermicomposting (worms) and bokashi (controlled anaerobic).

  • How it Works: Waste is placed in large piles with ventilation systems, like perforated pipes or blowers, providing oxygen without manual turning.

    Pros: Faster than windrow composting, minimal labor required.

    Cons: Higher initial setup costs, requires precise monitoring of aeration systems.

    Best For: Large-scale facilities and waste management centers.

  • How it Works: Organic waste is mixed with a microbial inoculant (often bran infused with beneficial bacteria) in an airtight container. The waste ferments rather than decomposes. After fermentation, it’s typically buried to finish breaking down.

    Pros: Handles a broader range of materials, including meat and dairy, compact and odorless.

    Cons: Requires specialized inoculant, additional steps for finishing decomposition.

    Best For: Urban households.

  • How it Works: Organic waste is placed in enclosed containers (e.g., drums or silos), where conditions like temperature, moisture, and aeration are tightly controlled.

    Pros: Rapid decomposition, efficient odor and pest control, compact.

    Cons: High equipment and operational costs.

    Best For: Urban and industrial composting facilities.

  • How it Works: Organic material is spread directly over the soil surface, where it decomposes and acts as mulch simultaneously.

    Pros: Improves soil fertility and prevents erosion with minimal effort.

    Cons: May attract pests, slow decomposition in colder climates.

    Best For: Gardens, agricultural fields, and orchards.

  • How it Works: Organic waste is buried in trenches or pits, where it decomposes naturally over time.

    Pros: Low-maintenance, no equipment needed.

    Cons: Slow decomposition, limited to areas with available land.

    Best For: Farms, gardens, and areas with poor soil needing improvement.

  • How it Works: Red worms (e.g., red wigglers) digest organic materials, producing castings rich in nutrients and beneficial microbes.

    Pros: Efficient for small-scale operations, minimal odor, produces high-quality compost (vermicast).

    Cons: Limited to certain organic materials (no meat, dairy, or oily foods), sensitive to temperature and moisture.

    Best For: Indoor composting, households, and schools.

  • How it Works: Organic material is piled in elongated rows (windrows) that are periodically turned to maintain aeration and proper temperature.

    Pros: Cost-effective for processing large quantities of waste.

    Cons: Requires space, equipment for turning, and careful monitoring to avoid odors or pests.

    Best For: Industrial-scale operations, farms, and municipalities.

Key Words

  • The presence of oxygen.

  • The lack of oxygen.

  • he Biodegradable Products Institute (BPI) is a non-profit organization that certifies compostable products and materials in North America. BPI ensures that products labeled as compostable meet specific standards for composting in municipal or industrial facilities.

  • Carbon-rich materials such as dry leaves, straw, twigs, and cardboard. They are essential for balancing nitrogen in the compost pile.

  • The balance between carbon-rich materials (browns) and nitrogen-rich materials (greens) needed for stable compost. A typical ratio is about 30:1.

  • The process of cutting or tearing compostable materials into smaller pieces to accelerate decomposition by increasing surface area.

    Missoula Compost customers do not need to chop or shred material. This is done at the industrial compost facility.


  • The final product of decomposed organic matter that is rich in nutrients and used to enrich soil.


  • All compostable servingware is made from renewable resources. Required to break down in an industrial compost facility within 90 days without leaving toxic residues. 


  • A liquid made by steeping compost in water. It’s used as a liquid fertilizer for plants.

  • The final stage in the composting process. The material sits for a period (several weeks) to stabilize and mature before being used in the garden.

  • Microorganisms, fungi, worms, and insects that break down organic materials in the compost pile.

  • Nitrogen-rich materials like food scraps, grass clippings, and coffee grounds that help provide protein for the microbes that break down the organic matter.


  • The stable, dark, nutrient-rich material produced after composting. It's beneficial for soil structure.

  • Water content in the compost pile.

  • Polylactic acid is a thermoplastic (heat-softened) monomer (bonded atoms) derived from renewable, organic sources such as corn starch, potato starch, or sugar cane. Industrial composting conditions create chemical hydrolysis (water breakdown) followed by microbial digestion to degrade the PLA into the soil; unlike traditional plastics. 

  • Refers to heat-loving microorganisms that thrive at high temperatures (131–170°F)

  • TÜV is a global organization that provides inspection, testing, and certification services for a wide range of products, systems, and processes.

    The name "TÜV" stands for Technischer Überwachungsverein, which translates to Technical Inspection Association in English.

The Compost Elements

Oxygen

Bacteria consume oxygen from the water content and surrounding atmosphere as they process material. Aerating compost is necessary to replenish oxygen that keeps bacteria happy. Lack of oxygen fosters bad bacteria that produce methane.

Moisture

Water content is crucial for the production of quality compost.

If moisture content falls below 45 %, the microbial activity will slow down or become dormant.

Heat

Microorganisms generate heat as they digest organic material. A compost pile with temperatures between 90 – 150° F is composting efficiently. Higher temperatures will begin to kill off some of the beneficial organisms in the pile; turning is needed to release heat.

Time

The composting process takes time. Stages of compost:

  1. Psychrophilic stage: the bacteria begin to colonize and generate heat. This will take a few days.

  2. Mesophilic stage: bacteria will take over – this will take a few more days depending on the weather, moisture, oxygen level, etc.

  3. Thermophilic stage: may take from a few days to several weeks and allows the heat-loving bacteria that digest the more resistant fats, cellulose, and proteins to thrive.

  4. The compost will need to cure for up to several months.

Balance

Balancing carbon and nitrogen is key to producing good compost. The ratio should be roughly 30 parts carbon to 1 part nitrogen (30:1) by weight.

The composting process slows if there is not enough nitrogen, and too much nitrogen may cause the generation of excess moisture and ammonia gas; which can create unpleasant odors.

Fun Fact: Coffee grounds have a carbon-to-nitrogen ratio of about 20:1 making it an ideal item for stabilizing a compost pile.

Exposure

The more the surface of a compostable material is exposed to the elements, the quicker and more completely it will decompose.

The increased surface area also means that microorganisms multiply more quickly, therefore digesting more, which will generate heat-increasing critter activity.

Element icons from “Avatar: The Last Airbender”… with a few handmade friends.

Developing Your Compost Spidy-senses

Composting can be confusing, but just like anything else the more you do it, the better you will get. Developing compost senses can help sort compost on the spot. Knowing the basic qualities of compostable and non-compostable items can help navigate day-to-day items.

  • Natural Look: Items that appear natural (e.g., fruit peels, vegetable scraps, or leaves) are compostable.

    No Synthetic Materials: Avoid items that look shiny, plastic-coated, or overly processed, as they are often synthetic.

    Breakdown Signs: Items already showing signs of decomposition (like mold, softness, or discoloration) are compostable.

  • Fibrous Texture: Materials that feel soft, fibrous, or crumbly (like paper, cardboard, or plant matter) are usually compostable.

    No Slick or Waxy Feel: Avoid items that feel slick, waxy, or rubbery; these often contain non-compostable coatings or chemicals.

  • Earthy or Natural Aroma: Compostable items often smell like earth, plants, or food.

    No Chemical Odors: Avoid items with strong chemical or artificial smells (e.g., cleaning products, heavily dyed paper).

  • Crisp or Dry Sound: Dry organic materials like leaves or paper may crinkle or snap and are often compostable.

    No Metallic or Plastic Sounds: Items that clang, crinkle sharply, or are rigid may contain metals or plastics and are not compostable.

  • Edible Items: If it’s something you’d safely eat (e.g., fruits, vegetables, grains), it’s compostable.

    Non-Edible Natural Items: While you shouldn’t taste-test non-food items, if it's an untreated natural material like clean wood shavings, it's compostable.

The F.B.I - Compost Critters

A large variety of small critters and creatures do all the work transforming compostable materials into usable compost soil.

  • Microorganisms including molds, mushrooms, and yeast. Common in cooler temperatures. They specialize in decomposing woodier components of plant matter like cellulose and lignin. Found in leafy or woody materials.

  • Single celled organisms. Mesophilic bacteria thrive in moderate temperatures and do most of the work on sugars and starches. As they eat, they produce heat, raising the temperature of compost piles.

    The heat kills off the original bacteria and are replaced by heat-loving thermophilic bacteria that can survive up to 160 degree’s Fahrenheit. These bacteria focus on proteins, fats, and complex carbohydrates. This heat (above 131 degrees) successfully kills off much unwanted pathogens and weed seeds.

    Eventually thermophilic bacteria run out of material to eat and diminish, cooling the pile, and allowing fungi and mesophilic bacteria to clean up the job.

  • Mites, grubs, insects, spiders, slug, but most of all earthworms consume organic material and excrete nutrient rich matter. Compost with earthworms is called

    Vermicomposting. Worms help aerate the soil, consume organic matter, and act as a subway for microbes throughout the soil. The best worm is the Red Wiggler.

The Value of Compost Soil

Soil created through composting is often referred to by farmers as “black gold” due to its dense nutrient content. Compost soil is also highly stable and can withstand erosion and flooding, it is more resilient to extreme heat and runoff, and helps neutralize soil pH levels. Compost soil can be used for gardening, horticulture, landscaping, and agriculture to create a more stable environment to grow healthier plants.

  • Plants deplete nutrients from soil while they grow. The 13 mineral nutrients in the soil are dissolved in water and absorbed through a plant's roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why many farmers and gardeners use fertilizers, to add nutrients to the soil.

  • Chemical and synthetic fertilizers are intense and short lasting. If too much is applied it can actually harm the plant by “scorching” the plants roots. Unnatural fertilizers don’t help improve soil overall health or life span, which limits their long-term effectiveness. The nutrients they provide are quickly drained away into nearby waterways.

    The natural nutrients from mature composts are released to plants slowly and steadily. The benefits last for longer than one season. It stabilizes the volatile nitrogen of raw materials to form large protein particles when composting, which reduces the loss of nitrogen.

    Compost soil helps soils hold more plant nutrients by improving the Cation Exchange Capacity (CEC) and Anion Exchange Capacity (AEC) or exchange positive and negative charged ions, respectively, between a neutral atom. This allows nutrients to have stronger bonds with the soil, preventing them from being washed away.

  • Studies have shown that composts are able to help fight the spread of plant disease (e.g., Pythium root rot, Rhizoctonia roots rot chili wilt and parasitic nematodes) and decrease the losses of crops. Micronutrients and other critters in compost soil help to breakdown undesirables and toxins that cause plant disease into harmless and consumable materials.

  • Compost increases quality of soil structure, air flow, and water content leading to quicker establishment of new vegetation and decreases erosion rates. Compost protects the soil's surface from wind and water erosion by decreasing the action of soil dispersion by raindrops beating against the soil, increasing the infiltration rate, as well as reducing water runoff and increasing the surface wetness. It is vital to prevent erosion to safeguard waterways as well as maintain the efficiency and quality of the soil.

  • Using compost soil in landscaping and gardening increases the grounds ability to retain water by 2.5 times. Using compost soil reduces periods of water stress on plants and lessens the amount of water needed for healthy lawns, gardens, and houseplants.

  • If a soil becomes too basic or too acidic, plants can suffer from nutrient deficiencies or nutrient toxicities. Soil with a neutral pH level helps prevent plants from consuming environmental toxins, like lead and other heavy metals.

  • Compost reduces the soils bulk density and improves soil structure directly by loosening heavy soils with organic matter. Becuase of this, integrating composts into compacted soils can improve root penetration and turf growth.

Compostable Serving Ware

Using compostable serving ware is an eco-friendly alternative to traditional plastics because they are designed to break down into natural components in an industrial composting environment. Unlike conventional plastic that can take hundreds of years to decompose and contribute to environmental pollution, compostables offer a more sustainable option to single use serving ware.

It's essential to follow proper disposal guidelines for compostable cups and other compostable disposables. If placed in a landfill they will not break down as intended; if they are placed in recycling, they will contaminate the waste stream.

  • Compostable serving ware is typically made from renewable resources such as cornstarch, sugarcane, potato starch, or other plant-based materials. Some may also combine these materials with biodegradable polymers.

  • While the terms "biodegradable" and "compostable" are often used interchangeably, they have distinct meanings.

    Compostable materials break down in a determined amount of time and leave no harmful residues in the soil.

    Biodegradable materials break down in an undetermined amount of time. It could be a few days, it could be 50 years. For this reason they are not accepted as compost.

  • BPI or the Biodegradable Products Institute runs tests on bio plastic to ensure that the compostables meet industry standards for compostability. They then certify the brand. There are other compostable certifications, but we like BPI the best because they have the most rigorous testing.

  • Compostable serving ware requires specific conditions to break down properly. Temperature needs to reach a certain level for a certain amount of time. This only happens in industrial compost facilities; backyard methods are not sufficient to break down compostable serving ware. 

    Compostable material cannot break down properly in traditional landfills.


What is Industrial Composting?

Missoula Compost delivers all collections to Missoula’s municipal compost facility, Garden City Compost. This is why we can accept such a vast array of organic material often left out of backyard compost piles.

  • When material goes to an industrial compost facility, it decomposes through a more rigorous process than it would in your backyard compost bin.

    Material is broken down as small as possible, temperatures reach a high temperature for a required amount of time, and oxygen is more abundant. This creates ideal environments for critters and microorganisms that thrive during each part of the compost cycle.


  • Industrial composting means you can compost more material!

    Meat, bones, dairy, eggs, and compostable serving ware can all be safely composted in an industrial facility.

  • Temperatures that occur in an industrial compost facility stay over 130℉ while organic material breaks down. To achieve this temperature, oxygen is typically pumped into static piles or piles are turned over on a regular basis to keep them from going anaerobic (that is, breaking down without oxygen).

    This high consistent temperature kills bad bacteria and pathogens that would normally survive in backyard methods.


    that would cultivate in backyard composts.

  • Large-scale composting facilities have revolutionized composting. They are designed to handle large varieties of organic waste in high volumes and process it at an accelerated rate. Meaning we can create more nutrient rich soil, faster. 

    Soil is produced within three months of arrival and is sold to farms, plant nurseries, and individuals.

Benefits of Curbside Composting

  • One of the primary cost-saving benefits of composting is the reduction in waste disposal costs.

    By diverting organic waste, such as kitchen scraps and yard trimmings, from landfills, individuals and businesses can decrease the volume of waste that needs to be processed and disposed of in landfills.

    Landfill disposal typically incurs fees, so diverting organic waste to composting facilities can lead to direct cost savings.

  • Waste management companies often charge fees based on the amount of waste sent to landfills. Composting reduces the quantity of waste going to landfills, which can result in lower fees for waste disposal.

  • Compost is a nutrient-rich soil that can enhance soil fertility. By using compost in gardens, landscaping, or agriculture, individuals and businesses can reduce the need for chemical fertilizers.

    This not only saves money on fertilizer purchases but also helps maintain the long term health of soils and plants.

  • Compost improves soil structure and water retention, reducing the need for additional irrigation in gardens and agricultural settings.

    By enhancing water retention, compost helps plants access water more efficiently, leading to potential water savings and lower water bills.

  • Traditional waste processing methods, such as incineration, require significant energy inputs. Composting generally consumes less energy. The energy savings associated with composting contribute to overall environmental and economic benefits.

  • Composting offers a range of economic benefits by reducing waste management costs, improving soil health and productivity, creating jobs, and reducing overall environmental impact.

    The best part is by supporting a locally owned and operated organic waste management company, all the economic benefits are reaped locally.

  • Composting can foster community engagement and education about sustainable waste management practices.

    Communities that actively compost may experience improved environmental awareness, which can lead to long-term cost savings through reduced waste.

What is actually composted?

Everything we can. Missoula Compost never takes trips to the landfill. All our collections end up at Missoula’s compost facility. Unlike other large scale collectors, we guarantee the organics you put in your bin will be composted.

  • Everything we can. If we see any non-compostable material we will leave it behind.

    We sort every bin we collect from events like concerts or the Western Montana Fair. We then leave any contamination behind, as we have never taken a load to the landfill.

    Event compost is a lot of food scraps and BPI Certified disposable serving ware.

  • Everything we can. If we see any non-compostable material we will leave it behind.

    Home compost ends up being a lot of food scraps and yard/garden organics.

  • Everything we can. If we see any non-compostable material we will leave it behind.

    The type of compost at your work can vary depending on the type of work you do. In restaurants, it is almost entirely food scraps. At an office it can be a lot more paper and serving ware. At coffee shops, all grounds are gladly collected.

Compost soil improves the soils Cation Exchange Capcity (CEC)

In general, soil with larger amounts of organic material holds more negative charges resulting in a higher CEC. Similar to how a stronger magnet can hold more paper clips.

Wamt to learn more? This video breaks it down for you!