Composting has been practiced for thousands of years around the world to produce richer soil, higher crop yield, and sustainable waste management. While formally farmers had to rely on trade secrets and constant modification, scientists in the past 50 years have extensively studied the composting process, resulting in more precise methodology and advanced options for creating nutrient-dense, disease fighting compost, an indispensable element for growing high quality, high yield produce.

What are the most efficient methods of composting in large-scale and commercial farming?

A Thermophilic composting system creates ideal conditions for “heat-loving” bacteria to break down matter and kill pathogens and diseases. In all methods of decomposition, the work is done by both micro and macro-organisms. However, with thermophilic composting, the bulk of the work is done by heat producing micro-organisms. As a thermophilic compost pile is turned and monitored, the compost reaches temperatures high enough for thermophilic bacteria to thrive and break down dangerous pathogens. A successful thermophilic system will only maintain these high temperatures for 3-5 days and then return to a lower temperature suited for the survival of mesophilic bacteria. The high temperatures achieved kills diseases at the following rate: Compost that stays 122 degrees Fahrenheit for 24 hours is safe to grow with. Compost that stays 115 degrees Fahrenheit is safe to use within one week, and compost kept at 143.6 degrees Fahrenheit will kill pathogens in one hour. It is not recommended that compost sustain temperatures higher than 160 degrees as the compost may become sterile and ineffective for fighting off fungus and diseases once integrated into the soil.

Vermicomposting is the process of composting food waste and other organic matter with various species of worms, most commonly red wigglers, blue worms, white worms, and other earthworms species. These are all considered macro-organisms. In fact, these macro-organisms feed on the micro-organisms that precede thermophilic bacteria, making high temperatures an impossibility. While degradation occurs at a slower rate without the high sustained temperatures created by the thermophilic bacteria, vermicomposting is just as effective in killing pathogens and creating a nutritional soil additive. Some scientists believe the slower rate of degradation may produce a more chemically stable product than that of thermophilic compost systems.

For large scale vermicomposting, a “windrow” may be effective. This method lays down organic matter in large scale rows for worms to dwell in and feed from. Though this method doesn’t “trap” the worms, the overabundant nutrients will keep the worms within close proximity. “Flow through” beds are another popular method for large scale vermicomposting.

How long does composting take?

The length of the composting process is dependent upon which method and ingredients are used, as well as the environmental factors surrounding the compost. Under optimum conditions and with frequent management, thermophilic composting may be complete in 1-2 months while vermicomposting requires a minimum of 3-6 months to break down food scraps. As a general rule, it’s best to let all compost “cure” for several months even if it appears done. The extended time will allow degradation to take place at a slower rate, resulting in a more chemically stable product.

What are the essential elements?

Carbon, nitrogen, oxygen and moisture. Carbon acts as energy and protein to the micro-organisms that begin and maintain the composting process. Carbon-rich materials tend to be dry and brown such as leaves, straw, and wood chips. Essential to the cell growth and functioning of organisms is nitrogen. Nitrogen-rich materials tend to be wet and green. The ratio of carbon to nitrogen does not need to be exact, but it should be close to 25:1-30:1, or 25-30 parts carbon to one part nitrogen by weight. As composting proceeds, the finished product will yield a C/N ratio closer to 10:1. Keeping the moisture level of the compost pile balanced will ensure a stable environment for the organisms to work effectively. Too much or too little water will cause temperatures to fluctuate and thus organisms to be unproductive or die off. Finally, oxygen is essential for producing energy and generating new life (this is why compost needs to be turned, or aerated).

Will composting kill diseases found in animal waste?

When properly timed and maintained, composting will effectively break down animal waste.  However, the source of the animal waste should always be considered. It is not recommended that household pet waste be added to a compost pile. Only if sufficient knowledge of the animal’s health is available should their manure be added to a compost pile. Generally, that means most farm livestock manure is safe if sanitation measures are routinely taken. For more information on guidelines for manure use, see the NOP’s requirements listed on the USDA website. 

Are there any ingredients that should not be composted?

Yes. Chemically/pressure treated wood, grass and plant clippings treated with pesticides and other chemicals, inorganic material such as plastic should not be used. Some pesticides will degrade and become harmless in the composting process, however, only add if knowledge about the chemical compound is accessible. Most pesticide products will provide consumers with information about disposal and decomposition viability. Finally, a good rule of thumb for what to include in your compost pile is to keep it vegetarian. Meats, eggs, cheese and fats will attract animals to a compost pile and will not serve the microbial environment well.

How will I know if the compost is good and ready?

Finished compost will drop considerably in temperature, signifying that the chemical changes are near completion and stable. Good compost will not smell rotten or like waste. Rather, it will smell sweet and organic. Texture of the compost will range depending on C/N ratio, however, a  dark, crumbly, non-clay like texture is ideal.