In general terms a compostable material is any product that when placed into a mixture of decaying biodegradable materials will eventually turn into a nutrient-rich material that may be reused. There are home composting operations, farm composting facilities and then there are industrial composting facilities that help accelerate the biodegradation and stabilization of organic materials under more controlled conditions.
Agricultural composting is a bit different and according to the Massachusetts Department of Agricultural Resources, ag composting is specifically defined as “The composting of certain organic materials, including animal manures, vegetation and food processing by-products, for beneficial (on farm or off-farm) agricultural use.”
In some cases, agricultural composting is considered an agricultural practice, but depending on the scope of the operation, along with materials being composted, it may be considered solid waste management. The distinction between waste management vs. compost plays a role in both the financial and legal implications for agricultural composters when it comes to transforming waste.
An agricultural composting operation, defines any composting that takes place on the actual farm and may not include composting of nonorganic municipal solid waste or municipal sludge, septage, industrial solid waste or industrial sludge. An organic farm also cannot compost materials with a moderate or high risk of contamination from heavy metals, volatile and semivolatile organic compounds, polychlorinated biphenyls or dioxin.
NOP covers general composting in § 205.203, and the final rule says:
- Raw animal manure must be composted before use if used on crops meant for human consumption. Raw manure can be used without composting if "It's incorporated into the soil not less than 120 days prior to the harvest of a product whose edible portion has direct contact with the soil surface or soil particles; or if it's incorporated into the soil not less than 90 days prior to the harvest of a product whose edible portion does not have direct contact with the soil surface or soil particles."
- Composted plant and animal materials need to be produced though "A process that establishes an initial C:N ratio of between 25:1 and 40:1; and maintains a temperature of between 131 °F and 170 °F for 3 days using an in-vessel or static aerated pile system; or maintains a temperature of between 131 °F and 170 °F for 15 days using a windrow composting system, during which period, the materials must be turned a minimum of five times."
Many states have their own rules regarding agricultural composting. To learn more about regulations and tips for composting on the farm visit the following links.