01-001-560 Me. Code R. § 4
Compost - Organic materials which have undergone biological decomposition, and have been disinfected using composting or similar technologies, and have been stabilized to a degree which is potentially beneficial to plant growth.
Compost Grades - Classifications of compost materials based on nutrient content.
Some suggested grades are:
Nutrient grade compost - A compost applied to soil as a nutrient source. Nutrient levels are measurable and meet state's minimum levels to qualify for fertilizer status( see Appendix). Conductivity is greater than 4 mmhos/cm. It may contain appreciable lime equivalent.
Topsoil grade compost - Compost or compost soil mixture with organic content 4 - 40%, conductivity less than 2 mmhos/cm Used as a soil replacement. Density is normally 1000-1600 lbs. per cubic yard.
Horticultural grade - A compost with organic matter greater than 25%. Conductivity is less than 1 mmhos/CM or mixed with other materials to achieve this level. Density is normally less than 1000 lbs. per cubic yard.
Composting - The process by which biological decomposition of organic materials is carried out under controlled aerobic conditions, and which stabilizes the organic fraction into a material which can easily and safely be stored, handled and used in an environmentally acceptable manner. (The presence of anaerobic zones within the composting material will not cause the process to be classified as something other than composting.) Simple exposure of solid waste under uncontrolled conditions resulting in natural decay is not composting.
Conductivity - A measure of the soluble salts in the soil. This is used as an overall indicator of the level of macro and micro nutrients in the soil. Conductivity is measured in units of milli mhos per centimeter (mmhos/cm).
D.E.P. - The Department of Environmental Protection including the Board of Environmental Protection and the Commissioner.
Foreign Matter - Sticks, stones, clods, roots, glass, plastic, metal or other unwanted non-compostable materials that may be present in compost.
Heavy Metals - Those elements that are regulated because of their potential for human, plant or animal toxicity including but not limited to cadmium (Cd), copper (Cu), chromium (Cr), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn).
Loam. Soil textural class that consists of a mixture of sand (52%), silt (28-50%), and clay (7-27%) measured on a weight basis.
Mesophilic Stage - The stage of the composting process in which the rate of biological activity is high enough to maintain an average pile temperature of at least 90 degrees F( 32(c). This stage follows the thermophilic stage. It is in this stage that continued decomposition and stabilization occurs.
Mulch - A protective covering of various substances, especially organic, placed around plants to prevent erosion, compaction, evaporation of moisture, and freezing of roots and to control weeds.
On-site mixing - The practice of creating a soil mixture by spreading compost on the surface of the site to be prepared and tilling it into the top 3 to 6 inches of the existing soil. This practice would be used primarily for establishing grass cover (or other crop) on large open areas.
Pathogen - An organism, chiefly a microorganism, including viruses, bacteria, fungi, and all forms of animal parasites and protozoa, capable of producing an infection or disease in a susceptible plant or animal host.
PCB's - Polychlorinated Biphenyls; A class of chlorinated aromatic hydrocarbons representing a mixture of specific biphenyl hydrocarbons which are thermally and chemically very stable.
PFRP - A Process to Further Reduce Pathogens. The D.E.P. considers the following compost processes to qualify as a PFRP.
| Method | MinimumTemperature | MinimumTime |
| Static Aerated Pile | 55c | 3 days* |
| Within Vessel | 55c | 3 days* |
| Windrow | 55c | 15 days* |
Using the windrow composting method, there will be a minimum of five turnings of the windrow during the high temperature period.
* Aerated static piles must remain in the pile for at least 21 days. All three approaches are required to retain compost in a curing pile for at least 21 days following the active composting period.
Attaining a PFRP is essential for composts containing sludge or septage if the compost is to be distributed to the public.
PSRP - A Process to Significantly Reduce Pathogens. The D.E.P. considers the following composting processes to qualify as a PSRP.
| Method | MinimumTemperature | MinimumTime |
| Static Aerated Pile | 40c | 5 days |
| Within Vessel | 40c | 5 days |
| Windrow | 40c | 5 days |
For four hours during this period the temperature exceeds 55 degreesC.
Compost attaining a PSRP may be spread only on restricted sites.
Putrefactive - As result of the partial decay of organic matter.
Saturated Paste Extract Method - An approach for analyzing compost materials in which water is added to the compost until it just reaches saturation. This mixture is then allowed to sit for about 1 1/2 hours prior to performing tests. Conductivity, soluble nutrients and pH are often tested using this approach.
Stabilized - Means that the compost has at least passed through the thermophilic stage, and that biological decomposition of the organic materials has occurred to a sufficient degree that will allow beneficial use. See Section 5.A. for a description of stability levels and the methods for distinguishing them.
Static Aerated Pile Method - A method of composting in which materials are piled over perforated pipes or air ducts so that the piles may be aerated using blowers to either force air up through or draw air down through the compost mass.
Thermophilic Stage - The stage of the composting process in which the rate of biological activity is high enough to maintain an average pile temperature of at least 130 degrees F(55C). This stage favors decomposition by thermophilic (heat loving) bacteria. It is in this stage that the most rapid destruction of pathogenic organisms occurs.
Topsoil - Soil that consists of various mixtures of sand, silt, clay and organic matter. Normally considered to be the nutrient rich top layer of soil that supports plant growth.
Windrow Method - A method of composting in which materials are placed in long narrow piles (windrows) and aerated by physically turning the materials.
Within-vessel Method - A method of composting in which compostable materials are placed in an enclosed drum, bin or other vessel. Aeration is accomplished through rotation of the drum or through forced aeration.
01-001 C.M.R. ch. 560, § 4