Dairy manure separator solids are combined with green and equestrian materials, formed into windrows on the composting pad and adjusted for moisture as needed. Windrows are managed in accordance with CalRecycle (and Nicasio Blend under the USDA National Organic Program (NOP)) guidelines to reduce pathogens and weed viability to negligible levels. Microbes, naturally present in the compost pile, cause the pile to heat up. Temperatures are taken daily to assure that sufficient high temperature levels have been met. A mechanical screen is used to separate coarse from fine material at the end of the process once the compost has reached maturity.
WMC does accept almost all “weeds.” Most weeds and weed seeds are destroyed by the high temperatures of the thermophilic composting process. One notable exception is the seeds of common field bindweed (Convolvulus arvensis), which have been shown to survive temperatures of up to 180 F. Consequently, we do not accept this material at the drop off site. Some plant species do not like to be ground like bamboo and palm. While the irritant of poison oak breaks down in the composting process, until then it can cause our employees to be affected by poison oak. Most other plant material is accepted. Clopyralid, a broadleaf herbicide, does not break down in a timely manner. Green material and manures that contain clopyralid are not allowed.
Through the composting process nutrients are immobilized by the microorganisms. As a result, the nutrients are being conserved, not washed away by rain or irrigation. As the microbes die, new nutrients become available, hence a slow release of nutrients is provided throughout the growing season. Because finished compost is a dry material, typically less than 50% moisture at maturity, it is less costly to spread than wet manure (typically 75-95% water). In addition, finished compost is odorless. Compost is often used as an erosion control material to help prevent soil movement on disturbed sites. Properly composted material does not contain viable weed seeds, which liquid manure often does, so spreading compost does not spread thistles or other weeds.