NCSU Vermiculture Conference topic: Pre-composting: 9.5 out of 10 Worms Recommend It
Speaker: Dr. Rob Rynk, State University of New York. Here are my notes:
Precomposting food before feeding it to worms is often done with force-aerated composted bins. This has also been done for years in the mushroom growing industry.
Reasons for precomposting worm feedstocks:
Improve environment, prevent overheating, and to heat sanitizes the product
Pre-composted materials more likely to meet conditions that worms like (moisture level, etc.) It reduces ammonia levels, may neutralize pH, decomposes potential toxins, and reduces volume and weight of feed. It becomes more stable in general and still provides worms the food value.
Cons of precomposting – effort and number of time materials are handled
Consideration as to how long to precompost — microbial population is highest when the compost is hot. So you may want to interrupt the hot composting process to put the feed in worm bin in smaller quantities.
For hot composting heat to 131 degrees F for 3-15 days depending on type of composting process (PFRP regulations). Some people are more comfortable with using heat than worm composting to kill pathogens — there is currently more research on this than on using worms to reduce pathogens.
You may be able to feed worms materials that are precomposted that you can’t feed them uncomposted (for example — high nitrogen foods that emit ammonia). So you may want to precompost for 6 days. (If you can smell ammonia it is probably toxic to worms).
Raw feedstocks can attract pests and flies and can smell, so precompost to avoid this.
Pre-composting can break down toxins and pesticides that can be in produce and other feed.
How to precompost:
Passive aeration (in a basic pile or windrow)
Forced aeration — pipe blowing air into compost pile or sucking air out. Air sucked out can be used to heat a soil bed in a greenhouse. The soil bed is a biofilter to take out the moisture, etc. Or you can use a heat exchanger to use the energy from the warm moist air.
Turning windrow or compost pile. Now you often see a windrow system with covers and using a tractor to turn.
Passive aerated static piles — pipes with holes in them going through pile
Turning the compost pile is recommended — even if it is just one turn.
The reference text sold at the conference, Vermiculture Technology: Earthworms, Organic Wastes, and Environmental Management, is available on Amazon.com in hardcover and for Kindle.