Worm Compost Comparison and Uses Why Worm Composting in addition to or rather than Hot Composting?
• Can be done in small or large space. No minimal pile size although larger piles can reduce the risk of stressing the worms. Piles are normally shallow, with 1.5 to 2’ maximum for active composting, but outdoor windrows can be deeper.
• Can be done with limited equipment; worms can do much of the work of “turning”.
• More manageable / practical under winter weather conditions and in closed spaces.
• Turning of hot compost in an enclosed environment is not recommended due to negative potential health impact of gasses (ammonia) and molds on human lung function (breathing).
• Can probably retain more of the nitrogen that can be lost to the atmosphere in hot composting.
• Hot composting is by thermophilic bacteria at temperatures over 110 to 120oF and up to 160oF which can decrease the diversity of microorganisms.
• Vermicomposting is by mesophilic microorganisms in addition to worms at a temperature of less than 100oF. Worms eat microorganisms which can increase in the gut of the worm. The diversity of microorganisms, including fungi, reportedly increases during vermicomposting. In the study cited, the diversity of microorganisms decreased after the worms were removed.
• Finished worm compost or castings reportedly can have a higher concentration of available minerals, particularly phosphorus.
• Can be fast (40 to 60 days; 6 to 8 weeks) if worm population is high; with reportedly no requirement for a maturation phase that is needed with hot composting. While freshly harvested worm compost can clearly be used for application to established plants, it is not clear if it is acceptable for seed germination or seedling production.
• High moisture materials with potential for unpleasant odors are transformed into easy to handle and odor free from materials (usually also true for hot composting).
• Worm composting is generally more exciting / interesting to the non-farming or gardening public and is a visual way of teaching the importance of organic matter and nutrient cycling for the long term sustainability of farms. The soil food web is more visible through the worms.
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