In a conventional sense, composting entails mixing “brown” (carbon-rich) materials with “green” (nitrogen-rich) ones, in an approximate 3:1 ratio, aiming for an ultimate C:N ratio of 30:1. Innovations, however, on the standard thermophilic composting system offer opportunities to increase microbial diversity of the compost, thereby potentially improving their utilization rate and uptake by plants, increasing water holding capacity, and over all increasing benefits provided to plant and soil health.
In general, thermophilic composting offers a rapid, relatively straightforward method of turning waste products into a valuable resource. Criticisms, however, are that the thermophilic process destroys fungi, reduces populations of soil-beneficial bacteria, eliminates larger organisms and hence, trophic diversity, and overall, results in simplified, less useful compost than slower methods.
Animal-based composting is one potential method of avoiding these disadvantages while offering substantial benefits in higher microbial diversity, in addition to valuable products including meat, eggs, and hides or fiber, or proteins and fats that can be fed to other livestock, in the case of black soldier fly larvae, mealworms, and composting worms. It is also possible that animal-based composting is a more effective method of destroying pathogens of both humans and livestock, as the animal gut is particularly primed to kill and digest bacteria and smaller organisms encountered in wastes. Vermicomposting has long been used to process human waste, and more recently is being shown empirically to substantially or even completely reduce E. coli and eggs of Ascaris mites. It is not known if the use of livestock are a viable method of breaking down biological wastes at larger scales, including abbatoir waste, dead animals from natural causes, or, importantly, animals dead of various diseases, particularly transmissable ones.
Currently the standard method of disposing of large amounts of animal wastes is through incineration or, in some cases, mass burial. Both present substantial problems in terms of pollution, either air-borne or in soil and water; run-off and leachate from burial pits can potentially carry disease organisms far from their site of origin to affect other populations of both people and animals.
We are interested in investigating the potential of microlivestock – various insects and invertebrates – to break down large amounts of biological waste into safe, immediately usable compost products. This includes monitoring for pathogen travel through the composting system, and elimination of pathogenic organisms entirely by the end of the process; reduction in greenhouse gas emissions relative to thermophilic composting; production of useful byproducts including fats, proteins and products for human consumption or use; and description of microbial populations (fungal, bacterial, archaeal) in the compost throughout the process, followed by assessment of their transfer to and residency in the soil microbiome.
These results will help to shift the use of composting technology from a ‘plants and vegetables’ dominated system to a broader, more flexible means of dealing with large amounts of biological waste whose elimination currently entails large amounts of greenhouse gas emissions, effluent, and wasted biological material. It will also potentially enable the more effective diversification of depleted soil microbiomes, an important factor in improving soil health and by extension, water holding capacity, plant health, livestock health, and ultimately, human health.