A Comparison of the Greenhouse Gas Production of Black Soldier Fly Larvae versus Aerobic Microbial Decomposition of an Organic Feed Material
Most of the food waste and manure produced in developed countries is currently disposed of by use of either aerobic or anaerobic microbial decomposition. The former occurs with composting, while the latter takes place in lagoons and landfills. Microbial decomposition or organic matter emits substantial amounts of greenhouse gases each year, primarily in the form of carbon dioxide (CO2) and methane (CH4). The Food and Agriculture Organization of the United Nations estimates that these emissions totalled 3.5 Gt CO2 equivalent in 2011. One potential advantage of using Black Soldier Fly larvae (BSFL) is the animal’s ability to recycle large amounts of carbon into edible insect proteins and oils rather than simply breaking it down into carbon dioxide and methane. We sought to experimentally quantify the potential impact on greenhouse gas emissions that might be produced by utilizing BSFL as an economically and environmentally useful reservoir for carbon that would otherwise be emitted into the atmosphere by microbial decomposition. Identical quantities of moist feed material were allowed to be completely consumed by BSFL or microbes. BSFL completely consumed the feed material in 7 days; microbial decomposition required 45 days before the material appeared to be completely consumed. Based on carbon mass balance, when BSFL were present, 28.54% of the carbon initially present within the system was lost to the atmosphere in the form of CO2 along with a negligible amount of methane. When BSFL were not present, 48.62% of the original carbon present was lost to the atmosphere. The difference between the two systems with respect to carbon lost to the atmosphere was statistically significant (p<0.05). Insect larvae converted an average of 41% of the feed carbon present into body mass in the forms of protein, edible oil, and chitin.
Douglas A Perednia